JP7169246B2 - semiconductor equipment - Google Patents

Description

The technology disclosed in this specification relates to a semiconductor device. In particular, the present invention relates to a semiconductor device in which a gap between a power card and a cooler facing the power card is filled with grease.

In-vehicle semiconductor devices have been developed to control power applied to motors of hybrid automobiles, electric automobiles, and the like. The semiconductor device has a power card in which the semiconductor element and the heat transfer plate are covered with a resin package with one surface of the heat transfer plate exposed. Cool the curd. In order to reduce the thermal resistance between the heat transfer plate and the cooler, a technique of filling the gap between the heat transfer plate and the cooler with grease has been developed. This specification discloses a technique related to a semiconductor device in which a power card and a cooler are opposed to each other via grease.

When a semiconductor device is operated, the semiconductor elements generate heat, the heat transfer plate expands and becomes thicker, the distance between the heat transfer plate and the cooler decreases, and the grease is pushed out from between the heat transfer plate and the cooler. . When the semiconductor device stops operating, the semiconductor element is cooled, the heat transfer plate shrinks, the thickness decreases, the distance between the heat transfer plate and the cooler increases, and the grease is restored. Actually, when the distance increases, a phenomenon occurs in which part of the grease does not return completely. By repeating this, a phenomenon occurs in which the grease is removed and air bubbles enter between the heat transfer plate and the cooler. In this specification, this is referred to as grease removal.

Japanese Patent Laid-Open No. 2002-200001 discloses a technique for preventing the grease from coming off. In this technique, a plurality of spiral grooves are two-dimensionally arranged on the surface of either the power card filled with grease or the cooler. In this technology, the slippage of grease is suppressed by shortening the distance of the flat surface where grease easily moves due to the plurality of spiral grooves.

JP 2016-062917 A

The inventors considered the grease normally treated as a viscous fluid to be a viscoelastic body, clarified the characteristics of the grease when the grease escapes, and came up with the idea of suppressing the grease escape from the characteristics. A viscoelastic body has both viscous and elastic properties, unlike a viscous fluid. The inventors confirmed that the elasticity of the grease is a factor that causes the grease to return between the heat transfer plate and the cooler when the volume of the gap between the power card and the cooling plate returns to its original size. It was confirmed that the higher the temperature, the more the grease returned. In other words, it was confirmed that if the elasticity of the grease is high and the viscosity is low, the grease is difficult to come off, and conversely, if the elasticity of the grease is low and the viscosity is high, the grease is easy to come off.

Furthermore, the inventors paid attention to the loss tangent, which is one of the characteristics of the viscoelastic body. Here, the loss tangent is an index representing the relationship between viscosity and elasticity when a viscoelastic body is deformed. The lower the loss tangent, the more elastic the grease. Also, the higher the loss tangent of the grease, the higher the viscosity of the grease. That is, if the loss tangent is low, the grease will not come out easily, and if the loss tangent is high, the grease will come out easily. In other words, the loss tangent of grease has a correlation with ease of grease coming off. In addition, the inventors have found that the loss tangent is approximately proportional to the rate at which the volume of the space in which the grease exists has changed. That is, in order to increase the elasticity of the grease, it is effective to increase the volume of the space in which the grease exists.

In order to increase the volume of the space in which the grease exists, it is necessary to widen the gap between the heat transfer plate exposed on the surface of the power card and the cooler. If the gap is widened, the thermal resistance between the heat transfer plate and the cooler increases, degrading the heat radiation performance of the cooler.

On the other hand, in the semiconductor device disclosed in Patent Document 1, since the gap between the heat transfer plate and the cooler is narrow, the heat radiation performance of the cooler does not deteriorate. However, in the semiconductor device of Patent Document 1, a space for grease to exist cannot be secured, and the elasticity of the grease is reduced. That is, in the semiconductor device of Patent Document 1, the grease is easily removed. This specification discloses a semiconductor device capable of efficiently suppressing grease leakage by making use of the above-described characteristics of grease.

