contacting medium and process for contacting electrical parts

p0001The present invention relates to sintered preforms and a method of joining at least two components, wherein these sintered preforms are used.

p0002In the field of power electronics provides the connecting at least two components, such as substrates with electronic components, such as LEDs or very thin silicon chips, which have a high pressure and temperature sensitivity, a special challenge.

p0003Therefore substrates with such pressure and temperature sensitive devices are often connected by gluing. Suitable conductive adhesives typically contain silver particles, thermosetting polymers and reactive diluents. however, the bonding technique has the disadvantage that contact points between the substrate and device can be created which have only an insufficient thermal conductivity and electrical conductivity.

p0004To solve this problem it has been proposed to connect devices with substrates by sintering.

p0005In this sintering process usually pastes are used, which consist of the metal powder to be sintered and a solvent.

p0006The <patcit id="pcit0001" dnum="DE3414065C2"><text>DE 34 14 065 C2</text></patcit> proposes for this purpose, (i) applying such a paste to the surface to be bonded of an electronic component or substrate, (ii) applying the component to the substrate, wherein the paste is disposed between the component and the substrate, (iii) the solvent from expel the composite thus produced, and (iv) to sinter the composite.

p0007With this sintering method, the secure bonding of the electronic component with the substrate is possible. A disadvantage, however, has proved that the solvent is only expelled after the composite has been made of electronic component and substrate already. As the solvent containing the paste is available in this composite already in contact with the surfaces to be joined of electronic component and the substrate, a simple and rapid outgassing is no longer possible, so that the composite a longer time has to be dried.

p0008In order to solve this problem, according to the <patcit id="pcit0002" dnum="EP0242626B1"><text>EP 242 626 B1 0</text></patcit> applied the paste on the surface to be bonded of the electronic component or substrate and dried immediately afterwards. After drying, the component is applied to the substrate, wherein the dried paste is arranged between the electronic component and the substrate. Thereafter, the composite thus produced is sintered.

p0009A further development of this method is known from <patcit id="pcit0003" dnum="DE102004019567B3"><text>DE 10 2004 019 567 B3</text></patcit> known. There it is proposed to apply a paste as a layer on a carrier film and dried. Thereafter, one or more components are placed on the layer of dried paste. The composite of device layer of dried paste and carrier film is then subjected to pressure to increase the adhesive force between the dried paste and the component, so that the dried paste adheres to the component and can thus be lifted away from the carrier film. In the following, the component with the dried paste can be positioned on the substrate and the composite of substrate component and intermediate layer are sintered from dried paste.

p0010This procedure has proven economically advantageous because it allows a rational and at least partially parallel processing of a plurality of components and a structured design of the sintered layer.

p0011A disadvantage, however, is that this sintering process as well as other conventional sintering process either a high process pressure (for example, more than 30 MPa) require or high process temperature (over 250 ° C). These conditions often lead to damage of the components to be connected, so that conventional sintering methods retire for many applications.

p0012In the <patcit id="pcit0004" dnum="DE102007046901A1"><text>DE 10 2007 046 901 A1</text></patcit> proposes a sintering technique with which it is possible to build very good electrically conductive and thermally conductive interconnect layers for power electronics. In this sintering process, a metal paste is used which contains an alcoholic solvent, a silver compound which decomposes below 300 ° C to elemental silver. These metal pastes allow a reduction of the process pressure below 3 bar, and a reduction in the process temperature to below 250 ° C. This sintering technology represents a major leap in quality in the connection of substrates is with pressure and temperature-sensitive components.

p0013However, it would be desirable for many applications, when the process temperature could be further lowered. This would provide for a lower load on the components to be connected and thus to a further increase in quality of components in the field of power electronics. In addition, energy costs could be saved in a further reduction of process temperature to a considerable extent.

p0014The invention is therefore based on the object to provide a method for connecting at least two components are available, which enables process economically advantageous, and at least partially parallel processing of a plurality of components, a structured design of the sintered layer and a lowering of the sintering temperature to below 250 ° C ,

p0015This object is achieved by a method for connecting at least two components, in which<ol><li>(I) a sintered preform provides, comprising a carrier having a surface comprising at least one structural element containing the solidified paste, the solidified paste (a) metal particles having a coating containing at least one organic compound, and (b) at least one sintering aid selected from the group consisting of organic from (b1) peroxides, (b2) inorganic peroxides, (b3) inorganic acids, (B4) salts of organic acids, the organic acids 1 - having 4 carbon atoms, ( b5) acid esters of organic acids, the organic acids 1 - having 4 carbon atoms, and (b6) carbonyl is, contains, and the surface of the support having the solidified paste to the ingredients of the paste is non-reactive,</li><li>(Ii) providing at least a first component having a surface to be joined and a second component having a surface to be joined,</li><li>(Iii) at least one structural element on the surface of the carrier preform with the sinter of the surface to be joined of the first member contacted to provide an assembly of the first component and the at least one structural element which is in contact with the support,</li><li>(Iv) the arrangement of the first component and the at least one structural element away from the carrier,</li><li>(V) the surface to be bonded of the second component with a structural element of the assembly of the first component and the at least one structure member contacts at least to provide a sintering arrangement comprising the first component, second component and disposed therebetween structural element, and</li><li>(Vi) sintering the sintering arrangement.</li></ol>

p0016In this method, a sintered preform a support is used comprising a surface having at least one structural element containing solidified paste, the paste solidified<ol><li>(A) metal particles having a coating containing at least one organic compound, and</li><li>(B) at least one sintering aid selected from the group consisting of organic from (b1) peroxides, (b2) inorganic peroxides, (b3) inorganic acids, (B4) salts of organic acids, the organic acids 1-4 carbon atoms comprise (b5) acid esters of organic acids, the organic acids 1 - having 4 carbon atoms, and (b6) is carbonyl contains, and the surface of the support having the solidified paste to the ingredients of the paste is non-reactive.</li></ol>

p0017In the method according to the invention at least two devices are connected to each other.

p0018Preferably, a plurality of devices side by side, for example in a plane mounted on another component.

p0019The term component is not further restricted. In the broadest sense this will include objects that can be linked together.

p0020According to a preferred embodiment, for one of the components to be connected to an electronic component and the other component to be bonded to a substrate.

p0021According to a particularly preferred embodiment, the inventive method using the sintered preform according to the invention a plurality of electronic components adjacent to each other, for example in a plane mounted on a substrate.

p0022Among electronic component is understood in general an object, which can be part of an electronic device. According to a preferred embodiment, including a further fold-item not understood, which can serve as a component of an electronic circuit. The electronic component may optionally exist as a unit consisting of several components. In the electronic component can be, for example, an active device or a passive component. According to particular embodiments, the electronic components used in high-performance electronics. According to a preferred embodiment, the electronic component is selected from the group consisting of diodes (LEDs, for example,<i>Light Emitting Diodes,</i> light emitting diodes), transistors (e.g., IGBTs, <i>Insulated Gate Bipolar Transistors,</i> Bipolar transistors with insulated gate electrode), integrated circuits, semiconductor chips, bare chips (<i>This</i>), Resistors, sensors, capacitors, inductors and heat sinks is.

p0023Under substrate is understood in general terms an object, which is connectable to an electronic component. According to a preferred embodiment, the substrate is selected from the group consisting of lead frames, the DCB substrates (<i>Direct Copper Bonded-</i>Substrates) and ceramic substrates is.

p0024According to a preferred embodiment, the following pairs of electronic component and substrate are connected to each other: LED / leadframe, LED / ceramic substrate, <i>The</i>/ Leadframe, <i>The</i>/ Ceramic substrate, <i>The</i>/ DCB-substrate diode / leadframe, diode / ceramic substrate diode / DCB substrate, IGBT / leadframe, IGBT / ceramic substrate, IGBT / DCB substrate, integrated circuit / leadframe, integrated circuit / ceramic substrate, integrated circuit / DCB substrate, sensor / leadframe, sensor / ceramic substrate heat sink (preferably copper or aluminum heatsink) / DCB, heat sink (preferably copper or aluminum heatsink) / ceramic substrate heatsink / leadframe, capacitor (preferably tantalum capacitor, more preferably in ungehäustem state) / leadframe.

p0025The components to be connected may comprise a metallization respectively least. This metallization layer may comprise, for example pure metal or metal alloy. , The metallization layer on a metal, it is preferably selected from the group consisting of copper, silver, gold, palladium and platinum. , The metallization layer on a metal alloy, this preferably contains at least one metal selected from the group consisting of silver, gold, nickel, palladium and platinum. The metallization layer may also have a multilayer structure. According to a further preferred embodiment, the metallization layer includes a glass. According to the invention will be understood on a second device below the connecting at least two components, the fastening of a first component. In this context, "on 'only in that a surface of the first component is bonded to a surface of the second component, whereby it does not depend on the relative position of the two components or the assembly that includes the at least two components.

p0026first a sintered preform according to the invention is provided for the novel process.

p0027Among sintered preform is in the broadest sense means a configuration that enables a simple manner on the surfaces of two components, a paste can be applied, which is used in the sintering process of the invention.

p0028These sintered preform includes a substrate having a surface comprising at least one structural element containing solidified paste.

p0029The carrier has a surface made of a material which is resistant to the constituents of the paste or the paste itself not reactive, in particular chemically inert.

p0030In the invention, the material of the carrier surface is non-reactive when it is not sinterable. The material of the carrier surface is not capable of sintering, if it is such that no diffusion processes occur between the material of the carrier surface and the metal particles contained in the paste. Accordingly, it is preferable that at a temperature of 25 ° C and a pressure of 1013 hPa no interaction between the material of the support surface and the paste constituents take place that make the carrier for receiving the paste and the paste for a sintering process unusable. Further, the substrate surface should be made of a material which allows an easy release of the solidified paste from the support.

