Method for low temperature pressure interconnection of two connection partners and assembly manufactured using same

p0001The invention describes a manufacturing process for low-temperature pressure sintering connection of two link partner to be connected with each of contact surfaces as well as a device manufactured by this method.

p0002Such arrangements are known by way of example in the field of power electronic circuits well. There power semiconductor devices are exemplified firmly bonded to substrates and arranged in power semiconductor modules.

p0003Exemplary describes the <patcit id="pcit0001" dnum="DE102005058794A1"><text>DE 10 2005 058 794 A1</text></patcit> a device for a clocked process for the formation of such a compound wherein the pressing device for the pulsed operation comprises a press die and a heated press table and wherein a pressure-stable conveyor belt is positioned directly above the Gradient press table. In addition, a protective film is provided between the substrate with arranged thereon components and the press die.

p0004However, the known processes have the disadvantage that the solvent in the low-pressure device for interconnecting the temperature loading takes place only after the placing of the connection partner, and it is therefore of cavities in the formation of the connection. Such voids are gas inclusions in the sintered metal layer having a diameter of at least 30 microns.

p0005The invention is based on the object, a manufacturing method and thereby be formed assembly with a material connection in the form of a low-pressure sintering connection between two connection partners present, the formation of voids in the sintered metal layer of the low-temperature pressure sintering connection prevents or at least their size is significantly reduced.

p0006The object is achieved according to the invention, by a method having the features of claim 1 and by an arrangement according to claim 7. Preferred embodiments are described in the respective dependent claims.

p0007By means of the method of the invention, an arrangement is made with a first and a second link partner, wherein said link partners are firmly bonded together by means of a low-temperature pressure sintering connection. Here, each of the connecting partners at each one to be connected with the other link partner contact surface, wherein a sintered metal layer is arranged between these contact surfaces. This method comprises the steps mentioned below. As part of the method steps d) and f) is advantageously in the order named to run. However, it may also be preferred for only one of the two steps d) or f) to carry out alternatively.<ol><li>a) providing a first connection partner with a first contact surface, which preferably has a noble metal surface. Below it is advantageous, by the action of ultrasound to release this contact surface impurities present. The effect of ultrasound can be completed before the next step, however, it is particularly advantageous to prevent renewed contamination to let this influence overlap in time with the next processing step.</li><li>b) applying a layer of a sintered paste consisting of sintered metal particles, preferably silver particles, and a solvent, onto the first contact surface. </li><li>c) temperature exposure of the sintered paste and thereby driving off the solvent to form the sintered layer, which consists of not yet interconnected sintered metal particles.</li><li>d) applying a liquid on the sintered layer, said liquid is a polar liquid as exemplified is preferably glycerol. This liquid is used in the subsequent step of fixing the second connection partner on the sintered layer, which has only low adhesive forces to fixation of the second communication partner after the expulsion of the solvent.</li><li>e) placing the second link partner such that its second contact surface on the layer of sintered paste, respectively in the presence of the liquid according to step d) expressed precisely comes to lie on this.</li><li>f) placing an adhesive agent in the edge region of the sintered layer and the second connection partner with contact of the adhesive agent for the first connection partner for fixing the connection partners to each other. In this case, it may be sufficient, the adhesion agent, which is preferably a silicone, applied only at least two discrete locations of the array. however, it is this entire area peripherally bear this adhesive agent is particularly advantageous.</li><li>g) Further action on the arrangement with temperature and pressure for the formation of the material low-pressure sintered connection between the connection partners. Here, the liquid which can be arranged in accordance with step d) between the scale layer and the second link partner expelled and converting the sintered layer to the homogeneous sintered metal layer. Homogeneous sintered metal layer having a maximum diameter of 10 microns is here a metal layer understood with voids is.</li></ol>

p0008Using the procedure described invention thus creates an arrangement of two connection partners with a connecting their contact surfaces sintered metal layer. These sintered metal layer is formed according to the invention as a homogeneous layer comprises exclusively voids with a maximum diameter of 10 microns.

