A contact element for a power modules

Abstract

This present disclosure relates to power modules with inserted pins and more specifically, but not by way of limitation to design and integration of at least a contact element within such a power module. The contact element is adapted to be soldered to an object, wherein the contact element has a cylindrical body having a virtual center line and two opposing ends crossing the center line, wherein at least one of the two opposing ends is provided with at least a flange protruding with respect to the cylindrical body in a direction away from the center line and at least the other of the two opposing ends is provided with an opening for receiving a pin.

Description

[0001] Title: A contact element for a power modules

[0002] Technical field:

[0003] This present disclosure relates to power modules with inserted pins and more specifically, but not by way of limitation to design and integration of at least a contact element within such a power module.

[0004] Background:

[0005] Power modules typically have a metalized area (bonding pad) that must be electrically connected to other components (such as a gate driver board), which is achieved using inserted contact pins such as a press-fit pin or soldering pin. Inserted contact pins are used in power modules for their efficiency, cost-effectiveness, and design flexibility. They enable automated assembly, reduce production time and defects, and support cost-effective production and optimized performance, making them ideal for high-volume applications.

[0006] Conventional contact elements have flange surface areas and are soldered onto the module’s metal surface (bonding pad) to support inserted contact pins. The contact element should also facilitate electrical connection. A flange of a known contact element is embodied such that when the contact element is placed / soldered with a bottom side of the flange ahead onto a plane perpendicular to the longitudinal direction or center line of the contact element, the flange has a concave central portion which strongly reduces the contact surface seen in a radial direction from the center line of the lowest bottom side (end face) of the flange (Patent document 1).

[0007] This conventional design lacks uniform load distribution, leading to localized stress concentrations, increased wear, and unpredictable performance. The conventional contact element flange may not provide sufficient support for the inserted pins, limiting the durability and reliability of the module’s connections.

[0008] Patent document 1 : US 2015 / 0340333 A1Summary:

[0009] A summary of aspects of certain working examples disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain working examples and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects and / or a combination of aspects that may not be set forth.

[0010] The present disclosure is a contact element (also called rivet), designed to improve the stability and reliability of soldering contact elements to bonding pads in power modules. The contact element has a cylindrical body with a hollow core configured to hold a pin. This core helps keep the pin in place during operation, where it may reduce the risk of movement that could cause wear or issues with connectivity. One or both ends of the body are fitted with a flange, which serves as a base for soldering the contact element to a bonding pad. This flange may help maintain both the electrical and mechanical stability of the connection and it may ensure that the contact element bonds to the module surface, where it may withstand mechanical and thermal stresses. The contact element is made from an electrically conductive material that may allow electrical flow between the pin and the bonding pad.

[0011] The inventors have found that it may be beneficial to add at least one recess or recessed details in a planar contact surface of the bottom side without reducing the radial width of the planar contact surface. This is achieved by a planar contact surface extending between an inner edge and an outer edge of the bottom side and extending continuously around the virtual center line. “Continuously around” means in a closed or endless manner, i.e. , without interruptions around the virtual center line. The bottom side is configured for soldering the contact element to a metal object. The at least one recess is provided in the planar contact surface. The at least one recess in the planar contact surface or recessed details on a bottom side of the flange can include dimples, (closed or radially seen open) holes, (closed or radially seen open) grooves, or knurling patterns. These recessed features may enhance the available surface area for soldering, improving both the mechanical and electrical connection between the contact element and the bonding pad. The increased surface area may enhance theeffectiveness of the soldering process and may increase the solder joint's mechanical strength, i.e. , stability, it may further improve thermal and electrical conductivity, and it may minimize the risk of detachment due to thermal or mechanical stresses.

[0012] The design of the contact element can vary depending on the intended application. For example, some versions may have a blind hole in the cylindrical body to help ensure a secure electrical connection when the pin is inserted. Other versions may feature flanges at both ends of the body, where it may provide easier or faster installation because the contact element can be soldered independent of its orientation. Thus, the end provided with the opening for receiving the pin may comprise a further flange having a top side facing away from the cylindrical body. The top side of the further flange and the bottom side of the flange may have an identical configuration or a non-identical configuration. The non-identical configuration may comprise a planar contact surface without a recess or a different designed planar contact surface. The inner edge and the outer edge of the bottom side may extend continuously around the virtual center line, for example in a closed loop or in a circular manner. The outer edge and / or the inner edge may be non-circular shaped.

