Carrier substrate for electric components, and method for manufacturing a carrier substrate

Translation of description of equivalent WO 2018114880 A1

0001Carrier substrate for electrical components and

0002Method for producing a carrier substrate

0003The present invention relates to a carrier substrate for electrical, in particular electronic components and to a method for producing a carrier substrate.

0004Carrier substrates are known, for example, as printed circuit boards or circuit boards from DE 10 2004 033 933 A1. Typically, electrical components and interconnects are arranged on a component side of the carrier substrate, wherein the electrical components and the interconnects can be switched together to form electrical circuits. For special applications, such carrier substrates have proved to be particularly advantageous, which for electrical insulation of the individual electrical components and interconnects have an insulating layer with high electrical insulation strength, such as a made of ceramic primary layer.

0005During operation of these carrier substrates, the electrical components are typically stressed in such a way that they heat up and form local heat sources on the component side. In order to prevent damage to the electrical components or the carrier substrate caused by the heating, the state of the art, for example from DE 10 2009 022 877 A1, therefore knows of heat sinks or cooling structures which, as a rule, are located on a cooling side opposite the component side when formed on the primary layer adjacent copper layer or copper base is soldered. In order to provide sufficient heat capacity through the heat sink or through the cooling structure, the heat sinks and / or the cooling structures must be dimensioned correspondingly large, In addition, certain electrical components or their power density make increased demands on the cooling performance of the carrier substrate. Furthermore, when the electrical components are used, parasitic inductances can occur on the carrier substrate, which adversely affect the operation of the carrier substrate. Finally, in the case of such carrier substances, the electromagnetic compatibility places great demands on the conductor structures used or the metallic structures in general.

0006It is thus an object of the present invention to provide carrier substrates with a primary layer, for example made of ceramic, in particular with regard to

0007Size, weight, cooling performance, electromagnetic compatibility and parasitic inductances.

0008This object is achieved by a carrier substrate for electrical components according to claim 1 and a method according to claim 11. Further advantages and features of the invention will become apparent from the subclaims and the description and the accompanying figures.

0009According to the invention, a carrier substrate is provided for electrical components, in particular electronic components, wherein the carrier substrate has a component side and a cooling side opposite the component side with a cooling structure, wherein the carrier substrate for electrical isolation faces one of the component side and in particular made of ceramic, eg Al 2 O 3, Si 3 N₄AIN or HPSX ceramics (ie a ceramic with an Al2O3 matrix containing an x-percentage of ZrO2, for example Al2O3 with 9% ZrO₂ = HPS9 or AI2O3 with 25% ZrO₂ = HPS25), manufactured primary layer and for stiffening the carrier substrate comprises a cooling side facing secondary layer, wherein for transferring heat from the component side to the cooling side between the primary layer and the secondary layer, a metallic intermediate layer is disposed, wherein the metallic intermediate layer thicker than the primary layer and / or Secondary layer is.

0010The primary layer has an insulation layer with high electrical insulation strength, preferably of more than 5 kV / mm, more preferably of more than 10, 20 or even more than 30 kV / mm and / or with high thermal conductivity, preferably of more than 10W / mK, more preferably of more than 20W / mK or even more than 60W / mK, such as. As technical ceramics or filled with thermally conductive materials organic insulation materials. The thickness of the primary layer and / or the secondary layer is preferably configured or selected such that it meets the requirements for dielectric strength or breakdown field strength. It has been found that this requires in the majority of applications, a thickness of the primary layer and / or the secondary layer of 0.1 - 0.4 mm of the aforementioned ceramic materials. In the case of such carrier substrates, the example In the case of high-voltage direct current transmission, for example, a voltage strengths of 10 to 15 kV with novel SiC-based semiconductor components are required, whereas layer thicknesses of the primary layer and / or the secondary layer of up to 2 mm and more are required. Compared to the prior art, the carrier substrate is provided in a sandwich construction in which the primary layer and the secondary layer are spaced apart by the metallic intermediate layer. Due to the intermediate layer, the heat flow emanating from the local heat source can spread better in the direction of the secondary layer or the cooling side and ensure a larger-area heat distribution on the cooling side, which forms the critical heat transfer surface for the removal of the heat. This makes it possible to improve the static thermal resistance (RTH) of the entire carrier substrate, ie the thermal resistance, which sets in stationary operation of the carrier substrate. For example, static thermal thermal resistance can be improved by up to 30% in this way. As a result, an oversized cooling structure, which otherwise includes a 3 mm to 5 mm thick bottom plate, can be dispensed with on the radiator side of the carrier substrate. This not only advantageously leads to the fact that it is possible to dispense with material and thus the production costs can be reduced, but it also makes it possible to embody the carrier substrate symmetrically, in particular with regard to a metal coating on the component side and on the cooling side, whereby thermally induced mechanical stresses or mechanical leverage can be counteracted during operation. Otherwise, such mechanical stresses can be applied, for example in the form of bi-metal effect - and in particular when using thick cooling structures, lead to bending of the carrier substrate.

0011In addition, the intermediate layer causes the transient or dynamic thermal resistance (ZTH) is sufficiently dimensioned, since at start-up operations or power peaks, the intermediate layer can absorb or store the heat in the short term. It should be noted here that the carrier substrate is preferably designed with regard to its static thermal resistance. In this case, the static thermal heat resistance preferably starts after about 20 to 30 seconds and is advantageous to measure on the component. For the comparison of the dynamic behavior of different systems, it is also conceivable to measure the thermal resistance 300 ms after the start of the switch-on process.

0012Furthermore, it proves to be advantageous that the comparatively thick intermediate layer contributes to the stiffening or stabilization of the entire carrier substrate. In this case, the carrier substrate proves to be particularly effective both against residual stresses and against external forces, as they are, for. B. act through the coolant to the carrier substrate, as sufficiently rigid. Furthermore, the

0013Reduce layer thickness of the ceramic layers in an advantageous manner.