p0031According to a preferred embodiment, the material of the carrier surface is such that no diffusion predominate interactions between the material of the carrier surface and the metal particles contained in the paste, but probably adhesive interactions between the material of the carrier surface and the solidified paste.

p0032Characterized in that the material of the carrier surface to the constituents of the paste or the paste itself is non-reactive, it is ensured that, for carrying out the process according to the invention an assembly of a first structural element and the at least one structural member can be easily detached from the support.

p0033According to a preferred embodiment, the carrier is selected from the group, which consists of non-metallic materials, metallic ceramics and metallic materials having on their surface an oxide layer.

p0034As non-metallic materials in particular, polymers, glasses and non-metallic ceramics into consideration. According to a particularly preferred embodiment the carrier consists of polyester, polyimide or polyether sulfone is produced.

p0035Among metallic ceramics ceramics are understood to comprise at least one metal. For example, can be used as metallic ceramic for the carrier, an aluminum oxide ceramic.

p0036Metallic materials having on their surface an oxide layer are preferably metals passivation in the presence of atmospheric oxygen. These include in particular aluminum, nickel and iron.

p0037According to the invention the carrier has a surface having at least one structural element containing solidified paste.

p0038The at least one structural element is located according to the invention on the surface of the carrier.

p0039According to a preferred embodiment, the carrier has a surface having a plurality of structural elements containing the solidified paste. Several structural elements put by definition define a structure. These structural elements may have the same or a different geometry. Furthermore, the individual structural elements can be arranged regularly or irregularly. Preferably the structural elements on the support spaced side by side, ie in a plane.

p0040The number and the geometry of the structural elements and the arrangement of the structural elements on the carrier are not limited. Preferably, the number and geometry of the structural elements and the arrangement of the structural elements on the carrier, however, selected so that the pattern generated by the structural elements corresponding to the pattern to be attached to the individual, side by side, for example, in a plane, the components on it on another device to ,

p0041For example, multiple electronic components, for example semiconductor chips, comprising a substrate, for example, a lead frame, are connected. Conventionally, such a lead frame on contact points provided for the connection to the semiconductor chip. In such a case can be designed such the sintered preform that structural elements containing solidified paste, are arranged on the surface of the substrate in a pattern corresponding to the pattern of the contact pads on the leadframe. This arrangement of the structural elements on the carrier ensures that the later fitted with the semiconductor chip structural elements can be transferred to the contact points of the lead frame and the semiconductor chips are on the appropriate contact points on the leadframe.

p0042The structural elements on the surface of the carrier contain a solidified paste.

p0043This paste is such that it enables stable joining of the components at temperatures below 250 ° C.

p0044The paste used in the invention contains metal particles (a).

p0045The term metal particles is within the scope of the invention is not limited to particles of pure metals. Conceptually includes metal particles are in fact all particles having a metal content. This metal content is preferably at least 50 weight percent, more preferably at least 70 weight percent, more preferably at least 90 weight percent, and most preferably at least 95 weight percent, based on the weight of the metal particles. In particular, within the concept of metal particles fall even particles of a metal alloy or an intermetallic phase. Furthermore, metal particles are of the term also includes particles containing at least two layers which may have different metals, metal alloys or intermetallic phases. These metal particles can also be similar or different metal particles. In particular, various metal particles can be contained in the paste blends.

p0046In the present invention, the term metal refers to an element but in the periodic table of the elements in the same period, such as boron, but left of boron, in the same period as silicon, but left of silicon, in the same period as germanium, left of germanium, and in the same period as antimony, but is left of antimony, as well as on all the elements, which have a higher atomic number than 55th

p0047According to a particularly preferred embodiment, the paste contains metal particles, which in a purity of at least 95 percent by weight, preferably more of at least 98 weight percent, even more preferably of at least 99 weight percent, and most preferably of at least 99.9 weight percent. A metal

p0048According to a further preferred embodiment, the metal is selected from the group consisting of copper, silver, nickel and aluminum. According to a particularly preferred embodiment, the metal is silver or copper. According to a particularly preferred embodiment, the metal is silver.

p0049in the paste used in the invention are metal particles contain, having a metal alloy, this preferably comprises at least one metal selected from the group consisting of aluminum, nickel, copper, silver, gold, palladium and platinum. The metal alloy comprises in a particularly preferred embodiment, at least two metals which are selected from the group consisting of aluminum, nickel, copper, silver, gold, palladium and platinum. It may further be preferred that the proportion of the metals which are selected from the group consisting of aluminum, nickel, copper, silver, gold, palladium and platinum, on the metal alloy contains at least 90 weight percent, more preferably at least 95 weight percent, more preferably at least 99 weight percent, and most preferably 100 weight percent. The alloy can, for example, an alloy containing copper and silver, copper, silver and gold, copper and gold, silver and gold, silver and palladium, platinum and palladium or nickel and palladium.

p0050in the paste used in the invention are metal particles contain, comprising at least two layers having different metals, metal alloys or intermetallic phases, so these are preferably particles made of a metal, a metal alloy or an intermetallic phase comprising at least one metal selected from is selected of the group consisting of aluminum, nickel, copper, silver, gold, palladium and platinum, said particles are surrounded with a dissimilar coating of a metal, a metal alloy or an intermetallic phase, containing at least one metal selected from the group is selected, which is made of aluminum, nickel, copper, silver, gold, palladium and platinum. Very especially preferred are copper particles that are coated with silver.

p0051The metal particles may be of different shape. For example, the metal particles may be in the form of flakes or spherical (spheroidal) shape. According to a particularly preferred embodiment, the metal particles in the form of flakes. However, this does not exclude that, of the metal particles used, a minor portion may have a different shape. However, it is preferred that at least 70 weight percent, more preferably at least 80 weight percent, even more preferably at least 90 weight percent or 100 weight percent of the particles are in the form of flakes.

p0052If the metal particles in spherical form, the metal particles preferably have an average particle diameter from 0.1 to 20 .mu.m, more preferably from 1 -15 microns and more preferably 2-10 .mu.m. Under average particle diameter is understood according to the invention that at least 90 percent of the particles have a particle diameter in the specified range. For example, a mean particle diameter from 0.1 to 20 .mu.m, d ass is at least 90 percent of the particles have a particle diameter in the range 0.1 to 20 microns and less than 10 percent of the particles have a diameter of less than 0.1 micron or more than having 20 microns.

p0053According to the invention, the metal particles are coated.

p0054Under a coating of particles is understood according to the invention an adherent layer on the surface of particles. According to the invention means adherent layer that the layer is not already gravitationally detached from the metal particles.

p0055According to the invention, the coating of the metal particles at least one coating compound. This at least one coating compound is an organic compound.

p0056In this at least one coating compound is preferably a compound which is selected from the group consisting of fatty acids, fatty acid salts and fatty acid esters. These coating compounds are said to avoid agglomeration of the metal particles contained in the paste and contribute to the stabilization of the paste.

p0057The coating compounds employed in this invention are preferably selected from the group consisting of saturated compounds, mono-unsaturated compounds, polyunsaturated compounds and mixtures thereof.

p0058The coating compounds are furthermore preferably selected from the group consisting of branched compounds, unbranched compounds, and mixtures thereof.

p0059The coating compounds preferably 8-28, even more preferably 12-24 and most preferably 12-18 carbon atoms.

p0060According to a preferred embodiment, in the coating compounds thereof to mono fatty acids, salts of mono fatty acids, mono-fatty acid esters and mixtures thereof.

p0061The fatty acid salts are preferably salts come into consideration whose anionic component represents the deprotonated fatty acid, and whose cationic component selected from the group selected consisting of ammonium ions, Monoalkylammoniumionen, dialkylammonium, trialkylammonium, lithium ions, sodium ions, potassium ions, copper ions and aluminum ions.

p0062Preferred fatty acid esters are derived from the corresponding fatty acids wherein the hydroxyl group of the acid units are replaced by alkyl groups, especially methyl groups, ethyl groups, propyl groups or butyl groups.

p0063According to a preferred embodiment, the at least one coating compound is selected from the group consisting of caprylic acid (octanoic acid), capric acid (decanoic acid), lauric acid (dodecanoic acid), myristic acid (tetradecanoic acid), palmitic acid (hexadecanoic acid), stearic acid (octadecanoic acid), mixtures thereof, and the corresponding esters and salts and mixtures thereof, is made.

p0064According to a particularly preferred embodiment, the at least one coating compound resulting from lauric acid (dodecanoic acid), stearic acid (octadecanoic acid), sodium stearate, potassium stearate, aluminum stearate, copper stearate, sodium palmitate and potassium palmitate is selected from the group consists.

p0065The metal particles used in the invention are commercially available. The coating compounds according to the invention can be applied to the surface of the metal particles by means of conventional and of the prior art known methods.

p0066For example, it is possible for the coating compounds, in particular the above-mentioned stearates or palmitates, suspend in solvents, and the slurried coating connections to ground in ball mills with the metal particles. After milling, the now coated with the coating compounds, metal particles are dried and then dusted.

p0067Preferably, the proportion of the at least one coating compound which is selected from the group consisting of fatty acids, fatty acid salts and fatty acid esters, based on the total weight of the coating, at least 80 weight percent, more preferably at least 90 weight percent, more preferably at least 95 percent by weight, very particularly preferably at least 99 weight percent, and more preferably 100 percent by weight.

p0068According to a preferred embodiment the proportion of the coating compounds 0.05 to 3 percent by weight, more preferably 0.07 to 2.5 weight percent, and even more preferably from 0.1 to 2.2 weight percent, based on the weight of the coated metal particles.

