JP2000058727A - Power semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the thickness of grease by arranging attaching holes in the peripheral section of the bottom face of a power semiconductor module, and forming projections on the bottom face of the module on the outer peripheral side than the attaching holes. SOLUTION: A power semiconductor module is provided with a resin case A101, another resin case B102, and a metallic base 114. The cases A101 and B102 are firmly formed integrally with a filling resin 113, and the case A101 is fixed to the base 114 with an adhesive. Attaching holes 115 are arranged along the two parallel sides of the bottom face of the module. Two stripe-like projections 117 are arranged on the outside of the attaching holes 115 on the metallic base 114. Therefore, the heat generated from a power semiconductor element in the module can be effectively taken out to a heat sink on the outside of the module by suppressing the thickness of heat conductive grease.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power module and a mounting structure for mounting the power module to a mounting member such as a heat sink.

[0002]

2. Description of the Related Art Power semiconductor devices tend to handle larger voltages and currents. The energy generated by the semiconductor element in the semiconductor device during switching increases as the voltage handled and the current handled increase. In order to efficiently release the heat generated in the semiconductor element, it is important not to increase the density of the heat emitted from the semiconductor element. Therefore, the total area of semiconductor elements mounted in the semiconductor device tends to increase with an increase in the amount of heat generated,
As a result, the semiconductor device tends to be large. The mainstream of the power semiconductor device has been a so-called press-contact type in which main electrodes are arranged above and below, and a water-cooling block is used as appropriate. In recent years, moisture resistance of semiconductor elements has been improved, soldering techniques have been improved, and materials such as ceramics and resins have been improved, and module types that are easier to use have been increasing. In the module type, electrical connection is made on the top surface and heat is released only from the bottom surface.

Unlike the pressure contact type, it is difficult to apply pressure to the entire surface of the module. Therefore, when the size of the module is increased, it is difficult to make the entire bottom surface of the module and the mounting surface (the surface of the heat sink) adhere to each other. Generally, a heat transfer grease is interposed in this portion in order to easily release heat. However, since the portion is made of an organic material, its thermal conductivity is small, and it is very important to reduce its thickness. In many cases, the module is attached only to the peripheral portion, and the grease thickness in the central portion tends to increase as the size of the module increases.

[0004] As a technique for reducing the grease thickness, Japanese Patent Application Laid-Open Nos. Hei 7-211825, Hei 9-134983, and Heisei
As disclosed in Japanese Patent Application Laid-Open No. 6-232232, etc., disclosure of a technique of applying grease only directly under (directly above) a semiconductor element or reducing the grease thickness immediately under (directly above) a semiconductor element is recognized. These are effective means for a relatively small semiconductor device.

However, in the power semiconductor device to which the present invention is applied, a technique of applying grease only to a part cannot be adopted from the standpoint of reliability. This is because the grease may move in a long-term use. The prior art described above does not disclose a technique that leads to a technique for reducing the grease thickness at the center of a large-sized modular semiconductor device.

[0006]

As described above, the prior art does not specifically disclose a module structure effective as means for suppressing the thickness of grease and a module mounting structure.

An object of the present invention is to provide a power semiconductor module capable of suppressing the thickness of grease and a mounting structure thereof.

[0008]

The power semiconductor module according to the present invention has a mounting hole at the periphery of the bottom surface of the module, and has a projection at a portion located on the peripheral side of the mounting hole at the bottom surface of the module.

In the power semiconductor module mounting structure according to the present invention, the power semiconductor module according to the present invention is filled with grease between a mounting member and the power semiconductor module.
Tighten to the mounting member with screws passing through the mounting holes.

Further, in another mounting structure of the power semiconductor module according to the present invention, the power semiconductor module having the mounting hole disposed in the peripheral portion of the module bottom surface is provided on a portion located on the peripheral side of the module bottom surface with respect to the mounting hole. A thin plate is sandwiched between the power semiconductor module and the mounting member, and grease is filled between the power semiconductor module and the mounting member, and is fastened to the mounting member with a screw passing through the mounting hole.

According to the present invention, when the power semiconductor module is fastened to the mounting member with a screw, a force is generated to bring the module bottom surface close to the mounting member surface. For this reason, the grease thickness at the center of the module bottom surface can be reduced.

Next, the present invention will be described in some detail with reference to FIGS.