0014According to a preferred embodiment of the present invention, it is provided that the intermediate layer is between 1, 1 and 10 times, preferably between 1, 2 and 5 times, particularly preferably between 1, 3 and 3 times or even substantially 1, 5 times as thick as the primary layer and / or the secondary layer. The intermediate layer may also have other thicknesses. In particular, the intermediate layer is between 1 mm and 10 mm, preferably between 1 mm and 5 mm, particularly preferably between 1, 5 mm and 5 mm or even substantially 1, 5 mm thick. It has surprisingly been found that the static thermal resistance outside these ranges of values, ie deteriorates both with increasing and decreasing intermediate layer thickness, in particular based on the thicknesses of the primary layer and / or the secondary layer. According to a preferred embodiment of the present invention, it is provided that the intermediate layer is between 2.5 and 100 times, preferably between 3.5 and 50 times, particularly preferably between 10 and 25 times or even essentially 20 times is as thick as the primary layer and / or the secondary layer. The intermediate layer may also have other thicknesses. In particular, the intermediate layer is between 1 mm and 10 mm, preferably between 1 mm and 5 mm, more preferably between 1, 5 mm and 5 mm or even substantially 3 mm thick. Such thick intermediate layers advantageously allow optimal heat spreading in the intermediate layer, whereby advantageously the transported heat is distributed as evenly as possible before it is discharged via the cooling structure.

0015According to another embodiment of the present invention, it is provided that the intermediate layer is thicker than 1 mm, preferably thicker than 1.4 mm and particularly preferably thicker than 1.9 mm. These comparatively thick intermediate layers prove to be advantageous for heat spreading, in particular for a majority of different types of carrier substrate. It is advantageously possible to make the intermediate layers so thick that the cooling structure on the cooling side in turn can be dimensioned smaller in size. It is even conceivable that, despite the increase in the interlayer thickness, the cooling structure can be dimensioned so small that overall a total thickness of the carrier substrate can be reduced. Appropriately, it is intended the cooling structure has a base body region and a land region, wherein a ratio (SD / BD) between a land region thickness to a base body thickness is between 1.2 to 6, preferably between 1.4 and 3, and particularly preferably between 1, 6 and 2, 5 assumes. With comparable cooling performance, it has been shown to advantage that the land area, ie, for example, the fins of a heat sink, can be dimensioned significantly shorter. The result is a more compact design of the carrier substrate and optimized flow conditions. It has proven to be particularly advantageous to select the ratio between 1, 6 and 2.5, since this results in both an improved preferably between 1, 4 and 3 and more preferably between 1, 6 and 2.5. With comparable cooling performance, it has been shown to advantage that the land area, ie, for example, the fins of a heat sink, can be dimensioned significantly shorter. The result is a more compact design of the carrier substrate and optimized flow conditions. It has proven to be particularly advantageous to select the ratio between 1, 6 and 2.5, since this results in both an improved preferably between 1, 4 and 3 and more preferably between 1, 6 and 2.5. With comparable cooling performance, it has been shown to advantage that the land area, ie, for example, the fins of a heat sink, can be dimensioned significantly shorter. The result is a more compact design of the carrier substrate and optimized flow conditions. It has proven to be particularly advantageous to select the ratio between 1, 6 and 2.5, since this results in both an improved Cooling effect can be achieved, as well as a comparatively compact design of the carrier substrate. The web region is preferably formed by webs or fins projecting perpendicularly from the base body region, while the base body region forms in particular a solid or closed region. It is also conceivable that the webs are inclined relative to a vertical alignment with the base body region. In particular, the web area thickness and the base body thickness are dimensioned in a direction perpendicular to the main extension plane.

0016Preferably, a cooling structure thickness, in particular an effective cooling structure, is 0.03 to 1 times, preferably 0.1 to 0.5, and particularly preferably 0.15 to 0.3, as large as the metallic intermediate layer. Surprisingly, it has been found that such thin cooling structure thicknesses can be realized. In addition to reducing the total thickness, it is advantageously possible to dimension the cooling structure thicknesses such that they have a thickness, in particular an effective cooling structure thickness, which is comparable to the thickness of a metallization on the opposite side of the component. In the case of the effective cooling structure thickness, it is taken into account that the cooling structure is not flat, but structured, ie a thickness equivalent of the structured cooling structure is assumed to be a non-structured cooling body.

0017In principle, the primary layer, which is made of ceramic in particular, is flat and plate-shaped and preferably extends over the entire component side of the carrier substrate, the secondary layer being aligned in particular parallel to the primary layer. On the component side, more specifically on the side facing away from the intermediate layer side of the primary layer, in particular metallic connection elements and conductor tracks are arranged, which are preferably provided for the control of attached to the connection elements electrical components, which are electrically conductively connected to the metallic connection elements , Furthermore, it is provided according to an embodiment of the invention that the cooling structure on the cooling side directly adjoins the secondary layer, ie between the cooling structure and the secondary layer is no solder or the like arranged with the exception of the solder metals, which allow a direct connection of the cooler with the secondary layer, for example by an active soldering or a DCB process. Furthermore, a part of the cooling structure which extends continuously parallel to the primary layer and adjoins directly the secondary layer is thinner than the metallic intermediate layer. The layer thickness is to be understood as meaning the extent of the respective layer, ie the intermediate layer, the primary layer and the secondary layer, perpendicular to the main extension plane of the primary layer, wherein the primary layer, the intermediate layer and the secondary layer are stacked above one another, in particular along the direction perpendicular to the main extension plane of the primary layer are arranged. Furthermore, it is conceivable that the intermediate layer is configured in multiple layers. In this case, the carrier substrate can be produced by joining together an at least three-layered upper multilayer layer, consisting of conductor track (possibly equipped with components), primary layer and first layer of the intermediate layer and an at least three-layer lower multilayer, consisting of second layer of the intermediate layer, secondary layer and cooling structure, are produced. Upper and lower multi-layer layer can by means of a DCB process, a DAB process, diffusion bonding, a solder joint or by a sintering process, such as silver sintering, or another layer, such as a thermally conductive, adhesive insulating layer, such as an epoxy or a polyamide layer, be connected with each other. Secondary layer and cooling structure to be produced. Upper and lower multi-layer layer can by means of a DCB process, a DAB process, diffusion bonding, a solder joint or by a sintering process, such as silver sintering, or another layer, such as a thermally conductive, adhesive insulating layer, such as an epoxy or a polyamide layer, be connected with each other. Secondary layer and cooling structure to be produced. Upper and lower multi-layer layer can by means of a DCB process, a DAB process, diffusion bonding, a solder joint or by a sintering process, such as silver sintering, or another layer, such as a thermally conductive, adhesive insulating layer, such as an epoxy or a polyamide layer, be connected with each other.

