Power semiconductor module with a potting body and method for manufacturing

Abstract

A power semiconductor module is presented, comprising a substrate, a power semiconductor device arranged thereon, a connection device, external connection elements, a potting compound, and a pressure device. The substrate has an insulating body and substrate conductor tracks arranged thereon. The power semiconductor device is arranged on one of these substrate conductor tracks. The connection device is designed as a film stack with a first electrically conductive film, a second electrically conductive film, and an electrically insulating film arranged between them. The external connection elements each have a contact device for an associated substrate conductor track. The potting compound completely covers the entire connection device and encloses the substrate as well as the external connection elements except for external contact sections.and wherein the pressure device is designed to exert pressure directly on the potting body by means of a spring element.

Description

The invention describes a method for producing and a power semiconductor module having a substrate, having a power semiconductor component arranged thereon, having a connecting device, having external connection elements, having a potting body and having a printing device.DE 10 2013 104 949 B3 discloses a switching device having a substrate, a power semiconductor component, a connecting device, load connection devices and a printing device. In this case, the substrate has electrically insulated conductor tracks and a power semiconductor component is arranged on a conductor track. The connecting device is designed as a foil composite with an electrically conductive and an electrically insulating foil and has a first and a second main surface. The switching device is connected internally in the circuit-appropriate manner therewith. The printing device has a printing body with a first recess from which a printing element is arranged protruding, wherein the printing element presses onto a section of the second main surface of the foil composite and in this case this section is arranged within the surface of the power semiconductor component in projection along the normal direction of the power semiconductor component.DE 10 2017 125 052 A1 discloses a power semiconductor module having a switching device which has a substrate, a power semiconductor component and a film stack and having a pressure device which is formed such that it can be moved in the normal direction of the substrate, the film stack having a first main surface facing the substrate and a second main surface facing away from the substrate, the pressure device having a pressure body and a first metal spring, the pressure body exerting a force on the first metal spring in the direction of the substrate, the first metal spring exerting pressure on the power semiconductor component on a first region of the second main surface, via a pressure transmission surface of the first metal spring facing the first region of the second main surface, and in the process the first region of the second main surface and the pressure transmission surface of the first metal spring, in the normal direction of the substrate, above a first surface of the power semiconductor component facing away from the substrate, are arranged in alignment with the first surface of the power semiconductor component.With the knowledge of the stated circumstances, the object of the invention is to simplify the structure of the known power semiconductor module and to reinforce it structurally and to present a method for producing such a power semiconductor module.This object is achieved according to the invention by a power semiconductor module having a substrate, having a power semiconductor component arranged thereon, having a connecting device, having external connection elements, having a potting body and having a printing device, wherein the substrate has an insulating body and substrate conductor tracks arranged thereon, wherein the power semiconductor component is arranged on one of these substrate conductor tracks and is electrically conductively connected thereto, wherein the connecting device is formed as a foil stack having a first electrically conductive foil, having a second electrically conductive foil and an electrically insulating foil arranged therebetween, wherein the external connection elements each have a contact device to an associated substrate conductor track, wherein the potting body, which completely covers the entire connecting device and surrounds the substrate, and also the external connection element, up to external contact sections, and wherein the pressure device is configured to apply pressure to the casting body directly on the casting body by means of a spring element or indirectly exclusively via a metal plate.The pressure of the pressure device is thus exerted, when using the power semiconductor module, on the potting body, which directly presses on the connecting device, which directly presses on the power semiconductor components and thus presses the substrate on a cooling device. The construction is thus simple and has additional stability due to the casting body.It is advantageous if the electrically conductive foils each form a plurality of foil conductor tracks.It can be advantageous if the casting body is formed as an epoxy resin.It is preferred if the casting body has an elastic modulus between 2000 MPa and 6000 MPa, preferably between 3000 MPa and 4200 MPa. Alternatively or additionally, it may be preferred if the casting body has a coefficient of linear expansion CTE of between 1 ppm / K and 200 ppm / K, preferably between 2 ppm / K and 50 ppm / K and particularly preferably between 3 ppm / K and 20 ppm / K.It can be advantageous if the casting body has an intermediate casting body which directly covers the connecting device and which preferably has a modulus of elasticity which is lower by at least 10%, advantageously by at least 20%.It can be preferred if the substrate, the connecting device and the casting bodies and, if present, also the metal plate each have recesses which are aligned with one another and each pass through, through which a pressure introduction element projects.It can also be preferred if a surface of the casting body facing away from the substrate has a contour element which, for example, projects like a wart.In the case of a power semiconductor module having a metal plate, it may be preferred if a surface of the metal plate facing the substrate has a contour element which projects in the manner of a wart, for example.It can be particularly advantageous if the spring element has a finger with a finger contact surface. In this case, it can also be advantageous if the finger contact surface is aligned with a power semiconductor component or with the center point of a group of two or three power semiconductor components in the normal direction.The above-mentioned object is furthermore achieved according to the invention by a method for producing such a power semiconductor module having the following working steps, in particular in the sequence a-b-c-d or a-b-d-c: a. forming a substrate with a power semiconductor component arranged on one of the substrate conductor tracks and connected thereto; b. arranging the