FIG. 2 shows a cross section in a state where a typical module is mounted. In this figure, the module 203 is composed of a resin case 201 and a metal base 202. In actuality, there are electrodes on the resin case 201, and inside the resin case 201, there are semiconductor devices, wiring members, and other components necessary for satisfying the functions. The module 203 is fixed to the heat sink 205 with left and right mounting screws 206. In order to effectively release the heat generated inside the module 203 to the heat sink 205, a space between the metal base 202 and the heat sink 205 is filled with a heat conductive grease 204.

The heat conductive grease 204 is
3 and the heat sink 205 can hold down the outer periphery,
Pressure is generated inside. This pressure pushes the metal base 202 up, albeit only slightly. This pushing force is shown as a repulsive force 209 of the heat conductive grease in the figure. According to an experiment, when the periphery of a copper plate having a size of 100 mm × 200 mm and a thickness of 5 mm was fastened to an aluminum block having a thickness of 40 mm via thermal conductive grease, a deformation of several tens μm occurred at the center of the copper plate. At this time, the pressure of the grease is such that it is pressed with a fingertip.

Therefore, the heat conductive grease 204 is thicker at the center of the module 203 than at the periphery. Although the thermal conductivity of the thermal conductive grease 204 is a high value as a resin, it is about two orders of magnitude smaller than that of a metal. Therefore, as the thermal conductive grease 204 becomes thicker, the thermal resistance at that portion increases significantly. Therefore, thermal conduction grease 2
04 must be as small as possible. Moreover, the module 203 is provided at the center of the metal base 202.
Since the functional elements inside are concentrated, the calorific value is generally larger than that of the peripheral part.
If the thickness is too large, the temperature rise due to the heat generated by the module 203 increases, and the maximum value of the current and voltage that can be handled decreases, and the reliability is impaired.

In order to overcome this unfavorable situation,
It is assumed that the central part of the resin case 201 is pressurized in order to make the heat conductive grease 204 in the central part thin. The force is represented as an external pressure arrow 207. As mentioned earlier, since various functional parts are packed in the module 203, it can be imagined that a force is exerted on the central part of the metal base 202 through them, but in reality, as shown in the figure, the case As shown by the inner transmission path arrow 208, the resin case 2
Power is transmitted along 01. When external force is applied to the internal functional components, reliability is reduced, and in extreme cases, it is destroyed.Therefore, various structural measures are taken to prevent internal force from being applied. It is.

As described above, it is impossible to directly press the central portion. The present invention provides a structure for generating a force for reducing the thickness of the thermal conductive grease at the center of the module by using the tightening force of the outer periphery of the module instead of directly pressing the center.

FIG. 3 shows a basic configuration of the present invention. The member 301 is attached to the member 303 with a mounting hole 304 opened around the member 301. The spacer 302 is provided on the peripheral side from the mounting hole 304.

When the tightening force 305 acts, the member 301 is fixed to the member 303. At that time, the spacer 302 serves as a fulcrum, and the central portion of the member
Rotational moment 30 that deforms the center of 03 upward
6 occurs. As a result, the center of the member 301 is
The central part of the member 303 is pressed against the member 301 on the 03 side. Since the member 303 is thicker and has higher rigidity than the member 301, deformation mainly occurs in the member 301, and the member 301 is deformed. As a result, the central portion of the member 301 and the member 303
The central part of approaches.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to examples. Note that the present invention is not limited to these examples.

Embodiments 1 to 5 of the present invention will be described with reference to FIGS.
This will be described with reference to FIG.

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIG. 1 and FIGS. FIG.
Is a power semiconductor module according to a first embodiment of the present invention. FIG. 1A shows the module as viewed obliquely from above. FIG. 1B shows the module as viewed obliquely from below.

The module according to the present invention comprises a resin case A
101, a resin case B102, and a metal base 114. In this embodiment, the resin case is divided into two for convenience in manufacturing. The resin case A101 and the resin case B102 are firmly integrated with the filling resin 113. Also, the resin case A101 and the metal base 1
14 is fixed with an adhesive (not shown). In order to supplement the strength of the adhesive, it is fixed at eight places by case fixing screws 116. The mounting holes 115 are arranged along two parallel sides of the module bottom surface.

Terminals are arranged on the upper surface of the module. The main terminal through which the main current flows is the emitter terminal A
103, emitter terminal B104, emitter terminal C10
5, there are six collector terminals A106, collector terminal B107, and collector terminal C108. The control terminals include an auxiliary emitter terminal 109 and a gate terminal 11.
0, and an auxiliary collector terminal 111.

