Patent ID: 12205867

DESCRIPTION OF EMBODIMENTS

Hereinafter, a heat sink and a semiconductor module according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments are not intended to limit the invention.

First Embodiment

FIG.1is an exploded perspective view illustrating a semiconductor module1according to a first embodiment of the present invention. Arrows illustrated inFIG.1indicate flows of a coolant. As illustrated inFIG.1, the semiconductor module1includes a semiconductor device2, which is an object to be cooled, and a heat sink3. The semiconductor device2is, for example, a light-emitting device or a power semiconductor. The light-emitting device is, for example, a single laser device or an array laser device. The power semiconductor is formed on a substrate such as a Si substrate, a GaN substrate, or a SiC substrate. When the semiconductor device2is driven, heat is generated from the semiconductor device2.

The heat sink3is a member that dissipates heat generated in the semiconductor device2. The heat sink3is formed by stacking a heat transfer plate31, a first flow path-forming plate32, a junction flow path-forming plate33, a second flow path-forming plate34, and a bottom plate35. From the side closer to the semiconductor device2, the heat transfer plate31, the first flow path-forming plate32, the junction flow path-forming plate33, the second flow path-forming plate34, and the bottom plate35are arranged in this order. The heat transfer plate31, the first flow path-forming plate32, the junction flow path-forming plate33, the second flow path-forming plate34, and the bottom plate35are each formed of a metal material having high thermal conductivity. The metal material having high thermal conductivity is, for example, copper or aluminum. The plates31to35are preferably formed of the same type of metal material. A method of joining the plates31to35is, for example, diffusion bonding. The plates31to35, which are not limited to a particular shape, are rectangular in the first embodiment. In the first embodiment, the number of plates forming the heat sink3is five, but the number of plates forming the heat sink3may be six or more. A coolant flow path4through which the coolant flows is formed inside the heat sink3. The coolant is, for example, pure water or antifreeze solution. The coolant flow path4will be described in detail later.

The heat transfer plate31, which is a first plate, has a first surface31aon which the semiconductor device2is disposed and a second surface31bthat is the back surface of the first surface31a. Heat from the semiconductor device2is directly transferred to the heat transfer plate31. The first surface31afaces the outside of the heat sink3. The second surface31bfaces the inside of the heat sink3. A method of joining the heat transfer plate31and the semiconductor device2is, for example, soldering. A first opening8and a second opening9are formed in the heat transfer plate31. The first opening8and the second opening9are provided in positions away from the semiconductor device2. The first opening8and the second opening9pass through the heat transfer plate31in the thickness direction of the heat transfer plate31. In the first embodiment, the first opening8serves as a coolant inlet that causes the coolant to flow into the heat sink3. In the first embodiment, the second opening9serves as a coolant outlet that causes the coolant to flow out of the heat sink3. The first opening8may be used as a coolant outlet, and the second opening9may be used as a coolant inlet.

The first flow path-forming plate32is a plate that forms a first flow path5between the heat transfer plate31and the junction flow path-forming plate33. In the first flow path-forming plate32, a first outer peripheral wall15, a plurality of first partition walls12, and a plurality of first fins13are formed. The first outer peripheral wall15, the first partition walls12, and the first fins13will be described in detail later. In the first flow path-forming plate32, a plurality of first divided regions51, a first common header region52, and a third opening10are formed. The first divided regions51, the first common header region52, and the third opening10pass through the first flow path-forming plate32in the thickness direction of the first flow path-forming plate32. In a planar view, the third opening10is disposed in a position coinciding with the first opening8. The third opening10communicates with the first opening8. A first dividing wall14bis provided around the third opening10. The third opening10is separated from the first divided regions51and the first common header region52by the first dividing wall14b. This prevents the coolant flowing through the third opening10from meeting the coolant flowing through the first divided regions51and the first common header region52. The first divided regions51and the first common header region52will be described in detail later.