connecting device; c. arranging the external connection elements and connecting contact devices of these external connection elements to associated substrate conductor tracks; d. covering and enclosing the entire connecting device, the substrate and the external connection element, with the exception of external contact sections, with a potting compound which forms the potting body in a cured manner.It is preferred if the spring device is arranged after the last method step.Of course, unless explicitly or per se excluded or contradicting the idea of the invention, the features or groups of features mentioned in the singular, for example the power semiconductor component, can be present multiple times in the power semiconductor module according to the invention.It is understood that the various embodiments of the invention, regardless of whether they are mentioned in connection with the power semiconductor module or with the method, can be realized individually or in any combinations in order to achieve improvements. In particular, the features mentioned and explained above and below can be used not only in the combinations indicated, but also in other combinations or alone, without departing from the scope of the present invention.Further explanations of the invention, advantageous details and features, are given in the following description of the exemplary embodiments of the invention schematically illustrated in FIGS. 1 to 6, or of respective parts thereof. FIG. 1 shows a step of the method according to the invention for producing a power semiconductor module according to the invention. FIG. 2 shows a section through a first configuration of a power semiconductor module according to the invention. FIG. 3 shows a second configuration of a power semiconductor module according to the invention. FIGS. 4 and 5 show three-dimensional views of power semiconductor modules according to the invention. FIG. 6 shows a plan view of a power semiconductor module according to the invention.FIG. 1 shows a method step, more precisely method step d) of the method according to the invention for producing a power semiconductor module according to the invention. The starting point is a substrate 2 defining a normal direction N. This substrate 2 is here embodied purely by way of example as a ceramic substrate 20 customary in the art having a plurality of substrate conductor tracks 22 made of copper. On one of these substrate conductor tracks 22, a power semiconductor component 3, here purely by way of example a silicon carbide MOS-FET, is arranged in a materially bonded and electrically conductive manner.This power semiconductor component 3 is connected to a further substrate conductor track 22 by means of a module-internal connecting device 4 in a circuit-appropriate manner. The connecting device 4 is designed as a foil stack of two electrically conductive foils 40, 44 with an electrically insulating foil 42 arranged between the conductive foils 40, 44 The electrically conductive foils 40, 44 are structured and thus each form foil conductor tracks which are insulated from one another.Also shown are external connection elements 70, 72, of which two DC voltage connection elements are shown here, which form a stack in sections in order to keep parasitic inductances low. These DC voltage connection elements 70, 72 have respective contact surfaces contactable from the normal direction N, cf. also FIGS. 4 and 5.Prior to this method step illustrated here, the external connection elements 70, 72, more precisely their contact elements, have been connected to associated substrate conductor tracks 22. The illustration now shows the beginning of the covering of the power semiconductor component 3, of the connecting device 4 and parts of the external connection elements, cf. FIG. 2, with a potting compound 500.FIG. 2 shows a section through a first configuration of a power semiconductor module 1 according to the invention arranged on a cooling device 9, in this case a liquid cooling device. The original casting compound 500 now forms, in the cured state, a casting body 5 made of an epoxy resin, which has an elastic modulus of 3500 MPa and a CTE value of 5 ppm / K.Also shown is a pressure device 6 having a spring element 60 which applies pressure directly, i.e. directly, to the potting body 5, here more precisely to two wart-like contour elements 50 which project in the normal direction N and are formed integrally with the remaining potting body and thus produces a thermally conductive connection between the power semiconductor component 3 and the cooling device 9. For simplification, instead of an explicit cooling device 9, a metallic base plate can also be provided here.FIG. 3 shows a second configuration of a power semiconductor module 1 according to the invention, wherein here the potting body 5 additionally has a metal plate 54 facing the spring element 62 of the pressure device 6. This metal plate 54 serves for better pressure distribution on the casting body 5, which otherwise has the same abovementioned properties. This is subject to specifications.The casting body 5 and also the pressure device have two recesses which are each aligned in the normal direction N and through which a screw as a pressure introduction body 68 extends in each case. This screw 68 furthermore extends through two connecting elements 700, 740 and through two of the external connection elements 72, 76, more precisely the external load connection element, and finds an abutment 90 in the cooling device 9. The connecting elements 700, 720, 760 are connected, for example, to an electric motor or to a battery.FIGS. 4 and 5 show three-dimensional views of power semiconductor modules 1 according to the invention with a basic structure according to FIG. 4. The spring element 66 of the pressure device 6 itself is designed here as a disk spring.In contrast to the potting bodies 5 of the first embodiment, the potting body 5 of this embodiment has an intermediate potting body 52, which directly covers the connecting device 4 and therefore also the power semiconductor component and which has a modulus of elasticity which is lower by 20% than the other potting body 5 and is otherwise likewise formed as an epoxy resin.FIG. 4 shows a power semiconductor module 1 having two external DC voltage connection elements 70, 72 and one external AC voltage connection element 76.FIG. 5 shows a power semiconductor module 1 having three external DC voltage connection elements 70, 72, 74 and one external AC voltage connection element 76.The respective contactable contact surfaces of the external connection elements 70, 72, 74, 76 are shown shaded.FIG. 6 shows a plan view of a power semiconductor module 1 according to the invention. Here, the two external DC voltage connection elements 70, 72 are configured next to one another viewed from the normal direction N, that is to say not forming a stack.The spring element 66 of the pressure device 6 is configured in the manner of a spider with a plurality, here four, fingers, the finger contact surfaces of which are assigned to a group of power semiconductor components 3 in each case for the introduction of pressure onto the potting body 5 and are aligned with the centre point thereof, as viewed from the normal direction N.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2013 104 949 B3

