Sintered power electronic module

Abstract

The invention relates to a sintered power electronic module (100) with a first plane (E1) and second plane (E2) that differs from the first plane (E1). To provide a power module that is sintered completely and in several planes and can be sintered in one working step, the following steps are proposed: 10 - a first substrate (10) with a first metallisation (12) that is arranged on the first plane (E1), - a second substrate (20) with a second metallisation (22) that is arranged on the second plane (E2), - one or more switchable dies (40), which each have at least one first power terminal (42) and at least one second power terminal (44), wherein the dies (40) are arranged between the first substrate (10) and the second substrate (20) and the first power terminal (42) of the dies is joined to the first metallisation (12) via a first sintered connection (31) in the first plane (E1) and the second power terminal (44) of the dies is joined to the second metallisation (22) via a second sintered connection (32) in the second plane (E2) and wherein a surface area (A1) of all the sintered connections (31) of the first plane (E1) is between 90 and 110%, more particularly between 95% and 105% of a surface area (A2) of all the sintered connections (32) of the second plane (E2). The invention further relates to a method for producing sintered connections (31,32) of a power module (100).

Description

[0001] Description

[0002] Sintered power electronic module

[0003] The invention relates to a sintered power electronic module and a method for producing sintered connections of a power electronic module.

[0004] Such a power module is used, for example, in converters in industry and in electric vehicles.

[0005] Power electronics assembly systems with different joining levels can be metallurgically joined to achieve electrical / thermal and mechanical connections. For design and production requirements, pressure sintered joints made of Ag or soft solder joints are primarily used to create these joining levels. Pressure sintered joints have preferred properties with regard to their electrical and high-temperature properties. A challenge is the necessary processing using mechanical pressure, typically in the range of around 10 - 20 MPa, and the need for elevated temperatures. When sintering in multiple levels and for more complex assemblies, the arrangement consists of effective joining zones that are parallel and / or in series with regard to force / pressure.

[0006] The invention is based on the object of enabling a power module that is completely sintered in several levels and can be sintered in one operation.

[0007] This object is achieved by a sintered power module having the features specified in claim 1.

[0008] The sintered power electronic module with a first level and a second level different from the first level, has a first substrate with a first metallization arranged on the first level, a second substrate with a second metallization arranged on the second level, and one or more switchable dies, each having at least one first power connection and at least one second power connection. The dies are arranged between the first substrate and the second substrate and are each joined with the first power connection to the first metallization via a first sintered connection in the first level and with the second power connection to the second metallization via a second sintered connection in the second level.To ensure a constant pressure within the tolerable range during sintering, the surface area of ​​all sintered joints in the first level is advantageously between 90 and 110%, and in particular between 95 and 105%, of the surface area of ​​all sintered joints in the second level. The power module defined in this way can be sintered in a single process step and can therefore be manufactured more easily.

[0009] The surface area is the cross-sectional area of ​​the sintered joint that is relevant with regard to the pressure in the surface. Therefore, the cross-sectional areas of the sintered joints can be used for simplification. Since the presses used in sintering are force-controlled, it is important that the module is designed accordingly so that the pressures generated in the sintered joints or their precursor sintered materials lead to a high-quality sintered joint. Adjusting the surface areas of the sintered joints, with a constant force acting on the entire module or stack, leads to an even pressure distribution in the individual sintered joints.

[0010] The switchable die is a semiconductor component that can be designed as an IGBT or MOSFET, for example. It is an unhoused semiconductor and is also referred to as a bare die or a naked chip. So-called “wide bandgap” semiconductors are preferably used. The substrates can be a metal-ceramic substrate. In particular, the so-called direct-bonded copper and active metal brazing substrates are worth mentioning here. It is also possible to use plastic circuit boards for one of the substrates, e.g. fiber-reinforced plastic circuit boards, such as FR4 circuit boards, so-called high-Tg PCBs (having a glass transition temperature TG of greater than 150 °C), made of polyimide and / or designed as a pre-molded leadframe. High-temperature interposer materials such as PI, PEEK or LCP have proven successful for high-temperature applications.