In the semiconductor device disclosed in this specification, the gap between the power card and the cooler facing the power card is filled with grease. The power card covers the semiconductor element and the heat transfer plate with a resin package with one surface of the heat transfer plate exposed. At least one of the face where the heat transfer plate of the power card is exposed and the facing face of the cooler has a plurality of crossings in a region overlapping with the semiconductor element when viewed in a direction orthogonal to the facing face. A microgroove is provided and an annular groove surrounding the semiconductor element is provided. Further, in this semiconductor device, the depth of the minute groove is shallower than the depth of the annular groove.

As will be described later with reference to FIG. 4, the amount of heat generated when the semiconductor element operates is large in the central portion of the semiconductor element and small in the peripheral portion. At least one of the exposed surface of the heat transfer plate and the opposed surface of the cooler of the semiconductor device described above is provided with a plurality of microgrooves that intersect each other in a region overlapping with the semiconductor element when viewed from a direction orthogonal to the opposed surface. It is Grease moves easily on flat surfaces. Since the microgrooves of the semiconductor device described above intersect with each other, the plane distance between them is short. Therefore, in the central portion where the amount of heat generated by the semiconductor element is large, the minute grooves suppress the movement of the grease.

Since the amount of heat generated is small in the peripheral portion of the semiconductor element, even if the gap between the heat transfer plate and the cooler is widened, the heat radiation performance of the cooler is less affected. At least one of the exposed surface of the heat transfer plate and the opposed surface of the cooler of the semiconductor device described above is provided with an annular groove surrounding the semiconductor element when viewed from a direction orthogonal to the opposed surface. This annular groove increases the volume of the grease existing space. When the volume of the space in which the grease exists increases, the elasticity of the grease increases, making it difficult for the grease to come off. Therefore, according to the semiconductor device disclosed in the present specification, the minute grooves suppress the movement of grease in the portion overlapping with the semiconductor element that generates a large amount of heat, and the annular groove prevents the grease from coming off in the peripheral portion of the semiconductor element that generates a small amount of heat. Suppress. That is, according to the above-described semiconductor device, by making use of the properties of the grease, it is possible to efficiently suppress the leakage of the grease while suppressing the influence on the heat radiation performance of the cooler. The annular groove is provided to increase the volume of the grease existing space. On the other hand, the minute grooves are provided in order to shorten the linear distance of the plane on which the grease is applied. The circular groove should be deep, but the micro-groove may be shallow. That is, the depth of the microgroove may be shallower than the depth of the annular groove.

Further, in the semiconductor device described above, the annular groove may be provided in the resin package. The resin package has a low thermal conductivity, and it is difficult to transmit the heat generated by the semiconductor element to the cooler. Therefore, by providing the resin package with an annular groove that increases the gap between the power card and the facing surface of the cooler, the effect on the heat dissipation performance can be suppressed.

Conversely, the annular groove may be provided in the heat transfer plate. By providing an annular groove in the heat transfer plate located closer to the semiconductor element than the resin package, it is possible to prevent grease from escaping from the portion overlapping with the semiconductor element that generates a large amount of heat.

Further, when the annular groove is provided in the heat transfer plate, the width of the annular groove provided at a position distant from the center of the semiconductor element is wider than the width of the annular groove provided at a position close to the center of the semiconductor element. You may By changing the width of the annular groove in this way, it is possible to narrow the width of the annular groove near the center of the heat transfer plate where the amount of heat generated by the semiconductor element is large. can be suppressed. In addition, by providing a wide annular groove in the peripheral portion of the heat transfer plate where the amount of heat generated by the semiconductor element is small, the space volume where the grease exists is increased in the portion where the effect on the heat dissipation performance of the cooler is small, and the elasticity of the grease is increased. can be increased to suppress grease leakage.

Details and further improvements of the technique disclosed in this specification are described in the following "Mode for Carrying Out the Invention".