p0069The degree of coating, which is defined as the ratio of the mass of coating compounds for surface of the metal particles is preferably from 0.00005 to 0.03 g, more preferably from 0.0001 to 0.02 g and even more preferably from 0.0005 to 0.02 g coating of compounds per square meter (m²) Surface of the metal particles.

p0070The paste contains the invention at least one sintering aid. This sintering aid is preferably able to ensure during the sintering process at temperatures below 250 ° C a burn-off of the coating compounds at below 250 ° C, so as to allow sintering at temperatures below 250 ° C. Particularly suitable sintering aids ensure burning off the coating compounds at temperatures below 250 ° C, either directly or indirectly through intermediate compounds formed.

p0071The sintering aid is in the present invention selected from the group consisting of organic from (b1) peroxides, (b2) inorganic peroxides, (b3) inorganic acids, (B4) salts of organic acids, the organic acids 1 - having 4 carbon atoms, (B5) esters of organic acids, the organic acids 1 - having 4 carbon atoms, and (b6) is carbonyl.

p0072The sintering aids as used in accordance with an embodiment of the organic peroxides (b1), inorganic peroxides (b2) and inorganic acids (b3) represent the oxidant.

p0073Under oxidizing agent is a substance to be understood, which can be oxidized other substances and itself becomes reduced. An oxidizing agent can accept electrons and thus is an electron acceptor. Preferably, the sintering aids according to this embodiment also an oxygen transfer agent. In order for a substance is meant, which can release oxygen. These compounds can serve as sintering aids, as they contain at least one oxygen atom and which allow burning of the coating compounds that are present on the metal particles of the paste at a temperature of below 250 ° C.

p0074The suitability of (b1) an organic peroxide, (b2) inorganic peroxides, and (b3) inorganic acids, to serve as a sintering aid, is due to the realization that it is advantageous for the sintering of devices using pastes if in the particles contained paste, preferably with fatty acids, coated. If the metal particles are not coated, then there occurs an agglomeration of the metal particles in the metal paste and clumping of the metal particles at an early stage during the sintering process. This has often inhomogeneous contact between the components to be joined result.

p0075Surprisingly, it was found that such coated metal particles are, however, also the main reason why the sintering temperature can not be lowered to below 250 ° C. As long as the coating compounds present on the surface of the metal particles, namely an agglomeration of the metal particles is prevented on the one hand. On the other hand be also the surfaces of the metal particles not for the sintering process is available so that the metal particles may not be sintered.

p0076In conventional sintering process, the coating compounds are burned at temperatures of well over 250 ° C commonly used for sintering during the sintering process. Only after the burning of the coating compounds according to the surfaces of the metal particles are accessible to the sintering process. Therefore, sintering processes are widely possible above 250 ° C with the metal particles conventionally employed, coated at temperatures of.

p0077Surprisingly, it was found that (b1) organic peroxides, (b2) ensure inorganic peroxides and (b3) inorganic acids burning off the coating compounds at temperatures below 250 ° C. These sintering aids is oxygen-containing oxidizing agent to ensure that the coating compounds contained on the metal particles are removed at temperatures below 250 ° C. even at temperatures below 250 ° C, the surfaces of the metal particles for the sintering process thus available. was also surprising that, in spite of the burning of the coating compounds at temperatures below 250 ° C does not lead to agglomeration of the metal particles, but instead are homogeneous and stable contact points between the components to be joined.

p0078Further, it was also surprisingly found that the coating lying under the surface layer of the metal particles is usually oxidized at least in part. Such metal oxide impair required for sintering diffusion processes and thus have a slowdown in the rate of diffusion result. Therefore, it has conventionally been necessary during sintering by means of these oxidized on the surface of metal particles using high process temperatures well above 250 ° C.

p0079According to the invention produced when burning off the coating compounds including carbon monoxide. The liberated during sintering, carbon monoxide is a reducing agent and as such is able to reduce existing on the surface of the metal particles metal oxide. The removal of the metal oxide ensures disability-free diffusion and, consequently, an increase in the diffusion rate. With this reduction of the metal oxide will also<i>in situ</i> reactive metal produced which further promotes the sintering process. Furthermore, this reactive metal fill existing gaps during the sintering process between the metal atoms of the metal particles and thus significantly reduce the porosity of the contact point between the to be connected components. This extremely stable and thermally conductive and electrically conductive contact points are generated.

p0080Under (b1) organic peroxides are in the present invention are meant compounds containing the superoxide anion O₂^2- contain or peroxide group -O-O- and at least one organic group which is linked directly to the peroxide. Organic peroxides may also contain inorganic residues that are directly related to the peroxide, as long as at least one organic group is present, which is directly linked to the peroxide in the invention thus. This linkage is preferably covalent nature.

p0081Among organic radicals are preferably radicals which contain at least one carbon atom, wherein the carbon atom with the peroxide group is directly, preferably linked by a covalent bond.

p0082According to a preferred embodiment, when used in the invention organic peroxides hydroperoxides and percarboxylic acids and salts thereof. Peroxycarboxylic acids are derived from carboxylic acids, preferably the hydroxyl group of the carboxylic acid moiety is replaced by a Hydroxyperoxylgruppe. Hydroperoxides turn are formally derived from ethers and alcohols from which the oxygen bridge linking the alkyl, alkenyl or aryl radicals with each other or with a hydrogen atom, is replaced by a peroxide group.

p0083The organic peroxides used in the invention have at least one peroxide group. They can thus have two or more peroxide groups.

p0084In the inventively used organic peroxide, the organic groups may be identical to or different.

p0085The organic radicals to carry heteroatoms itself. In this case, it is at the heteroatoms preferably oxygen atoms, nitrogen atoms or halogen atoms. Contain the organic radicals are halogen atoms, then fluorine atoms, chlorine atoms, bromine atoms or iodine atoms are preferred. The hetero atoms may also be part of a functional group. Suitable functional groups are preferably carboxylic acid groups, ester groups, keto groups, aldehyde groups, hydroxyl groups, amino groups, amide groups, azo groups, imide groups, cyano groups or nitrile groups into consideration.

p0086The organic radicals of the organic peroxides preferably have 1-20, more preferably 2-15 and even more preferably 2 - 10 carbon atoms.

p0087The organic radicals may be branched or unbranched.

p0088The organic radicals may be aliphatic or aromatic radicals.

p0089In the case of aliphatic radicals, the organic group may also have a cyclic radical. The ring of the cyclic moiety is preferably of 4 - 8 atoms, which may preferably be carbon atoms. however, the ring of the cyclic moiety may also contain heteroatoms preferably contain one or more nitrogen atoms or oxygen atoms.

p0090In the case of aromatic radicals, the organic group may have aromatic groups having preferably 5 or 6 carbon atoms.

p0091The organic radicals can be saturated or unsaturated. In the organic radicals can therefore multiple bonds, preferably double bonds, but also triple bonds be present.

p0092The organic peroxides may also contain at least one inorganic residue which is linked directly to the peroxide.

p0093Inorganic residues are understood according to the invention residues, which are linked with the peroxide group of the organic peroxide, wherein the linkage does not take place through a carbon atom.

p0094The linking of the inorganic residue of the peroxide group of the organic peroxide can in principle take place by all atoms except carbon atoms. The linking is preferably effected by a hydrogen atom or a heteroatom. As a hetero atom of metal atoms or nitrogen atoms may be preferred.

p0095Are hetero atoms directly linked to the peroxide, then the hetero atom may be part of a group that contains other atoms in addition to the hetero atom. These further atoms may preferably be carbon atoms, hydrogen atoms or other hetero atoms as further hetero atoms, nitrogen atoms, oxygen atoms, phosphorus atoms and halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms or iodine atoms may be preferred.

p0096As metal atoms, which can be directly linked with the peroxide, are preferably metals of the first, second and third group of the periodic table of elements into consideration. Accordingly are linked according to a preferred embodiment of lithium atoms, sodium atoms, potassium atoms, beryllium, magnesium atom, calcium atom, strontium atoms, boron atoms or aluminum atoms with the peroxide.

p0097The inorganic radical which is linked via a hetero atom with the peroxide, it can preferably be an ammonium radical. It may also be preferred that one or more hydrogen atoms of the ammonium radical are substituted by organic or inorganic groups. Preferably, one or more hydrogen atoms of the ammonium radical are replaced by alkyl groups. These alkyl groups may be branched or unbranched but are preferably unbranched. The alkyl groups which substitute one or more hydrogen atoms of the ammonium moiety preferably have 1 - 10, more preferably 1-6 and still more preferably 1-4 carbon atoms. The alkyl, substituted one or more hydrogen atoms of the ammonium moiety may be the same or different from each.

p0098Preferred inorganic radicals are ammonium radicals, monomethyl ammonium radicals, Dimethylammoniumreste, Trimethylammoniumreste, Monoethylammoniumreste, Diethylammoniumreste, triethyl, Monopropylammoniumreste, Dipropylammoniumreste, Tripropylammoniumreste, Monoisopropylammoniumreste, Diisopropylammoniumreste, Triisopropylammoniumreste, Monobutylammoniumreste, Dibutylammoniumreste and Tributylammoniumreste. The organic peroxide used in this invention may also be a cyclic organic peroxide. More particularly, the peroxide group of the organic peroxide may be part of a cyclic system itself.

p0099The organic peroxides used in the invention preferably have a decomposition temperature below 200 ° C. In this context, however, surprisingly found that some organic peroxides, having a decomposition temperature of over 200 ° C, in the presence of water contained in the metal paste metal having a decomposition temperature below 200 ° C. This appears to be due to the fact that in the metal paste contained metal catalyses the decomposition of organic peroxides.