0018Moreover, it is furthermore conceivable for the carrier substrate in the sandwich construction to have one or more further primary layers for electrical insulation, one or more further secondary layers for stabilizing the carrier substrate and / or a plurality of further intermediate elements for heat transport from the component side to the cooling side. The electrical component is, for example, a semiconductor component made of Si, SiC or GaN.

0019Further advantages and features will become apparent from the following description of preferred embodiments of the subject invention. Individual features of the individual embodiments can be combined with each other within the scope of the invention. In order to ensure a sufficient heat capacity of the intermediate layer, it is further provided that the layer thickness of the intermediate layer is greater, preferably more than twice as large, preferably more than three times as large and more preferably more than five times as large as the added layer thickness of the primary layer and the secondary layer. It is also conceivable that the ratio between the layer thickness of the intermediate layer to the total thickness of the carrier substrate has a value between 0.2 and 0.8, preferably a value between 0.3 and 0.7 and particularly preferably a value between 0.4 and 0, 6 assumes. In this case, the total thickness of the carrier substrate is measured in a direction perpendicular to the primary layer extending direction of the conductor tracks on the component side to the completion of the cooler structure on the cooling side of the carrier substrate. In a particularly compact embodiment, the total thickness of the carrier substrate is less than 8 mm, preferably less than 6 mm and particularly preferably substantially 4 mm. It is preferably provided that the conductor tracks, the metallic connection elements, the intermediate layer and / or the cooling structure are made of a material comprising aluminum, molybdenum, tungsten, CuMo, CuW, Invar, Kovar and / or silver. Particularly preferably, the conductor tracks, the metallic connection elements, the intermediate layer and / or the cooling structure are made of a material comprising copper. It is also conceivable that the interconnects, the metallic connection elements, the intermediate layer and / or the cooling structure of composite materials such as a lamination of said metals or realized as a powder metallurgy produced metal-matrix composite. Such composites may preferably be made of the aforementioned metals, but for the purpose of CTE adaptation and increased rigidity with metal matrix composite materials are realized, which are filled with ceramic particles such as AI with Al2O3 and / or SiC and / or Si3N₄ or graphite or diamond powder. In order to ensure sufficient stability of the carrier substrate, the primary layer and / or the secondary layer is designed such that a modulus of elasticity for the primary layer and / or the secondary layer is greater than the elastic modulus of the conductor tracks. Moreover, it is provided in an advantageous embodiment that the primary layer and optionally the secondary layer are made of a material whose electrical insulation strength greater is as 5 kV / mm, preferably greater than 10 kV / mm and more preferably greater than 20 kV or whose thermal conductivity is greater than 10 W / mK, preferably greater than 20 W / mK and more preferably greater than 60 W / mK. For example, these are technical ceramics or in particular in the secondary layer to an organic insulating material filled with thermally conductive materials, such. B epoxy or polyimide. As particularly advantageous for the formation of the primary layer and / or the secondary layer or as a filler for the organic insulating materials prove to AI2O3, Si3N₄, AIN, BeO, SiC or MgO. Likewise advantageous are the ceramics based on Al 2 O 3 which besides typical sintering additives, for the purpose of conversion amplification, may have different ZrO 2 contents, for example Al 2 O 3 with 9% ZrO 2 - HPS 9 or Al 2 O 3 with 25% ZrO₂ - HPS25. According to a further embodiment of the present invention, it is provided that the metallic intermediate layer is designed in one layer. Under single-layer is to be understood in particular that the metallic intermediate layer is designed in one piece and at least partially connects the primary layer and the secondary layer to each other throughout. In other words, the single-layered intermediate layer adjoins the primary layer on one side and the secondary layer on the other side. As a result of the single-layer configuration, it is advantageously possible to reduce the outlay in the production of the carrier substrate since it is possible to dispense with stacking and connecting a plurality of layers to form the intermediate layer. In a particularly advantageous embodiment of the present invention, it is provided in that a primary substrate and a secondary substrate are adapted to one another in order to prevent bending of the carrier substrate with regard to their thermal expansions, in particular with regard to their expansion coefficients. In this case, the primary substrate comprises a part of the intermediate layer and the conductor track layer in addition to the primary layer, and the secondary substrate comprises, in addition to the secondary layer, a further part of the intermediate layer and the cooling structure. Between the primary substrate and the secondary substrate, the intermediate substrate or the middle part of the intermediate layer is arranged. Preferably, the In this case, the primary substrate comprises a part of the intermediate layer and the conductor track layer in addition to the primary layer, and the secondary substrate comprises, in addition to the secondary layer, a further part of the intermediate layer and the cooling structure. Between the primary substrate and the secondary substrate, the intermediate substrate or the middle part of the intermediate layer is arranged. Preferably, the In this case, the primary substrate comprises a part of the intermediate layer and the conductor track layer in addition to the primary layer, and the secondary substrate comprises, in addition to the secondary layer, a further part of the intermediate layer and the cooling structure. Between the primary substrate and the secondary substrate, the intermediate substrate or the middle part of the intermediate layer is arranged. Preferably, the Layer thicknesses and / or the materials of the primary substrate and / or the secondary substrate adapted to each other so that the Trägerubsubstrat extends equally in the region of the primary layer and in the region of the secondary layer. As a consequence, thermal stresses, which may occur due to the temperature during operation or during the production of the carrier substrate, can be counteracted in an advantageous manner and thus the probability of a bimetallic effect bulging the carrier substrate can be reduced without losing the electrical insulating properties of the Deteriorate carrier substrate.