1 is a perspective view of a semiconductor device of an example; FIG. 2 is a plan view of a power card of the semiconductor device of FIG. 1; FIG. 3 is a partial cross-sectional view of the power card taken along line III-III of FIG. 2; FIG. FIG. 4 is a plan view showing the temperature distribution of the heat transfer plate when the semiconductor element generates heat; It is a top view of the power card of the semiconductor device of a 1st modification. FIG. 11 is a plan view of a power card of a semiconductor device according to a second modified example; FIG. 11 is a plan view of a power card of a semiconductor device according to a third modified example; FIG. 11 is a plan view of a power card of a semiconductor device according to a fourth modified example; FIG. 20 is a plan view of a power card of a semiconductor device according to a fifth modified example;

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 2 of an embodiment. The semiconductor device 2 is a unit in which a plurality of power cards 20 and a plurality of coolers 8 are stacked. In FIG. 1, only one power card is denoted by reference numeral 20, and the reference numerals of other power cards are omitted. In FIG. 1, likewise, only one cooler is denoted by reference numeral 8, and the reference numerals of the other coolers are omitted. Also, a case 16 that houses the semiconductor device 2 is represented by a phantom line so that the entire semiconductor device 2 can be seen. One power card 20 is sandwiched between two coolers 8. - 特許庁An insulating plate 22 is sandwiched between the power card 20 and one cooler 8 , and an insulating plate 44 is sandwiched between the power card 20 and the other cooler 8 . A gap between the power card 20 and the insulating plates 22 and 44 facing the power card 20 is filled with grease. In FIG. 1, one power card 20 and insulating plates 22 and 44 are extracted from the semiconductor device 2 to facilitate understanding.

The power card 20 and the cooler 8 are both of a flat plate type, and are stacked such that the flat surface (wide surface) with the largest area among the plurality of side surfaces faces each other. The power cards 20 and the coolers 8 are alternately stacked, and the coolers 8 are positioned at both ends of the semiconductor device 2 in the stacking direction. The cooler 8 is a channel through which a coolant passes. A plurality of coolers 8 are connected by connecting pipes 10 and 12 . A coolant supply pipe 4 and a coolant discharge pipe 6 are connected to a cooler 8 positioned at one end in the stacking direction of the semiconductor devices 2 . A coolant supplied through the coolant supply pipe 4 is distributed to all the coolers 8 through the connection pipe 10 . As the coolant passes through each cooler 8 it absorbs heat from the adjacent power card 20 . The refrigerant that has passed through each cooler 8 passes through the connecting pipe 12 and is discharged from the refrigerant discharge pipe 6 . The refrigerant is a liquid, specifically water or antifreeze.

The semiconductor device 2 is housed in a case 16 with a leaf spring 14 at one end in the stacking direction. The semiconductor device 2 in which the power card 20, the insulating plates 22 and 44, and the cooler 8 are stacked is pressed by the leaf spring 14 from both sides in the stacking direction. By pressurizing in the stacking direction, the gap between the power card 20, the insulating plates 22 and 44, and the cooler 8 can be reduced, and the cooling efficiency is enhanced.

The power card 20 will be explained. The power card 20 is a device in which semiconductor elements 24 and 26 are encapsulated in a package 34 made of resin. The semiconductor elements 24 and 26 are switching elements for power conversion, and are specifically IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). Heat transfer plates 28 and 30 are exposed on one wide surface 32 facing the insulating plate 22 . The exposed surfaces of the heat transfer plates 28 and 30 are rectangular, and concave portions are provided along the outer periphery. That is, the heat transfer plates 28 and 30 have annular grooves 29a and 31a (in FIG. 1, the annular grooves 29a and 31a are emphasized and enlarged for better understanding). Another heat transfer plate 48 , 50 is exposed on a wide surface 52 (not shown in FIG. 1, see FIG. 3) opposite to the wide surface 32 . Similar to the heat transfer plates 28, 30, the heat transfer plates 48, 50 are also rectangular and have annular grooves 49a, 51a on their outer peripheries. A portion of the exposed surface of each of the heat transfer plates 28, 30, 48, 50 is provided with a minute groove (see FIG. 3), which will be described later, but is not shown in FIG. The semiconductor element 24 is sandwiched between heat transfer plates 28 and 48 , and the semiconductor element 26 is sandwiched between heat transfer plates 30 and 50 . The heat transfer plates 28, 30, 48, 50 are made of copper.

The semiconductor elements 24 and 26 have a collector electrode exposed on one surface and an emitter electrode exposed on the other electrode. The heat transfer plates 28 , 30 , 48 , 50 are electrically connected to one of the electrodes of the semiconductor elements 24 , 26 inside the package 34 .

