Method for manufacturing a power semiconductor module

Abstract

Method for manufacturing a power semiconductor module (1) comprising the following process steps: a) providing a substrate (2) on which a power semiconductor device (13) is arranged and electrically connected to the substrate (2), and providing an electrically conductive contact spring (3) having a first and a second contact device (3a, 3b) and a resilient spring section (3c) arranged between the first and second contact devices, and providing a spring guide element (4) made of a plastic, which has a shaft (5), wherein the shaft (5) has a first opening (8) on a first side (6) of the spring guide element (4) and a second opening (9) on a second side (7) of the spring guide element (4), wherein the spring guide element (4) forms a housing part of the power semiconductor module (1), b) arranging the substrate (2) and the spring guide element (4) such thatthat after arranging the substrate (2) and the spring guide element (4), the second opening (9) is arranged facing the substrate (2), c) Inserting at least a part of the contact spring (3) into the shaft (5) via the first opening (8), whereby at least a part of the second contact device (3b) is guided through the shaft (5) and through the second opening (9), d) Plastically deforming a material (11, 11') of the spring guide element (4) arranged in a region (10) of the spring guide element (4) adjacent to the first opening (8) such that at least at one point (12, 12') in the region (10) of the spring guide element (4) adjacent to the first opening (8), material (11, 11') of the spring guide element (4) is deformed into the first opening (8), wherein the material (11, 11') deformed into the first opening (8) Movement of the contact spring (3) in the direction from the second opening (9) to the first opening (8) is limited.

Description

The invention relates to a method for manufacturing a power semiconductor module. From DE 10 2008 057 832 A1, a power semiconductor module with a pre-tensioned contact spring is known. The contact spring serves to electrically connect an external printed circuit board to a substrate of the power semiconductor module. The contact spring is arranged in a shaft of a spring guide element of the power semiconductor module. In power semiconductor modules where contact springs arranged in slots are used to electrically connect an external circuit board to a substrate of the power semiconductor module, there is a technical requirement to secure the contact springs against falling out of the slot, as they could otherwise be lost, for example, during transport or installation in a higher-level electrical system. Furthermore, such power semiconductor modules should be easy and efficient to manufacture. From DE 10 2006 006 421 B4 a power semiconductor module is known which has contact springs arranged in shafts for electrically conductive connection of an external printed circuit board to a substrate of the power semiconductor module. From DE 10 2015 113 111 A1, a power semiconductor module is known which comprises a substrate for thermally conductive mounting on a heat sink, at least one semiconductor device arranged on the substrate, at least one electrically conductive connection element connected to the semiconductor device, which has a contact section at its free end, and an electrically insulating housing in which the substrate and the at least one semiconductor device are at least partially enclosed, wherein the housing has at least one opening for the connection element, wherein the at least one connection element is arranged to extend through the opening, and wherein a layer of a material that is plastically or elastically deformable compared to the housing material is provided on the outside of the housing, adjacent to the outside of the housing and surrounding the connection element.the contact section is positioned extending beyond the layer and the outer surface of the housing. The object of the invention is to provide a method for manufacturing a power semiconductor module in which a contact spring of the power semiconductor module, arranged in a shaft of a spring guide element of the power semiconductor module, is reliably secured against falling out of the shaft in a shaft of the power semiconductor module, wherein the method enables a rational manufacturing of the power semiconductor module. This problem is solved by a method for manufacturing a power semiconductor module comprising the following process steps: a) providing a substrate on which a power semiconductor device is arranged and electrically connected to the substrate, and providing an electrically conductive contact spring having a first and a second contact device and a resilient spring section arranged between the first and second contact devices, and providing a spring guide element made of plastic having a shaft, wherein the shaft has a first opening on a first side of the spring guide element and a second opening on a second side of the spring guide element, the