[0013] The bottom side may have a single planar contact surface. Such a single planar contact surface extends in a continuous manner around the center line and with a relatively large radial width, i.e. the distance between the inner edge and the outer edge of the bottom side.

[0014] The at least one recess may have an endless shaped recess opening which extends in the same plane as the planar contact surface.

[0015] The at least one recess may further be open in a radial direction.

[0016] These different design options may further allow customization to suit various power module configurations and requirements.

[0017] The inventors found that the contact element may address issues found in traditional power module connections, including stability concerns, susceptibility to mechanical stress, and the need for better electrical performance. The addition of recessed features in the flange, the increased contact surface may all contribute to a stronger, more reliable connection. The inventors have found that it may make the contact element well-suited for applications that require power modules, such asrenewable energy systems, electric vehicles, industrial machinery, and power electronics.

[0018] Brief description of the figures:

[0019] Fig 1 is a cross-sectional view of the power module with soldered contact elements and contact pins inserted in the contact elements.

[0020] Fig. 2a-c show a perspective view, a bottom view and a cross-sectional view of a first working example of a contact element.

[0021] Fig. 3a-c show a perspective view, a bottom view and a cross-sectional view of a second working example of a contact element.

[0022] Fig. 4a-c show a perspective view, a bottom view and a cross-sectional view of a third working example of a contact element.

[0023] Fig. 5a-c show a perspective view, a bottom view and a cross-sectional view of a fourth working example of a contact element.

[0024] Fig. 6a-c show a perspective view, a bottom view and a cross-sectional view of a fifth working example of a contact element.

[0025] Fig. 7a-c show a perspective view, a bottom view and a cross-sectional view of a sixth working example of a contact element.

[0026] Fig. 8a-c show a perspective view, a bottom view and a cross-sectional view of a seventh working example of a contact element.

[0027] Detailed description:

[0028] The present disclosure is described in conjunction with the appended figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0029] It is noted that in the description of the figures, same reference numerals refer to the same of similar components performing a same of essentially similar function.

[0030] A more detailed description is made below with reference to particular examples, some of which are illustrated in the appended drawings, such that thefeatures of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the claims. The drawings are incorporated for facilitating an understanding of the disclosure. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

[0031] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively.

[0032] Fig. 1 depicts a semiconductor package or a power module 16 comprising contact elements 1 (also called rivets). The contact elements 1 are provided on the semiconductor package, each on an object, i.e., a bond pad 23 by means of soldering. Solder material 22 is shown for fixing the contact element 1 to the bond pad 23. The contact elements 1 each comprise a (cylindrical) cavity 24, arranged for receiving the connection pin, such as the press-fit pin 26’ or soldering pin 26.

[0033] Figs. 2a-8c each depict a contact element 1 adapted to be soldered to the (metal) object, i.e. the bond pad 23. The contact element 1 has a cylindrical body 11 having a virtual center C line. The contact element 1 further has two opposing ends 13a; 13b crossing the center line C.

[0034] At least one of the two opposing ends, i.e., the bottom end 13b is provided with at least a flange 3 protruding with respect to the cylindrical body 11 in a direction away from the center line. The circular shaped flange 3 is formed at a lower end portion of the cylindrical body 11 and has a diameter larger than an external diameter of the cylindrical body 11.

[0035] At least the other 13a of the two opposing ends of the contact element 1, i.e. the top end 13a, is provided with an opening 17a for receiving a pin 26; 26’.

[0036] The flange 3 has a bottom side 5; 105; 205; 305; 405; 505; 605 facing away from the cylindrical body 11, wherein the bottom side is configured for soldering thecontact element to the bond pad 23. The bottom side 5; 105; 205; 305; 405; 505; 605 has a planar contact surface 9; 109; 209; 309; 409; 509; 609 extending between an inner edge 2a; 2a’ and an outer edge 2b; 2b’ of the bottom side 5; 105; 205; 305; 405; 505; 605. The maximum radial width W of the bottom side 5; 105; 205; 305; 405; 505; 605 is defined by the planar contact surface 9; 109; 209; 309; 409; 509; 609. The planar contact surface 9; 109; 209; 309; 409; 509; 609 extends continuously around the virtual center line C. The planar contact surface is relatively large and / or adapted to provide maximum stability, wherein the at least one recess in the planar contact surface or the recessed features in the planar contact surface enhances the available surface area for soldering, improving both the mechanical and electrical connection between the contact element and the bonding pad. In addition, The flange 3 of the contact element 1 as shown in Figs. 2a-8c has a single planar contact surface 9; 109; 209; 309; 409; 509; 609.