As shown in FIG. 1, three terminals 38, 40, 42 extend from one narrow side of package 34 of power card 20, and control terminal 36 extends from the opposite narrow side. The two semiconductor elements 24 and 26 are connected in series inside the package 34 , and the positive terminal 42 is electrically connected to the positive side of the series connection of the two semiconductor elements 24 and 26 inside the package 34 . ing. A negative terminal 40 is electrically connected to the negative station side of the series connection. A midpoint terminal 38 is electrically connected to the midpoint of the series connection inside the package 34 . The terminals 38 , 40 , 42 are electrically connected to the electrodes of the semiconductor elements 24 , 26 through one of the heat transfer plates 28 , 30 , 48 , 50 . A description of the conductive paths between the semiconductor elements 24, 26 and the terminals 38, 40, 42 is omitted. The control terminal 36 is connected to the gate electrodes of the semiconductor elements 24 and 26, the sense emitter electrode, the terminal of the temperature sensor, and the like. Wiring of the control terminal 36 inside the package 34 is also omitted from illustration and description.

The shape of the surface of the power card 20 will be described with reference to FIG. FIG. 2 is a plan view of the power card. The power card 20 is stacked with the cooler 8 and another power card via an insulating plate 22 in the plan view direction shown in FIG. That is, FIG. 2 shows the shape of the surface of the power card 20 when viewed from a direction orthogonal to the opposing surface of the insulating plate 22. As shown in FIG. The heat transfer plates 28 and 30 are surrounded by a resin package 34 when viewed from above. In FIG. 2, the semiconductor elements 24 and 26 are drawn with broken lines, and the semiconductor element 24 is provided on the back side of the heat transfer plate 28 in the plane of the drawing, and the semiconductor element 26 is provided on the back side of the heat transfer plate 30 in the plane of the drawing. . That is, the power card 20 has the semiconductor elements 24 and 26 and the heat transfer plates 28 and 30 covered with a resin package 34 with one surface of the heat transfer plates 28 and 30 exposed.

The minute grooves 28a and 30a will be described. The minute grooves 28a, 30a are recesses provided in part of the exposed surfaces of the heat transfer plates 28, 30. As shown in FIG. Here, the minute grooves 28a will be described. As shown in FIG. 2, the minute groove 28a is a collection of a plurality of circular recesses when viewed from above. As shown in FIG. 2, the circles drawn by the microgrooves 28a are arranged so as to partially overlap. Therefore, the respective circles of the minute grooves 28a intersect each other. Further, as shown in FIG. 2, the minute grooves 28a are arranged so as to overlap the semiconductor element 24 indicated by the dashed line. That is, the surface of the power card 20 where the heat transfer plate 28 is exposed is provided with a plurality of mutually intersecting minute grooves 28a in a region overlapping with the semiconductor element 24 . The microgroove 30a has the same shape as the microgroove 28a, and the relationship with the semiconductor element 26 is also the same, so the description is omitted.

The annular grooves 29a and 31a will be explained. As described above, the annular grooves 29a and 31a are recesses provided on the outer peripheries of the exposed surfaces of the heat transfer plates 28 and 30, respectively. Here, the annular groove 29a will be explained. In FIG. 2, the region where the annular groove 29a is provided is indicated by oblique lines. As shown in FIG. 2, the annular groove 29a is provided on the side of the outer circumference of the heat transfer plate 28 in the Z-axis direction. It is approximately twice the width of the annular groove 29a. The semiconductor element 24 is arranged inside the oblique line indicating the region where the annular groove 29a is provided. That is, the annular groove 29a surrounds the semiconductor element 24 when viewed in a direction orthogonal to the facing surface of the insulating plate 22. As shown in FIG. Note that the annular groove 31a has the same shape as the annular groove 29a, and the relationship with the semiconductor element 26 is also the same, so a description thereof will be omitted.

In FIG. 2, the insulating plate 22 is drawn with a dashed line. The heat transfer plates 28 and 30 are entirely overlapped with the insulating plate 22 in plan view. As described above, grease is applied to the gap between the power card 20 and the insulating plate 22 . Furthermore, in FIG. 2, the region where the grease is applied is drawn with a two-dot chain line G. As shown in FIG. That is, at least the gaps positioned inside the outer peripheries of the annular grooves 29a and 31a are filled with grease. In this embodiment, as shown by the two-dot chain line G, the grease is applied to the outside of the outer circumferences of the annular grooves 29a and 31a. Entering is called grease removal. In terms of the original function of the grease, it is sufficient if the inside is filled with grease.