0020For this purpose, the carrier substrate is preferably designed to be thermomechanically mirror-symmetrical with respect to the intermediate layer, ie the layer thickness and the materials from which the primary layer and the secondary layer are made correspond to each other, in particular in the thermomechanical behavior. Alternatively, it is also conceivable that with the same geometry of the primary layer and secondary layer, the material of the secondary layer has a coefficient of expansion which corresponds to that of the material of the primary layer, or at least comparable in size, that a uniform expansion of the primary layer and the secondary layer at which takes place to the expected temperature distribution. It is also conceivable that in the selection and design of the primary layer and the secondary layer also a possible or

0021Advantageously, a cooling structure provided for fluid cooling directly adjoins the secondary layer on the cooling side as a termination of the carrier substrate, wherein the cooling structure is designed in particular as a ribbed, needle and / or knobbed structure. In particular, the cooling structure is integrated in the carrier substrate. In principle, gases and cooling liquids are conceivable as fluids. By using a cooling liquid which comes into contact with the cooling structure for heat exchange, the heat transported to the cooling side can be led away from the carrier substrate as quickly and efficiently as possible. This advantageously further increases the cooling performance. The use of the metallic intermediate layer also results in a synergistic effect that can reduce a profile depth of the cooling structure. preferably less than 3 and especially preferably less than 1. Another advantage of cooling structures with small aspect ratios is their stability. Furthermore, the cooling structure for corrosion protection is preferably with a corrosion protection layer, such. B. in particular a NiP, Ni, S1O2, Al2O3, TiOx, NiAu, NiPdAu layer, coated. As a result, the realized cooling performance of the carrier substrate can be maintained as long as possible over the service life of the carrier substrate, as well as the lifetime of the entire cooling system or its further components.

0022In accordance with a further embodiment of the present invention, it is provided that the primary layer has a through-contact and / or the intermediate layer has a contact element for forming a further conductor track. As a result, the metallic intermediate layer can advantageously be used as a further conductor track, via which currents can be conducted to drive individual components, whereby parasitic inductive interference fields or interference effects for improving the activation of the electrical components and the electromagnetic compatibility can be reduced or reduced . can be improved and provide a low-inductance carrier substrate.

0023In order to electrically connect the intermediate layer with the metallic connection elements on the primary layer, the vias are provided. In this case, the plated-through holes are designed as through-holes in the primary layer, wherein the through-hole is in each case filled with an electrically conductive filling material, in particular an electrically conductive paste. Preferably, the plated-through holes are arranged in a direction perpendicular to a main extension plane of the primary layer, directly below a metallic connection element. For driving the metallic intermediate layer or for applying a voltage, it is provided that the metallic intermediate layer has its own contact element or is in electrically conductive connection via a plated-through contact with a contact element on the component side, ie on the side of the primary layer facing away from the intermediate element. It is also conceivable that a control of the electrical components on the component side does not take place via a via, but by conductor webs which partially or partially revolve the primary layer and thereby establish contact between the component side and the intermediate layer.

0024Preferably, the secondary layer is made of ceramic or of molybdenum, tungsten or composites based on WCu or MoCu. With a secondary layer of ceramic, a particularly stable carrier substrate can be provided, wherein the secondary layer made of ceramic is particularly suitable for electrical insulation when the intermediate layer is used as a further conductor track. Therefore, the use of a secondary layer made of ceramic proves to be advantageous when a semiconductor element made of SiC or GaN is provided as an electrical component. In order to reduce the production costs, however, a secondary layer of molybdenum can be used in an advantageous manner, especially in those cases in which a corresponding insulation is not required are of minor importance.

0025In a further embodiment of the present invention, it is provided that the metallic intermediate layer, the conductor track and / or the cooling structure has structures etched in order to increase the thermal shock resistance on the side facing the primary layer and / or the secondary layer. As a result, openings, ie "hidden dimple" structures, which are directed onto the primary layer and / or the secondary layer are formed on the surface of the intermediate layer, the conductor tracks and the metallic connection elements, whereby the thermal shock resistance of the carrier substrate up to around 10 These structures are etched in a punctiform or linear manner. The metallic intermediate layer preferably has etched structures both on the side facing the primary layer and on the side facing the secondary layer. It is also conceivable that the intermediate layer has at least one etched through hole or has punctiform etched structures arranged along a line, which are not arranged one above the other.

0026It is preferably provided that the carrier substrate is a housing part which encloses the component side, in particular a housing part designed as a cast part, wherein the housing part preferably terminates flush with the cooling structure arranged on the cooling side. The housing part advantageously protects the electrical components on the component side against external influences. In order to communicate with the electrical components on the carrier substrate, the contact elements preferably run through the housing part and are available to a user as contacts on the outside of the housing part. The flush closing of the housing part with the cooling structure proves to be advantageous insofar as it leaves open the possibility for the user to mount or mount the carrier substrate on a heat sink, in particular on a solid serving as a heat sink, for example together with other carrier substrates the cooling structure is a shell element or

0027In an advantageous embodiment of the present invention, it is provided that the cooling structure has a recess in the metal layer to form an expansion joint in a region adjacent to the edge course of the secondary layer. In particular, it is preferred that the recess serving as an expansion joint is not covered by the secondary layer. As a result, it is advantageously possible that a thermal longitudinal extent of the cooling structure does not lead to the formation of mechanical stresses in that the recess serving as an expansion joint catches the longitudinal extent of the cooling structure.

0028Another object of the present invention is a method for producing a carrier substrate. All features described for the carrier substrate according to the invention and their advantages can likewise be transferred to the method according to the invention and vice versa.