[0037] The bottom side 5; 105; 205; 305; 405; 505; 605 further has at least one recess 7; 107; 207; 307; 407; 507; 607 in the planar contact surface 9; 109; 209; 309; 409; 509; 609. The bottom side 5; 105; 205; 305; 405 may have a plurality of recesses 7, 7’; 107, 107’; 207, 207’; 307; 407 or the bottom side 505; 605 may have a single recess 507; 607. The recess 7; 107; 307; 407; 507 may have an endless shaped recess opening which extends in the same plane as the planar contact surface and / or the endless shaped recess opening is defined by the planar contact surface 9; 109; 209; 309; 409; 509; 609. The at least one recess 7’; 107’; 207; 607 may also be open in a radial direction. Such a recess 7’; 107’; 207; 607 is provided by a cut-out portion in the circumference face 12’; 12” of the flange 7’; 107’; 207; 607.

[0038] The radially seen outermost face section 12; 12’; 12” defines the outer edge 2b; 2b’; 2b” of the bottom side 5; 105; 205; 305; 405; 505; 605. The outermost recesses 207 seen in a radial direction have been provided by cutouts (Figs. 4a-c) forming the outermost face 12”. The outermost recess(es) 7’; 107’; 607 are provided by cutout portions in the outermost face section 12’.

[0039] The recess 7; 7’; 107; 107’; 207; 307; 407; 507; 607 in the planar contact surface 9; 109; 209; 309; 409; 509; 609 extends in a direction facing away from the planar contact surface 9; 109; 209; 309; 409; 509; 609 towards the cylindrical body.The flange 3 may have a thickness T measured in the direction of the center line, wherein a maximum depth D of the at least one recess 7; 7’; 107; 107’; 307; 507; 607 in the planar contact surface 9; 109; 309; 409; 509; 609 into the flange 3 is smaller than the thickness of the flange.

[0040] The flange 3 may also have a thickness measured T in the direction of the center line, wherein a maximum depth D of the at least one recess 207; 407 is substantially equal to the thickness of the flange. In other words, recesses 207 are provided by half circular cutouts through the flange 3, wherein recesses 407 are through holes in the flange 3.

[0041] The at least one recess 7; 7’; 107, 107’; 507; 607 comprises a planar bottom surface 8; 108; 508; 608 extending parallel to the planar contact surface.

[0042] As shown in Figs. 5a-c, the at least one recess 307 may comprises a non-planar recess bottom surface 308’, for example the at least one recess is defined by a single non-planar recess bottom surface 308’. For example a non-planner recess bottom surface 308’ may be provided by a hemispherical recess bottom surface 308’.

[0043] In the contact element 1 as shown in the figures the opening 17a provides access into a through hole 15 defined by a cylindrical wall of the hollow cylindrical body 11 and the flange 3 comprising a further opening 17b, wherein the virtual center line C crosses the centers of the opening 17a and the further opening 17b. The flange 3 and / or further flange 4 extend radially with respect the cylindrical body 11, i.e., extend in a direction substantially traverse to the center line C. The flange 3 and / or further flange 4 extend continuously around the virtual center line C, i.e., without interruptions. The flange 3 and / or further flange 4 form an endless shaped flange 3; 4 around the center line, for example a circular or gear-like (Figs. 4a-c) shaped flange.

[0044] The at least one recess in the planar contact surface or recessed details on a bottom side of the flange can include a recess or recesses provided by :

[0045] knurling patterns as shown in Figs. 2a-3c,

[0046] radially seen open holes / cutouts as shown in Figs. 4a-4c,

[0047] dimples as shown in Figs. 5a-5c,

[0048] through holes as shown in Figs. 6a-6c

[0049] a closed or radially seen open groove as shown in Figs. 7a-8c.The further flange 4 has a top side 6; 106; 206; 306; 406; 506; 606 facing away from the cylindrical body 11 , wherein the top side of the further flange 4 and the bottom side 5; 105; 205; 305; 405; 505; 605 of the flange 3 have an identical configuration. It is also possible that the top side of the flange 4 and the bottom side of the flange 3 gave a non-identical configuration, wherein the non-identical configuration comprises a planar contact surface without a recess or a different designed planar contact surface (not shown).LIST OF REFERENCE NUMERALS USED