p0009The main advantage of the method according to the invention or the arrangement thus produced according to the invention is that the reduced number and / or smaller size of the voids in the sintered metal layer, the electrical properties are improved, specifically reducing the ohmic resistance, is and also improves the durability of the connection becomes. Especially in connection with the loading by ultrasound in addition to the pressure required for the formation of this compound compared to the prior art by more than 10% can be reduced. Any reduction in the necessary and applied pressure directly increases the yield of the process, since this reduces the breakage rate can be reduced.

p0010The inventive solution is in accordance with reference to the embodiment <figref idrefs="f0001 f0002">Fig. 1</figref> explained further wherein <figref idrefs="f0001 f0002">Fig. 1</figref> different steps of the manufacturing method according to the invention.

p0011<figref idrefs="f0001">Fig. 1A</figref> shows as a first link partner a section of a typical substrate (10), as it applies in the field of power electronics. This substrate (10) consists of an insulating body (12), preferably an industrial ceramics such as for example aluminum nitride and at least one of the main surfaces of this insulating material body (12) a plurality of metallic wires (14) one of which is shown. These conductor tracks (14) are preferably formed of copper and electrically insulated against each other constitute the switching structures of the substrate (10).

p0012The contact surface of the substrate to be brought into electrically conductive contact with the second link partner has a, a low-temperature pressure sintering connection accessible surface. For this purpose, it is preferred that the contact surface (16) has a noble metal surface (18). Also shown is a contact on this surface (16) arranged sintering paste (30), which in turn consists of silver particles and a solvent. Ahead of applying this sintering paste (30) started the surface to apply ultrasonic (20). This impingement continued even during the application of sintering paste (30). This measure impurities that could affect the subsequent formation of the low-temperature pressure sintering connection removed.

p0013<figref idrefs="f0001">Fig. 1B</figref> schematically shows a subsequent process step, the temperature-induced expulsion of the solvent from the sintering paste. The effect of temperature (22) for this purpose can be formed as desired, by way of example they can besides the direct exposure to the sintering paste (30) also has a heating of the substrate (10) are formed. The main advantage of expelling the solvent already at this point is that at a later expelling the arrangement of the second connection partner, this can not be achieved in such peripherally. Residual solvent leads to voids formed substantially smaller in the inventive method.

p0014After this process step are of the sintered paste (30, pursuant <figref idrefs="f0001">Fig. 1A</figref>) Almost exclusively before the noble metal particles, which will be referred to as sintered layer (32). In contrast to the represented by the proportion of solvent at sintering pastes adhesive effect on a surface disposed on the second link partner, the sintered layer (32) no or very low adhesive forces its free surface on the second link partner.

p0015To still a fixing of the second connection partner is reached, shown in <figref idrefs="f0001">Fig. 1C</figref>A liquid (40) applied to the free surface of the sintered layer (32). When placing the second connection partner this liquid (40) forms a very thin layer, the adhesive forces between the sintered layer (32) and the second connecting lines, here a power semiconductor component (50, see.<figref idrefs="f0002">Fig. 1d</figref>) Forms. Thus, this power semiconductor component (50) is fixed in its position on the sintered layer (32), whereby the further handling is simplified considerably during the process. Particularly suitable liquid have here short chain polyols such as glycerol, proved due to their physical properties such as low vapor pressure combined with low boiling temperature.

p0016Alternatively, more preferably, in addition to fixing as below <figref idrefs="f0001">Fig. 1C</figref> described, the second link partner with its contact surface (56), the power semiconductor component (50), also by means of another adhesive agent (60) in his and the edge region of the sintering layer (32) and in contact with the first link partner, the substrate (10), are fixed on this.

p0017Here it may be sufficient to provide this fixation to two or three places in the described edge region. However, if a fixation is not given by the above-described liquid (40), it is advantageous to provide this adhesion agent rings around the entire edge region.

p0018Both versions are basically two variants the same effect and also equally preferred. <figref idrefs="f0002">Fig. 1d</figref> the left shows an arrangement of the adhesive agent (60) which up to the top of the second link partner of the power semiconductor component (50) extends, while the adhesion agent (62) is right otherwise equal to the arranged exclusively laterally to the power semiconductor component (50) and on the right side ,