0029Specifically, the method for producing a carrier substrate suggests that the conductor track layer, the primary layer, the secondary layer, the intermediate layer and the cooling structure are joined or bonded by a uniform connection method, in particular simultaneously in a common method step. In particular, it is provided that the cooling structure is connected to the secondary layer within the framework of the carrier substrate production. By the simultaneous joining or Bonding of the individual layers can be advantageously avoided bending the individual layers, as is customary in the subsequent addition of the cooling structure in the production. As joining method or connection method, a DCB method, active soldering, brazing or gluing is conceivable.

0030Alternatively, it is also conceivable to manufacture two or more partial substrates separately in a first step using joining methods already mentioned, such as, for example, the primary layer with the conductor track layer and a part of the metallic intermediate view, and the secondary layer with a part of the metallic intermediate layer and the cooler structure. These two individual laminates are joined in a second joining step to the substrate according to the invention, by means of common joining processes such as DCB methods, brazing, soft soldering, diffusion welding or a sintering process. By a "direct copper bond technology" (DCB), the person skilled in the art understands such a method, for example, for joining metal layers or sheets (eg copper sheets or foils) to one another and / or with ceramic or ceramic layers serves, namely, using metal or copper sheets or metal or copper foils having on their surface sides a layer or coating (reflow layer) of a chemical compound of the metal and a reactive gas, preferably oxygen. In this process described, for example, in US Pat. No. 3,744,120 A or in DE 23 19 854 C2, this layer or coating (melting layer) forms a eutectic with a melting temperature below the melting temperature of the metal (eg copper), so that by laying the film on the ceramic and by heating all the layers they can be joined together, by melting the metal or copper substantially only in the region of the reflow layer or oxide layer. In particular, the DCB method then z. B.

0031- Oxidizing a copper foil such that a uniform copper oxide layer results; - placing the copper foil on the ceramic layer;

0032- Heating the composite to a process temperature between about 1025 to 1083 ° C, z. B. to about 1071 ° C;

0033- Cool to room temperature.

0034Under an active soldering method z. B. for connecting metal layers or metal foils, in particular also of copper layers or copper foils with ceramic material is a method to understand, which is also used especially for the production of metal-ceramic substrates, at a temperature between about 650- 1000 ° C a Connection between a metal foil, such as copper foil, and a ceramic substrate, such as aluminum nitride ceramic, prepared using a brazing filler, which also contains an active metal in addition to a main component, such as copper, silver and / or gold. This active metal, which is for example at least one element of the group Hf, Ti, Zr, Nb, Ce, establishes a connection between the solder and the ceramic by chemical reaction,

0035In particular, it is provided that the cooling structure is connected or joined as part of the carrier substrate production. As a result, the temperature stability in the interface regions is increased to the areas of the carrier substrate affected by the brazing or DCB method. The consequence is that the carrier substrate can also be used for components made of semiconductor materials, such as SiC or GaN, which can be operated at temperatures above 200 ° C., or in the downstream structure and connection processes for module production no limitation, for example up to 400 ° C. the process temperatures exist

0036According to a further embodiment of the present invention, the carrier substrate is virtually decomposed into a primary substrate, a secondary substrate and, preferably, an intermediate virtual interface d15.2. The primary substrate is formed from layers d12, d10 and d15.1 and the secondary substrate from layers d15.3, d20 and d30. When dimensioning, a thermomechanical symmetry between the primary substrate and the secondary substrate desired, ie, the coefficient of thermal expansion (CTE) of both substrates should preferably be the same or at least similar, for example within a tolerance of +/- 20% or preferably +/- 10%, more preferably +/- 5% match. This is necessary to reduce possible thermomechanical stresses and the resulting deflection effects. The resulting coefficient of thermal expansion CTE 'of a layered composite material is approximately calculated as follows:<img id="imgf000018_0001" he="12" wi="45" file="imgf000018_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" /> By an approximate understanding of the skilled person in particular, that the specific coefficient of thermal expansion deviates up to 2 to 4% of the actual thermal expansion coefficient.

0037In this case, it is assumed that the respective sub-substrate does not or only slightly flexes. In addition to the respective coefficients of expansion CTE, the modulus of elasticity E, as well as the layer thickness d, also enter here in each case. The possible bending is avoided by the two-sided metallizations in thermomechanical terms are the same or similar, which means that, for example, in full surface metallization both metal layers are the same or at least similar thickness. It follows that is preferably d15.1 = d12 and d15.3 = d30E, where d30E is an effective layer thickness of the radiator layer, in which a possible structuring of the cooling structure is taken into account.

0038The following applies to the primary substrate:

0039CTE12 E12 dl2 + CTE10 E10 dlO + CTE15.1 £ 15.1 dl5.1

0040CTEW =

0041E12 dl2 + E10 dlO + £ 15.1 dl5.1 and the secondary substrate:

0042CTE15.3 £ 15.3 dl5.3 + CTE20 £ 20 d20 + CT £ 30 £ 30 d30 £

0043CT £ 20 '=

0044£ 15.3 dl5.3 + £ 20 d20 + £ 30 d30 £ where d30E is the thermomechanically effective thickness of the cooling structure 30. The thickness d30E depends on the structuring of the cooling structure 30, for which the following applies: d30.1 &lt;d30E &lt;d30

0045If it is not sensibly possible to set a complete thermomechanical symmetry (CTE10 '= CTE20') when dimensioning the individual components or layers of the carrier substrate, a temperature-dependent bending is to be expected. The described approach serves primarily to optimize the layer structure in FIG thermomechanical aspects with the aim to realize as flat as possible carrier substrates.

0046The choice of the intermediate layer 15 and thus the thickness of the resulting virtual intermediate layer d15.2 is dependent on the necessary thermal mass, which defines the temporal behavior of the carrier substrate 1 significantly. The layers relevant for the thermal mass are the conductor tracks d12, the intermediate layer d15 and the base thickness d30.1 of the cooling structure 30. The thickness of the thermal buffer layers is thus defined as dCujh = dl2 + dl5 + d30.l. The thickness of the thermal buffer layers dCujhst between 1 and 10 mm, preferably between 1, 1 and 5 mm, more preferably between 1, 2 and 3 mm.