The junction flow path-forming plate33, which is a second plate, is a plate forming a plurality of junction flow paths7. The junction flow path-forming plate33has a third surface33afacing the second surface31band a fourth surface33bthat is the back surface of the third surface33a. The junction flow paths7and a fourth opening11are formed in the junction flow path-forming plate33. The junction flow paths7and the fourth opening11pass through the junction flow path-forming plate33in the thickness direction of the junction flow path-forming plate33. In a planar view, the fourth opening11is disposed in a position coinciding with the first opening8and the third opening10. The fourth opening11communicates with the first opening8and the third opening10. The junction flow paths7will be described in detail later.

The second flow path-forming plate34is a plate that forms a second flow path6between the bottom plate35and the junction flow path-forming plate33. In the second flow path-forming plate34, a second outer peripheral wall20, a plurality of second partition walls17, and a plurality of second fins18are formed. The second outer peripheral wall20, the second partition walls17, and the second fins18will be described in detail later. In the second flow path-forming plate34, a plurality of second divided regions61and a second common header region62are formed. The second divided regions61and the second common header region62pass through the second flow path-forming plate34in the thickness direction of the second flow path-forming plate34. The second divided regions61and the second common header region62will be described in detail later.

The bottom plate35, which is a third plate, is disposed opposite the heat transfer plate31with the first flow path-forming plate32, the junction flow path-forming plate33, and the second flow path-forming plate34interposed therebetween. The bottom plate35is a flat plate without openings.

Next, the coolant flow path4will be described in detail. The coolant flow path4includes the first opening8, the second opening9, the third opening10, the fourth opening11, the first flow path5, the second flow path6, and the plurality of junction flow paths7. The first flow path5is formed by the heat transfer plate31, the junction flow path-forming plate33, and the first outer peripheral wall15. The second flow path6is formed by the junction flow path-forming plate33, the bottom plate35, and the second outer peripheral wall20. The plurality of junction flow paths7connect the first flow path5and the second flow path6.

The first opening8, the third opening10, and the fourth opening11serve as an inlet flow path for causing the coolant to flow into the heat sink3. A pipe (not illustrated) for supplying the coolant into the heat sink3is connected to the first opening8. A pipe (not illustrated) for discharging the coolant to the outside of the heat sink3is connected to the second opening9. The first opening8and the second opening9are connected to a reservoir tank (not illustrated) via the pipes. By driving a pump (not illustrated), the coolant is supplied from the reservoir tank to the first opening8through the pipe.

FIG.2is a perspective view illustrating the first flow path-forming plate32according to the first embodiment. In the first flow path5, the plurality of first divided regions51and the first common header region52are formed. The plurality of first divided regions51are separated by the first partition walls12. In the first embodiment, part of the first flow path5is divided into four first divided regions51by four first partition walls12. In addition to serving the function of dividing part of the first flow path5into the plurality of first divided regions51, the first partition walls12also serve as fins that transfer heat from the heat transfer plate31to the coolant. The four first partition walls12extend radially from a center point. The four first partition walls12are disposed at 90 degree intervals along a circumferential direction around the center point. When the four first partition walls12are distinguished, they are referred to as first partition walls12a,12b,12c, and12d. When the four first divided regions51are distinguished, they are referred to as first divided regions51a,51b,51c, and51d.

A first dividing wall14aprotruding to the opposite side of the first divided region51bis formed at the distal end of the first partition wall12b. The distal end of the first partition wall12cis connected to the first dividing wall14badjacent to the first divided region51b. A first dividing wall14cprotruding to the opposite side of the first divided region51dis formed at the distal end of the first partition wall12d. The distal end of the first partition wall12ais connected to the first outer peripheral wall15. A space partitioned off by the first partition walls12aand12band the first dividing wall14ais the first divided region51a. A space partitioned off by the first partition walls12band12cand the first dividing wall14bis the first divided region51b. A space partitioned off by the first partition walls12cand12dand the first dividing wall14cis the first divided region51c. A space partitioned off by the first partition walls12aand12dand the first outer peripheral wall15is the first divided region51d.