p0100It may also be preferred that the organic peroxides used in the invention (1013 hPa) are liquid at room temperature (20 ° C) and normal pressure.

p0101Among particularly preferred embodiments, said organic peroxide is a compound selected from the group, 1,1,3,3-tetramethylbutyl peroxyneodecanoate-from diisobutyryl peroxide, Cumolperoxyneodecanoat, di-n-propyl peroxydicarbonate, tert- amyl peroxyneodecanoate, di (2-ethylhexyl) peroxydicarbonate, tert-butyl peroxyneodecanoate, di-n-butyl peroxydicarbonate, 1,1,3,3-Tetramethylbutylperoxypivalat, tert-butyl peroxyneoheptanoat, tert-amyl peroxypivalate, tert-butyl peroxypivalate, di- (3,5,5-trimethylhexanoyl) peroxide, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxyisobutyrat, 1,1-di- (tert-butylperoxy) -3, 3,5-trimethylcyclohexane, 1,1-di- (tert-butylperoxy) cyclohexane, tert-butylperoxy-3,5,5-trimethylhexanoate, 2,2-di- (tert-butylperoxy) butane, tert-butylperoxy isopropyl carbonate, tert-butyl peroxyacetate, 2,5-dimethyl-2,5-di (2-ethylhexanoylperoxy) hexane, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amyl peroxy-2-ethylhexanoate, tert -butyl-peroxydiethylacetat, tert-amyl peroxy-2-ethylhexyl carbonate, tert-butyl peroxy-2-ethylhexyl carbonate, tert-butyl peroxybenzoate, di-tert-amyl peroxide, 2,5-dimethyl-2,5-di- ( tert-butylperoxy) hexane, tert-Butylcumyl peroxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3, di-tert-butyl peroxide, 3,6,9-triethyl-3,6 , 9-trimethyl-1,4,7-triperoxonane, di-isopropylbenzene-mono-hydroperoxide, p-methane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, and 1,1,3,3-tetramethylbutyl hydroperoxide is.

p0102As a sintering aid can also be used further (b2) inorganic peroxides.

p0103Inorganic peroxides are within the scope of the invention, compounds which have the superoxide anion O₂^2- or the peroxide group -O-O- and exclusively inorganic residues contained. In the invention, inorganic peroxides are preferably all peroxides that are not organic peroxides. Inorganic residues are inventively residues that are directly related to the peroxide group on an atom other than a carbon atom.

p0104Two inorganic residues that are connected to a peroxide group of the inorganic peroxide may be identical or different.

p0105The link with the peroxide group can be carried out preferably by one or more hydrogen atoms and / or one or more heteroatoms. Heteroatoms metal atoms, boron atoms or nitrogen atoms may be preferred.

p0106Are hetero atoms directly linked to the peroxide, then the hetero atom may be part of a group that contains other atoms in addition to the hetero atom. These further atoms may be in accordance with a preferred embodiment, carbon atoms, hydrogen atoms or other hetero atoms as further hetero atoms, nitrogen atoms, oxygen atoms, phosphorus atoms and halogen atoms, especially fluorine atoms, chlorine atoms, bromine atoms or iodine atoms may be preferred.

p0107Preferred metal atoms, which can be directly linked with the peroxide, are metals of the first, second and third group of the periodic table of elements. Consequently, it may be preferred, the lithium atoms, sodium atoms, potassium atoms, beryllium, magnesium atom, calcium atom, strontium atoms, boron atoms or aluminum atoms are linked with the peroxide.

p0108Preferably, the at least one inorganic radical which is linked via a hetero atom with the peroxide group of the inorganic peroxide to an ammonium radical. in the inorganic peroxide are two ammonium radicals associated with peroxide, then the ammonium groups may be identical to or different.

p0109It may also be preferred that one or more hydrogen atoms of the ammonium radical are substituted by organic or inorganic groups. Preferably, in this case, or replace more hydrogen atoms of the ammonium radical by alkyl groups. These alkyl groups may be branched or unbranched but are preferably unbranched. The alkyl groups which substitute one or more hydrogen atoms of the ammonium moiety preferably have 1 - 10, more preferably 1-6 and still more preferably 1-4 carbon atoms. The alkyl, substituted one or more hydrogen atoms of the ammonium moiety may be the same or different from each.

p0110Preferred inorganic radicals are ammonium radicals, monomethyl ammonium radicals, Dimethylammoniumreste, Trimethylammoniumreste, Monoethylammoniumreste, Diethylammoniumreste, triethyl, Monopropylammoniumreste, Dipropylammoniumreste, Tripropylammoniumreste, Monoisopropylammoniumreste, Diisopropylammoniumreste, Triisopropylammoniumreste, Monobutylammoniumreste, Dibutylammoniumreste and Tributylammoniumreste.

p0111The inorganic peroxide may also be a peroxoborate. Under peroxoborates be understood, in which at least one oxygen atom is replaced by a peroxide borates according to the invention. Borates according to the invention are salts or esters of boric acid. The peroxoborates can preferably also be present as hydrates. Further, it may be in the order Peroxoboraten peroxysalts with annular anion.

p0112Preferred Peroxoborates are Ammoniumperborate, Alkylammoniumperborate and alkali metal perborates.

p0113According to the invention covered by the term Alkylammoniumperborate Ammoniumperborate, in which one or more hydrogen atoms of the ammonium moiety are replaced by one or more alkyl groups. These alkyl groups may be branched or unbranched. Preferably, these alkyl groups 1 - 10 carbon atoms, more preferably 1-6 carbon atoms and more preferably 1-4 carbon atoms.

p0114Preferred alkali metal perborates are Lithiumperborat, potassium perborate and sodium.

p0115The inorganic peroxides used in the invention preferably have a decomposition temperature of not more than 200 ° C.

p0116Further, it may be preferred that the inorganic peroxides used in the invention (1013 hPa) are liquid at room temperature (20 ° C) and normal pressure.

p0117According to a particularly preferred embodiment, the inorganic peroxides, hydrogen peroxide, ammonium peroxide, Monomethylammoniumperoxid, Dimethylammoniumperoxid, Trimethylammoniumperoxid, Monoethylammoniumperoxid, Diethylammoniumperoxid, Triethylammoniumperoxid, Monopropylammoniumperoxid, Dipropylammoniumperoxid, Tripropylammoniumperoxid, Monoisopropylammoniumperoxid, Diisopropylammoniumperoxid, Triisopropylammoniumperoxid, Monobutylammoniumperoxid, Dibutylammoniumperoxid, Tributylammoniumperoxid, lithium peroxide, sodium peroxide, potassium, magnesium , calcium, barium, Ammoniumperborat, Lithiumperborat, potassium perborate or sodium used.

p0118In a particularly preferred embodiment, the inorganic peroxides hydrogen peroxide, ammonium peroxide, sodium peroxide and Ammoniumperborat.

p0119As contained in the paste used in the invention may further sintering aids and (b3) act inorganic acids.

p0120Preferably, the inorganic acids are oxygen-containing inorganic acids.

p0121According to a further preferred embodiment, phosphoric acids are used as inorganic acids. Among phosphorus are to be understood in general, inorganic acids which have at least one phosphorus atom.

p0122Preferred phosphoric acids, which can be used according to the invention as a sintering aid, are ortho-phosphoric acid, pyrophosphoric acid, metaphosphoric and polyphosphoric.

p0123According to a further preferred embodiment, the at least one sintering aid to (b4) a salt of an organic acid wherein the organic acid is 1 - having 4 carbon atoms, (b5) an ester of an organic acid wherein the organic acid is 1 - 4 carbon atoms having, or (b6) a carbonyl complex. These sintering aids ensure apparent that the sintering process disturbing metal oxides which may be present on the surface of the metal particles contained in the paste can be reduced. For this reason, such compounds can be used which release a reducing agent in the course of the sintering process as a sintering aid. With this reducing agent there is preferably carbon monoxide. Salts of organic acids, the organic acids 1 - having 4 carbon atoms, esters of organic acids, the organic acids 1 - having 4 carbon atoms and carbonyl complexes can serve as a sintering aid, by obvious release during the sintering process carbon monoxide and so a reduction in metal oxides, which are contained on the surface of the metal particles contained in the paste, to allow the corresponding metal at a temperature of below 250 ° C.

p0124The suitability of (B4) salts of organic acids, the organic acids 1 - having 4 carbon atoms, (b5) acid esters of organic acids, the organic acids 1 - having 4 carbon atoms, and (b6) carbonyl complexes to serve as a sintering aid, also goes back to the above-described knowledge, that it is on the one hand advantageous for the sintering of devices using pastes, when the particles contained in the paste, preferably with fatty acids, coated to prevent agglomeration of the particles, this coating but On the other hand the cause for this is that the sintering temperature can not be lowered below 250 ° C. The suitability of the compounds used according to this embodiment to be able to serve as a sintering aid is further based, also on the already explained above knowledge that the underlying the coating layer surface of the metal particles is usually oxidized at least in part and this will affect the required for the sintering diffusion processes

p0125Salts of organic acids, the organic acids 1 - having 4 carbon atoms, esters of organic acids, the organic acids 1 - having 4 carbon atoms, and carbonyl may be according to the invention used as sintering aids, as they release carbon monoxide during the sintering process or during their combustion carbon monoxide is formed. The liberated during sintering, carbon monoxide is a reducing agent and as such is able to reduce existing on the surface of the metal particles metal oxide. The removal of the metal oxide ensures disability-free diffusion and, consequently, an increase in the diffusion rate. With this reduction of the metal oxide will also<i>in situ</i> reactive metal produced which further promotes the sintering process. Furthermore, this reactive metal fill existing gaps during the sintering process between the metal atoms of the metal particles and thus significantly reduce the porosity of the contact point between the to be connected components. This extremely stable and thermally conductive and electrically conductive contact points are generated.