[0011] In a further embodiment, the power electronics module has at least one electrically conductive contact that connects an electrical potential of the first level to the second level. The contact is connected to the first and second metallizations via compensating sintered connections, which have different surface areas. This advantageously compensates for surface differences between the sintered connections in the first and second levels, resulting in uniform pressure in both levels and, accordingly, high-quality sintered connections.

[0012] In a further embodiment, the contacting arrangement has a first contact surface and a second contact surface with different surface areas. Thus, the shape of the contacting arrangement can contribute to better force distribution and better transfer the force into the differently sized sintered joints.

[0013] In a further embodiment, the power electronics module has at least two switchable dies, each of which has sintered connections to the metallizations. The architecture is particularly advantageous when a plurality of dies are arranged, since this allows optimal pressure distribution to be achieved and the number of dies required for the application is sintered. In a further embodiment, the power electronics module has at least two switchable dies with control connections. The dies are arranged differently with regard to the control connections and the adjacent level. In other words, the dies can be arranged alternately with their top and bottom sides. This does not have to be an immediate alternation; the aim is for the dies to be arranged in such a way that the surface area of ​​the sintered connections in the first level corresponds as closely as possible to the surface area of ​​the sintered connections in the second level.Since the top and bottom of the chip have different contact surfaces, alternating the chip orientation is one way to further adjust the surface area of ​​the sintered connections.

[0014] In a further embodiment, the power electronics module has one or more electrically insulating compensating elements that are arranged such that the sum of the surface areas of all sintered connections and the compensating elements in the first level corresponds to the sum of the surface areas of all sintered connections and the compensating elements in the second level, taking into account a maximum deviation of 10%. The electrically insulating compensating elements can thus further equalize the surfaces, since the pressure resulting from the force and the surfaces acts on them just as on the sintered connections. The compensating elements can protrude through both levels and be in mechanical contact with both metallizations of the substrates.

[0015] In a further embodiment, the power electronics module has a third level that is different from the first level and the second level. In the third level, third sintered connections contact a second metallization of the second substrate with connection elements. The connection elements can be metallic connection elements for thermally and / or electrically contacting the module with heat sinks or power connections. In a further embodiment, the sintered connections are designed as pressure-sintered connections. Due to the structure of the module, pressure-sintered connections can be produced particularly advantageously in a single operation in several levels. Suitable sintering materials here include, for example, silver-based pressure-sintered pastes and preforms.

[0016] The object is further achieved by a method for producing sintered connections of a power electronic module in the form of a stack in at least a first level and a second level different from the first level. The method comprises the steps:

[0017] - Providing a first substrate with a first metallization arranged on the first level, a second substrate with a second metallization arranged on the second level and one or more switchable dies arranged between the first substrate and the second substrate and each having at least one first power terminal and at least one second power terminal.

[0018] - Providing sintered material in the first level, which contacts the first power terminals to the first metallization, and providing sintered material in the second level, which contacts the second power terminal to the second metallization. The surface area of ​​the sintered material in the first level corresponds to at least 90% and at most 110%, in particular 95% to 105%, of the surface area of ​​the sintered material in the second level.

[0019] - Applying a force to the stack at a temperature such that pressure is created in the sintered materials of the first and second levels, resulting in the formation of first and second sintered bonds from the sintered materials. The sintered bonds in the different levels can be formed simultaneously or overlapping with a slight offset. The sintered material can be applied as a preform, as a screen print, or in other conventional forms.

[0020] When force is applied, e.g., using a sintering press, a pressure is created in the individual sintered joints depending on the cross-sectional areas of the sintered materials. The inventive method ensures that the pressure is similar in both planes due to the approximation of the surface areas, thus guaranteeing completion and high quality of the sintered joints in both planes.

[0021] The embodiments of the power electronic module are particularly applicable to the method with regard to the arrangement of the sintered joints (or the sintered material in the state before joining) and the surface area of ​​the sintered material in the planes. The method is used in particular for producing a power electronic module according to one or more of the embodiments described above.