The plurality of first fins13are disposed in each of the first divided regions51. The plurality of first fins13are arranged by being spaced side by side in parallel. The first fins13in all the first divided regions51are installed at equal intervals. The first fins13are formed in a flat plate shape. The first fins13protrude from each of the first partition walls12toward the first divided regions51. One end of each first fin13along the length direction is connected to the first partition wall12. The other end of each first fin13along the length direction faces the first common header region52. The first fins13disposed in the adjacent first divided regions51protrude from the different first partition walls12. The lengthwise directions of the first fins13disposed in the adjacent first divided regions51are orthogonal to each other. First inter-fin flow paths16are formed between the adjacent first fins13and13and between the first fins13and the first partition walls12adjacent to each other. First inter-fin flow paths16are also formed between the first fin13and each of the first dividing walls14ato14cadjacent to each other and between the first fin13and the first outer peripheral wall15adjacent to each other.

The first common header region52is a region provided in such a manner to surround the plurality of first divided regions51. The first common header region52communicates with the first inter-fin flow paths16in the first divided regions51. As illustrated inFIG.1, the first common header region52is arranged in a position coinciding with the second opening9in a planar view. The first common header region52communicates with the second opening9.

FIG.3is a perspective view illustrating the second flow path-forming plate34according to the first embodiment. In the second flow path6, the plurality of second divided regions61and the second common header region62are formed. The plurality of second divided regions61are separated by the second partition walls17. In the first embodiment, part of the second flow path6is divided into four second divided regions61by four second partition walls17. The four second partition walls17extend radially from a center point. The four second partition walls17are disposed at 90 degree intervals along a circumferential direction around the center point. When the four second partition walls17are distinguished, they are referred to as second partition walls17a,17b,17c, and17d. When the four second divided regions61are distinguished, they are referred to as second divided regions61a,61b,61c, and61d.

A second dividing wall19aprotruding to the opposite side of the second divided region61bis formed at the distal end of the second partition wall17b. The distal end of the second partition wall17cis connected to a second dividing wall19bthat is adjacent to the second divided region61b. A second dividing wall19cprotruding to the opposite side of the second divided region61dis formed at the distal end of the second partition wall17d. The distal end of the second partition wall17ais connected to the second outer peripheral wall20. A space partitioned off by the second partition walls17aand17band the second dividing wall19ais the second divided region61a. A space partitioned off by the second partition walls17band17cand the second dividing wall19bis the second divided region61b. A space partitioned off by the second partition walls17cand17dand the second dividing wall19cis the second divided region61c. A space partitioned off by the second partition walls17aand17dand the second outer peripheral wall20is the second divided region61d.

The plurality of second fins18are disposed in each of the second divided regions61. The plurality of second fins18are arranged by being spaced side by side in parallel. The second fins18in all the second divided regions61are installed at equal intervals. The second fins18are formed in a flat plate shape. The second fins18protrude from each of the second partition walls17toward the second divided regions61. One end of each second fin18along the length direction is connected to the second partition wall17. The other end of each second fin18along the length direction faces the second common header region62. The second fins18disposed in the adjacent second divided regions61protrude from the different second partition walls17. The lengthwise directions of the second fins18disposed in the adjacent second divided regions61are orthogonal to each other. Second inter-fin flow paths21are formed between the adjacent second fins18and18and between the second fins18and the second partition walls17adjacent to each other. Second inter-fin flow paths21are also formed between the second fin18and each of the second dividing walls19ato19cadjacent to each other, and between the second fin18and the second outer peripheral wall20adjacent to each other.

The second common header region62is a region provided in such a manner to surround the plurality of second divided regions61. The second common header region62communicates with the second inter-fin flow paths21in the second divided regions61. As illustrated inFIG.1, the second common header region62is arranged in a position that coincides with the first opening8, the third opening10, and the fourth opening11in a planar view. The first opening8, the third opening10, the fourth opening11, and the second common header region62communicate with each other.

