JP7143096B2 - circuit module - Google Patents

Description

The present invention relates to a circuit module such as a semiconductor module, and more particularly to technology for fixing the circuit module to a heat dissipation component or the like.

Some circuit modules have a circuit board made up of electronic components such as semiconductor elements (heat-generating components) installed on the surface of a metal base plate, and the circuit board is covered with a resin case ( For example, see Patent Document 1). According to such a circuit module, while the circuit board is modularized together with other parts (for example, external terminals, etc.), heat generated in the circuit board is transferred through the base plate to the back surface of the base plate (bottom surface of the circuit module). You can communicate effectively. Therefore, by fixing the circuit board with the back surface of the base plate in contact with a heat dissipation component such as a heat sink, the heat generated in the circuit board is efficiently released to the outside through the base plate and the heat dissipation component.

As a specific configuration for fixing the circuit module to the heat dissipating component, a pedestal for screwing formed by partially lowering the height of the case is provided close to the surface of the base plate. They are provided facing each other. The pedestal and the base plate are formed with through-holes for screwing through which the same one screw member is passed. A screw member passed through the through hole is screwed into the heat radiating component, whereby the circuit module is fixed with the back surface of the base plate in contact with the heat radiating component.

JP 2017-195421 A

However, when the circuit module is screwed and fixed, some kind of stress (bending stress, etc.) corresponding to the screwing amount of the screw member is generated in the case. Here, the pedestal for screwing is formed by partially lowering the height of the case, and is a thinner portion than the other portions. Therefore, the stress tends to concentrate on the corner formed by the pedestal and its surrounding thick portion. There is a risk of cracks occurring in the periphery.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a circuit module that can be screwed and fixed without cracking the case.

A circuit module according to the present invention includes a base plate, a circuit board installed on the surface of the base plate, and a case covering the circuit board. The case is provided with a pedestal that closely faces an area of the surface of the base plate that is different from the installation area of the circuit board. Further, through holes for screwing are formed in the pedestal and the base plate. The pedestal is provided with protrusions at positions around the through holes on the surface opposite to the base plate.

According to the above-described circuit module, when screwing the circuit module to the heat dissipation component, it is possible to screw the screw member into the heat dissipation component while crushing the projection. Therefore, the bending stress generated in the case gradually increases when the head of the screw member comes into contact with the tip of the protrusion. That is, until the tightening of the screw member is completed, the bending stress increases at a slower rate of change than when there is no protrusion. Therefore, an excessive increase in bending stress is suppressed by the protrusion.

According to the present invention, the circuit module can be screwed and fixed without cracking the case.

FIG. 1A is a perspective view conceptually showing a semiconductor module according to an embodiment of the present invention, and FIG. 1B is a perspective view showing the semiconductor module with its bottom facing upward. 1 is a longitudinal sectional view of a semiconductor module; FIG. 3A is an enlarged view of the IIIA region shown in FIG. 2, and FIG. 3B is a plan view of the base shown in FIG. (A) and (B) are plan views showing two modifications of the protrusion and the groove.

An embodiment in which the present invention is applied to a semiconductor module will be specifically described. FIG. 1A is a perspective view conceptually showing a semiconductor module. FIG. 1B is a perspective view showing the semiconductor module with the bottom surface facing upward. Also, FIG. 2 is a longitudinal sectional view of the semiconductor module. As shown in FIGS. 1A to 2, the semiconductor module of the present embodiment has a circuit board 1 and external terminals 2 which are modularized using a metal base plate 3 and a resin case 4. It is.

Specifically, the circuit board 1 is installed on the surface 3a (upper surface in this embodiment) of the base plate 3, and the external terminals 2 are connected to the circuit board 1 (see FIG. 2). Here, the circuit board 1 includes a semiconductor element 11 (heat-generating component) such as a diode, and an insulating substrate 12 on which the semiconductor element 11 is mounted. The external terminals 2 are for drawing out the connection terminals (input terminals, output terminals, etc.) for the circuit board 1 to the outside surface of the semiconductor module. In this embodiment, the base plate 3 is a rectangular metal plate (see FIG. 1B).

The case 4 is provided with an opening 40 closed by the base plate 3 . In this embodiment, the opening 40 is formed in a rectangular shape according to the shape of the base plate 3 , and the opening 40 is closed by fitting the base plate 3 into the opening 40 . More specifically, the base plate 3 is fitted in the opening 40 of the case 4 so that the back surface 3b (lower surface in this embodiment) of the base plate 3 serves as the bottom surface of the semiconductor module. Therefore, the circuit board 1 placed on the surface 3 a of the base plate 3 is covered with the case 4 and arranged in the space S surrounded by the base plate 3 and the case 4 . On the other hand, the external terminal 2 is arranged in a state of penetrating the case 4 so that a part of the external terminal 2 is exposed on the outer surface of the case 4 (the upper surface of the case 4 in this embodiment). In addition, the shape of the base plate 3 is not limited to a rectangular shape, and can be appropriately changed to various shapes. Also, the shape of the opening 40 of the case 4 can be changed as appropriate according to the shape of the base plate 3 .