The feature of this module is that the metal base 11
4, two stripe-shaped protrusions 117 arranged outside the module of the mounting hole 115.
The protrusion 117 is provided over the entire length of two parallel sides of the module bottom surface where the mounting holes 115 are arranged. The projection has a width of 2 mm and a height of 50 μm. Therefore, it cannot be confirmed as a projection from the naked eye. Apparently, the line at the end of the protrusion is visible. If you touch the surface, you can see that it is slightly higher than the surroundings. According to the study of the present inventor, the height of the projection 117 is preferably in the range of 20 μm to 200 μm.

The structure will be described in more detail using the cross section of the module. FIG. 4 shows a cross section cut at the center of the mounting hole 115. The mounting hole 115 passes through the resin case A101 and the metal base 114. On the resin case A101 above the mounting hole 115, a cylindrical mounting sleeve is provided. A screw passes through this sleeve and the mounting hole 115. It should be noted that a semiconductor element inside the module and a wiring path from the semiconductor element to the outside, and a silicone gel or the like which is a filler for protecting the semiconductor element and the wiring path from moisture are omitted.

The projection 117 is formed outside the module from the mounting hole 115. When the projection 117 is screwed into the mounting hole 115 and tightened, the metal base
Serves as a fulcrum for generating a moment to bend the central portion of 114 downward. According to an experiment performed by the inventor, an effect can be obtained if the protrusion 117 is formed outside the center of the mounting hole 115. In this embodiment, the mounting hole 1
Protrusions 117 are formed up to the outer edge of No. 15. Since the mounting hole 115 is widened near the surface, the width of the projection is narrow at that portion.

FIG. 5 shows a state where the module according to the present embodiment is mounted on a heat sink. Heat sink 502
Has a heat sink side mounting hole 504 at a location facing the mounting hole 115 on the module side, and the module is mounted with mounting screws 501 that pass through the mounting hole 115. As shown in FIG. 3, a moment is generated by the tightening force. In the present embodiment, the moment 505 is indicated by an arrow. This moment 5
05, the central portion of the metal base 114 is pressed downward, that is, toward the heat sink 502. In this embodiment, since the mounting holes 115, which are the fastening portions, are arranged in two rows, the projections are formed in a stripe shape so that the effect of generating a moment is increased. Of course, projections may be formed in the vicinity of all the mounting holes 115, that is, in only eight locations, or projections may be formed in a plurality of locations in all the mounting holes 115. Further, a protrusion may be formed at a position away from the mounting hole 115. In that case, it is necessary to form it only on the outside of the module from the straight line connecting the centers of the mounting holes 115. The reason for forming the stripe shape in this embodiment is that the effect can be expected from the intermittent form and that it is easy to form.

According to the measurement of the present inventor, when the protrusion 117 is not formed, the gap between the metal base 114 and the heat sink 502 at the center, that is, the heat conductive grease 503 is formed.
Has a thickness of about 200 μm. Also, the metal base 114
The thickness of the heat conductive grease 503 is almost zero in the peripheral portion, especially near the mounting hole 115. On the other hand, in the module according to the present embodiment, the thickness of the heat conductive grease 503 is 120 at the center of the metal base 114.
μm, the mounting holes 115 around the metal base 114.
, Even if it is far from the mounting hole 115,
0 μm. FIG. 6 is a graph showing the gap between the module and the heat sink in this embodiment. The horizontal axis of the graph is the horizontal direction in FIG. 4 or FIG. 5, the vertical axis is the distance between the bottom surface of the metal base 114 and the surface of the heat sink 502 in FIG.
That is, it is the thickness of the thermal conductive grease 503.

As is apparent from FIG. 6, the use of the module according to the present embodiment has the effect of making the grease thickness uniform over the entire surface of the metal base 114. As described above, the thermal conductivity of the thermal grease 503 is the same as that of the metal base 1.
Compared with the heat sink 14 or the heat sink 502, the thickness is estimated to be 1/100 or less, which is extremely small. According to this embodiment, the heat generated by the power semiconductor element in the module can be effectively taken out to the heat sink 502 outside the module by keeping the thickness of the heat conductive grease small. Therefore, the module according to the present embodiment has the effect of making the temperature inside the module uniform and reducing the variation in reliability between semiconductor elements in the module.

In this embodiment, the protrusion 1 of the metal base 114 is used.
A mold was used to form 17. Projection 11 of the present embodiment
Since 7 has a stripe shape, it is easy to form a step by machining.

(Embodiment 2) A second embodiment of the present invention will be described with reference to FIGS.