Also, on the rear surface of the power card 20, the relationship between the heat transfer plates 48, 50 (see FIG. 3), the package 34, and the insulating plate 44 (see FIG. 3) is the same. The relationship between the annular grooves 49a, 51a of the heat transfer plates 48, 50 and the semiconductor elements 24, 26 is the same. Furthermore, grease is applied to the wide surface 52 (see FIG. 3), which is the rear surface of the power card 20, in the gap between it and the insulating plate 44, as with the wide surface 32 on the front side.

The structure between the power card 20 and the cooler 8 facing the power card 20 will be described with reference to FIG. FIG. 3 is a partial cross-sectional view of the power card 20 taken along line III--III of FIG. As described above, the semiconductor element 24 is sandwiched between a pair of heat transfer plates 28,48. Semiconductor device 24 is a flat chip. A collector electrode is exposed on the wide surface of the semiconductor element 24 on the upper side of the drawing (that is, on the positive side in the X-axis direction), and an emitter electrode is exposed on the wide surface on the lower side of the drawing. The heat transfer plate 28 is connected to the collector electrode of the semiconductor element 24 by solder 54 and is electrically connected. The heat transfer plate 48 is connected to the emitter electrode of the semiconductor element 24 by solder 54 and is electrically connected. Similarly, the semiconductor element 26 is also sandwiched between a pair of heat transfer plates 30,50. The semiconductor element 26 is also joined to the heat transfer plates 30 and 50 by solder 56 and is electrically connected. Between the semiconductor element 24 and the heat transfer plate 28 or the heat transfer plate 48 and between the semiconductor element 26 and the heat transfer plate 30 or the heat transfer plate 50, spacers made of a conductor such as copper are provided as necessary. may be provided.

The heat transfer plates 28 , 30 , 48 , 50 serve to transfer the heat of the semiconductor elements 24 , 26 to the cooler 8 , and also serve as conductors connecting the electrodes of the semiconductor elements 24 , 26 and the terminals 38 , 40 , 42 (see FIG. 1 ). Play the role of pathway. Heat transfer plates 28 , 30 , 48 , 50 are electrically connected to semiconductor elements 24 , 26 . The cooler 8 is also made of metal with high thermal conductivity, such as aluminum, and has electrical conductivity. An insulating plate 22 is sandwiched between the power card 20 and the cooler 8 on the positive side of the X axis to prevent short circuits between the heat transfer plates 28 , 30 , 48 , 50 and the cooler 8 . On the other hand, an insulating plate 44 is sandwiched between the power card 20 and the cooler 8 on the negative side of the X axis. As described above, the gap between the power card 20 and the insulating plates 22 and 44 and the gap between the insulating plates 22 and 44 and the cooler 8 are coated with the grease 46 . Grease 46 is applied to improve heat transfer efficiency. As shown in FIG. 3, grease 46 is applied to gaps between the insulating plates 22 and 44 on substantially the entire wide surfaces 32 and 52 of the power card 20 . That is, the grease 46 fills at least the gaps located inside the annular grooves 29a, 31a, 49a, 51a.

A pair of coolers 8 sandwiching the semiconductor elements 24 and 26 face both wide surfaces of the semiconductor elements 24 and 26, respectively. As described above, the heat transfer plates 28, 48 are exposed on the wide surfaces 32, 52 of the package 34, respectively, and substantially the entire surfaces of the wide surfaces 32, 52 are coated with the grease 46. As shown in FIG. Insulating plates 22 and 44 are sandwiched between the wide surfaces 32 and 52 and the cooler 8, respectively. Grease 46 is also applied between the insulating plates 22 and 44 and the cooler 8 . Heat from the semiconductor element 24 is absorbed by the cooler 8 through the heat transfer plates 28 , 48 , grease 46 and insulating plates 22 , 44 . Similarly, the heat of the semiconductor element 26 is absorbed by the cooler 8 through the heat transfer plates 30, 50, the grease 46, and the insulating plates 22, 44. Grease 46 has a higher thermal conductivity than air. In other words, if grease leakage occurs between the semiconductor elements 24 and 26 and the cooler 8 , the heat from the semiconductor elements 24 and 26 is less likely to be transmitted to the cooler 8 . In other words, the heat radiation performance of the cooler 8 with respect to the semiconductor elements 24 and 26 deteriorates. The cooler 8 is hollow inside, and the hollow serves as a coolant flow path. In FIG. 2, the coolant flows in the positive direction of the Y axis. That is, the coolant flows from the semiconductor element 24 toward the semiconductor element 26 . That is, in order not to deteriorate the heat radiation performance of the cooler 8, it is important that the inside of each annular groove is filled with the grease 46. FIG. In the following description, the phenomenon that grease moves from the inside to the outside of each annular groove and does not return to its original position is referred to as grease removal.