Here, since the case 4 is an exterior part of the semiconductor module, it is preferably made of a resin having appropriate hardness. Moreover, since the temperature during use of the semiconductor module may exceed 150° C., the case 4 is preferably made of a resin having appropriate heat resistance. In the present embodiment, PPS (polyphenylene sulfide) is used as a resin having such moderate hardness and heat resistance. Incidentally, the resin constituting the case 4 is not limited to PPS, and can be appropriately changed according to the hardness and heat resistance required for the case 4 .

The space S in the case 4 is filled with a sealing material 5 (epoxy resin or the like), thereby firmly integrating the base plate 3 and the case 4, and the circuit board 1 and the external terminals 2. is modularized. The space S in the case 4 is filled with the sealing material 5 in a softened state, for example, by injecting it from an injection port (not shown) provided in the case 4 . After that, the semiconductor module is produced by curing the sealing material 5 .

According to such a semiconductor module, while the circuit board 1 is modularized together with the external terminals 2 , the heat generated in the circuit board 1 can be efficiently transferred to the back surface 3 b of the base board 3 through the base board 3 . Therefore, by fixing the semiconductor module in a state in which the back surface 3b of the base plate 3 is in contact with a heat dissipation component (not shown) such as a heat sink, the heat generated in the circuit board 1 is transferred to the outside through the base plate 3 and the heat dissipation component. can be efficiently released to

In this embodiment, the circuit board 1 is installed in the central portion of the surface 3a of the base plate 3 (see FIG. 2). Therefore, it is preferable that the central portion of the rear surface 3b of the base plate 3 is always in contact with the heat dissipating component so that heat can be efficiently conducted from the base plate 3 to the heat dissipating component when the semiconductor module is fixed to the heat dissipating component. For this reason, although not shown in the drawings, the base plate 3 is curved such that the back surface 3b thereof is convex. Specifically, the base plate 3 is curved such that the back surface 3b is convex in a longitudinal section (the longitudinal section shown in FIG. 2) in the longitudinal direction D1.

The semiconductor module is screwed and fixed to the heat dissipating component at two locations on both ends in the longitudinal direction D1. Specifically, one pedestal 41 is provided at each end of the case 4 in the longitudinal direction D1 (see FIG. 2). Here, the pedestal 41 is formed by partially lowering the height of the case 4 so that the pedestal 41 closely faces the end region R2 different from the mounting region R1 of the circuit board 1 on the surface 3a of the base plate 3. It is formed so that it is thinner than other parts. Each pedestal 41 and a portion of the base plate 3 facing the pedestal 41 are formed with screw-fastening through holes 41c and 3c through which the same screw member 6 is passed.

On the other hand, if the base plate 3 is curved so that the back surface 3b is convex, both ends of the base plate 3 in the longitudinal direction D1 are lifted from the surface of the heat dissipation component. Therefore, when both ends of the semiconductor module are fixed by the screw members 6 respectively, a bending stress corresponding to the screwing amount of the screw members 6 is generated in the case 4 . Here, the pedestal 41 for screwing is a portion thinner than other portions as described above. Therefore, when a bending stress occurs in the case 4, the bending stress tends to concentrate on the corner P formed by the pedestal 41 and its surrounding thick portion. Therefore, if an excessive bending stress is applied to the case 4 when the screw member 6 is screwed in, cracks may occur in the corner P and its periphery.

Therefore, as shown in FIGS. 3A and 3B, the pedestal 41 is provided with projections 42 at positions around the through holes 41c on the surface 41a opposite to the base plate 3. . In this embodiment, the projection 42 has an annular shape centering on the through hole 41c. FIG. 3A is an enlarged view of the IIIA region shown in FIG. 3(B) is a plan view of the base 41 shown in FIG. 3(A) as viewed from its surface 41a.

Further, grooves 43 adjacent to the protrusions 42 are formed on the surface 41 a of the base 41 . In this embodiment, an annular groove portion 43A adjacent to the inner peripheral edge of the annular protrusion 42 and an annular groove portion 43B adjacent to the outer peripheral edge of the annular protrusion 42 are formed on the surface 41a of the base 41. ing.