[0022] In a further embodiment, the force is set such that a pressure of at least 10 MPa, in particular at least 15 MPa, is established in the sintered materials of the first and second levels. A pressure range of 10 to 20 MPa can be regarded as usual. If a medium range of approximately 15 MPa (12 to 18 MPa) is selected, larger surface deviations can be tolerated and the sintered connections are both satisfactorily formed and the dies are not exposed to excessive pressure. A temperature range of around 250 °C (220 to 280 °C) has proven advantageous.

[0023] In a further embodiment, the surface area of ​​the sintered material in the first and second levels is selected such that the pressure in the levels differs by a maximum of 1 MPa. Due to the relationship between area, force and pressure, the pressure in the levels can be set so that it differs only by permissible values. This allows the demands on the sintering press to be reduced. In a further embodiment, the force is applied to the entire stack using a punch. Due to the advantageous arrangement of the stack and the dimensioning of the sintered materials, the entire stack can be sintered in a single pressing process.

[0024] In a further embodiment, before the force is applied, compensating elements are arranged in such a way that any bulging of at least one of the substrates is reduced. If one of the substrates extends over a larger area than the other substrate, compensating elements can be arranged temporarily for the pressing process. These compensating elements are preferably arranged in such a way that they are directly connected to the press on one side. This ensures an even distribution of force across parts of the module that are not directly mechanically connected in the press.

[0025] In a further embodiment, the force F for creating the sintered joints is applied continuously until the sintered joints are completed in both planes. In other words, the force F can be applied to the entire stack without interruption, and the sintered joints are completed in all planes by the pressure that can be adjusted based on the surface area.

[0026] In a further embodiment, a maximum of 180 seconds passes from the application of force F to the completion of all sintered joints ( ) in all planes. This method can significantly shorten the process time for completing sintered joints, since not only can the intermediate steps after sintering in a single plane be eliminated, such as re-application of sintering material, but also the sequential durations of the actual sintering process. It is conceivable that the sintering process in multiple planes takes somewhat longer than in a single plane, but the time advantage is nevertheless enormous.

[0027] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. They show:

[0028] FIG 1 shows an embodiment of a power electronic module,

[0029] FIG 2 a section through the first level in plan view,

[0030] FIG 3 a section through the second plane in plan view,

[0031] FIG 4 shows a further embodiment of the power electronic module in a sintering press and

[0032] FIG 5 shows a force curve in the power electronic module in the pressed state.

[0033] FIG 1 shows an embodiment of a power electronics module 100, with a first level E1 and a second level E2 which is different from the first level E1. The levels E1 and E2 are arranged parallel to a first substrate 10 and a second substrate 20 of the module 100. The first substrate 10 has a first metallization 12 which is arranged on the first level E1 and faces a second metallization 22 of the second substrate 20. The second substrate 20 is arranged with its second metallization 22 on the second level E2. In the present case, two switchable dies 40 are arranged between the metallizations 12, 22, each of which has a first power connection 42 and a second power connection 44. The dies 40 each have a control connection 45. The first power connections 42 are connected to the first metallization 12 via first sintered connections 31.The first metallization 12 is structured so that the electrical components can form a functional unit. For example, joining surfaces are provided on the metallization. Analogously, the second power connections 44 are connected to the second metallization 22 via second sintered connections 32. The second metallization is structured in the same way. The control connections 45 are here joined to the second metallization 22 via joining connections 35. However, the control connections could just as easily be joined to the first metallization 12 or differently to the first and second metallization 12, 22. Depending on their size, the joining connections can also be sintered or designed as a solder connection that is created during sintering.

[0034] For example, the power module 100 can be configured as a half-bridge, full-bridge, or a so-called six-pack, each with one or more dies 40 per functional switch (e.g., depending on whether MOSFETs or IGBTs are used). Another electronic component 41 has two terminals and, like the dies 40, is arranged between the metallizations 12, 22.