0047The optimum bend h is zero in most applications. The amount of bending h is less than 200 μιτι, preferably less than 100 μιτι and particularly preferably less than 50μηη.

0048All statements made above are to be understood approximately, since the respective structuring in particular of the conductor tracks d12 and the cooling structure 30 as well as deviating edge effects at the edges of the components can not be considered as a whole. The above models are based on a purely elastic behavior of the materials. The influence of plastic deformation plays a minor role here. According to a further embodiment of the present invention, it is provided that in the determination of the thermal expansion coefficient CTE, a transverse contracting behavior is taken into account. In particular, it is provided that the thermal expansion coefficient is determined as a function of a transverse contraction number v or vi, preferably in accordance with

0049<img id="imgf000020_0001" he="19" wi="57" file="imgf000020_0001.tif" img-format="tif" img-content="drawing" orientation="portrait" inline="no" />

0050This allows the coefficient of thermal expansion to be determined even more accurately.

0051Further advantages and features will become apparent from the following description of preferred embodiments of the subject invention with reference to the accompanying drawings. 1 shows a carrier substrate for electrical components according to a first exemplary embodiment of the present invention.

00522 shows a carrier substrate for electrical components according to a second exemplary embodiment of the present invention

00533 shows a carrier substrate for electrical components according to a third exemplary embodiment of the present invention

00544 shows a carrier substrate for electrical components according to a fourth exemplary embodiment of the present invention

0055Fig. 5, the carrier substrate of Figure 4 in a bent state

00566 shows a cooling structure for a carrier substrate according to a fifth embodiment of the present invention. 1 shows schematically a carrier substrate 1 for electrical components 13 according to a first exemplary embodiment of the present invention in a sectional view. This is preferably a ceramic-containing carrier substrate 1 which is advantageous for special applications. In particular, the carrier substrate 1 has a component side 4, on which mutually electrically insulated metallic conductor tracks 12, for example of copper or aluminum, are provided for electrical components 13 or modules. By connecting electrical components 13 to the metallic conductor tracks 12 and connecting the conductor tracks 12, electrical circuits can be realized with which the electrical components 13 can be actuated. In order to counteract a heat development occurring during operation and emanating from the electrical components 13, in particular a heat development occurring locally in areas with electrical components 13, a cooling structure 30 integrated into the carrier substrate 1 is provided on a cooling side 5 opposite the component side 4. In particular, the cooling structure 30 is a metallic needle or pin structure, along which a fluid, preferably a cooling liquid, flows during operation, as a result of which the heat released from the cooling structure 30 to the fluid can be removed continuously in an advantageous manner , In order to provide on the component side 4 for an electrical insulation between the individual conductor tracks 12, a primary layer 10 made of ceramic is provided on the component side 4. Here, the primary layer 10 is designed plate-shaped. To form a sufficient stability or rigidity, a secondary layer 20 is provided in addition to the primary layer 10. In this case, it is provided that the material from which the primary layer 10 and the secondary layer 20 are made has a modulus of elasticity or modulus of elasticity which is greater than that of the material from which the conductor tracks are made. In order to counteract a bi-metal effect occurring when the temperature changes and arching the carrier substrate 1, it is further preferably provided that the carrier substrate 1 is thermally symmetric or substantially thermomechanically mirror-symmetrical to a metallic intermediate layer 15 which is between the primary layer 10 and the secondary layer 20 is arranged, For example, with regard to its sequence of layers, ie with regard to the number and type of layers, the carrier substrate 1 is configured with mirror symmetry with regard to the respective layer thicknesses and / or with respect to the materials used for the layers, or the individual layers are adapted to one another in this regard. In particular, the secondary layer 20 is made of a material whose coefficient of expansion preferably corresponds to that of the material from which the primary layer 10 is made. It is conceivable that the secondary layer 20 is made of ceramic, molybdenum, tungsten or composites based on WCu or MoCu. In the illustrated embodiment, the secondary layer 20 is made of ceramic. It is also conceivable the coefficients of expansion of the primary substrate 10 'and of the secondary substrate 20' coincide within a specified tolerance range. Preferably, the coefficients of expansion of the primary substrate 10 'and the secondary substrate 20' are less than +/- 20%, preferably less than +/- 10% from each other. By means of a corresponding selection of the materials with regard to the expansion coefficients for the primary substrate 10 'and the secondary substrate 20', not only the rigidity of the carrier substrate 1 can be advantageously achieved by configuring the carrier substrate 1 with the primary substrate 10 'and the secondary substrate 20' Way, it will also increase any thermal stresses,

0057In order to improve the heat transfer from the component side 4 to the cooling side 5, it is furthermore provided that a multilayer or a single-layer metallic intermediate layer 15 is arranged between the primary layer 10 and the secondary layer 20. In this case, the metallic intermediate layer 15 is thicker than the primary layer 10 and / or the secondary layer 20, in particular thicker than a sum of the primary layer thickness and the secondary layer thickness. Preferably, the intermediate layer 15 is greater than twice, preferably greater than three times or particularly preferably greater than five times the summed layer thickness of the primary layer 10 and the secondary layer 20. This forms a thermal mass in the form of the intermediate layer 15. The arrangement of the metallic intermediate layer 15 acting as a thermal mass between the primary layer 10 and the secondary layer 20 proves to be advantageous insofar as the intermediate layer 15 serves as an intermediate memory, which proves to be particularly advantageous in switch-on and / or overload situations. As a result, higher short-term peak performance over the heat capacity of the intermediate layer 15 can be intercepted and in the event of failure of the connected to the cooling side heat exchanger or the heat sink, the period is increased in which can respond to the failure without permanent damage to the carrier substrate 1 left behind. Furthermore, the secondary layer 20 ensures sufficient stability, which makes it possible to reduce the layer thickness of the primary layer 10. This has a particularly advantageous effect on the thermal resistance due to the immediate proximity of the primary layer 10 to the heat-emitting components 13 on the carrier substrate 1. In addition, the heat emanating from the local heat sources on the component side 4 is distributed over a larger area in the intermediate layer 15, since the thickness of the intermediate layer 15 permits a sufficient spreading or non-directional spreading of the heat over a comparatively large distance, which likewise has an advantageous effect thermal resistance effect. Furthermore, the comparatively large thickness of the intermediate layer 15 proves to be advantageous in that it further increases the rigidity of the carrier substrate 1 and thus prevents bending, caused by different expansion coefficients and external stresses and forces, such as those caused by the pressure of the cooling liquid to the substrate, counteracts. In order to reduce the parasitic induction effects occurring on the carrier substrate 1 during operation, it is furthermore preferably provided that the metallic intermediate layer 15 is used as a further conductor track. In this case, a through-connection 1 1, ie a via, is provided in the primary layer 10, via which the metallic intermediate layer 15 can be acted upon by a current or via an electrically conductive connection between the metallic intermediate layer 10 and a metallic connection element on the primary layer 10 is realized. To ensure sufficient electrical insulation, insulating layer, for example, another ceramic layer. In the embodiment shown in FIG. 1, contact elements are provided on the component side, ie contact elements mounted on the primary layer, by means of which voltage can be applied to the metallic intermediate layer 15.