p0126From a yet unknown reason seem salts of organic acids, the organic acids 1 - having 4 carbon atoms, esters of organic acids, the organic acids 1 - to have 4 carbon atoms and carbonyl complexes also the burning of the coating compounds contained in the silver particles temperatures to favor below 250 ° C. even at temperatures below 250 ° C, the surfaces of the metal particles for the sintering process thus available.

p0127According to the invention as a sintering aid (B4) salts of organic acids with 1-4 carbon atoms are used.

p0128According to a preferred embodiment a salt is used by an organic acid, the 1 - contains 3 carbon atoms.

p0129Organic acids are within the scope of the invention, organic compounds which have at least one carboxylic acid group. They can be represented by the formula          R-COOH Formula (I), where R is an organic radical.

p0130Accordingly, salts of organic acids according to the invention compounds which contain at least one anionic component comprising at least one unit having a carboxylic acid group in which formally a proton is split off, and having as the cationic component is a cationic species other than protons. Consequently, salts of organic compounds by the following formula can be represented          R-COOX Formula (II) wherein X is any cationic component.

p0131According to the invention R is an organic radical, the 1 - having 3 carbon atoms.

p0132In the context of the invention it may be preferred that the salt is not present in the metal paste in dissociated form. Accordingly, in one embodiment of the present invention in the sintering aids as a salt of an organic acid having 1-4 carbon atoms is used, than in the paste of the invention, any solvent used, preferably an aprotic solvent.

p0133The organic acid, 1 - 4 carbon atoms may preferably be a monoacid or a diacid. The organic acid may be a monobasic acid or a polybasic acid, especially a dibasic acid.

p0134The organic acid may include a further functional groups in addition to the at least one carboxylic acid group and at least. This functional group may be, for example a further carboxylic acid group, ester group, ketone group, aldehyde group, hydroxyl group, amino group, amide group, imide group, cyano group, nitrile group or a halogen atom, particularly fluorine atom, chlorine atom or bromine, act.

p0135The organic acid may in addition to the C = O group of the double bond at least one carboxylic acid unit contained formally contain further double bonds.

p0136are preferably used as sintering aids used salts of an acid which is selected from the group consisting of acetic acid, carbonic acid, formic acid, lactic acid and oxalic acid.

p0137As cationic component of the salts employed in this invention can be used preferably metal cations.

p0138The metal cations are preferably cations of metals having a high affinity for oxygen. It is believed that these metals can bind oxygen during the sintering process and thus shift the equilibrium of the reaction of liberated carbon monoxide by means of a sintering aid with the present on the surface of the metal particles metal oxides to carbon dioxide and the metals to the product side.

p0139Preferred metal cations are magnesium, aluminum, copper (I), copper (II), silver (I), silver (II), manganese (III), iron (II), iron (III), cobalt (II) and tin (II).

p0140According to a particularly preferred embodiment, the used as a sintering aid at least one salt of an organic acid having 1 - selected 4 carbon atoms selected from the group acetate, copper (II), iron (II) acetate, tin (II) acetate, iron (II) carbonate, copper (II) carbonate, magnesium formate, aluminum formate, iron (II) formate, tin (II) formate, copper (II) formate, silver (II) formate, manganese (III) - formate, copper (II) lactate, silver (I) lactate, iron (II) oxalate, iron (III) oxalate, and cobalt (II) oxalate is.

p0141Under the invention, however, also covers embodiments in which it may be possible that the metal paste as an organic acid salt with 1 - 4 carbon atoms, carbonate, lactate or formate of copper, silver, gold, nickel, palladium or platinum, especially silver silver lactate, copper lactate Silberformiat or contains.

p0142According to the invention can be used as a sintering aid and (b5) an ester of an organic acid wherein the organic acid is 1 - has 4 carbon atoms.

p0143The organic acid with 1 - 4 carbon atoms, from which derives the esters used in the invention, it is preferably an organic acid having 1 - 4 carbon atoms, as described above in connection with salts of organic acids, the 1 - having 4 carbon atoms , has been described.

p0144Consequently, it is the ester used in the invention is preferably a monoester or a multi-ester, in particular a diester.

p0145In the invention, ester refers to a compound in which at least one hydrogen of at least one carboxylic acid moiety of the organic acid with 1 - 4 carbon atoms is replaced formally by an organic group.

p0146Accordingly esters represent connections, which can be described by the above formula (II), but wherein X represents an organic group.

p0147Will as esters of organic acids having 1 - 4 carbon atoms used diesters, then the hydrogen atoms from two carboxylic acid moieties or the hydrogen atoms of a carboxylic acid unit of dibasic acid are formally replaced by organic groups. These organic groups may be identical or different.

p0148According to the invention is in this at least one organic group in at least one carboxylic acid moiety of the organic acid with 1 - at least replaced 4 carbon atoms is a hydrogen atom formal, preferably a group having 1 - 10, more preferably from 1 - 7 and even more preferably 1 - 4 carbon atoms.

p0149This organic group may be branched or unbranched but is preferably unbranched.

p0150The organic group may have one or more hetero atoms. Heteroatoms are in particular oxygen, nitrogen, and halogens, such as fluorine, chlorine, bromine or iodine, into consideration. It may also be preferred that the organic group carries no heteroatoms.

p0151Are in the organic group heteroatoms present, then this part of a functional group may be. Examples of such functional groups are carboxylic acid groups, ester groups, keto groups, aldehyde groups, amino groups, amide groups, azo groups, imide groups, cyano groups and nitrile groups.

p0152The organic group may be an aliphatic or aromatic group. Preferably, the organic group is an aliphatic group.

p0153According to a particularly preferred embodiment, the aliphatic group is an alkyl group. This alkyl group preferably has 1 - 10, more preferably 1-7 and still more preferably 1-4 carbon atoms. According to this embodiment, the alkyl group is unbranched. Preferably, this alkyl group contains no heteroatoms. Particularly preferred alkyl groups are methyl groups, ethyl groups, propyl groups and butyl groups.

p0154Accordingly, the esters of organic acids used in the invention, wherein the organic acids 1 - having 4 carbon atoms, preferably selected from the group consisting of methyl esters, ethyl esters, propyl esters and butyl esters.

p0155According to this embodiment, in the inventive esters of organic acids having from 1-4 carbon atoms for compounds which can be represented by formula (II), wherein X is an alkyl group, preferably a methyl group, ethyl group, propyl group or butyl group stands.

p0156Particularly preferred esters of organic acids with 1-4 carbon atoms are thus methyl acetate, ethyl acetate, propyl acetate, butyl acetate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, Ethylbutylcarbonat, methyl formate, ethyl formate, propyl formate, butyl formate, methyl lactate, ethyl lactate , propyl lactate, butyl lactate, dimethyl oxalate, Dieethyloxalat, dipropyl and dibutyl oxalate.

p0157As sintering aids according to the invention also (b6) carbonyl complexes can be used.

p0158The term carbonyl invention describes carbonyl metal complexes in which at least one CO molecule is coordinated to at least one metal atom.

p0159In addition to the at least one CO molecule, the carbonyl can also have further ligands. These further ligands can be either elementary or molecular ligands.

p0160The ligands can be monodentate or mehrzahnig.

p0161Preferred basic ligands are hydrogen and halogens. Halogens fluorine, chlorine, bromine and iodine are preferred.

p0162Preferred molecular ligands are nitrogen oxides, cyanides and organic ligands.

p0163The organic ligand is preferably ionic or unsaturated ligands.

p0164As the organic ligand organic ligands come with at least one carbon atom into consideration. Preferably, when the organic ligand having at least one carbon atom to organic ligands, 2 - 20, more preferably 2 - 16, and more preferably 2 - 12 carbon atoms.

p0165The organic ligand may be branched or unbranched.

p0166The organic ligand may also be saturated or mono- or polyunsaturated.

p0167The organic ligand may further have a ring structure. In this ring structure may also be included at least one heteroatom. This at least one hetero-atom may preferably be nitrogen or oxygen.

p0168The organic ligand may be also be aromatic ligands.

p0169As ionic ligands may be preferred alkyl ligands, preferably unbranched alkyl ligands, such as methyl ligands or cyclopentadienyl.

p0170As unsaturated organic ligand alkenes, conjugated or non-conjugated diene and allyls may be preferred. According to the invention as well as organic groups π-allyl and aromatics-transition metal complexes are provided.

p0171The carbonyl complexes employed in this invention can contain one or more metal atoms or. Assign the carbonyl several metal atoms, then these metal atoms may be the same or different from each.

p0172As metals of the carbonyl complexes preferably are used metals having a high affinity for oxygen.

p0173Preferably, the carbonyl complexes have at least one element of transition metals, ie, elements of the 3rd to 11th group of the periodic table of the elements, on.

p0174According to the invention it may further be preferred that the at least one metal of the metal carbonyls used in the invention is a metal which is selected from the group consisting of vanadium, molybdenum, tungsten, manganese, iron, ruthenium, Osram, cobalt, and nickel.

p0175According to a preferred embodiment, at the carbonyl complexes to metal carbonyls.

p0176The term metal carbonyls to the present inventors describe compounds which are mono- or polynuclear coordination compounds in which only carbon monoxide molecules are coordinated to metal atoms,

p0177Metal carbonyls may contain according to the invention is a metal atom or a plurality of metal atoms.

p0178The metal atoms contained in the metal carbonyls may be identical to or different.