spring guide element forming a housing part of the power semiconductor module, b) arranging the substrate and the spring guide element such thatthat, after arranging the substrate and the spring guide element, the second opening is arranged facing the substrate; c) Inserting at least a part of the contact spring into the shaft via the first opening, whereby at least a part of the second contact device is guided through the shaft and through the second opening; d) Plastically deforming a material of the spring guide element arranged in an area of ​​the spring guide element adjacent to the first opening such that, at least at one point in the area of ​​the spring guide element adjacent to the first opening, material of the spring guide element is deformed into the first opening, whereby the material deformed into the first opening limits movement of the contact spring in the direction from the second opening to the first opening. Advantageous configurations of the power semiconductor module result analogously to advantageous configurations of the process and vice versa. Advantageous embodiments of the invention result from the dependent claims. It proves advantageous that process step b) can be performed either before process step c) or after process step d). This gives the process a high degree of flexibility. Furthermore, the following additional process step proves to be advantageous: e) Moving the spring guide element towards the substrate, wherein at least after this movement the second contact device has a mechanical contact with an electrically conductive contact surface of the substrate and at least a part of the first contact device extends beyond the first opening in the direction away from the substrate. This allows the electrically conductive contact between the contact surface of the substrate and the contact spring to be easily tested at the manufacturer of the power semiconductor module. Furthermore, it proves advantageous if the plastic deformation is carried out by hot riveting, since hot riveting achieves a precise plastic deformation of the material of the spring guide element. Furthermore, it proves advantageous if the plastic deformation of the material of the spring guide element arranged in the area adjacent to the first opening is carried out in such a way that, at least at two points arranged opposite to the first opening in the area adjacent to the first opening, material of the spring guide element is deformed into the first opening, whereby the material deformed into the first opening limits the movement of the contact spring in the direction from the second opening to the first opening. This reliably reduces the size of the first opening. The spring guide element forms part of the housing of the power semiconductor module. This allows the power semiconductor module to be manufactured particularly efficiently. Furthermore, it proves advantageous if the spring section is designed as a helical spring, since a helical spring has a spring force proportional to the elongation range over a wide range of extension. An embodiment of the invention is explained below with reference to the figures shown below. Figure 1 shows a perspective sectional view of a power semiconductor module according to the invention in a final state of its manufacture; Figure 2 shows a contact spring of the power semiconductor module according to the invention; Figure 3 shows a perspective detail view of a region of the power semiconductor module according to the invention arranged around the first opening of the power semiconductor module according to the invention, in a state before the material of the spring guide element of the power semiconductor module according to the invention is plastically deformed.Fig. 4 shows a perspective detail view of a section of the power semiconductor module according to the invention arranged around the first opening of the power semiconductor module according to the invention, in a state after the material of the spring guide element of the power semiconductor module according to the invention has been plastically deformed, Fig. 5 shows a perspective detail view of a section of the power semiconductor module according to the invention arranged around the first opening of the power semiconductor module according to the invention, in a final state, and Fig. 6 shows a highly schematic sectional view of a tool punch for hot riveting. Figure 1 shows a perspective sectional view of a power semiconductor module 1 according to the invention in a final state of its manufacture as presented in the exemplary embodiment. Figure 2 shows a contact spring 3 of the power semiconductor module 1 according to the invention. Identical elements in the figures are designated with the same reference numeral. In a first process step a) of the inventive process for manufacturing the inventive power semiconductor module 1, a substrate 2 is provided on which one or more power semiconductor devices 13 are arranged and electrically connected to the substrate 2. Furthermore, in