JP2017139429A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique relevant to a semiconductor device in which a power card and a cooler are laminated by sandwiching an insulating plate therebetween and a heat-transfer agent is coated between the power card and the insulating plate and between the insulating plate and the cooler, and a load is applied in a direction where the power card, the insulating plate and the cooler are laminated, to simply prevent the heat-transfer agent between the insulating plate and the cooler from spreading.SOLUTION: A semiconductor device disclosed in the present specification includes: a power card 10c having a groove 13a on a lateral face 12c opposite to an insulating plate 21; a first heat-transfer agent 23a which is coated between the lateral face and the insulating plate 21 and prevented from spreading by the groove 13a; and a second heat-transfer agent 24a which is coated between the insulating plate 21 and a cooler 3c and has viscosity higher than that of the first heat-transfer agent 23a.SELECTED DRAWING: Figure 2

Description

  In the technology disclosed in this specification, a power card and a cooler are stacked with an insulating plate interposed therebetween, and a heat transfer agent is applied between the power card and the insulating plate, and between the insulating plate and the cooler, The present invention relates to a semiconductor device in which a load in the stacking direction is applied to the stacked body.

  The above-described type of semiconductor device has a high cooling performance with respect to the semiconductor element accommodated in the power card, and is used, for example, in an inverter of a drive system of an electric vehicle. An example of such a semiconductor device is disclosed in Patent Document 1.

  Patent Document 1 discloses a power conversion device in which an insulating plate and a cooler are stacked on a side surface of a power card with a heat sink exposed on the side surface via heat radiation grease (corresponding to the heat transfer agent of the present application) Corresponding to a semiconductor device). A load is applied to the laminated body of the power card, the insulating plate, and the cooler in the laminating direction, and the heat dissipating grease is thinly extended. In such a power conversion device, a heat sink is deformed by thermal expansion due to heat generation of the semiconductor element, and a phenomenon occurs in which heat radiation grease between the heat sink and the insulating plate is pushed out by the deformed heat sink and diffuses around the heat sink. Specifically, this is a phenomenon in which part of the extruded heat dissipation grease is broken from the lump of grease, and even if the deformation of the heat sink returns, the broken heat dissipation grease piece does not return to its original location. In Patent Document 1, in order to prevent the above-described phenomenon, a convex portion that protrudes toward the insulating plate on the exposed surface of the heat sink and has a closed loop shape when the surface is viewed in plan view. The providing technique is disclosed. Even when the heat sink thermally expands due to this convex portion, the heat radiation grease remains in the space between the inside of the convex portion and the insulating plate, and the above phenomenon is prevented.

  Patent Document 2 discloses a semiconductor device in which a semiconductor module is fixed to the bottom of a housing via grease. In this semiconductor device, an annular groove is formed in a region of the bottom surface facing the semiconductor module. The casing is deformed by thermal expansion, and the grease (heat transfer agent) inside the groove pushed out by the deformation is blocked by the grease accumulated in the groove and is difficult to diffuse to the outside of the groove.

JP2015-208113A JP 2013-138113 A

  With the technique disclosed in Patent Document 1, diffusion of heat radiation grease between the heat sink and the insulating plate can be prevented. However, in the technique disclosed in Patent Document 1, when the heat sink thermally expands, the heat sink contacts the insulating plate, and the insulating plate can be deformed by a force acting from the heat sink. Therefore, there is a possibility that the heat radiation grease between the insulating plate and the cooler is pushed out and diffused by the deformed insulating plate. In order to prevent the diffusion of heat radiation grease between the insulating plate and the cooler, it is conceivable to provide the insulating plate or the cooler with grooves or protrusions as disclosed in Patent Documents 1 and 2, but the semiconductor device This increases the manufacturing cost. In this specification, a power card and a cooler are stacked with an insulating plate interposed therebetween, and a heat transfer agent is applied between the power card and the insulating plate, and between the insulating plate and the cooler, and is insulated from the power card. A technique for easily preventing diffusion of a heat transfer agent between an insulating plate and a cooler is provided for a semiconductor device in which a load is applied in the direction in which the plate and the cooler are stacked.