FIG. 7 shows a second embodiment of the present invention in which a power semiconductor module is mounted on a support member. The support member (heat sink) is not displayed, and only the module and the insertion member are displayed for easy understanding. In addition, it is the figure seen from diagonally downward, that is, from the heat sink side. FIG. 8 shows a cross section of the second embodiment of the present invention. In this drawing, the heat sink 801 is not omitted.

In this embodiment, as in the first embodiment, the mounting holes 703 are arranged in two rows. However, if the number is 1
There are six per row, twelve for the whole module.

In this embodiment, no special processing is applied to the module, and the thin plate 704 is sandwiched between the module and the heat sink 801. The material of the thin plate 704 is stainless steel. The thickness of the thin plate 704 is the same as that of the protrusion 11 of the first embodiment.
The thickness was 100 μm, which was larger than 7. The width is 10 mm. The width only needs to be equal to or greater than the width that reaches the outer circumference of the metal base 702 when the thin plate 704 is pressed against the mounting screw 802. In this embodiment, the minimum required width is 3 mm. The thickness is set to 10 mm in consideration of workability.

The assembling process will be described.

1. Thermal conductive grease 803 is applied to the lower surface of metal base 702.

2. In order not to cover the heat sink side mounting hole 804 of the heat sink 801, a thin plate 7
Put two 04.

3. The module is lowered in accordance with the position of the heat sink side mounting hole 804. 4. Pass through the mounting screw 802 and lightly screw it.

5. The end surface of the thin plate 704 is the mounting screw 80
The thin plate 704 is slid toward the center of the module until it slightly hits 2.

6. Fully tighten the mounting screw 802.

As shown in FIG. 8, a moment 805 acts by the force of the final tightening so as to bring the center of the metal base 702 closer to the heat sink 801.

In this embodiment, since the thin plate 704 is thicker than the projection 117 of the first embodiment, the moment is larger than that of the first embodiment. The amount of protrusion around the base is appropriately determined depending on the module size, the material and thickness of the base, and the required grease thickness. In our study, 20 μm to 200 μm
The effect appears between μm.

(Embodiment 3) A third embodiment of the present invention will be described with reference to FIG.

In the third embodiment, the mounting holes 904 are arranged around the module 903. As a result, the protrusions 905 are formed on the entire outer peripheral portion of the metal base.
In Examples 1 and 2, the base warpage when tightened is cylindrical, whereas in this example it is mortar-shaped,
There is a similar effect. However, since the moment generated from the fastening force of the mounting hole 904 has elements that suppress each other, the effect is smaller than the above two examples.

Of course, the projection 905 does not need to be provided on the entire circumference, but may be formed only near the mounting hole 904.
In that case, the excess grease can be guided outside using the portion where the protrusion 905 is not formed. further,
The projections 905 do not need to be formed corresponding to all the mounting holes 904, and may be provided as appropriate.

(Embodiment 4) A fourth embodiment of the present invention will be described with reference to FIGS.

FIG. 10 shows the module according to the fourth embodiment viewed obliquely from below. In this embodiment, three mounting holes 1004 are arranged in two rows. Therefore, the protrusion 1005 is in the form of two stripes. The feature of this embodiment lies in a central projection 1006. Central projection 1006
There are 12 in the center of the module. The height of the projection 1005 is 100 μm, whereas the height of the central projection 1006 is 50 μm. The shape forms part of a sphere, with a bottom diameter of 10 mm.

FIG. 11 shows a cross section taken at the center of the central projection 1006 in FIG. Central projection 10
06 three sections are visible. There are three rows of semiconductor elements 1105 inside the module 1003, and the central protrusion
06 is present. The heat generated by module 1003 is
Since most of the heat is from the semiconductor element 1105, it is effective to reduce the thickness of the heat conductive grease 1102 immediately below the semiconductor element 1105 to improve the thermal performance. Central projection 1006
Are arranged for such a purpose.

(Embodiment 5) A fifth embodiment of the present invention will be described with reference to FIG.

FIG. 12 is a sectional view of a module mounting structure according to the fifth embodiment. It is almost the same as the second embodiment. This embodiment is different from the second embodiment in that a column 1207 reaching the metal base 1202 is provided at the center of the resin case 1201. Providing the pillar 1207 at the center in this way ensures the effect of keeping the thickness of the heat conductive grease 1204 at the center of the metal base 1202 small.