p0179Preferably, when the metal atoms of the metal carbonyls to elements of the transition metals, ie by elements of the 3rd to 11th group of the Periodic Table of the Elements.

p0180According to a preferred embodiment, wherein at least one metal of the metal carbonyls used in the invention is a metal selected from the group consisting of vanadium, molybdenum, tungsten, manganese, iron, ruthenium, Osram, cobalt, and nickel.

p0181The metal carbonyl may be electrically neutral or salt. The salt may be a monovalent or polyvalent salt.

p0182According to a particularly preferred embodiment, the metal complex used in the invention as a sintering aid is a metal complex which is selected from the group consisting of vanadium hexacarbonyl (V (CO)₆), Molybdenum hexacarbonyl (Mo (CO)₆), Tungsten hexacarbonyl (W (CO)₆), Dimanganese decacarbonyl (Mn₂(CO)₁₀), Methylcyclopentadienyl ((CH₃C₅H₄) Mn (CO)₃), Iron pentacarbonyl (Fe (CO)₅) Diiron (Fe₂(CO)₉), Triiron dodecacarbonyl (Fe₃(CO)₁₂), Diprototetracarbonylferrat (II) (H₂[Fe (CO)₄]), Dicarbonyldiiodeisen (Fe (CO)₂I₂) Trikaliumcarbonylpentacyanoferrat (K₃[Fe (CN)₅CO], 1,2-bis (hexamethylbenzene) -tetracarbonyldieisen (0) (C₁₂H₁₈Fe (CO)₄FeCl₁₂H₁₈) Carbidopentaeisenpentadecacarbonyl (Fe₅C (CO)₁₅, Ruthenium pentacarbonyl (Ru (CO)₅, Dirutheniumnonacarbonyl (Ru₂(CO)₉) Triruthenium dodecacarbonyl (Ru₃(CO)₁₂, Hexarutheniumhexadecacarbonyl (Ru₆(CO)₁₆) Osrampentacarbonyl (Os (CO)₅) Triosramdodecacarbonyl (Os₃(CO)₁₂) Pentaosramhexadecacarbonyl (Os₅(CO)₁₆) Hexaosramoktadecacarbonyl (Os₆(CO)₁₈) Dicobaltoktacarbonyl (Os₂(CO)_8th) Tetracobalt (Os₄(CO)₁₂) Hexadecacarbonylhexacobalt (Co₆(CO)₁₆), Nickel tetracarbonyl (Ni (CO)₄) Dinatriumcarbonylferrat (Na₂[Fe (CO)₄]) consists.

p0183the process temperature during sintering can thus be significantly reduced by the use of the sintering aids as described above. It is surprising that, in spite of the burning of the coating compounds at temperatures below 250 ° C does not lead to agglomeration of the metal particles, but instead are homogeneous and stable contact points between the components to be joined.

p0184According to a particularly preferred embodiment, the molar ratio of sintering aids is to that contained in the coating of the metal particles organic compounds (coating compounds) in the range from 1: 1 to 150: 1, more preferably in the range from 3: 1 to 100: 1, even more preferably in the range from 5: 1 to 80: 1 and in particular in the range from 10: 1 to 80: 1. molar ratio of sintering aids to coating compounds according to the invention, the quotient of (i) the sum of the amounts of the sintering aid contained in the paste, and ( ii) referred to the sum of the amounts of the coating compounds contained in the coating of the metal particles. Contains a paste, for example, as a sintering aid 0.025 mol aluminum formate and 0.015 mole copper and the only coating compound 0.0008 mol potassium, so the molar ratio of sintering aids to coating compounds 50: 1.

p0185A ratio of sintering aids to coating compounds in accordance with the invention the preferred range has further advantageous effects. So is characterized on the one hand ensures that there is enough carbon monoxide to reduce the metal oxides are available during the sintering process as a result of burning the coating compounds. On the other hand, the amount of sintering aids then not so high that thereby the sintering process would be impaired. As explained above, it may be preferable in the invention, if it is at the present in the coating of metal particles organic compounds to free fatty acids, fatty acid salts or fatty acid esters, preferably 10 - have 18 carbon atoms - 24 and more preferably 12th

p0186The effects described above seem to lead to the result that it is possible when using the sintering aid used to lower the sintering temperature to below 250 ° C and produce yet stable and thermally conductive and electrically conductive contact points between to be joined by the sintering process components.

p0187According to a preferred embodiment, the paste contains at least one metal precursor.

p0188Under metal precursor is understood in the context of the invention a compound which is decomposed at temperatures of below 250 ° C in the presence of the metal particles contained in the paste to the metal of the metal precursor. Preferably, therefore, when using a metal precursor during the sintering process<i>in situ</i> a metal. It can be determined in a simple manner, whether a compound is a metal precursor according to this preferred embodiment. For example, a paste that contains a compound to be tested is deposited on a substrate with a silver surface, are heated to 250 ° C and kept at this temperature for 20 minutes. Thereafter, it is checked whether or not under these conditions has decomposed compound to be tested to a metal. For example, use before the test, the content of the metal-containing paste ingredients balanced and from the theoretical mass of metal can be calculated. After the test, the mass of deposited on the substrate material is determined gravimetrically. Does the mass of deposited on the substrate material of the theoretical mass of the metal, the usual measurement errors are taken into account, it concerns with the tested compound to a metal precursor according to this preferred embodiment.

p0189According to a further preferred embodiment, the metal precursor to a metal contained in the metal particles. According to a particularly preferred embodiment, therefore, the metal precursor on silver or copper as the metal.

p0190It may be preferred, as metal precursor metal carbonates, Metalllactate, metal formates, Metallcitrate, metal oxides or metal salts of fatty acids, fatty acid salts to be used preferably with 6 to 24 carbon atoms.

p0191In particular embodiments, are used as metal precursor silver carbonate, silver (I) lactate, silver (II) formate, silver citrate, silver oxide (for example, AgO or Ag₂O), copper (II) lactate, copper stearate, copper oxides (Cu, for example,₂O or CuO) or gold oxides (eg Au₂O or AuO) used.

p0192According to a particularly preferred embodiment, the metal precursor is selected from the group consisting of silver carbonate and silver oxides.

p0193If present, the metal precursor is preferably in the paste in particulate form, more preferably in the form of flakes, above.

p0194The use of a metal precursor, which during the sintering process <i>in situ</i> Metal releases, with the result that the <i>in situ</i> Metal formed during the sintering process gaps between the metal particles contained in the paste includes. In this manner, the porosity of a contact point between the two may be reduced to be joined components.

p0195The paste contains, at least in the non-solidified state, further comprising at least one compound which can act as a solvent. For this purpose the solvents commonly used for metal pastes come into consideration. For example, as a solvent, α-terpineol ((R) - (+) - α-terpineol, (S) - (-) - α-terpineol or racemates), β-terpineol, γ-terpineol, ö-terpineol, mixtures of the above said terpineols, N-methyl-2-pyrrolidone, ethylene glycol, dimethylacetamide, 1-tridecanol, 2-tridecanol, 3-tridecanol, 4-tridecanol, 5-tridecanol, 6-tridecanol, isotridecanol, dibasic esters (preferably dimethyl esters of glutaric, adipic or succinic acid or mixtures thereof), glycerol, diethylene glycol, triethylene glycol or mixtures thereof are used.

p0196The paste may further contain at least one polymer, to impart desired properties to the paste. On the other hand, it may be of advantage that the paste contains no polymers or their share is low as polymers, in particular thermosets, usually burn out at temperatures of more than 250 ° C and, therefore, adversely affect the sinterability of the paste. This is especially true of for thermosets or precursors. Among precursors of thermosetting compounds which, which can harden in the presence of other paste components to thermosets. These thermosets or precursors thereof usually have a weight average molecular weight of less than 700th In a preferred embodiment, the proportion of polymers having a weight average molecular weight of less than 700, no more than 6 weight percent, based on the total weight of the paste.

p0197Moreover, in the metal paste further ingredients, such as for example, customary dispersants, surfactants, defoamers, binder or viscosity controlling agent may be contained.

p0198The paste used in the invention is preferably applied to a surface of a support, to produce at least one structural element. These structural elements on the surface of the carrier therefore first have not yet solidified paste, which is then solidified.

p0199The application of the paste on the surface of the support is performed such that the desired pattern of structural elements which contain the paste, is provided on the surface of the carrier.

p0200The application of the paste on the surface of the support can be carried out by conventional methods. Preferably, the paste is applied by a printing process, for example by screen printing or stencil printing.

p0201The distances between the individual structural elements of paste are preferably chosen so that a pattern is generated that corresponds to the pattern with which the later on the sintered preform adjacent components are arranged after the sintering process on the to be connected component.

p0202The geometry of the paste applied is preferably chosen such that after solidification of the paste a structural element is obtained that is able to be equipped with a device that a desired region of the surface of the component is in contact with paste. It is possible that only a part of the surface or the entire surface of the component with which the structural member is loaded, with the structural element is in contact.

p0203The thickness of the applied paste is preferably adapted to the dimensions of the components to be connected. For example, if a first semiconductor chip are connected with a first contact surface of a lead frame, which is located in a recess, and a second semiconductor chip having the second contact surface of a lead frame are connected, is not located in a recess, then to produce the structural member via the first semiconductor chip is to be connected to the first contact surface of the lead frame, a larger application thickness of the paste can be selected as for the production of the structural member through which the second semiconductor chip with the second contact surface of the leadframe is to be connected. As a result, a structure may be provided having structural elements of different heights depending on the distance between the connected components.

p0204The application thickness of the paste is not further restricted. It is usually in the range 10-300 microns, preferably in the range 10-200 microns and more preferably in the range 20-50 microns.