  A semiconductor device disclosed in the present specification is a power card that contains a semiconductor element, and a power card in which one surface of a heat radiating plate in contact with the semiconductor element is exposed on one side surface of the main body. And a cooler facing one side including the heat sink with the insulating plate interposed therebetween, and a load member for loading a power card, a laminate of the insulator and the cooler in the stacking direction thereof. A first heat transfer agent is applied between one side of the power card and the insulating plate, and a second heat transfer agent is applied between the insulating plate and the cooler. And the diffusion prevention means which prevents the spreading | diffusion of a 1st heat transfer agent is provided in the one side of a power card, and the viscosity of a 2nd heat transfer agent is larger than the viscosity of a 1st heat transfer agent. Here, the “diffusion prevention means” is, for example, a protrusion or groove provided so as to surround the heat sink when one side of the power card is viewed in plan.

  According to this configuration, the diffusion preventing means provided on the surface of the power card prevents the first grease between the surface of the power card and the insulating plate from diffusing. Furthermore, even if the insulating plate is deformed by the force acting from the thermally expanded heat radiating plate by applying the second grease having a viscosity higher than that of the first grease between the cooler and the insulating plate, the deformed insulating plate A part of the extruded second grease is hardly broken off from the lump of grease, and the second grease is prevented from diffusing. Thereby, it is possible to easily prevent the second grease between the cooler and the insulating plate from diffusing without providing the diffusion preventing means on the cooler or the insulating plate.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a perspective view of the semiconductor device of an Example. It is a fragmentary sectional view of the semiconductor device of an example. It is the graph which showed the characteristic of the viscosity with respect to the temperature of a heat-transfer agent. It is a table | surface which shows the experimental result whether the spreading | diffusion of a heat-transfer agent generate | occur | produced.

  A semiconductor device according to an embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of a semiconductor device 100 according to an embodiment. The semiconductor device 100 includes a stacked body 2 in which a plurality of power cards 10a-10f and a plurality of coolers 3a-3g are stacked, and a case 31 that houses the stacked body 2. The case 31 is drawn with imaginary lines so that the entire laminate 2 can be seen. Further, FIG. 1 shows one power card 10c (and insulating plates 21 and 22) extracted from the laminate 2 for easy understanding. In FIG. 1, an XYZ coordinate system is drawn, and the X-axis direction coincides with the direction in which the power cards 10a-10f and the coolers 3a-3g are stacked (hereinafter referred to as a stacking direction).

  The power cards 10a-10f and the coolers 3a-3g are both flat plate types, and are stacked such that the flat surfaces having the largest areas face each other among the plurality of side surfaces. The power cards 10a-10f and the coolers 3a-3g are alternately stacked one by one, and the coolers 3a, 3g are located at both ends in the stacking direction. For example, the power card 10c is sandwiched between the cooler 3c and the cooler 3d. Furthermore, insulating plates 21 and 22 are sandwiched between the cooler 3c and the power card 10c and between the cooler 3d and the power card 10c, respectively. That is, the power card 10c is opposed to the cooler 3c (3d) with the insulating plate 21 (22) interposed therebetween. The material of the insulating plate 21 (22) is, for example, a high thermal conductive ceramic. Although details will be described later, a heat transfer agent is applied between the insulating plate 21 (22) and the power card 10c and between the insulating plate 21 (22) and the cooler 3c (3d). In this embodiment, the heat transfer agent is a gel or a fluid. The heat transfer agent is not shown in FIG. An insulating plate is similarly sandwiched between the other power card and each cooler of the two coolers that sandwich the other power card on both sides in the stacking direction, and the other power card is also insulated. It faces each cooler across the plate.

  The configuration of the power cards 10a-10f will be described. The power cards 10a to 10f have the same configuration. Hereinafter, the power card 10c will be described as a representative. The power card 10c includes four semiconductor elements and a resin main body 12 containing the four semiconductor elements. The main body 12 is formed by injection molding and seals the semiconductor element. Specifically, the four semiconductor elements are two transistors Ta and Tb and two diodes Da and Db. On the side surface 12c facing the insulating plate 21 of the main body 12, the heat radiating plates 16a and 16b are exposed. The material of the heat sinks 16a and 16b is a metal having a high thermal conductivity, for example, copper. In the side surface 12c, annular grooves 13a and 13b are provided. The groove 13a (13b) is provided so as to surround the heat sink 16a (16b) when the side surface of the main body is viewed in plan. Similarly, a heat radiating plate and a groove (not shown in FIG. 1) are also provided on the side surface 12d facing the insulating plate 22 of the main body 12, that is, the side surface located behind the side surface 12c. Note that three electrode terminals 7a, 7b, 7c extend from the upper surface (the surface facing the positive direction of the Z axis in the figure) of the power card 10c, and the lower surface (the surface facing the negative direction of the Z axis direction in the figure). The control terminal 29 extends from.