[0035] The dies 40 and the further electronic component 41 are each connected to the substrates 10, 20 or their metallizations 12, 22 via sintered connections.

[0036] Furthermore, electrically conductive recontacts 50 with compensating sintered connections 36, 38 are arranged such that the surface area of ​​all sintered connections in the first plane E1 approximates the surface area of ​​all sintered connections in the second plane E2. In the present case, the compensating sintered connection 36 arranged above the recontact 50 is smaller than the compensating sintered connection 38 arranged below the recontact 50. The compensating sintered connections 36, 38 can be freely selected in size if they exceed the required minimum size (e.g., specified by the current-carrying capacity). The recontact 50 can be a molded copper part, which can be designed, for example, as a cuboid or as a truncated pyramid or polyhedron with at least two parallel joining surfaces.The size of the compensating sintered connections 36,38 does not have to correspond to the size of the contact surfaces on which they rest, but can also be selected to be smaller.

[0037] FIG 2 shows a schematic section through the first plane E1 of the power electronic module 100 in a plan view, showing the first substrate 10 made of a substrate material 11 with its first metallization 12 and the joining surfaces formed therefrom. For the sake of simplicity, only joining surfaces of one of the recontacts 50 and the two dies 40 from FIG 1 are shown. The first sintered connections 31, the power connections of the dies 40 and the compensating sintered connection 36 can be seen on the metallization 12. All sintered connections 31, 36 contribute to the surface area A1 of the sintered connections, since the force of the sintering press creates a pressure there which creates the sintered connections from the sintered materials used.

[0038] The central joining surface of the metallization 12 has two separate sintered connections 31, which are designed to correspond to the first power connections 42 of the respective die 40. These often have separate surfaces for the power connections, which are at the same potential. This depends on the design and make of the die.

[0039] The compensating sintered connection 36 has a smaller area compared to the existing joining surface of the metallization 12, this shows that an adaptation of the surface Al of the sintered connections can take place here.

[0040] FIG 3 shows schematically and analogously to FIG 2 a section through the second plane E2 of the power electronic module 100 in a plan view, wherein the second substrate 20 made of a substrate material 21 with its second metallization 12 and the joining surfaces formed therefrom can be seen. Second sintered connections 32, a compensating sintered connection 38 and a joining connection 35 of a control connection (e.g. gate or collector) of the die 40 contribute to the second area A2. It can be seen that the second sintered connections 32 have a smaller area than the first sintered connections 31 on the other side of the die, i.e. in plane E1, as shown in FIG 2, due to the design of the dies 40 and also due to the joining connections 35 of the control connections 45. The middle joining surface has two second joining connections 32; power connections divided in this way are common for some dies. The right joining surface of the metallization 22

[0041] Furthermore, it can be seen that the compensating sintered connection 38 in the second plane E2 has a larger area than the compensating sintered connection 36 of FIG. 2 in the first plane E1.

[0042] It is thus possible, by selecting the surfaces of the compensating sintered connections 36, 38 in addition to or as an alternative to arranging the dies and other components, to adjust the surface areas A1, A2 of the sintered connections in the planes E1, E2 to each other. This advantageously leads to

[0043] FIG. 4 shows a further embodiment of the power electronic module 100 between the tools of a sintering press. The power electronic module 100 is based on the embodiment shown in FIG. 1 and has been expanded on the second substrate 20.

[0044] The sintering press has a punch 200 with a support 201 , which is intended to exert a force F from above onto the module 100 .

[0045] The second substrate 20 has several layers and a second metallization 27. The second metallization 27 serves to connect connection elements 70, which are joined to the second metallization 27 in a third plane E3 by third sintered connections 33. In this case, the connection elements 70 are designed as metal pins, which can provide both thermal and electrical connections. The pins can be pressed in, for example.

[0046] A lower tool 210 serves as a counterpart to the punch 200 and has an adapter plate 212 mounted on a support 211. In this case, the adapter plate has recesses adapted to the second substrate 20 or the connecting elements 70 attached thereto.