p0205The paste used in the invention is solidified on the surface of the carrier for generating the at least one structural member. In the invention, the paste is solidified when their consistency is imparted with the paste gravitationally no shape change subject.

p0206The solidification of the paste is preferably effected by removal of the liquid components of the paste at room temperature, in particular the solvent. To remove the liquid ingredients at room temperature, the paste is preferably dried.

p0207Under drying is understood, accordingly, the removal of the contained in the paste, at least one solvent. The removal of the solvent can be carried out quantitatively. On the other hand, it is also possible that still remain residues of solvents in the paste.

p0208According to a preferred embodiment, during the drying at least 99.5 percent by weight, more preferably at least 99.7 weight percent, and even more preferably at least 99.9 weight percent of solvent, based on the weight of the originally present in the paste solvent removed.

p0209Preferably, the solidified paste contains no more than 0.5 weight percent, more preferably not more than 0.4 weight percent, even more preferably not more than 0.3 percent by weight, more preferably not more than 0.2 weight percent, and most preferably not more than 0.1 weight percent of solvent, based on the weight of the dried paste.

p0210It is particularly preferred that the solidified paste not more than 0.5 percent by weight, more preferably not more than 0.4 weight percent, even more preferably not more than 0.3 percent by weight, more preferably not more than 0.2 weight percent, and most is preferably not more than 0.1 percent by weight of compounds that are liquid at a temperature of 25 ° C and a pressure of 1013 hPa, based on the weight of the dried paste containing.

p0211According to a preferred embodiment, the solidified paste 75 to 95 percent by weight metal particles, 0.1 -15 percent by weight sintering aid, 0 to 0.5 percent by weight of solvent, 0 -12 weight percent metal precursor and 0 -10 weight percent of other constituents, based on the weight of the solidified paste ,

p0212According to a particularly preferred embodiment, the solidified paste 80 to 95 percent by weight of metal particles, 2 to 15 percent by weight sintering aid, 0 to 0.3 percent by weight of solvent, 0 -12 weight percent metal precursor and 0 - 10 percent by weight of further constituents, based on the weight of the solidified paste.

p0213According to a very particularly preferred embodiment, the solidified paste 80 to 95 percent by weight metal particles 3 -15 weight percent sintering aid, 0 to 0.1 percent by weight of solvent, 0 to 12 weight percent metal precursor and 0 - 10 percent by weight of further constituents, based on the weight of the solidified paste ,

p0214The solidification of the paste, preferably, the drying of the paste is carried out under conditions which ensure that it does not come to a complete sintering of the paste. It is necessary therefore that the solidified paste comprises at least one residual reactivity for the later following sintering process. However, it may well be advantageous for the drying conditions are selected, in which it already comes to a Teilversinterung the paste. This may for example be desired in order to increase the stability of the paste, and the adhesion of the paste on the substrate. The stability of the paste, and the adhesion of the paste on the substrate can be apparently increased by the addition at least one organic compound, which is located as a coating on the metal particles. This is probably due to the fact that detach at a temperature increase small amounts of coating compounds and serve as a bonding agent between the metal particles of paste or between the metal particles of the paste and the support.

p0215The drying of the paste is therefore preferably at a temperature, a pressure, a humidity and for a time suitable to remove the solvent from the paste as much as possible, without, however, after drying, the sintering processes are complete within the paste.

p0216Preferably, the drying takes place at temperatures below 200 ° C and more preferably below 150 ° C and for example at about 120 ° C for a period of preferably 3-60 minutes. Dry conventional drying equipment can be used. usually on solidification of the paste there is an increase in the porosity of the paste. It has surprisingly been shown that the binding of the structural member of solidified paste to the component to be assembled can be effected in a particularly simple manner when the porosity of the solidified paste is increased. Under porosity is the volume of the solidified paste meant herein the volume fraction of pores, based. In a preferred embodiment, preferably, the porosity of the solidified paste is at least 20 percent by volume, more preferably at least 40 volume percent, more preferably at least 60 volume percent, more preferably at least 80 volume percent, and most preferably at least 90 percent by volume. The porosity of the solidified paste can be adjusted in a simple manner on the proportion and the nature of the solvent contained in the paste, the drying time and the drying temperature.

p0217On at least one structural element containing the solidified paste, also a film may be applied. This film can be used in particular to preserve the structural element from damage, for example by mechanical stress. Preferably, the film covers the entire, formed from the individual structural elements of the support structure on the surface of the sintered preform. The film may be for example a sheet of polymer or a paper. If a film has a structural element on which at least is present, this is removed during the process of the invention. The removal of the film takes place before the, at least, contact with a structural element on the surface of the sintered preform containing the solidified paste to the surface to be joined of the first member.

p0218According to the invention at least two devices are connected to each other. These each have at least on a surface to be bonded. Under surface of a component to be connected to a surface of a component is herein understood to be connected to the surface of another component by sintering.

p0219The to be connected to at least two components are referred to herein as a first component or as a second component. The terms "first" and "second" only to that distinguish conceptual components to be connected in this case serve. In particular, this no requirements regarding the type and shape of the components are made.

p0220For connecting the at least one structural element is placed on the surface of the carrier preform with the sinter of the surface to be joined of the first member in contact. Upon contacting the at least one structural element on the surface of the carrier preform with the sinter of the surface to be joined of the first member an assembly of the first component and the at least one structural element is thus provided, which is in contact with the carrier. This arrangement is connected to the carrier via the at least one structural element in contact, usually a responsibility of the assembly is ensured on the support due to adhesive forces.

p0221Preferably a plurality of structural elements are arranged on the surface of the support of the sintered preform. In this case, it is preferable that a plurality of structure elements on the surface of the carrier, the sintered preform, particularly preferably all of the structural elements on the surface of the carrier, the sintered preform, with components, including the first component, are provided. Preferably another device is placed on each structural member. Accordingly, preferably a plurality of structure elements on the surface of the carrier, the sintered preform, particularly preferably all of the structural elements on the surface of the carrier, the sintered preform, provided independently of each other with components. These components are preferably arranged side by side in a plane.

p0222According to a preferred embodiment, the first component is arranged with the carrier on the surface of the sintered preform, at least one structural element so contacted that on the first component may be present metallization is in contact with the structural member. If several devices next to each other are brought into contact with a plurality of structural elements, the contacting is preferably carried out also such that optional metallization stand on the individual components of the structural elements in contact.

p0223The contacting of the at least one structural element with the surface to be joined of the first member, preferably the contacting of a plurality structural elements independently of one another with the surfaces to be connected of individual components is carried out according to a preferred embodiment, by pressing. In this case, on the one hand are pressed onto the surface to be bonded of the first component, the sintered preform having the structural element so that the structural element and the surface to be bonded of the first member are connected together. On the other hand, the surface to be bonded of the first member can be pressed onto the at least one structural element of the sintered preform.

p0224This pressing makes no special measures required. Preferably, the pressing is performed at temperatures below the sintering temperature, and more preferably at temperatures below 200 ° C, for example at temperatures in the range 100-200 ° C. It may be preferable to heat the sintered preform provided with at least the first component to the desired Anpresstemperatur. The pressing can under moderate pressure, preferably at a pressure of at least 0.1 N / mm², More preferably at a pressure of at least 0.5 N / mm², Even more preferably at a pressure of at least 1.0 N / mm² and more preferably at a pressure of at least 2 N / mm² done. For the pressing of conventional stamp devices or pressing devices can be used.

p0225The pressing is preferably carried out such that a bond between the at least one structure element and the first component is achieved, which allows simple removal of the assembly of the first component and the at least one structural element of the carrier of the sintered preform.

p0226After contacting the at least one structural element to the surface to be joined of the first component is thus a with the support in contact, preferably on the carrier adhering arrangement before having at least one structural element and at least the first component, wherein the optionally on the surface of the metallization first component contained is the structural element in contact.

p0227Subsequently, the assembly is removed from the first component and the at least one structural element of the support. For this purpose, one part of the support which the now present on at least the first component at least one structural element covered, will be deducted from the at least one structural element of the sintered preform. Preferably, the carrier is then removed from all the structural elements of the sintered preform. On the other hand, the arrangement of the first component and the at least one structural element of the carrier are lifted. This is possible, because the adhesion between the first component and the at least one structural element is greater than the adhesion between the assembly and the carrier.

p0228After removing the assembly from the first component and the at least one structure element of the carrier is engaged with the first component related structural element for making contact with the second component is available. Goods on the sintered preform several structural elements are present, are after the removal of assemblies from the support accordingly provided with several components structural elements for making contact with the second component available.

p0229Subsequently, according to the invention the surface to be bonded of the second component with the at least one structural element of the assembly of the first component and the at least contact a structural member to provide a sintering arrangement comprising the first component, second component and disposed therebetween a structural element.

p0230According to a preferred embodiment, the surface to be bonded of the second component is a structural element in such a manner contacted with the at least that an optionally present on the surface of the second component a metallization layer structure element is in contact with the at least. In this case, preferably, a sintering arrangement is created which comprises the first component having a metallization layer, the second component having a metallization layer and an interposing structure element, wherein the metallization of the first component and the metallization layer of the second device via the structural element are interconnected.

p0231According to a further preferred embodiment, the surface to be bonded of the second component may already have at least one structural element. This structural element may for example be formed by having a herein sintered preform described, there is provided a structural element on the surface of the carrier, the sintered preform is at least contacted with the surface to be joined of the second component, and the arrangement of the second component and the structural element from the carrier the sintered preform is removed. According to this embodiment, both the first component and the second component already on at least one structural element. These structural elements of the first component and the second component may eventually be contacted to provide a sintering arrangement comprising the first component, second component and disposed therebetween a structural element. In this case originates a part of the structural element from the contact of a sintered preform to the first component and another part of the structural element by the bonding to another sintered preform to the second component. If below from the surface of the second component is mentioned, as is also the case thereof comprises that the second component has already according to the embodiment described above, a structure element. Thus, in the present process the surface to be bonded of the second component with the at least one structural element of the assembly of the first component and the at least one structural member can be contacted also via a further structural member, which is part of an assembly of the second component and this structural element.