  The configuration of the coolers 3a-3g will be described. A flow path extending in the Y-axis direction is formed inside each cooler, and the refrigerant passes through the flow path. Each cooler cools the semiconductor element of the power card facing each cooler with the insulating plate interposed therebetween by the refrigerant passing through the flow path. The material of each cooler is a material having high thermal conductivity, for example, aluminum. The coolers 3a to 3g are connected by connecting pipes 5a and 5b. A supply pipe 4a and a discharge pipe 4b are connected to the cooler 3a at one end in the stacking direction. The refrigerant supplied through the supply pipe 4a is distributed to the coolers 3a-3g through the connection pipe 5a. The refrigerant absorbs heat from the power cards facing each other across the insulating plate while passing through each cooler. The refrigerant that has passed through the coolers 3a to 3g is collected in the connecting pipe 5b and discharged from the discharge pipe 4b. Note that the refrigerant is a liquid, typically water.

  The semiconductor device 100 further includes a leaf spring 32 disposed between the cooler 3g located at one end in the stacking direction of the stacked body 2 and the inner surface of the case 31. The laminate 2 is pressed against the inner surface of the case 31 by the load of the leaf spring 32. Thereby, a load is applied to the stacked body 2 from both sides in the stacking direction. The load is, for example, 3 [kN]. A heat transfer agent is applied between the insulating plate and the power card, and between the insulating plate and the cooler. However, a high load of 3 [kN] extends the heat transfer agent layer thinly, Increase heat transfer efficiency from the insulation plate and insulation plate to the cooler. The thickness of the heat transfer agent layer stretched by the leaf spring 32 is, for example, 100 microns or less.

  A detailed structure between the power card, the insulating plate, and the cooler will be described with reference to FIG. FIG. 2 is a partial cross-sectional view of the power card 10c and the coolers 3c and 3d of FIG. 1 cut along a plane parallel to the XY plane of the coordinate system in the drawing and across the transistors Ta and Tb. The structure between the other power card and the two coolers sandwiching the other power card on both sides is the same as the structure described below.

  As shown in FIG. 2, one side of the heat sinks 16a and 16b is exposed flush with the side surface 12c on the side surface 12c of the main body 12 of the power card 10c. Also on the side surface 12d on the back side of the side surface 12c, one surface of the heat radiating plates 17a and 17b is exposed flush with the side surface 12d. The heat sinks 16 a and 17 a are in contact with the transistor Ta inside the main body 12, and the heat sinks 16 b and 17 b are in contact with the transistor Tb inside the main body 12. The heat of the transistor is transmitted to the heat sink that is in contact therewith. Further, since the insulating plate 21 is sandwiched between the side surface 12c where the heat sinks 16a and 16b of the power card 10c are exposed and the cooler 3c, the heat sinks 16a and 16b in contact with the transistor Ta are cooled. Insulation with the container 3c is ensured.

  A low-viscosity heat transfer agent 23 a is applied between the side surface 12 c of the main body 12 and the insulating plate 21. The viscosity of the low-viscosity heat transfer agent 23a is 250 to 350 [Pa · s] at room temperature. The low-viscosity heat transfer agent 23a is applied to the side surface 12c so as to cover the heat sinks 16a and 16b and the grooves 13a and 13b when viewed from the normal direction of the side surface 12c (that is, the X-axis direction). Therefore, the low-viscosity heat transfer agent 23a enters the grooves 13a and 13b. Similarly, a low-viscosity heat transfer agent 23b is applied between the side surface 12d of the main body 12 and the insulating plate 22, and the low-viscosity heat transfer agent 23b enters the grooves 14a and 14b.

  A high-viscosity heat transfer agent 24a is applied between the insulating plate 21 and the cooler 3c. The viscosity of the high-viscosity heat transfer agent 24a is 800 to 900 [Pa · s] at room temperature. That is, the viscosity of the high-viscosity heat transfer agent 24a is higher than that of the low-viscosity heat transfer agent 23a at room temperature. Similarly, a high-viscosity heat transfer agent 24b is applied between the insulating plate 22 and the cooler 3d.