this process step, one or more electrically conductive contact springs 3 are provided, each having a first and a second contact element 3a and 3b and a resilient spring section 3c arranged between the first and second contact elements. The spring section 3c is preferably designed as a helical spring.Furthermore, in this process step, a spring guide element 4 made of plastic is provided, which has one or more channels 5, wherein each channel 5 has a first opening 8 on a first side 6 of the spring guide element 4 and a second opening 9 on a second side 7 of the spring guide element 4. As can be seen by way of example in Fig. 1, the first and the second sides 6 and 7 of the spring guide element 4 can have a complex geometric shape. The spring guide element 4 forms a housing part of the power semiconductor module 1. The respective power semiconductor device 13 is preferably in the form of a power semiconductor switch or a diode. The power semiconductor switches are generally in the form of transistors, such as IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), or in the form of thyristors. The substrate 2 comprises an electrically non-conductive insulating body 2a (e.g., a ceramic body) and an electrically conductive, structured first conduction layer 2b arranged on a first side of the insulating body 2a and connected to the insulating body 2a. Due to its structure, the first conduction layer 2b forms electrically conductive contact surfaces 14 arranged in a manner that is inconsistent with one another on the insulating body 2a. The contact surfaces 14 are electrically insulated from one another on the insulating body 2a.Preferably, the substrate 2 has an electrically conductive, preferably unstructured, second conduction layer 2c connected to the insulating body 2a, wherein the insulating body 2a is arranged between the structured first conduction layer 2b and the second conduction layer 2a. The substrate 2 can be configured, for example, as a Direct Copper Bonded Substrate (DCB substrate), as an Active Metal Brazing Substrate (AMB substrate), or as an Insulated Metal Substrate (IMS). Power semiconductor devices 13 are preferably bonded to the contact surfaces 14 of the substrate 6 by means of a solder or sintered layer. In the exemplary embodiment, the power semiconductor devices 13 are electrically interconnected, e.g., by means of bond wires (not shown in Fig. 1), e.g., to form half-bridge circuits, which can be used, e.g., for rectifying and inverting electrical voltages and currents. In a second process step b), preferably following the first process step a), the substrate 2 and the spring guide element 4 are arranged such that, after the arrangement of the substrate 2 and the spring guide element 4, the second opening 9 is oriented towards the substrate 2. Preferably, the spring guide element 4 is arranged above a pressure piece 17 previously arranged on the substrate 2, on which a pressure pad 16, preferably made of an elastomer, is arranged, wherein the pressure pad 16 is positioned between the pressure piece 17 and the spring guide element 4 after the arrangement of the spring guide element 4. The elastomer is preferably designed as a cross-linked silicone rubber, in particular as a cross-linked liquid silicone rubber or as a cross-linked solid silicone rubber. In a third process step c), preferably following the second process step b), at least a part of the contact spring 3 is inserted into the shaft 5 via the first opening 8, whereby at least a part of the second contact element 3b is guided through the shaft 5 and through the second opening 9. Fig. 3 shows a detailed view of the power semiconductor module 1 after completion of the third process step c). Because, in the invention, the contact spring 3 is inserted into the shaft 5 via the first opening 8, and thus the insertion of the contact spring 3 occurs from the side 6 of the spring guide element 4 facing away from the substrate 2, the power semiconductor module 1 can be manufactured particularly efficiently. The contact spring 3 is preferably inserted into the shaft 5 until the second contact element makes mechanical contact with a contact surface 14 of the substrate 2. In a fourth process step d) following the third process step c), a material 11 or 11' of the spring guide element 4, arranged in a region 10 adjacent to the first opening 8, is plastically deformed such that at least at one point 12 or 12' in the region 10 adjacent to the first opening 8, the material 11 or 11' of the spring guide element 4 is deformed into the first opening 8, whereby the movement of the contact spring 3 in the direction from the second opening 9 to the first opening 8 is limited by the material 11 or 11' deformed into the first opening 8. Fig. 4 shows a detailed view of the power semiconductor module 1 after carrying out the fourth process step d). The material 11 or 11' deformed into the first opening 811' reduces the size of the first opening 8, so that when the contact spring 3 moves from the second opening 9 to