p0232Contacting the surface to be joined of the second component with the at least one structural element is preferably carried out by pressing. On the one hand, the

p0233Assembly comprising the first component and the structural element are pressed onto the surface to be bonded of the second component so that the first component of the structural element with the surface to be joined of the second component is connected. On the other hand, the surface to be bonded of the second component can be pressed onto the device connected to the first structural element.

p0234This pressing makes no special measures required. Preferably, the pressing is performed at temperatures below the sintering temperature, and more preferably at temperatures below 200 ° C, for example at temperatures in the range 100-200 ° C. It may be preferred to the arrangement of the first component and the at least one structural element prior to contacting to a temperature in the range 100 - to heat 200 ° C. It may also be preferred that the second component prior to contacting to a temperature in the range 100 - to heat 200 ° C. Particularly preferably, it may be, both the arrangement of the first component and the at least one structure element and the second component prior to contacting to a temperature in the range 100 - to heat 200 ° C. The pressing can under moderate pressure, preferably at a pressure of at least 0.1 N / mm², More preferably at a pressure of at least 0.5 N / mm², Even more preferably at a pressure of at least 1.0 N / mm² and more preferably at a pressure of at least 2 N / mm² done. For the pressing of conventional stamp devices or pressing devices can be used.

p0235The sintering arrangement comprising the first component, the second component and interposing structural element is finally sintered.

p0236This sintering process is a low temperature sintering process. Under low-temperature sintering process according to the invention, a sintering process to understand, which is preferably at a temperature of below 250 ° C, more preferably at a temperature of below 220 ° C, even more preferably at a temperature of below 200 ° C and particularly preferably at a temperature below 180 ° C expires.

p0237The process pressure during sintering is preferably less than 30 MPa, more preferably below 5 MPa, and more preferably less than 1 MPa. Due to the use of the paste of the invention, the sintering succeed even without any application of process pressure, ie at a process pressure of 0 MPa.

p0238The sintering time depends on the process pressure and is preferably in the range 2-45 minutes.

p0239According to the invention, the sintering process take place in an atmosphere which is not further restricted. Preferably, however, the sintering is carried out in an atmosphere containing oxygen.

p0240Sintering is carried out in a conventional, suitable for sintering apparatus in which preferably can adjust the process parameters described above.

p0241The above described method for connecting at least two components allows a process economically advantageous, and at least partially parallel processing of a plurality of components, a structured design of the sintered layer and a lowering of the sintering temperature to below 250 ° C.

p0242In process-economic point of view, the inventive method is particularly advantageous because the production of the compound is carried out using an already solidified paste. Thus, no drying of the paste is more accordance with the invention immediately prior to sintering. This allows a substantial shortening of the process times are achieved. Furthermore, no application of the paste is required on the user side. This application is conventionally done with special application devices, always waste is produced, which is usually precious metals. According Needless on the user side, both the problem of waste disposal and waste recycling as well as the extensive cleaning of the application devices.

p0243Since according to the invention is solidified the paste prior to contacting the components produced when contacting the components on the structural element, a very homogeneous, void-free layer. Thereby, the reliability of the connection established to be significantly improved.

p0244Characterized in that the individual structural elements can be vordimensioniert on the carrier, the sintered preform and made with different geometries and thicknesses, it is possible to produce connections with contact faces of components, even if the contact surfaces do not lie in one plane. In particular, curved leadframes or leadframes so can be connected to trough shape with the corresponding components.

p0245Due to the possibility of a single dimensioning with regard to the thickness, geometry, composition and the volume of the individual structure elements and the structure, reproducible properties of the contact layer between the to connected components can be achieved which allow the use of the method according to the invention for applications in requiring utmost precision is required.

p0246An essential advantage of the method is that the required sintering temperature can be significantly reduced through the use of sintering aids in the solidified pastes.

<u>Examples:</u>

Example 1:

p0247By stirring of mixtures having the following compositions were prepared homogeneous metal pastes, the pastes 1 - 4 were designated:<tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="5" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="30mm" /><colspec colnum="2" colname="col2" colwidth="21mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><colspec colnum="4" colname="col4" colwidth="21mm" /><colspec colnum="5" colname="col5" colwidth="21mm" /><thead><row><entry valign="top" /><entry valign="top">paste 1</entry><entry valign="top">paste 2</entry><entry valign="top">paste 3</entry><entry valign="top">paste 4</entry></row></thead><tbody><row><entry>silver</entry><entry>83 wt.%</entry><entry>83 wt.%</entry><entry>83 wt.%</entry><entry>80 wt.%</entry></row><row><entry>aluminum formate</entry><entry align="center">-</entry><entry align="center">-</entry><entry>5 wt.%</entry><entry>5 wt.%</entry></row><row><entry>silver</entry><entry align="center">-</entry><entry align="center">-</entry><entry align="center">-</entry><entry>5 wt.%</entry></row><row><entry>terpineol</entry><entry>17 wt.%</entry><entry>9 wt.%</entry><entry>12 wt.%</entry><entry>10 wt.%</entry></row><row><entry>tridecanol</entry><entry align="center">-</entry><entry>8 wt.%</entry><entry align="center">-</entry><entry align="center">-</entry></row></tbody></tgroup></table></tables>

p0248The pastes 1-4 were in separate experiments plotted as defined structural elements with a thickness of 50 microns on a polyester film and then dried at a temperature of 100 ° C for a period of 10 minutes to the sintered preforms 1 - to obtain 4 each a support (polyester film) with structural elements of solidified paste 1-4 contained.

p0249Then, chips which a nickel-silver metallization and an area of ​​25 mm² had, at a pressure of 2 MPa to the structural elements of each sintered preforms 1-4 set. Here assemblies of chip and structural element were obtained, which were in contact with the carrier. Thereafter, the arrays of chip and structure element were withdrawn from the support and on the nickel-gold metallization of a DCB (<i>Direct Bonded Copper</i>) Substrate set. This sandwich arrangement of DCB-substrate chip and intervening element structure was sintered at a temperature of 200 ° C and a pressure of 10 MPa for a period of 2 minutes in the connection between two heating plates.

Result of Example 1:

p0250The shear strengths obtained in Example 1 between contact layers DCB substrate and chip were determined by a conventional shear tests.

p0251The results of the shear tests are summarized in the following table:<tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="26mm" /><colspec colnum="2" colname="col2" colwidth="35mm" /><colspec colnum="3" colname="col3" colwidth="36mm" /><colspec colnum="4" colname="col4" colwidth="35mm" /><colspec colnum="5" colname="col5" colwidth="35mm" /><thead><row><entry valign="top">sintered preform</entry><entry valign="top">1</entry><entry valign="top">2</entry><entry valign="top">3</entry><entry valign="top">4</entry></row></thead><tbody><row><entry>shear strength</entry><entry>Very low</entry><entry>Very low</entry><entry>High</entry><entry>Very high</entry></row><row><entry>note</entry><entry>Virtually no connection between chip and substrate possible</entry><entry>Virtually no connection between chip and substrate possible; Scherfesigkeit but slightly higher than # 1</entry><entry>Stable connection between the chip and substrate; Shear strength significantly higher than with # 1 and # 2</entry><entry>Very stable connection between the chip and substrate; Shear strength significantly higher than with # 1 and # 2; Shear strength slightly higher than # 3</entry></row></tbody></tgroup></table></tables>

p0252It turned out that the addition of aluminum formate resulted in a significant increase in the shear strength of the sintered preforms obtained using the contact layers between the chip and substrate. An even more stable connection was achieved by the joint addition of aluminum formate and silver.

Example 2:

p0253By stirring of mixtures having the following compositions homogeneous metal pastes were prepared which were designated as pastes 5 and 6:<tables id="tabl0003" num="0003"><table frame="none"><tgroup cols="3" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="27mm" /><colspec colnum="2" colname="col2" colwidth="21mm" /><colspec colnum="3" colname="col3" colwidth="21mm" /><thead><row><entry valign="top" /><entry align="center" valign="top">paste 5</entry><entry align="center" valign="top">paste 6</entry></row></thead><tbody><row><entry>silver</entry><entry align="right">80 wt.%</entry><entry align="right">80 wt.%</entry></row><row><entry>dicumylperoxide</entry><entry align="right">-</entry><entry align="right">5 wt.%</entry></row><row><entry>silver</entry><entry align="right">5 wt.%</entry><entry align="right">5 wt.%</entry></row><row><entry>terpineol</entry><entry align="right">15 wt.%</entry><entry align="right">10 wt.%</entry></row></tbody></tgroup></table></tables>

p0254The pastes 5 and 6 were used for the production of sintered preforms (sintered preforms 5 and 6), which in turn were used for attaching a chip to a substrate. In this case the procedure was similar to Example 1, but using a chip with an area of ​​100 mm² has been used.

Result of Example 2:

p0255The shear strengths obtained in Example 2 Contact between layers DCB substrate and chip were determined by a conventional shear tests.

p0256It turned out that the contact layer manufactured using the sintered preform 6 is a significantly higher shear strength than having the contact layer, which was obtained using sintered preform fifth Accordingly, the addition of the sintering aid according to the invention acts also a positive effect on the stability of the contact layer formed between chip and substrate.