Four junction flow paths7are disposed at 90 degree intervals along a circumferential direction around a center point. The four junction flow paths7are disposed at equal intervals. When the four junction flow paths7are distinguished, they are referred to as junction flow paths7a,7b,7c, and7d. The junction flow paths7, which are not limited to a particular shape, are in an elongated rectangular shape in the first embodiment. The length directions of the adjacent junction flow paths7are orthogonal to each other. In a planar view, the first divided region51a, the second divided region61a, and the junction flow path7aare disposed at a position that coincides with each other. The length direction of the first fins13in the first divided region51aand the length direction of the second fins18in the second divided region61aare parallel to each other. In a planar view, the first divided region51b, the second divided region61b, and the junction flow path7bare disposed at a position that coincides with each other. The length direction of the first fins13in the first divided region51band the length direction of the second fins18in the second divided region61bare parallel to each other. In a planar view, the first divided region51c, the second divided region61c, and the junction flow path7care disposed at a position that coincides with each other. The length direction of the first fins13in the first divided region51cand the length direction of the second fins18in the second divided region61care parallel to each other. In a planar view, the first divided region51d, the second divided region61d, and the junction flow path7dare disposed at a position that coincides with each other. The length direction of the first fins13in the first divided region51dand the length direction of the second fins18in the second divided region61dare parallel to each other.

FIG.4is a plan view illustrating the first flow path-forming plate32according to the first embodiment.FIG.5is a cross-sectional view of the semiconductor module1taken along line V-V illustrated inFIG.4.FIG.6is a cross-sectional view of the semiconductor module1taken along line VI-VI illustrated inFIG.4.FIG.7is a cross-sectional view of the semiconductor module1taken along line VII-VII illustrated inFIG.4. InFIG.4, for explanatory convenience, the semiconductor device2is illustrated by a broken line. InFIG.4, for explanatory convenience, only the first flow path-forming plate32of the heat sink3is illustrated, and the positions of the cross sections of the semiconductor module1illustrated inFIGS.5to7are indicated using the first flow path-forming plate32. As illustrated inFIG.5, the first partition walls12are provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The first outer peripheral wall15is provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The second partition walls17are provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35. The second outer peripheral wall20is provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35.

As illustrated inFIGS.6and7, the first fins13are provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The second fins18are provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35. As illustrated inFIG.7, the first inter-fin flow paths16and the second inter-fin flow paths21communicate with each other through the junction flow paths7. The width of the first partition walls12and the width of the second partition walls17are equal. The width of the first fins13and the width of the second fins18are equal. The installation interval between the first fins13is equal to the installation interval between the second fins18. When the reduction of the pressure loss of the coolant, the improvement of the effect of cooling by the coolant, and the suppression of corrosion of the first fins13etc. are considered, it is preferable to approximately equalize the average flow velocity of the coolant flowing through the junction flow paths7and the average flow velocity of the coolant flowing through the first inter-fin flow paths16. For example, when the opening width of the junction flow paths7is set to about half the height of the first fins13, the average flow velocity of the coolant flowing through the junction flow paths7and the average flow velocity of the coolant flowing through the first inter-fin flow paths16can be approximately equalized.

FIG.8is a plan view illustrating the first partition walls12, the first fins13, and the junction flow paths7projected onto the first surface31a. InFIG.8, for ease of explanation, the first partition walls12and the first fins13are illustrated by solid lines, and the junction flow paths7and the semiconductor device2are illustrated by broken lines. InFIG.8, for ease of explanation, the heat transfer plate31is drawn extremely small. A position where a part of the first partition walls12, part of the first fins13, and part of the first inter-fin flow paths16are projected onto the first surface31acoincides with the semiconductor device2. In the first embodiment, the center point of the four first partition walls12coincides with the central part of the semiconductor device2. A position where a part of the first partition walls12are projected onto the first surface31acoincide with the central part of the semiconductor device2and with the periphery of the central part of the semiconductor device2. A position where a part of the first fins13and a part of the first inter-fin flow paths16are projected onto the first surface31acoincides with the periphery of the central part of the semiconductor device2. Although a position where a part of the first partition walls12are projected onto the first surface31acoincides with the central part of the semiconductor device2in the first embodiment, a position where a part of the first fins13are projected onto the first surface31amay coincide with the central part of the semiconductor device2.