The projecting portion 42 and the groove portion 43 are formed together with other portions of the case 4 by resin molding such as transfer molding. Therefore, the protrusion 42 is integrally formed with other parts (including the pedestal 41) of the case 4 using the same resin material.

When fixing the semiconductor module to the heat dissipation component by screwing, a tool such as a torque driver, which can tighten the screw member 6 with a predetermined torque, is used for the screwing. If there is no protrusion 42 around the through-hole 41 c , bending stress is generated in the case 4 from the moment the head 61 of the screw member 6 directly contacts the surface 41 a of the base 41 . For this reason, the bending stress rapidly increases until the screw member 6 is completely tightened with a predetermined torque, which tends to cause the bending stress to become excessively large.

On the other hand, since the protrusions 42 are provided around the through holes 41c as in the present embodiment, the screw member 6 can be screwed into the heat dissipation component while crushing the protrusions 42 when fixing the semiconductor module by screwing. becomes possible. In this embodiment, a resin (specifically, PPS) having moderate hardness is used as the resin forming the case 4 . Therefore, after the head 61 of the screw member 6 comes into contact with the projection 42 in the process of screwing the screw member 6 , the projection 42 is pushed and sheared by the head 61 of the screw member 6 . Transform gradually. As a result, the bending stress generated in the case 4 gradually increases along with the deformation of the protrusion 42 from the time when the head 61 of the screw member 6 contacts the tip of the protrusion 42 . That is, until the screw member 6 is completely tightened with a predetermined torque, the bending stress increases more slowly (that is, at a smaller rate of change) than when the protrusion 42 is not provided. Therefore, according to the semiconductor module of the present embodiment, an excessive increase in bending stress is suppressed by the protrusions 42, and as a result, the case 4 (mainly the corner P and its periphery) can be screwed without cracking. Can be fastened.

Further, according to the semiconductor module of the present embodiment, since the groove portion 43 is formed adjacent to the projection portion 42, the head portion 61 of the screw member 6 is pushed into the projection portion 42 while the screw member 6 is being screwed. At the point of contact with the tip and immediately after that, the protrusion 42 is likely to be deformed. Specifically, the protrusion 42 is easily crushed as its height becomes smaller. Therefore, when the head 61 of the screw member 6 contacts the tip of the protrusion 42 and immediately after that, the deformation of the protrusion 42 temporarily absorbs the bending stress. After that, the bending stress gradually increases as the deformation of the protrusion 42 becomes gentle. Therefore, it is possible to prevent a sudden increase in the bending stress at the moment when the head 61 of the screw member 6 contacts the tip of the projection 42, and as a result, the occurrence of cracks in the case 4 can be prevented more reliably. can be done.

Furthermore, in this embodiment, the protrusion 42 has an annular shape surrounding the through hole 41c. Therefore, when the head portion 61 of the screw member 6 comes into contact with the projection portion 42 while the screw member 6 is being screwed in, the head portion 61 is received by the projection portion 42 around the axis of the screw member 6 in a well-balanced manner. be done. Therefore, it is less likely that the screw member 6 is tilted due to loss of balance due to the protrusion 42 . Here, from the viewpoint of receiving the head portion 61 of the screw member 6 by the protrusion 42 in a well-balanced manner, the protrusion 42 may not be annular, but may be of a modified example described later (FIGS. 4A and 4B). ))), as long as it is composed of a first portion and a second portion located on both sides of the through hole 41c. It should be noted that the annular projection 42 can also be understood as being composed of, for example, two semi-annular portions (a first portion and a second portion).

4A and 4B are plan views showing two modifications of the protrusion 42 and the groove 43. FIG. As a first modification (see FIG. 4A), the protrusion 42 is composed of a first portion 421 and a second portion 422 located on both sides of the through hole 41c. The two portions 422 may extend parallel and linearly. Two linear grooves 431A and 431B adjacent to the first portion 421 and two linear grooves 432A and 432B adjacent to the second portion 422 are formed on the surface 41a of the base 41. may Here, the grooves 431A and 432A are located on the through hole 41c side with respect to the first portion 421 and the second portion 422, respectively, and the grooves 431B and 432B penetrate the first portion 421 and the second portion 422, respectively. It is located on the side opposite to the hole 41c.

As a second modification (see FIG. 4(B)), the protrusion 42 may be composed of a plurality of third portions 423 projecting in a conical or columnar shape around the through hole 41c. . Further, grooves 433 may be formed on the surface 41 a of the base 41 so as to be adjacent to the third portions 423 and surround the third portions 423 . In the example of FIG. 4B, the protrusion 42 is composed of eight third portions 423 that protrude conically or cylindrically, and the surface 41a of the base 41 has a surface 41a surrounding each third portion 423. An annular groove 433 is formed. In the example of FIG. 4B, two (or two sets) of the plurality of third portions 423 located on opposite sides with respect to the through hole 41c are arranged as the first portions composing the projecting portion 42, respectively. You may grasp|ascertain with a part and a 2nd part.