  The characteristics of the low-viscosity heat transfer agent and the high-viscosity heat transfer agent will be described with reference to FIG. FIG. 3 is a graph showing the viscosity characteristics of the low-viscosity heat transfer agent and the high-viscosity heat transfer agent with respect to temperature. It should be noted that the graph shown in FIG. 3 is a schematic graph showing a tendency of viscosity with respect to a temperature within a predetermined temperature range (for example, 0 to 120 ° C.). As shown in FIG. 3, at a temperature within a predetermined temperature range, the viscosity of the high-viscosity heat transfer agent is larger than the viscosity of the low-viscosity heat transfer agent, and the viscosity of both heat transfer agents is an exponential function with respect to the decrease in temperature. Viscosity increases. Here, the viscosity of the high-viscosity heat transfer agent increases with a decrease in temperature at a large rate compared to the low-viscosity heat transfer agent. At low temperature T1 (for example, 20 ° C.), the difference between the viscosity of the high viscosity heat transfer agent and the viscosity of the low viscosity heat transfer agent is large. On the other hand, at a high temperature T2 (for example, 80 ° C.), the difference is small. That is, the high-viscosity heat transfer agent shows a higher viscosity than the low-viscosity heat transfer agent in the low temperature range, but shows a viscosity that is not much different from the low-viscosity heat transfer agent in the high temperature range.

  The effect of the present embodiment will be described. When the transistor Ta generates heat, the heat dissipation plate 16a of the power card 10c expands due to the heat transmitted from the transistor Ta. On the other hand, since the material of the insulating plate 21 is a ceramic having a smaller thermal expansion coefficient than copper, which is the material of the heat radiating plate 16a, it is difficult for the insulating plate 21 to thermally expand due to the heat generated by the transistor Ta. Therefore, when the heat radiating plate 16a expands, the space between the heat radiating plate 16a and the insulating plate 21 becomes narrow, and the low-viscosity heat transfer agent 23a pushed out by narrowing the space tends to diffuse outside the heat radiating plate 16a. To do. Here, the groove | channel 13a is provided in the circumference | surroundings of the heat sink 16a, and the low-viscosity heat transfer agent 23a has accumulated in the groove | channel 13a. The low-viscosity heat transfer agent 23a on the heat dissipation plate 16a pushed out by the expansion of the heat dissipation plate 16a is blocked by the low-viscosity heat transfer agent 23a accumulated in the groove 13a and hardly diffuses outside the groove 13a. That is, the groove 13a prevents diffusion of the low-viscosity heat transfer agent 23a on the heat radiating plate 16a.

  Here, since the movement of the low-viscosity heat transfer agent 23a to the outside is blocked by the groove 13a, the force for expanding the heat radiating plate 16a is transmitted to the insulating plate 21 via the low-viscosity heat transfer agent 23a. The insulating plate 21 may be deformed by this force. When the insulating plate 21 is deformed, the space between the insulating plate 21 and the cooler 3c is narrowed, and the high-viscosity heat transfer agent 24a pushed out by the narrowing of the space tends to diffuse to the outside of the insulating plate 21. Here, the high-viscosity heat transfer agent 24a is a high-viscosity heat transfer agent, and even if the heat transfer agent diffuses to the outside of the insulating plate 21, a part of the heat transfer agent diffused to the outside is not removed from the heat transfer agent lump. It is hard to cut. A part of the heat transfer agent easily returns to the original position after the thermal expansion of the heat radiating plate 16a is settled and the deformation of the insulating plate 21 is settled. This prevents the heat transfer agent between the insulating plate 21 and the cooler 3c from diffusing.

  Moreover, as shown in FIG. 3, the high-viscosity heat transfer agent 24a exhibits high viscosity characteristics at low temperatures. Since the high-viscosity heat transfer agent 24a is applied between the cooler 3c and the insulating plate 21, the temperature thereof is a low temperature close to the temperature of the cooler 3c even when the semiconductor device is driven. Even when the semiconductor device is driven, the viscosity of the high-viscosity heat transfer agent 24a is maintained high, so that the high-viscosity heat transfer agent 24a between the insulating plate 21 and the cooler 3c is prevented from diffusing.

  Further, in this embodiment, in order to prevent diffusion of the heat transfer agent between the cooler 3c and the insulating plate 21, a groove 13a as provided in the power card 10c is provided in the cooler 3c and the insulating plate 21. There is no need to provide it. Thereby, the increase in the manufacturing cost of the semiconductor device 100 can be suppressed, and the diffusion of the heat transfer agent between the cooler 3c and the insulating plate 21 can be easily prevented.