When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, each junction flow path7is placed on the corresponding one of the plurality of first divided regions51and is formed elongatedly across the plurality of first fins13. The length direction of each junction flow path7is orthogonal to the length direction of the first fins13. Each junction flow path7is placed on root portions of the first fins13connected to the first partition wall12.

As described above, the coolant flow path4is formed hierarchically to include: the first flow path5closest to the first surface31aon which the semiconductor device2is disposed; the second flow path6formed farther away from the first surface31athan the first flow path5in the direction of the normal to the first surface31a; and the junction flow paths7placed between the first flow path5and the second flow path6and connecting the first flow path5and the second flow path6. The first flow path5has as its inner surfaces the second surface31bon the first surface31aside and the third surface33afacing the second surface31b. In the first flow path5, the plurality of first divided regions51are formed, and the plurality of first divided regions51are separated by the first partition walls12provided between the second surface31band the third surface33a. The first divided regions51include the plurality of first fins13arranged by being spaced side by side and formed to extend from the first partition walls12. A position where at least part of the first partition walls12are projected onto the first surface31aor a position where at least part of the first fins13are projected onto the first surface31acoincide with the central part of a region of the first surface31awhere the semiconductor device2is installed. When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, at least one of the junction flow paths7is placed on each of the plurality of first divided regions51and is formed elongatedly across the plurality of first fins13along the first partition wall12. In the heat sink3, the coolant flows between the first flow path5and the second flow path6through the junction flow paths7.

Next, the flow of the coolant will be described with reference toFIG.1. The coolant that has flowed from the first opening8into the heat sink3flows into the second common header region62through the third opening10and the fourth opening11. Then, the coolant flows from the second common header region62into the second inter-fin flow paths21in the second divided regions61. Then, the coolant flows from the second inter-fin flow paths21into the first inter-fin flow paths16in the first divided regions51through the junction flow paths7. At this time, the coolant in the second inter-fin flow paths21in the second divided region61aflows into the first inter-fin flow paths16in the first divided region51athrough the junction flow path7a. The coolant in the second inter-fin flow paths21in the second divided region61bflows into the first inter-fin flow paths16in the first divided region51bthrough the junction flow path7b. The coolant in the second inter-fin flow paths21in the second divided region61cflows into the first inter-fin flow paths16in the first divided region51cthrough the junction flow path7c. The coolant in the second inter-fin flow paths21in the second divided region61dflows into the first inter-fin flow paths16in the first divided region51dthrough the junction flow path7d. After that, the coolant flows from the first inter-fin flow paths16in the first divided regions51into the first common header region52. Then, the coolant flows from the first common header region52to the outside of the heat sink3through the second opening9.

Next, the functions and effects of the semiconductor module1according to the first embodiment will be described.

As illustrated inFIG.7, heat generated in the semiconductor device2is transferred to the heat transfer plate31. The heat transferred to the heat transfer plate31is transferred to the first partition walls12and the first fins13. When the coolant flows in the first flow path5, heat exchange is performed between the heat transfer plate31and the coolant, between the first partition walls12and the coolant, and between the first fins13and the coolant. That is, the coolant absorbs the heat transferred to the heat transfer plate31, the first partition walls12, and the first fins13. Consequently, the semiconductor device2is cooled by the coolant via the heat transfer plate31, the first partition walls12, and the first fins13. As illustrated inFIG.8, in the first embodiment, a position where part of the first partition walls12is projected onto the first surface31acoincides with the central part of the semiconductor device2. A position where part of the first fins13is projected onto the first surface31acoincides with the periphery of the central part of the semiconductor device2. Thus, heat generated in the central part of the semiconductor device2is easily transferred to the first partition walls12and the first fins13through the heat transfer plate31. Since the heat transferred to the first partition walls12and the first fins13is absorbed by the coolant flowing through the first inter-fin flow paths16, the cooling effect on the central part of the semiconductor device2is enhanced.