0058In the illustrated embodiment, it is provided that the intermediate layer thickness b is between 1, 1 and 10 times, preferably between 1, 2 and 5 times, more preferably between 1, 3 and 3 times or even substantially 1, 5 times as thick is like the primary layer thickness a¹ and / or the secondary layer thickness a², For example, the intermediate layer thickness b assumes a value between 1 mm and 10 mm, preferably between 1 mm and 5 mm, particularly preferably between 1, 5 mm and 5 mm, or even a value of essentially 1.5 mm. Other deviating, in particular larger, intermediate layer thicknesses are also possible. Alternatively, it is provided that the intermediate layer thickness b between 2.5 and

0059100 times, preferably between 3.5 and 50 times, more preferably between 10 and 25 times or even substantially 2.0 times as thick as the primary layer thickness a¹ and / or the secondary layer thickness a², For example, the intermediate layer thickness b assumes a value between 1 mm and 10 mm, preferably between 1 mm and 5 mm, more preferably between 1, 5 mm and 5 mm or even a value of substantially 3 mm.

0060Furthermore, it is preferably provided that the primary layer thickness a¹ the secondary layer thickness a² essentially corresponds. Alternatively, it is conceivable that the secondary layer thickness a² is substantially 1.5 times to 5 times, preferably 1.3 times to 2.5 times and more preferably 1.1 to 2 times as thick as the primary layer thickness a¹, Furthermore, the thickness ratios can be structured such that a² = 0.5 - 2.0 a¹, preferably a² = 0.7 - 1, 6 a¹, more preferably a² = 0.8 - 1, 2 a¹ is. In other words, the thickness ratios can be structured such that a² = 0.5 a¹ up to 2.0 a¹, preferably a² = 0.7 a¹ to 1, 6 a¹, more preferably a² = 0.8 a¹ to 1, 2 a¹ is. Furthermore, it is provided that the cooling structure 30 has a base body region B1 and a web region S1. The web region S1 is preferably formed by webs or fins protruding perpendicularly from the base body region B1, while the base body region B1 forms, in particular, a solid region or unstructured body. Preferably, the base body portion B1 and the land portion S1 are integrally formed. In this case, a ratio between a web area thickness SD to a base body thickness BD assumes a value between 1.2 to 6, preferably between 1.4 and 3 and particularly preferably between 1.6 and 2.5. Furthermore, it is provided that a cooling structure thickness KD, in particular an effective cooling structure thickness d30.E be 0.03 to 1 times, preferably 0.1 to 0.5 and particularly preferably 0.15 to 0,

0061FIG. 2 schematically shows a carrier substrate 1 for electrical components 13 according to a second exemplary embodiment of the present invention in a sectional view. In this case, the carrier substrate 1 substantially coincides with that of FIG. In contrast to the embodiment of Figure 1 in this case a contact element 16 is provided on the intermediate layer 15. This contact element 16 allows a direct contacting of the intermediate element 15 in order to apply a voltage to this to reduce parasitic inductive effects on the carrier substrate 1 and thus cause a current in the intermediate layer 15. Furthermore, it is provided that the carrier substrate 1 is surrounded by a housing part 40 on the component side 4. In particular, this is a cast housing part 40. In order to contact the conductor tracks 12 on the primary layer 10, a contact element 16 is likewise provided. In order to apply a voltage to the conductor track 12 on the primary layer 10 and the intermediate layer 15, it is provided that the contact elements 16 of the intermediate layer 15 and the top side of the primary layer 10 are guided through the housing part 40. In this case, the contact elements 16 preferably project out of the housing part 40 on the same side of a housing partial wall. the contact elements 16 of the intermediate layer 15 and the top side of the primary layer 10 are guided through the housing part 40. In this case, the contact elements 16 preferably project out of the housing part 40 on the same side of a housing partial wall. the contact elements 16 of the intermediate layer 15 and the top side of the primary layer 10 are guided through the housing part 40. In this case, the contact elements 16 preferably project out of the housing part 40 on the same side of a housing partial wall.

0062In the illustrated embodiment, the carrier substrate 1 for forming a fluid channel 32, in which in operation, for example, a cooling liquid along a Flow direction is a shell member 50, in particular a plastic-containing shell member 50, which is preferably clipped to the cooling structure 30. To seal the connection between the cooling structure 30 and the shell element 50, a sealing element 31 is provided, which is embedded in a corresponding recess in the shell element 50. The needles or pins of the cooling structure 30 arranged on the cooling side 5 of the carrier substrate 1 protrude into the fluid channel 32 filled with the cooling liquid during operation.

