JP2013089711A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a semiconductor device which prevents the increase of heat resistance between a semiconductor module and a cooling device.SOLUTION: In a semiconductor device fixing a semiconductor module 10 to a cooling device 30 while pressurizing the semiconductor module 10 with a flat spring 20, at least more than half of areas of upper surfaces of semiconductor elements 12 is disposed in an outer periphery 24a of a pressurizing part 24 of the flat spring 20, and the semiconductor elements 12, which have a significant impact on heat resistance change, is intensively pressurized from the upper surface 10a of the semiconductor module 10. This structure inhibits the displacement of the semiconductor module 10 located immediately below the semiconductor elements 12 and allows the semiconductor module 10 to stably adhere to the cooling device 30. As a result, the increase of heat resistance between the semiconductor module 10 and the cooling device 30 is prevented.

Description

  The present invention relates to a semiconductor device, and more particularly to a semiconductor device in which a semiconductor module is screwed and fixed to a cooling device while being pressed by a leaf spring.

  A mobile device such as an electric vehicle or a hybrid vehicle is equipped with a semiconductor device in which a semiconductor module in which power semiconductor elements are combined is fixed to a cooling device. In such a semiconductor device, when the block-shaped housing of the semiconductor module is fixed to the cooling device, heat conduction grease is usually interposed between the semiconductor module and the cooling device.

  However, the thermal conductivity of the thermal conductive grease is usually about 1 W / mK to 5 W / mK, which is much higher than that of copper (Cu) or aluminum (Al) (400 W / mK and 200 W / mK, respectively). Small. For this reason, if the heat conductive grease remains in a partially thick state between the semiconductor module and the cooling device, the thermal resistance between the semiconductor module and the cooling device increases, which is not preferable.

  The semiconductor module is fixed to the cooling device by inserting a screw into a through hole provided in the center of the semiconductor module. To prevent the heat conduction grease from partially thickening, the semiconductor module is mounted on the cooling device. It is necessary to press evenly against the surface. However, since the bottom surface of the semiconductor module is not completely flat, and the resin-sealed casing has nonuniform rigidity, it is difficult to press it uniformly against the mounting surface. As a result, a pressing force is applied only to the periphery of the screw, and as the distance from the screw increases, there is a problem that the entire semiconductor module does not adhere to the mounting surface of the cooling device.

  For example, in the semiconductor device presented in Patent Document 1, the screw pressure is transmitted to the periphery of the semiconductor module by inserting the screw through a pent roof type leaf spring arranged so as to substantially cover the semiconductor module. I am doing so. However, with a pent roof type leaf spring, it is not possible to uniformly apply a spring pressure to the semiconductor module.

  Therefore, in recent years, a technique has been proposed in which a spring force is uniformly applied to a semiconductor module using a leaf spring (disc spring) having a truncated cone-shaped pressurizing portion that is a rotationally symmetric body. For example, Patent Document 2 includes a leaf spring having a truncated cone-shaped pressurizing portion and a spring retainer having a spring contact portion that keeps a constant interval with respect to the upper surface of the semiconductor module. A semiconductor device that suppresses and improves the controllability of the spring pressure has been proposed.

Japanese Patent No. 3725103 JP 2011-35265 A

  However, when the pressurizing part uses a truncated cone-shaped leaf spring, the spring pressure cannot be applied to the four corners of the block-shaped semiconductor module, and the four corners of the semiconductor module can be brought into close contact with the mounting surface of the cooling device. difficult. Therefore, in a high temperature environment, the four corners of the semiconductor module are greatly deformed by heat compared to the portion pressed by the spring. In particular, when semiconductor elements are arranged in the vicinity of the four corners, there is a problem in that the displacement of the semiconductor module increases immediately below it, the adhesion between the semiconductor module and the cooling device decreases, and the thermal resistance increases. Further, the semiconductor module is repeatedly displaced, so that the pumping out phenomenon of the heat conduction grease becomes remarkable, and there is a problem that durability against a temperature cycle is lowered.

  The present invention has been made to solve the above-described problems. In a semiconductor device in which a semiconductor module is fixed to a cooling device while being pressed by a leaf spring, a semiconductor element having a large influence on a change in thermal resistance is provided. An object of the present invention is to obtain a semiconductor device that can be intensively pressurized and can prevent an increase in thermal resistance between the semiconductor module and the cooling device.