Now, with reference to FIG. 4, the temperature difference between the heat transfer plates 28 and 30 when the semiconductor elements 24 and 26 generate heat will be described. FIG. 4 shows the temperature distribution of the heat transfer plates 28 and 30 measured when the semiconductor elements 24 and 26 generate heat. In FIG. 4, the white parts of the heat transfer plates 28 and 30 have a high temperature, and the dark hatched parts have a low temperature. As shown in FIG. 4, the temperature of the heat transfer plates 28 and 30 is high at the central portions of the semiconductor elements 24 and 26 . Also, the temperature of the heat transfer plates 28 and 30 decreases as the distance from the center of the semiconductor elements 24 and 26 increases. That is, when the semiconductor elements 24 and 26 generate heat, the heat is transferred to the cooler 8 (see FIG. 3) through the high-temperature center portions of the heat transfer plates 28 and 30 . In other words, the part that greatly affects the heat dissipation performance of the cooler 8 is the central part of the semiconductor elements 24 and 26 shown in FIG. 4, which is shown in white. On the other hand, the influence on the heat dissipation performance of the peripheral portions of the semiconductor elements 24 and 26 is small.

Returning to FIG. 3, the structure employed by the power card 20 of the semiconductor device 2 of the embodiment for suppressing the escape of grease will be described mainly with reference to the heat transfer plate 28. FIG. As described with reference to FIG. 2, microgrooves 28a are provided in regions of the exposed surface of the heat transfer plate 28 overlapping the semiconductor elements 24. As shown in FIG. In other words, the minute grooves 28 a are provided on the side of the heat transfer plate 28 that is electrically connected to the semiconductor element 24 and faces the cooler 8 . As described above, heat from the semiconductor element 24 is absorbed by the cooler 8 via the heat transfer plate 28 and the grease 46 . As described with reference to FIG. 4, the temperature of the heat transfer plate 28 also rises at the central portion of the semiconductor element 24 . In other words, the power card 20 is provided with the minute grooves 28a in the portion of the heat transfer plate 28 where the temperature is high. As described with reference to FIG. 2, the minute grooves 28a are intersected by a plurality of circular concave portions. Therefore, in the portion of the heat transfer plate 28 where the minute grooves 28a are provided, as shown in FIG. 3, the linear distance of the plane becomes short.

When the semiconductor device 2 of the embodiment is operated and the semiconductor element 24 generates heat, the heat transfer plate 28 thermally expands. As described above, the heat transfer plate 28 has its outer periphery sealed by the package 34 . Therefore, the heat transfer plate 28 cannot extend in the longitudinal direction (that is, the Y-axis direction) due to thermal expansion, and deforms so that the center approaches the insulating plate 22 . Therefore, when the semiconductor element 24 generates heat, the gap between the heat transfer plate 28 and the insulating plate 22 is the smallest at the central portion of the heat transfer plate 28 . As a result, the grease 46 filled in the central portion of the heat transfer plate 28 tries to push out the surrounding grease 46 to the outer periphery of the heat transfer plate 28 .

As described above, the central portion of the heat transfer plate 28 is provided with the minute grooves 28a. Therefore, in the central portion of the heat transfer plate 28, the linear distance of the plane is short. Grease 46 moves along the plane of the exposed surface of heat transfer plate 28 . That is, it is difficult for the grease 46 to move on the heat transfer plate 28 having a short linear distance on the plane. In this manner, the minute grooves 28a suppress the escape of grease in the central portion of the heat transfer plate 28. As shown in FIG.