[0047] The third sintered connections 33 in the third level E3 have a surface area which can be different from the surface areas A1, A2 of the sintered connections 31, 32 in the first and second level E1, E2. The difference in the surface areas would lead to a difference in the pressure during pressure sintering, so that in the present example compensation elements 80, 82 are provided. The compensation elements can be used to distribute the force F more evenly over the surface. When the sintering press is closed, the first compensation elements 80 are only in contact with the punch 200 and the side of the second substrate 20 facing the punch 200. The surface areas of the cross sections of the compensating elements 80, 82 in the various planes E1, E2, E3 can be used to adjust the sum of the surface areas in the respective plane to the other planes and thus to adjust the pressure during joining.In addition, warpage can also advantageously be avoided or reduced in the case of first and second substrates 10, 20 of different sizes.

[0048] Analogous to the first compensating elements 80, second compensating elements 82 are arranged below the second substrate 20 in order to reduce an overhang which the second substrate 20 has with regard to the connection elements 70. The compensating elements can be used multiple times and do not have to remain on the power electronics module 100. It is conceivable that compensating elements (not shown) are arranged and integrated in such a way that they can remain on / in the module 100. FIG. 5 now shows the embodiment from FIG. 4, wherein the sintering press is closed. The punch 200 therefore presses onto the power electronics module 100 with a force F. The division of the force F into individual force paths Fl, ..., Fn, which are shown in dashed lines, defines the respectively resulting pressure.The force introduction can be optimized by the design and process-engineering measures disclosed in this invention, thus improving pressure sintering in multiple planes. This results in significant time savings compared to sequential sintering.

[0049] In summary, the invention relates to a sintered power electronic module 100 having a first plane E1 and a second plane E2 different from the first plane E1. To enable a fully sintered power module in multiple planes that can be sintered in a single operation, the following steps are proposed:

[0050] - a first substrate 10 with a first metallization 12 arranged on the first plane El,

[0051] - a second substrate 20 with a second metallization 22 arranged on the second plane E2,

[0052] - one or more switchable dies 40, each having at least one first power terminal 42 and at least one second power terminal 44, wherein the dies 40 are arranged between the first substrate 10 and the second substrate 20 and are joined to the first metallization 12 by the first power terminal 42 via a first sintered connection 31 in the first level E1, and to the second metallization 22 by the second power terminal 44 via a second sintered connection 32 in the second level E2, and wherein an area A1 of all sintered connections 31 of the first level E1 is between 90 and 110%, in particular between 95% and 105% of an area A2 of all sintered connections 32 of the second level E2. The invention further relates to a method for producing sintered connections 31, 32 of a power module 100.

[0053] Reference symbol list

[0054] 100 sintered power electronic module

[0055] 10 , 20 first / second substrate

[0056] 11 Substrate material

[0057] 12 , 22 Metallization of the first / second substrate

[0058] 27 second metallization of the second substrate

[0059] 31 first sintered joints

[0060] 32 second sintered joints

[0061] 33 third sintered joints

[0062] 35 Joint connection of the control connection

[0063] 36 , 38 Compensating sintered joints

[0064] 40 switchable

[0065] 42 , 44 Power connections of the die

[0066] 45 Control connection of the die

[0067] 50 Recontacting

[0068] 70 connecting elements

[0069] 80 , 82 Compensating elements

[0070] El , E2 first and second level

[0071] Al , A2 Area of ​​all sintered joints in the first and second planes

[0072] Fl , ..., En Power Paths

[0073] 200 stamps of a sintering press

[0074] 201 edition of the stamp

[0075] 210 Lower tool of the sintering press

[0076] 211 Support of the lower tool

[0077] 212 Adapter plate for the lower tool

Claims

Patent claims 1. Sintered power electronic module (100) with a first level (El) and a second level (E2) different from the first level (El), comprising: - a first substrate (10) with a first metallization (12) arranged on the first plane (El), - a second substrate (20) with a second metallization (22) arranged on the second plane (E2), - one or more switchable dies (40), each having at least one first power terminal (42) and at least one second power terminal (44), wherein the dies (40) are arranged between the first substrate (10) and the second substrate (20) and are joined to the first metallization (12) with the first power terminal (42) via a first sintered connection (31) in the first plane (E1) and to the second metallization (22) with the second power terminal (44) via a second sintered connection (32) in the second plane (E2), and wherein an area (A1) of all sintered connections (31) of the first plane (E1) is between 90 and 110%, in particular between 95% and 105% of an area (A2) of all sintered connections (32) of the second plane (E2).