According to these modifications, as in the above-described embodiment, excessive increase in bending stress is suppressed by the protrusions 42, and as a result, cracks are generated in the case 4 (mainly the corners P and their periphery). It can be fixed with screws. Further, since the groove portion 43 is formed adjacent to the projection portion 42, when the head portion 61 of the screw member 6 contacts the tip of the projection portion 42 in the process of screwing the screw member 6 and immediately after that, , the protrusion 42 is easily deformed. Therefore, as in the above-described embodiment, the bending stress is prevented from suddenly increasing at the moment when the head 61 of the screw member 6 contacts the tip of the projection 42, and as a result, the case 4 cracks. can be prevented more reliably.

Furthermore, the head portion 61 of the screw member 6 can be received in a well-balanced manner by the first and second portions of the protrusion 42 described above. Therefore, as in the above-described embodiment, it is difficult for the screw member 6 to tilt due to loss of balance caused by the protrusion 42 .

The configurations of the protrusions 42 and the grooves 43 are not limited to those described in the above embodiments and modifications, and may be appropriately modified in consideration of how easily the protrusions 42 should be crushed. can be done. In addition, considering the easiness of forming the protrusions 42 and the grooves 43 by resin molding, the configurations of the protrusions 42 and the grooves 43 may be appropriately modified.

In the semiconductor modules described in the above embodiments and modified examples, the number of pedestals 41 may be one, or three or more. Moreover, the semiconductor module may have a configuration in which the surface 41a of the pedestal 41 is not formed with a groove.

Further, in the semiconductor modules described in the above embodiments and modified examples, the base plate 3 is not limited to having a convex back surface 3b. It can be changed as appropriate to a flat surface, a curved surface, or the like. In any case, if some stress tends to concentrate on the corner P formed by the pedestal 41 and its surrounding thick portion during fixing by screwing, the protrusion 42 and the groove may be used. By appropriately applying the configuration, it is possible to prevent the corner P from being subjected to excessive stress.

Moreover, the configuration of each part of the semiconductor module described in the above embodiments and modifications can be applied not only to semiconductor modules but also to various circuit modules having electronic components other than semiconductor elements.

The above description of the embodiments (including modifications) should be considered illustrative in all respects and not restrictive. The scope of the invention is indicated by the claims rather than the above-described embodiments. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and range of equivalents of the claims.

1 circuit board 2 external terminal 3 base plate 3a front surface 3b back surface 3c through hole 4 case 5 sealing material 6 screw member 11 semiconductor element 12 insulating substrate 40 opening 41 pedestal 41a surface 41c through hole 42 projections 43, 43A, 43B, 431A, 431B, 432A, 432B, 433 groove 61 head 421 first portion 422 second portion 423 third portion D1 longitudinal direction P corner R1 installation region R2 end region S space

Claims (5)

a base plate;
a circuit board installed on the surface of the base plate;
a case covering the circuit board;
a screw member;
A circuit module fixed to an object to be attached by the screw member,
The case is provided with a pedestal that closely faces an area of the surface of the base plate that is different from the installation area of the circuit board, and the pedestal and the base plate are provided with screws through which the screw member is passed. A through hole for fastening is formed,
The pedestal has a position around the through hole on the surface opposite to the base plate. It has a protrusion that is crushed by contact with the head ,
A circuit module according to claim 1, wherein a groove adjacent to said protrusion is formed in said surface of said base, and said groove is provided between said through-hole and said protrusion . 2. The circuit module according to claim 1, wherein said protrusion includes a first portion and a second portion located on opposite sides of said through hole. 3. The circuit module according to claim 2, wherein said projection has a ring shape centering on said through hole. 3. The circuit module of claim 2, wherein said first portion and said second portion extend parallel and linearly. a base plate;
a circuit board installed on the surface of the base plate;
a case covering the circuit board;
a screw member;
A circuit module fixed to an object to be attached by the screw member,
The case is provided with a pedestal that closely faces an area of the surface of the base plate that is different from the installation area of the circuit board, and the pedestal and the base plate are provided with screws through which the screw member is passed. A through hole for fastening is formed,
The pedestal has a position around the through hole on the surface opposite to the base plate. It has a protrusion that is crushed by contact with the head,
the protrusion includes a first portion and a second portion located on both sides of the through hole,
A circuit module, wherein the first portion and the second portion extend parallel and linearly.

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