  The advantage of applying the low-viscosity heat transfer agent 23a between the heat radiating plate 16a and the insulating plate 21 will be further described. Since the low-viscosity heat transfer agent 23a has a lower viscosity than the high-viscosity heat transfer agent 24a, the low-viscosity heat transfer agent 23a easily flows along the surface of the heat radiating plate 16a. Easy to change to force. Therefore, compared with the case where the high-viscosity heat transfer agent 24a is applied between the heat radiating plate 16a and the insulating plate 21, the low-viscosity heat transfer agent 23a is applied to the insulating plate 21 via the heat transfer agent. The force to do can be kept small. Further, when a high-viscosity heat transfer agent is applied between both the heat sink 16a and the insulating plate 21 and between the insulating plate 21 and the cooler 3c, a higher load is required to extend the heat transfer agent thinly. The manufacturing cost increases due to an increase in the size of the leaf spring 32 or the like. Furthermore, as shown in FIG. 3, the viscosity of the high-viscosity heat transfer agent is not much different from the viscosity of the low-viscosity heat transfer agent in a high temperature situation when the semiconductor device is driven. That is, an increase in manufacturing cost can be suppressed by applying a low viscosity heat transfer agent between the heat radiating plate 16a and the insulating plate 21.

  With reference to FIG. 4, the result of the experiment which confirms the condition where a heat-transfer agent diffuses in the some heat-transfer agent from which the characteristic of the viscosity with respect to temperature is different is demonstrated. The inventors applied a plurality of heat transfer agents having different viscosity characteristics with respect to temperature between two metal plates, and repeatedly applied a cooling cycle of −40 ° C. to 105 ° C. for each heat transfer agent, The state of diffusion of the heat transfer agent was confirmed. The plurality of heat transfer agents are five types of heat transfer agents each having a viscosity of 300, 500, 800, 1000, 1050 [Pa · s] at normal temperature. In this experiment, the ratio of the weight of the heat transfer agent existing between the two metal plates after the experiment to the weight of the heat transfer agent existing between the two metal plates before the experiment is a predetermined ratio or more. In this case, it is determined that there is no diffusion of the heat transfer agent. FIG. 4 is a diagram showing the results of this experiment. As shown in FIG. 4, in this experiment, the result that there was no diffusion of the heat transfer agent in the heat transfer agent having a viscosity at room temperature of 800 [Pa · s] or more was obtained. By selecting a heat transfer agent having a normal temperature viscosity of 800 [Pa · s] or more as the high viscosity heat transfer agent 24a, diffusion of the heat transfer agent between the cooler 3c and the insulating plate 21 can be prevented.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. The grooves 13a and 13b provided on the side surface 12c of the main body 12 of the power card 10c are an example of the “diffusion prevention means” in the claims. Instead, an annular protrusion that surrounds the heat sink 16a (16b) may be provided on the side surface 12c of the main body 12 when viewed from the normal direction of the side surface 12c. Moreover, the groove | channel 13a (13b) may not be cyclic | annular, and should just be a groove | channel extended in the direction which cross | intersects the direction where a heat-transfer agent diffuses at least. Moreover, you may provide a groove | channel or a protrusion on one surface of the heat sink 16a (16b) exposed from the main body 12 instead of the side surface 12c of the main body 12. FIG. Generally speaking, it is only necessary that a diffusion preventing means for preventing diffusion of the heat transfer agent is provided on one side surface where one surface of the heat dissipation plate of the power card is exposed.

  The leaf spring 32 is an example of the “load member” in the claims. For example, the stacked body 2 may be compressed in the stacking direction by brackets that sandwich both end surfaces in the stacking direction in the stacking direction. In this case, the bracket is an example of the “load member” in the claims.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Laminated body 3a-3g: Cooler 4a: Supply pipe 4b: Discharge pipe 5a, 5b: Connection pipe 10a-10f: Power card 12: Main body 12c, 12d: Side surfaces 13a, 13b: Grooves 16a, 16b, 17a, 17b : Heat sinks 21, 22: insulating plates 23a, 23b: low viscosity heat transfer agent 24a, 24b: high viscosity heat transfer agent 31: case 32: leaf spring 100: semiconductor device Da, Db: diode Ta, Tb: transistor

Claims (1)

A power card containing a semiconductor element, and a power card in which one side of the heat sink contacting the semiconductor element inside the main body is exposed on one side of the main body,
A cooler facing the one side surface including the heat radiating plate across an insulating plate;
A load member that loads the power card, the insulating plate, and the stack of the coolers in the stacking direction;
With
A first heat transfer agent is applied between the one side surface of the power card and the insulating plate,
A second heat transfer agent is applied between the insulating plate and the cooler;
Diffusion prevention means for preventing diffusion of the first heat transfer agent is provided on the one side surface of the power card,
The viscosity of the second heat transfer agent is greater than the viscosity of the first heat transfer agent;
A semiconductor device.

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