the first opening 8, a section of the contact spring 3, preferably spring section 3c, abuts the material 11 or 11' formed into the first opening 8, thereby blocking further movement of the contact spring 3 from the second opening 9 to the first opening 8. The material 11 or 11' formed into the first opening 8 limits the movement of the contact spring 3 from the second opening 9 to the first opening 8 by forming a positive connection with it. The first contact spring 3 is thus reliably secured against falling out of the shaft 5. The plastic deformation of the material 11 and 11' of the spring guide element 4 arranged in the area 10 adjacent to the first opening 9 preferably takes place, as shown by way of example in Fig. 4 and Fig. 5, such that at least at two locations 12 and 12' arranged opposite each other with respect to the first opening 8 in the area 10 of the spring guide element 4 adjacent to the first opening 8, the material 11 and 11' of the spring guide element 4 is deformed into the first opening 8, whereby the movement of the contact spring 3 in the direction from the second opening 9 to the first opening 8 is limited by the material 11 and 11' deformed into the first opening 8. The plastic deformation of material 11 or 11' is achieved by applying force and, preferably, additionally by applying heat to the material 11 or 11'. This plastic deformation is preferably achieved by hot riveting. In hot riveting, a heated tool punch is generally pressed against the material 11 or 11' of the spring guide element 4, thereby plastically deforming it. This deformation is permanent. Figure 6 shows a highly schematic sectional view of a tool punch 15 for hot riveting. During hot riveting, the two ends 15a and 15b of the heated tool punch 15 are pressed against the material 11 and 11', thereby plastically deforming it. The deformation remains even after the tool punch 15 is removed. Alternatively, hot riveting can also be carried out in such a way that the material 11 or 11, e.g.is heated without contact by a laser beam and / or infrared irradiation and is immediately afterwards or simultaneously deformed by force using a tool punch. In a preferably subsequent fifth process step e), following the fourth process step d), the spring guide element 4 is moved towards the substrate 2, wherein at least after this movement the second contact device 3b has mechanical contact with an associated electrically conductive contact surface 14 of the substrate 2 and at least a part of the first contact device 3a extends beyond the first opening 8 in the direction away from the substrate 2. Fig. 5 shows a detailed view of the power semiconductor module 1 after carrying out the fifth process step e). In the exemplary embodiment, when the spring guide element 4 is moved towards the substrate 2, the spring guide element 4 is pressed against the pressure pad 16 and the pressure pad is pressed against the pressure piece 17, thereby pressing the pressure piece 17, or more precisely its pressure elements 18, against the substrate 2.The power semiconductor module 1 can be connected to a base plate or a heat sink (not shown in the figures) by means of at least one screw 19, wherein the substrate 2 is pressed against the base plate or the heat sink by means of the at least one screw 19. A thermal paste can be applied between the substrate 2 and the base plate or the heat sink. It should be noted that the second process step b) can occur before the third process step c), as in the exemplary embodiment, or it can occur after the fourth process step d). The second process step b) occurs before the fifth process step e). The contact spring 3 is designed for electrically conductive connection of the substrate 2 with an electrically conductive external element, such as a conductor track of a printed circuit board or a busbar. The external element presses towards the substrate 2 against the first contact element 3a, which in turn presses the second contact element 3b against the substrate 2, more precisely against the contact surface 14 of the substrate 2, so that the external element is electrically contacted by pressure via the first contact element 3a and the second contact element 3b is contacted with the substrate 2, more precisely with the contact surface 14 of the substrate 2. The manufactured power semiconductor module 1 comprises a substrate 2 on which a power semiconductor device 13 is arranged and electrically connected to the substrate 2. Furthermore, the power semiconductor module 1 comprises an electrically conductive contact spring 3, which has a first and a second contact element 3a and 3b and a resilient spring section 3c arranged between the first and second contact elements 3a and 3b. The power semiconductor module 1 also comprises a spring guide element 4 made of plastic, which has a channel 5, wherein the channel 5 has a first opening 8 on a first side 6 of the spring guide element 3 and a second opening 9 on a second side 7 of the spring guide element 3, the second opening 9 being arranged