[0050] 1 Contact element (rivet)

[0051] 2a; 2a’ Inner edge of bottom side of flange

[0052] 2b; 2b’; 2b" Outer edge of bottom side of flange

[0053] 3 Flange

[0054] 4 Further flange

[0055] 5; 105; 205; 305; 405; 505; 605 Bottom side of flange

[0056] 6; 106; 206; 306; 406; 506; 606 Top side of flange

[0057] 7; 107; 207; 307; 407; 507; 607 Recess

[0058] 7’; 107’; 207; 607 Recess open in radial direction

[0059] 8; 108; 508; 608 Planar bottom surface of recess

[0060] 308’ Non-planar bottom surface of recess

[0061] 9; 109; 209; 309; 409; 509; 609 Planar contact surface of bottom side 11 Cylindrical body

[0062] 12; 12’; 12” Radially seen outermost face section

[0063] 13a Top end of flange

[0064] 13b Bottom end of flange

[0065] 15 Through hole

[0066] 15’ Blind hole

[0067] 16 Power module

[0068] 17a Opening of flange for receiving a pin

[0069] 17b Further opening of flange

[0070] 23 Object (bond pad)

[0071] 24 (Cylindrical) cavity

[0072] 26 Soldering pin

[0073] 26' Press-fit pin

[0074] C Virtual center line

[0075] T Thickness of flange

[0076] D Depth of recess

[0077] W Maximum radial width of bottom side

Claims

CLAIMS1. A contact element adapted to be soldered to an object, wherein the contact element has a cylindrical body having a virtual center line and two opposing ends crossing the center line, wherein at least one of the two opposing ends is provided with at least a flange protruding with respect to the cylindrical body in a direction away from the center line and at least the other of the two opposing ends is provided with an opening for receiving a pin,wherein the flange has a bottom side facing away from the cylindrical body, wherein the bottom side is configured for soldering the contact element to an object, wherein the bottom side has a planar contact surface extending between an inner edge and an outer edge of the bottom side and at least one recess in the planar contact surface, wherein the planar contact surface extends continuously around the virtual center line.

2. The contact element according to claim 1, wherein the end provided with the opening for receiving a pin comprises a further flange protruding with respect to the cylindrical body in a direction away from the center line, wherein the further flange has a top side facing away from the cylindrical body, wherein the top side of the further flange and the bottom side of the flange have an identical configuration or a nonidentical configuration, preferably the non-identical configuration comprises a planar contact surface without a recess or a different designed planar contact surface .

3. The contact element according to claim 1 or 2, wherein the inner edge and the outer edge extend continuously around the virtual center line, wherein the inner edge and / or the outer edge is non-circular shaped.

4. The contact element according to any of the preceding claims, wherein the opening provides access into a blind hole provided by the hollow cylindrical body.

5. The contact element according to any of the preceding claims 1-3, wherein the opening provides access into a through hole (provided by the hollow cylindrical body and the flange comprising a further opening, wherein the virtual center line crosses the centers of the opening and the further opening.

6. The contact element according to any of the preceding claims, wherein the bottom side has a single planar contact surface.

7. The contact element according to any of the preceding claims, wherein the at least one recess has an endless shaped recess opening which extends in the same plane as the planar contact surface.

8. The contact element according to any of the preceding claims, wherein the at least one recess is open in a radial direction, for example the recess is provided by a cut-out portion in the circumference of the flange.

9. The contact element according to any of the preceding claims, wherein the bottom side of the flange has a plurality of recesses.

10. The contact element according to any of the preceding claims, wherein the flange has a thickness measured in the direction of the center line, wherein a maximum depth of the at least one recess into the flange is smaller than the thickness of the flange.

11. The contact element according to any of the preceding claims 1-9, wherein the flange has a thickness measured in the direction of the center line, wherein a maximum depth of the at least one recess is substantially equal to the thickness of the flange.

12. The contact element according to any of the preceding claims, wherein the at least one recess comprises a planar bottom surface extending parallel to the planar contact surface.

13. The contact element according to any of the preceding claims, wherein the at least one recess comprises a non-planar recess bottom surface, for example the at least one recess is defined by a single non-planar recess bottom surface.

14. The contact element according to any of the preceding claims, wherein the contact element is made of an electrically conductive material.

15. A power module comprising at least one contact element according to any of the preceding claims.

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