[0002] DE 10 2017 125 052 A1

[0003]

Claims

Power semiconductor module (1) having a substrate (2), having a power semiconductor component (3) arranged thereon, having a connecting device (4), having external connection elements (70,72,74,76), having a potting body (5) and having a printing device (6), wherein the substrate (2) has an insulating body (20) and substrate conductor tracks (22) arranged thereon, wherein the power semiconductor component (3) is arranged on one of these substrate conductor tracks (22) and is electrically conductively connected thereto, wherein the connecting device (4) is designed as a film stack having a first electrically conductive film (40), having a second electrically conductive film (44) and an electrically insulating film (42) arranged therebetween, wherein the external connection elements (70,72,74,76) each have a contact device to an associated substrate conductor track (22), wherein the potting body (5) has a relatively low temperature, which completely covers the entire connecting device (4) and envelopes the substrate (2), as well as the external connection elements (70,72,74,76), except for external contact sections, and wherein the pressure device (6) is designed to exert pressure on the casting body (5) directly by means of a spring element (60,62,64,66) or indirectly exclusively via a metal plate (54).Power semiconductor module according to Claim 1, wherein the electrically conductive foils (40, 44) each form foil conductor tracks.Power semiconductor module according to one of the preceding claims, wherein the casting body (5) is formed as an epoxy resin.Power semiconductor module according to one of the preceding claims, wherein the potting body (5) has an elastic modulus between 2000 MPa and 6000 MPa, preferably between 3000 MPa and 4200 MPa.Power semiconductor module according to one of the preceding claims, wherein the potting body (5) has a coefficient of linear expansion CTE of between 1 ppm / K and 200 ppm / K, preferably between 2 ppm / K and 50 ppm / K and in particular preferably between 3 ppm / K and 20 ppm / K.Power semiconductor module according to one of the preceding claims, wherein the potting body (5) has an intermediate potting body (52) which directly covers the connecting device (4) and which preferably has a modulus of elasticity which is lower by at least 10%, advantageously by at least 20%.Power semiconductor module according to one of the preceding claims, wherein the substrate (2) and the connecting device (4) and, if present, also the metal plate (54) each have recesses which are aligned with one another and each pass through, a pressure introduction element (68) projecting through said recesses.Power semiconductor module according to one of the preceding claims, wherein a surface of the casting body (5) facing away from the substrate (2) has a contour element (50).Power semiconductor module with a metal plate according to one of the preceding claims, wherein a surface of the metal plate (54) facing the substrate (2) has a contour element (50).Power semiconductor module according to Claim 8 or 9, wherein one of the contour elements (50) is arranged in alignment with a power semiconductor component (3) in a normal direction (N) of the substrate (2).Power semiconductor module according to one of Claims 8 to 10, wherein the contour element (50) is formed protruding like a wart.The power semiconductor module according to any one of the preceding claims, wherein the spring member (66) has a finger having a finger contact surface.The power semiconductor module according to claim 12, wherein the finger contact surface is aligned with a power semiconductor device (3) or the midpoint of a group of two or three power semiconductor devices (3) in the normal direction (N).Method for producing a power semiconductor module (1) according to one of the preceding claims, having the following working steps, in particular in the sequence a-b-c-d or a-b-d-c: a. forming a substrate (2) with a power semiconductor component (3) arranged on one of the substrate conductor tracks (22) and connected thereto; b. arranging the connecting device (4); c. arranging the external connection elements (70,72,74,76) and connecting contact devices of these external connection elements (70,72,74,76) to associated substrate conductor tracks (22); d. covering and enveloping the entire connecting device (4), the substrate (2) and the external connection element (70,72,74,76), with the exception of external contact sections, with a potting compound (500) which curedly forms the potting body (5).Method according to claim 14, wherein after the last method step the spring device (6) is arranged.

Images