0063FIG. 3 schematically shows a carrier substrate 1 for electrical components 13 according to a third exemplary embodiment of the present invention in a sectional view. In this case, the carrier substrate 1 substantially coincides with that of FIG. In addition to the features of the carrier substrate 1 from FIG. 2, it is provided here that the cast housing part 40 terminates flush with the cooling structure 30 with respect to the cooling side 5. This advantageously allows the carrier substrate 1 simply to be placed on or attached to a cooling structure, for example onto a shell element 50. As a result, the carrier substrate 1 can be used particularly flexibly. For this purpose, provision is made in particular for the cooling structure 30 to have an undercut or a return in one or more edge regions,

0064FIG. 4 shows a carrier substrate for electrical components according to a fourth exemplary embodiment of the present invention. For the dimensioning of the primary layer, the secondary layer and the metallic intermediate layer, it is provided here that the carrier substrate 1 is virtually decomposed into a primary substrate 10 ', a secondary substrate 20 and preferably into a virtual intermediate layer 15' located therebetween. The primary substrate 10 'is formed of the layers d12, d10 and d15.1 and the secondary substrate of the layers d15.3, d20 and d30. In the dimensioning, a thermomechanical symmetry between the primary substrate and the secondary substrate is desired, ie the thermal expansion coefficient (CTE) of the primary substrate 10 'and of the secondary substrate 20'. wise within a tolerance of +/- 20 or preferably of +/- 10% match. This is necessary to reduce possible thermomechanical stresses and the resulting deflection effects. The resulting coefficient of thermal expansion CTE 'of a layered composite material is approximately calculated as follows:

0065Σ? = Ι CTEi Ei di

0066CTE =

0067T _{= 1} Egg di

0068It is assumed that the respective sub-substrate does not bend or only insignificantly. This possible bending is avoided by virtue of the fact that the two-sided metallizations are the same or similar in thermomechanical terms, which means that, for example, in the case of full-area metallizations, both metal layers are the same or at least similarly thick. As a result, it is preferable that d15.1 = d12 and d15.3 = d30E. The following applies to the primary substrate:

0069CTE12 E12 dl2 + CTE10 E10 d10 + CTE15.1 £ 15.1 «215.1

0070CTEW =

0071£ 12 dl2 + £ 10 dlO + £ 15.1 dl5.1 and the secondary substrate:

0072CT £ 15.3 £ 15.3 dl5.3 + CT £ 20 £ 20 d20 + CT £ 30 £ 30 d30 £

0073£ 15.3 dl5.3 + £ 20 d20 + £ 30 d30 £

0074Where d30 £ is the thermomechanically effective thickness of the cooling structure 30. The thickness d30 £ depends on the structuring of the cooling structure 30, for which the following applies:

0075«230.1 &lt;d30 £ &lt;d30

0076If it is not sensible to set a complete thermomechanical symmetry (CTE10 '= CTE20') when dimensioning the individual components or layers of the carrier substrate 1, a temperature-dependent bending is too expect. The described approach serves primarily to optimize the layer structure in thermomechanical terms with the aim of realizing carrier substrates 1 that are as flat as possible. The choice of the intermediate layer 15 and thus the thickness d15.2 of the resulting virtual intermediate layer, ie of the intermediate substrate 15 ', is dependent on the necessary thermal mass which decisively defines the temporal behavior of the carrier substrate 1. The relevant layers for the thermal mass or

0077Layer thicknesses are those of the conductor track d12, the intermediate layer d15 and the base thickness d30.1 of the cooling structure 30. The thickness of the thermal buffer layers is thus defined as dCujh = dl2 + dl5 + d30.l. The thickness of the thermal buffer layers dCujh is between 1 and 10 mm, preferably between 1, 1 and 5 mm, particularly preferably between 1, 2 and 3 mm. The optimum bend h is zero in most applications. The amount of bending h is less than 200 μιτι, preferably less than 100 μιτι and more preferably less than 50μηη. All statements made above are to be understood approximately, since the respective structuring in particular of the conductor tracks d12 and the cooling structure 30 as well as deviating edge effects at the edges of the components can not be considered as a whole. The above Models are based on a purely elastic behavior of the materials. The influence of plastic deformation plays a minor role here.

0078FIG. 5 shows the carrier substrate 1 for electrical components 13 according to the fourth exemplary embodiment of the present invention. In this case, the carrier substrate 1 is shown in a bent state, in which the carrier substrate 1 has a bend h.

0079FIG. 6 shows a cooling structure 30 for a carrier substrate 1 according to a fifth embodiment of the present invention. In this case, it is provided that a recess 8 is arranged on the side of the metal layer configured as a cooling structure 30 facing the secondary layer 20 and / or the primary layer 10. In particular, it is provided that the recess 8 is arranged offset in a direction parallel to the main plane extending direction relative to the primary layer 10 and / or secondary layer 20, wherein the cooling structure 30 relative to the Primary layer 10 and / or the secondary layer 20 protrudes. In particular, it is provided that the recess is designed as an expansion joint, in order to avoid that the thermal expansion of the cooling structure 30 causes mechanical stresses in the entire carrier substrate 1.

LIST OF REFERENCE NUMBERS

00811 carrier substrate

00824 component side

00835 cooling side

00848 recess

008510 primary layer

008610 'primary substrate

00871 1 through-hole

008812 trace

008913 electrical component

009016 contact element

009115 intermediate layer

009215 'intermediate substrate

009320 secondary layer

009420 'secondary substrate

009530 cooling structure

009631 sealing element

009732 fluid channel

009840 housing part

009950 shell element

0100a¹ Primary layer thickness

0101a² Secondary layer thickness

0102KD cooling structure thickness

0103BD base body thickness

0104SD bar area thickness

0105b Interlayer thickness

0106h bend d12, d10 and d15.1 Layer thickness contributions to the primary substrate d15.3, d20 and d30 Layer thickness contributions to the secondary substrate d15.2 Layer thickness of the intermediate substrate d30.E Effective layer thickness of the cooler structure d30.1, d30.2 Coating thickness contributions to the cooling structure