  According to a first aspect of the present invention, there is provided a semiconductor device in which a semiconductor element is sealed with a resin, a semiconductor module having a first through hole in a central portion, and a second through hole in the central portion that is disposed on an upper surface side of the semiconductor module. A frustoconical plate spring, a cooling device that is disposed on the lower surface side of the semiconductor module and has a screw hole in the center, and is screwed into the screw hole through the first through hole and the second through hole. And a screw for fixing the leaf spring to the cooling device. The leaf spring has a bottom portion having a second through hole, an upright portion that rises from the outer periphery of the bottom portion, and a pressing portion that extends from the upper end of the upright portion to the outside in a truncated cone shape and presses the upper surface of the semiconductor module. It is arranged so that more than half of the area of the upper surface falls within the outer periphery of the pressing part, and is pressed from the upper surface of the semiconductor module.

  According to a third aspect of the present invention, there is provided a semiconductor device in which a semiconductor element mounted on a heat spreader is resin-sealed and has a first through hole in the center, and is disposed on the upper surface side of the semiconductor module. A frustoconical leaf spring having a second through hole in the central portion, a cooling device disposed on the lower surface side of the semiconductor module and having a screw hole in the central portion, and the first and second through holes. A screw that is screwed into the screw hole and fixes the semiconductor module and the leaf spring to the cooling device is provided. The leaf spring has a bottom portion having a second through hole, an upright portion that rises from the outer periphery of the bottom portion, and a pressure portion that extends from the upper end of the upright portion to the outside in a truncated cone shape and pushes the upper surface of the semiconductor module. It is arranged so that more than half of the area is within the outer periphery of the pressurizing part, and is pressed from the upper surface of the semiconductor module.

  According to the semiconductor device of the first aspect of the present invention, since the semiconductor element is disposed so that more than half of the area of the upper surface of the semiconductor element falls within the outer periphery of the pressing portion of the leaf spring, the influence on the change in thermal resistance is affected. Pressure on a large semiconductor element can be intensively applied, and displacement of the semiconductor module immediately below the semiconductor element can be suppressed. As a result, the semiconductor module can be stably adhered to the cooling device, and an increase in thermal resistance between the semiconductor module and the cooling device can be prevented.

  According to the semiconductor device of the third aspect of the present invention, since it is arranged so that more than half of the area of the upper surface of the heat spreader on which the semiconductor element is placed falls within the outer periphery of the pressing portion of the leaf spring, Even when the pressure position cannot be limited to the semiconductor element, a plurality of semiconductor elements can be pressed together, and the displacement of the semiconductor module immediately below the semiconductor element can be suppressed. As a result, the semiconductor module can be stably adhered to the cooling device, and an increase in thermal resistance between the semiconductor module and the cooling device can be prevented.

It is sectional drawing which shows the semiconductor device which concerns on Embodiment 1 of this invention. It is sectional drawing which shows an example of the internal structure of the semiconductor module which concerns on Embodiment 1 of this invention. It is a top view which shows the positional relationship of the pressurization part of the semiconductor element and leaf | plate spring in the semiconductor device which concerns on Embodiment 1 of this invention. It is a top view which shows the positional relationship of the pressurization part of the semiconductor element and leaf | plate spring in the semiconductor device which concerns on Embodiment 1 of this invention. It is a top view which shows the positional relationship of the pressurization part of the semiconductor element and leaf | plate spring in the semiconductor device which is a comparative example of this invention. It is a top view which shows the semiconductor device which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
The semiconductor device according to the first embodiment of the present invention will be described below based on the drawings. FIG. 1 is a cross-sectional view showing the semiconductor device according to the first embodiment, and FIG. 2 is a cross-sectional view showing an example of the internal structure of the semiconductor module according to the first embodiment. In addition, in the figure, the same code | symbol is attached | subjected to the same part. The semiconductor device 100 according to the first embodiment is a semiconductor device used for a moving body such as an electric vehicle or a hybrid vehicle. As shown in FIG. 1, the semiconductor module 10, the leaf spring 20, the cooling device 30, and the screw 40.

  As shown in FIG. 2, the semiconductor module 10 has a first through hole 11 at the center thereof. A plurality of semiconductor elements 12 mounted on the semiconductor module 10 are placed on a heat spreader 13 and soldered. The heat spreader 13 disperses changes in thermal resistance of the plurality of semiconductor elements 12. A surface electrode (not shown) of the semiconductor element 12 is connected to the power connection terminal 14 and the output terminal 16 directly or via a wire 15. These semiconductor element 12, heat spreader 13, wire 15 and the like are sealed with a resin (for example, epoxy resin) 17.