facing the substrate 2.Part of the contact spring 3 is arranged in the shaft 5, with the second contact element 3b being arranged above a contact surface 14 of the substrate 2 or having mechanical contact with a contact surface 14 of the substrate 2. At least part of the first contact element 3a extends beyond the first opening 8 in a direction away from the substrate 2, wherein, through plastic deformation of material 11 or 11' of the spring guide element 4 arranged in a region 10 of the spring guide element 4 adjacent to the first opening 8, material 11 or 11' of the spring guide element 4 is deformed into the first opening 8 at least at one location 12 or 12 in the region 10 of the spring guide element 4 adjacent to the first opening 8. The material 11 deformed into the first opening 8 limits movement of the contact spring 3 in the direction from the second opening 9 to the first opening 8.The plastic deformation is preferably carried out by hot riveting, as described above. Preferably, by plastic deformation of material 11 and 11' of the spring guide element 4 arranged in the region 10 adjacent to the first opening 9, material 11 and 11' of the spring guide element 4 is deformed into the first opening 8 at least at two locations 12 and 12' opposite each other with respect to the first opening 8. The material 11 and 11' deformed into the first opening 8 limits the movement of the contact spring 3 in the direction from the second opening 9 to the first opening 8. Of course, unless this is excluded per se, the features mentioned in the singular, in particular the substrate 2, the contact surface 14, the shaft 5, the first and second openings 8 and 9 and the contact spring 3, can also be present multiple times in the power semiconductor module 1.

Claims

Method for manufacturing a power semiconductor module (1) comprising the following process steps: a) providing a substrate (2) on which a power semiconductor device (13) is arranged and electrically connected to the substrate (2), and providing an electrically conductive contact spring (3) having a first and a second contact device (3a, 3b) and a resilient spring section (3c) arranged between the first and second contact devices, and providing a spring guide element (4) made of a plastic, which has a shaft (5), wherein the shaft (5) has a first opening (8) on a first side (6) of the spring guide element (4) and a second opening (9) on a second side (7) of the spring guide element (4), wherein the spring guide element (4) forms a housing part of the power semiconductor module (1), b) arranging the substrate (2) and the spring guide element (4) such thatthat after arranging the substrate (2) and the spring guide element (4), the second opening (9) is arranged facing the substrate (2), c) Inserting at least a part of the contact spring (3) into the shaft (5) via the first opening (8), whereby at least a part of the second contact device (3b) is guided through the shaft (5) and through the second opening (9), d) Plastically deforming a material (11, 11') of the spring guide element (4) arranged in a region (10) of the spring guide element (4) adjacent to the first opening (8) such that at least at one point (12, 12') in the region (10) of the spring guide element (4) adjacent to the first opening (8), material (11, 11') of the spring guide element (4) is deformed into the first opening (8), wherein the material (11, 11') deformed into the first opening (8) Movement of the contact spring (3) in the direction from the second opening (9) to the first opening (8) is limited. The method of claim 1, wherein process step b) is performed before process step c) or after process step d). Method according to one of the preceding claims with the following further method step: e) Moving the spring guide element (4) towards the substrate (2), wherein at least after this movement the second contact device (3b) has a mechanical contact with an electrically conductive contact surface (14) of the substrate (2) and at least a part of the first contact device (3a) extends in the direction away from the substrate (2) beyond the first opening (8). Method according to one of the preceding claims, wherein the plastic deformation is carried out by hot riveting. Method according to one of the preceding claims, wherein the plastic deformation of the material (11, 11') of the spring guide element (4) arranged in the area (10) adjacent to the first opening (9) of the first opening (8) is carried out such that at least at two locations (12, 12') arranged opposite to the first opening (8) in the area (10) of the spring guide element (4) adjacent to the first opening (8), material (11, 11') of the spring guide element (4) is deformed into the first opening (8), wherein the material (11, 11') deformed into the first opening (8) limits a movement of the contact spring (3) in the direction from the second opening (9) to the first opening (8). Method according to one of the preceding claims, wherein the spring section (3c) is designed as a helical spring.

Images