2. Power electronic module (100) according to claim 1, further comprising at least one electrically conductive contact (50) which connects an electrical potential of the first level (E1) to the second level (E2), wherein the contact (50) is contacted with the first and the second metallization (12, 22) via compensating sintered connections (36, 38) which have a different surface area.

3. Power electronic module (100) according to claim 2, wherein the contacting (50) has a first contact surface and a second contact surface which have a different surface area.

4. Power electronic module (100) according to one of the preceding claims, comprising at least two switchable dies (40), each of which has sintered connections (31, 32) to the metallizations (12, 22).

5. Power electronic module (100) according to one of the preceding claims, comprising at least two switchable dies (40) with control terminals (45) which are arranged differently with respect to their control terminals (45) and the plane (E1, E2) adjacent thereto.

6. Power electronic module (100) according to one of the preceding claims, comprising one or more electrically insulating compensating elements arranged such that the sum of the surface areas of all sintered connections (32) and the compensating elements in the first plane (El) corresponds to the sum of the surface areas of all sintered connections (32) and the compensating elements in the second plane (E2), taking into account a maximum deviation of 10%.

7. Power electronic module (100) according to one of the preceding claims, with a third level (E3) different from the first level (E1) and the second level (E2), wherein in the third level (E3) third sintered connections (33) Connecting elements (70) to a second metallization (27) of the second substrate (20).

8. Power electronic module (100) according to one of the preceding claims, wherein the sintered connections (31, 32) are formed as pressure sintered connections.

9. A method for producing sintered connections of a power electronic module (100) in the form of a stack in at least a first level (El) and a second level (E2) different from the first level (El), comprising the steps of: - Providing a first substrate (10) with a first metallization (12) arranged on the first plane (El) a second substrate (20) with a second metallization (22) arranged on the second level (E2) and one or more switchable dies (40) arranged between the first substrate (10) and the second substrate (20) and each having at least one first power terminal (42) and at least one second power terminal (44), - Providing sintered material in the first level (El) that contacts the first power terminals (42) to the first metallization (12) and sintered material in the second level (E2) that contacts the second power terminal (44) to the second metallization (22), wherein a surface area of ​​the sintered material in the first level (El) corresponds to at least 90% and at most 110% of a surface area of ​​the sintered material in the second level (E2), and - applying a force (F) at a temperature (T) to the stack such that a pressure is established in the sintered materials of the first and second levels (E1, E2), which pressure leads to the formation of first and second sintered joints (31, 32) from the sintered materials.

10. The method according to claim 9, wherein the force (F) is adjusted such that a pressure of at least 10 MPa, in particular at least 15 MPa, is established in the sintered materials of the first and second levels (E1, E2).

11. The method according to claim 9 or 10, wherein the surface area of ​​the sintered material in the first plane (El) and in the second plane (E2) is selected such that the pressure in the planes (El, E2) differs by a maximum of 1 MPa.

12. Method according to one of claims 9 to 11, wherein the force (F) is applied to the entire stack with a stamp (200).

13. Method according to one of claims 9 to 12, wherein, before the application of the force (F), compensating elements (80, 82) are arranged such that a bulging of at least one of the substrates (10, 20) is reduced.

14. The method according to any one of claims 9 to 13, wherein the force F for producing the sintered joints is applied continuously until the sintered joints are completed in both planes.

15. Method according to one of claims 9 to 14, wherein a maximum of 180s elapses from the application of the force F to the completion of all sintered connections (31, 32) in all planes.

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