  The truncated conical plate spring 20 is disposed on the upper surface 10 a side of the semiconductor module 10, and has a second through hole 21 at the center of the bottom 22 thereof. The leaf spring 20 has an upright portion 23 that rises from the outer periphery of the bottom portion 22, and a pressing portion 24 that extends in a truncated cone shape from the upper end of the upright portion 23 and pushes the upper surface 10 a of the semiconductor module 10. The pressurizing force of the pressurizing unit 24 is designed to be a predetermined amount depending on the length of the upright unit 23 and the spring constant. Further, the outer periphery 24 a of the pressurizing unit 24 is designed to have a smaller diameter than each side of the upper surface 10 a of the semiconductor module 10.

  The cooling device 30 disposed on the lower surface side of the semiconductor module 10 has a screw hole 31 at the center of the upper surface. The screw 40 is screwed into the screw hole 31 of the cooling device 30 through the second through hole 21 of the plate spring 20 and the first through hole 11 of the semiconductor module 10, and the semiconductor module 10 and the plate spring 20 are connected to the cooling device 30. Fix it. In addition, between the semiconductor module 10 and the cooling device 30, heat conduction grease (not shown) is disposed.

  In the semiconductor device 100 configured as described above, the pressurizing unit 24 of the leaf spring 20 pressurizes the upper surface 10a of the semiconductor module 10 with the minimum required load obtained experimentally. The strength of the load is adjusted by the amount of deflection of the leaf spring 20, and screws are tightened so that a predetermined amount of deflection is obtained. Thereby, the pressing force of the screw 40 is transmitted to the periphery, and a uniform and appropriate pressing force is applied to the upper surface 10a of the semiconductor module 10.

  Next, the positional relationship between the semiconductor element and the pressing portion of the leaf spring in the semiconductor device according to the first embodiment will be described with reference to FIGS. In the example of the semiconductor device 100 shown in FIG. 3, all of the plurality of semiconductor elements 12 are arranged so that half or more of the area of the upper surface thereof falls within the outer periphery 24 a of the pressing portion 24 of the leaf spring 20.

In the example of the semiconductor device 100 a shown in FIG. 4A, the semiconductor element 12 a in which more than half of the area of the upper surface is within the outer periphery 24 a of the pressurizing unit 24 and the entire area of the upper surface of the pressurizing unit 24. The semiconductor elements 12b contained in the outer periphery 24a are mixed. Further, in the example of the semiconductor device 100 b shown in FIG. 4B, the entire upper surface area of the four semiconductor elements 12 c is arranged so as to enter the outer periphery 24 a of the pressurizing unit 24.

  Next, as a comparative example, the positional relationship between a semiconductor element and a pressing portion of a leaf spring in a conventional semiconductor device will be described with reference to FIG. In the semiconductor device 100c of the comparative example, the semiconductor element 12d is disposed in the vicinity of the four corners of the semiconductor module 10 to which the pressure applied by the leaf spring 20 is not applied. For this reason, more than half of the area of the upper surface of the semiconductor element 12 d is disposed outside the outer periphery 24 a of the pressurizing unit 24. In such a positional relationship, it is not possible to sufficiently pressurize the semiconductor element 12d that has a large influence on the thermal resistance change.

  As a result, in a high temperature environment, the displacement of the semiconductor module 10 immediately below the semiconductor element 12d disposed in the vicinity of the four corners increases, the adhesion between the semiconductor module 10 and the cooling device 30 decreases, and the thermal resistance increases. Will occur. Furthermore, repeated displacement of the semiconductor module 10 causes the pumping-out phenomenon of the heat conduction grease to become remarkable, and the durability against the temperature cycle decreases.

  In contrast to this comparative example, in the first embodiment, as shown in FIGS. 3 and 4, the semiconductor element 12 (12 a, 12 b, 12 c) is pressed against the leaf spring 20 by at least half of the area of the upper surface thereof. It arrange | positions so that it may enter in the outer periphery 24a of the part 24, and it is made to pressurize mainly on the semiconductor element 12 with the large influence on a thermal resistance change from the upper surface 10a of the semiconductor module 10. FIG.

  Therefore, according to the first embodiment, the displacement of the semiconductor module 10 immediately below the semiconductor element 12 can be suppressed, and the semiconductor module 10 can be stably adhered to the cooling device 30. As a result, an increase in the thermal resistance between the semiconductor module 10 and the cooling device 30 can be prevented, and the thermal resistance can be stabilized in a low state.

  Moreover, since the displacement of the semiconductor module 10 immediately below the semiconductor element 12 can be reduced, the pumping-out phenomenon of the heat conduction grease applied to that portion can be suppressed. As a result, stable heat conduction performance can be ensured over a long period of time, and a decrease in durability against temperature cycles can be prevented.