In addition, an annular groove 29a is provided around the heat transfer plate 28 of the power card 20. As shown in FIG. Annular groove 29a surrounds semiconductor element 24, as described in FIG. Also, as shown in FIG. 3, the annular groove 29a is deeper than the minute grooves 28a. Therefore, the annular groove 29a can increase the volume of the existence space of the grease 46 more than the fine groove 28a. As the existence space of the grease 46 increases, the elasticity of the grease 46 increases. When the elasticity of the grease 46 increases, the grease 46 easily returns to the inside of the annular groove 29a when the operation of the semiconductor device 2 is stopped and the semiconductor element 24 stops generating heat and is cooled to normal temperature. That is, the annular groove 29a increases the space in which the grease 46 exists, thereby suppressing grease leakage.

In the power card 20 provided in the semiconductor device 2 of the embodiment, the minute grooves 28a provided in the exposed surface of the heat transfer plate 28 move the grease 46 from the central portion to the peripheral portion of the heat transfer plate 28 when the semiconductor element 24 generates heat. restrain from doing. Further, the annular groove 29a makes it easier for the grease 46 to return to the inside of the annular groove 29a when the heat transfer plate 28 is cooled. A minute groove 28a provided in a region overlapping with the semiconductor element 24 is formed shallower than the annular groove 29a. Therefore, the gap between the heat transfer plate 28 and the cooler 8 is not widened. As a result, the heat transfer plate 28 can efficiently transfer the heat generated by the semiconductor element 24 to the cooler 8 . On the other hand, the annular groove 29a is formed deeper than the minute grooves 28a, but since the annular groove 29a is provided so as to surround the periphery of the semiconductor element 24, heat is transmitted from the heat transfer plate 28 to the cooler 8. heat does not decrease. As described above, the power card 20 included in the semiconductor device 2 of the embodiment utilizes the elasticity of the grease 46 to affect the heat radiation performance of the cooler 8 by using two types of grooves with different depths. It is possible to efficiently suppress grease leakage without The shapes such as the depth and width of the minute grooves 28a and the annular groove 29a differ depending on the characteristics of the grease to be filled, the heat generation temperature of the semiconductor element 24, and the like. The same applies to the minute grooves 30a, 48a, 50a and the annular grooves 31a, 49a, 51a provided in the other heat transfer plates 30, 48, 50 shown in FIG.

Modified examples of the shape of the minute groove and the annular groove will be described below with reference to the drawings. FIG. 5 shows a plan view of a power card 20 provided with minute grooves 28b and 30b, which are modifications of the minute grooves. As shown in FIG. 5, the minute grooves 28b and 30b are a collection of a plurality of recesses that form a substantially equilateral triangle when viewed from above. The triangles drawn by each of the minute grooves 28b are arranged so as to partially overlap each other, and the respective triangles intersect each other. Further, as shown in FIG. 5, the minute grooves 28b and 30b are arranged so as to overlap the semiconductor elements 24 and 26 indicated by broken lines. Even with such minute grooves 28b and 30b, like the minute groove 28a described with reference to FIG. 2, it is possible to shorten the linear distance of the planes of the heat transfer plates 28 and 30 and suppress the movement of grease.

Moreover, as shown in 58a and 58b in FIG. 6, the microgroove may be a collection of a plurality of recesses that form a substantially square shape when viewed from above. As described above, the fine grooves 58a and 58b shorten the linear distance of the plane of the heat transfer plate 58 and suppress the movement of grease.

Unlike the heat transfer plates 28,30 shown in FIG. 2, a rectangular heat transfer plate 58 extending in the Y-axis direction over the two semiconductor elements 24,26 is connected to the two semiconductor elements 24,26. 6 is formed in the package 34 instead of being part of the heat transfer plate 58. As shown in FIG. The annular groove 34a surrounds the two semiconductor elements 24,26. By forming the annular groove 34a in the package 34, the gap between the heat transfer plate 58 and the cooler 8 (see FIG. 3), which contributes to the heat dissipation of the semiconductor elements 24 and 26, is not widened. That is, by forming the annular groove 34a in the package 34, deterioration of the heat radiation performance of the cooler 8 can be further suppressed.