Of course, the column 1207 need not be a single column as here. Multiple pillars may be used. The column 1207 is desirably located at the center of the resin case 1201, but is not necessarily located at the center. Further, the cross-sectional shape of the pillar 1207 is rectangular, square,
Any shape such as a circle and an ellipse may be used, and the thickness of the upper portion and the lower portion may be different. Of course, a thick barrel type at the center or a thin thread-wound type at the center may be used. Further, a structure in which the inside of the module is separated by columns may be used. That is, the pillar 1207 has a shape extending to the module size in the direction perpendicular to the paper surface.

However, this structure reduces the usable area inside the module. For this reason, in the present embodiment, pillars are provided at two points, which are intersections when the module is divided into six. The thickness is 2 mm, and the cross-sectional shape is square.

[0054]

According to the present invention, it is possible to provide a power semiconductor module capable of reducing the grease thickness when attached to a member such as a heat sink.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a means according to the present invention.

FIG. 3 is a sectional view showing a means according to the present invention.

FIG. 4 is a sectional view showing a first embodiment of the present invention.

FIG. 5 is a sectional view showing a first embodiment of the present invention.

FIG. 6 is a graph showing a gap between a module and a heat sink according to the first embodiment of the present invention.

FIG. 7 is a perspective view showing a second embodiment of the present invention.

FIG. 8 is a sectional view showing a second embodiment of the present invention.

FIG. 9 is a perspective view showing a third embodiment of the present invention.

FIG. 10 is a perspective view showing a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing a fourth embodiment of the present invention.

FIG. 12 is a sectional view showing a fifth embodiment of the present invention.

[Explanation of symbols]

101: resin case A, 102: resin case B, 103
... Emitter terminals A, 104 ... Emitter terminals B, 105 ...
Emitter terminals C, 106: Collector terminal A, 107: Collector terminal B, 108: Collector terminal C, 109: Auxiliary emitter terminal, 110: Gate terminal, 111: Auxiliary collector terminal, 112, 806, 1104: Mounting sleeve, 113 ... filled resin, 114, 202, 702, 9
02,1002,1202 ... metal base, 115,30
4, 703, 904, 1004 ... mounting holes, 116 ...
Case fixing screw, 117, 905, 1005 ... projection, 2
01, 701, 901, 1001, 1201 ... resin case, 203, 903, 1003 ... module, 204,
503, 803, 1102, 1204: thermal conductive grease, 205, 502, 801, 1101, 1203: heat sink, 206, 501, 802, 1103, 120
5 mounting screw, 207 external pressure arrow, 208 internal case transmission path arrow, 209 repulsive force of thermal conductive grease, 301, 303 member, 302 spacer, 305
... Tightening force, 306, 505, 805, 1107, 12
08: moment, 504, 804: mounting holes on the heat sink side, 704, 1206: thin plate, 1006: central projection, 1105: semiconductor element, 1106: wiring board, 12
07 ... pillar.

Claims (9)

[Claims] 1. A power semiconductor module in which a mounting hole is arranged at a peripheral portion of a bottom surface, wherein the power semiconductor module has a projection on a bottom surface of the module closer to the peripheral side than the mounting hole. 2. The method according to claim 1, wherein said projection has a height of 20 μm or more.
2. The power semiconductor module according to claim 1, wherein the size is not more than 00 microns. 3. The module according to claim 1, wherein the mounting holes are disposed on two sides of the module bottom surface parallel to each other, and the projection is provided over the entire length of the two sides on which the mounting holes are disposed. Power semiconductor module. 4. The power semiconductor module according to claim 1, wherein a projection is provided on a bottom surface of the module immediately below the semiconductor element inside the module. 5. The power semiconductor module according to claim 1, wherein a column extending from the top surface of the module to the bottom surface of the module is mounted inside the module. 6. The power semiconductor module according to claim 1, wherein the mounting member is filled with grease between the mounting member and the mounting member, and is tightened by a screw passing through the mounting hole. A mounting structure for a power semiconductor module. 7. A mounting structure for mounting a power semiconductor module having a mounting hole at a peripheral portion of a bottom surface on a mounting member, wherein the power semiconductor module is mounted between the module bottom surface and the mounting member on a peripheral side of the mounting hole. A thin plate sandwiched between the power semiconductor module and the mounting member is filled with grease, and the power semiconductor module is fastened to the mounting member by a screw passing through the mounting hole. Semiconductor module mounting structure. 8. The thin plate having a thickness of 20 microns or more,
8. The mounting structure for a power semiconductor module according to claim 7, wherein the size is not more than 00 microns. 9. The module according to claim 7, wherein said mounting holes are disposed on two sides of said module bottom surface parallel to each other, and said thin plate is provided over the entire length of said two sides on which said mounting holes are disposed. Mounting structure of power semiconductor module.