Embodiment 2. FIG.
FIG. 6 is a top view showing a semiconductor device according to the second embodiment of the present invention. In FIG. 6, the same parts as those in FIG. In FIG. 6, the semiconductor element is not shown, but the semiconductor device 100 d according to the second embodiment has the semiconductor element mounted on the heat spreader 13.

  In the first embodiment, the semiconductor element 10 is disposed on the semiconductor element 12 from the upper surface 10a of the semiconductor module 10 by arranging so that more than half of the area of the upper surface of the semiconductor element 12 falls within the outer periphery 24a of the pressing portion 24 of the leaf spring 20. The pressure was intensively applied. However, since the semiconductor module 10 includes a composite of a plurality of semiconductor elements, it may be difficult to limit the pressing position by the pressing unit 24 on the semiconductor elements.

Therefore, in the second embodiment, the heat spreader 13 on which the semiconductor element is placed is arranged so that half or more (preferably all) of the area of the upper surface of the heat spreader 13 falls within the outer periphery 24a of the pressing portion 24 of the leaf spring 20, The pressure is applied from the upper surface of the semiconductor module 10. In the semiconductor device 100d configured as described above, the pressurizing unit 24 of the leaf spring 20 pressurizes the upper surface of the semiconductor module 10 with the minimum required load obtained experimentally. Thereby, the applied pressure of the screw 40 is transmitted to the periphery, and a uniform and appropriate applied pressure is applied to the upper surface of the semiconductor module 10.

  According to the second embodiment, even when the pressing position cannot be limited to the semiconductor element by pressing more than half of the area of the heat spreader 13 on which the plurality of semiconductor elements are mounted, The semiconductor elements can be pressurized together. Thereby, the displacement of the semiconductor module 10 can be suppressed, and the semiconductor module 10 can be stably adhered to the cooling device 30. Therefore, the same effect as in the first embodiment can be obtained.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted. For example, by combining the first embodiment and the second embodiment, more than half of the area of the upper surface of the semiconductor element 12 and more than half of the area of the heat spreader 13 are in the outer periphery 24a of the pressing portion 24 of the leaf spring 20. It may be arranged to enter.

  The present invention can be used as a semiconductor device used for a moving body such as an electric vehicle or a hybrid vehicle.

10 semiconductor module, 10a top surface, 11 first through hole,
12, 12a, 12b, 12c, 12d semiconductor element, 13 heat spreader,
14 power connection terminals, 15 wires, 16 output terminals, 17 resin, 20 leaf springs,
21 2nd through-hole, 22 bottom part, 23 upright part, 24 pressurization part, 24a outer periphery,
30 cooling device, 31 screw hole, 40 screw,
100, 100a, 100b, 100c, 100d Semiconductor device.

Claims (3)

A semiconductor module in which a semiconductor element is sealed with a resin and having a first through hole in a central portion; a truncated conical leaf spring disposed on an upper surface side of the semiconductor module and having a second through hole in the central portion; and the semiconductor A cooling device disposed on the lower surface side of the module and having a screw hole in the center, and screwed into the screw hole through the first through hole and the second through hole, and the semiconductor module and the leaf spring are With screws to secure the cooling device,
The leaf spring has a bottom portion having the second through hole, an upright portion rising from an outer periphery of the bottom portion, and a pressure portion that extends in a truncated cone shape outward from the upper end of the upright portion and presses the upper surface of the semiconductor module. The semiconductor device is arranged so that more than half of the area of the upper surface of the semiconductor element falls within the outer periphery of the pressurizing portion and is pressurized from the upper surface of the semiconductor module.   2. The semiconductor module according to claim 1, wherein the semiconductor element is placed on a heat spreader, and is arranged such that more than half of the area of the upper surface of the heat spreader falls within the outer periphery of the pressurizing unit. The semiconductor device described. A semiconductor element mounted on the heat spreader is resin-sealed, a semiconductor module having a first through hole in the center, and a truncated cone type having a second through hole in the center disposed on the upper surface side of the semiconductor module A plate spring, a cooling device disposed on the lower surface side of the semiconductor module and having a screw hole at the center, and screwed into the screw hole through the first through hole and the second through hole. A screw for fixing the module and the leaf spring to the cooling device;
The leaf spring has a bottom portion having the second through hole, an upright portion rising from an outer periphery of the bottom portion, and a pressure portion that extends in a truncated cone shape outward from the upper end of the upright portion and presses the upper surface of the semiconductor module. The semiconductor device is characterized in that more than half of the area of the upper surface of the heat spreader is disposed within the outer periphery of the pressurizing portion and is pressurized from the upper surface of the semiconductor module.

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