In the modification shown in FIG. 7, the diameter of the circle drawn by each minute groove is changed according to the distance from the annular grooves 29a and 31a. As shown in FIG. 7, the micro-grooves 28c and 30c located near the annular grooves 29a and 31a are formed by circles with a large diameter. On the other hand, the micro-grooves 28d and 30d, which are located away from the annular grooves 29a and 31a, are formed by small-diameter circles. As described above, at positions close to the annular grooves 29a and 31a, the elasticity of the grease increases, so the grease is difficult to come off. Therefore, in a portion close to the annular grooves 29a and 31a where the grease is difficult to escape due to the annular grooves 29a and 31a, a circular minute groove with a large diameter is formed to form minute grooves in a part of the exposed surface of the heat transfer plate. (for example, laser processing) can be shortened.

Also, the width of the annular groove may be widened in a portion where the influence on the heat radiation performance of the cooler is small. Modifications of the annular groove will be described with reference to FIGS. 8 and 9. FIG. The annular grooves 29b and 31b shown in FIG. 8 have a width W1 at positions near the centers of the semiconductor elements 24 and 26, and W1 at the corners of the heat transfer plates 28 and 30 away from the centers of the semiconductor elements 24 and 26. width W2. As shown in FIG. 8, width W2 is wider than width W1. In this way, by widening the width of the annular groove away from the center of the semiconductor elements 24 and 26 that generate heat, it is possible to further increase the space in which the grease exists in the portion where the influence on the heat radiation performance of the cooler is small. can. That is, by increasing the elasticity of the grease, it is possible to suppress grease leakage.

Furthermore, like the annular grooves 29c and 31c shown in FIG. 9, the inner corners of the annular grooves may be formed to draw circular arcs. The annular grooves 29c, 31c have a width W3 at positions near the centers of the semiconductor elements 24, 26, and a width W4 at the corners of the heat transfer plates 28, 30 away from the centers of the semiconductor elements 24, 26. . As shown in FIG. 9, width W4 is wider than width W3. That is, as described above, it is possible to suppress grease leakage by increasing the space in which the grease exists in the portion where the influence on the heat radiation performance of the cooler is small and increasing the elasticity of the grease.

Points to note in the examples are described below. Although the power card 20 of the semiconductor device 2 of the embodiment includes two semiconductor elements 24 and 26, the technology disclosed in this specification is not limited to this, and may include one or more semiconductor elements. It can also be applied to a semiconductor device having a power card. Also, the annular groove may be provided in the insulating plate. In the case of a semiconductor device that does not require an insulating plate, an annular groove may be provided on the surface of the cooler. Furthermore, the cross-sectional shape of the annular groove is not limited to a rectangle. For example, an annular groove with a triangular cross section may be used.

Although specific examples of the present invention have been described in detail above, 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 in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

2: Semiconductor device 4: Refrigerant supply pipe 6: Refrigerant discharge pipe 8: Cooler 10, 12: Connection pipe 14: Leaf spring 16: Case 20, 20a, 20b: Power card 22, 44: Insulating plate 24, 26: Semiconductor Elements 28, 30, 48, 50, 58: heat transfer plates 28a-d, 30a-d, 48a, 50a, 58a: minute grooves 29a-c, 31-c, 34a, 49a, 51a: annular grooves 32, 52: Wide surface 34: package 36: control terminals 38, 40, 42: electrode terminals 46: grease 54: solder W1 to W4: width

Claims (1)

A semiconductor device in which a gap between a power card and a cooler facing the power card is filled with grease,
The power card has a semiconductor element and a heat transfer plate covered with a resin package with one surface of the heat transfer plate exposed,
At least one of the face where the heat transfer plate of the power card is exposed and the facing face of the cooler has a plurality of heat exchangers in a region overlapping with the semiconductor element when viewed in a direction orthogonal to the facing face. are provided with microgrooves that intersect with each other, and an annular groove surrounding the semiconductor element is provided,
the depth of the minute groove is shallower than the depth of the annular groove,
The annular groove is provided in the heat transfer plate,
A semiconductor device according to claim 1, wherein the width of the annular groove provided away from the center of the semiconductor element is wider than the width of the annular groove provided at the position close to the center of the semiconductor element .

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