With reference toFIGS.1and9, the cooling effect by the coolant on the semiconductor device2will be described.FIG.9is a partially enlarged cross-sectional view of the semiconductor module1illustrated inFIG.7. In general, the temperature of heat generated in the semiconductor device2is higher toward the central part of the semiconductor device2. Consequently, unevenness occurs in the distributions of temperatures of the semiconductor device2and the heat transfer plate31. In the first embodiment, when the coolant flows in from the first opening8illustrated inFIG.1, the coolant that has flowed from the second inter-fin flow path21into the first inter-fin flow path16through the junction flow path7illustrated inFIG.9strikes the second surface31bof the heat transfer plate31at a position close to the central part of the semiconductor device2. Consequently, the temperature of the central part of the semiconductor device2can be lowered, and the unevenness of the temperature distribution in the semiconductor device2can be reduced. As illustrated inFIG.9, when the coolant flows into the first inter-fin flow path16, a vortex23is generated near a joint22between the heat transfer plate31and the first partition wall12in the first inter-fin flow path16, and coolant stagnation occurs in the first inter-fin flow path16. In places where the coolant stagnates, the cooling effect by the coolant on the heat transfer plate31decreases. In this regard, the first embodiment, in which the coolant strikes the second surface31bof the heat transfer plate31near the stagnant places, can suppress the temperature rise of the heat transfer plate31due to the coolant stagnation.

As illustrated inFIG.8, in the first embodiment, when the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, the junction flow paths7are formed elongatedly across the plurality of first fins13. Thus, the flow path area of the junction flow paths7is reduced, and the flow velocity of the coolant increases when passing through the junction flow paths7. As a result, the coolant increased in flow velocity strikes the second surface31bof the heat transfer plate31at positions close to the central part of the semiconductor device2, so that the temperature of the central part of the semiconductor device2can be further reduced, and the unevenness of the temperature distribution in the semiconductor device2can be reduced.

Here, assume that a wall formed by stacking the first partition wall12, the second partition wall17, and the junction flow path-forming plate33illustrated inFIG.9is a single central partition wall24. The junction flow path7is disposed adjacent to an intermediate portion of the central partition wall24in the height direction. This can change the flow of the coolant from the second inter-fin flow path21toward the first inter-fin flow path16in a direction perpendicular to the heat transfer plate31at a position as close as possible to the heat transfer plate31. Thus, the coolant that has passed through the junction flow path7strikes the second surface31bof the heat transfer plate31nearly perpendicularly to the heat transfer plate31. This can reduce the amount of generation of the vortex23. Consequently, the temperature of the central part of the semiconductor device2can be further lowered, and the unevenness of the temperature distribution in the semiconductor device2can be reduced.

The functions and effects of the semiconductor module1according to the first embodiment will be further described with reference toFIG.10.FIG.10is an explanatory diagram for explaining the flow of the coolant in the first flow path5of the heat sink3according to the first embodiment.

As illustrated inFIG.10, in the heat sink3according to the first embodiment, the first fins13disposed in the adjacent first divided regions51protrude from the different first partition walls12. The length directions of the first fins13disposed in the adjacent first divided regions51are orthogonal to each other. The length directions of the adjacent junction flow paths7are orthogonal to each other. The four junction flow paths7are disposed at equal intervals. The coolant in the first inter-fin flow paths16in the first divided region51aflows from the left to the right of the sheet ofFIG.10. The coolant in the first inter-fin flow paths16in the first divided region51bflows from the bottom to the top of the sheet ofFIG.10. The coolant in the first inter-fin flow paths16in the first divided region51cflows from the right to the left of the sheet ofFIG.10. The coolant in the first inter-fin flow paths16in the first divided region51dflows from the top to the bottom of the sheet ofFIG.10. That is, in the first embodiment, the coolant flows evenly to the top, to the bottom, to the left, and to the right of the sheet ofFIG.10in the first inter-fin flow paths16, thus being able to reduce the unevenness of the temperature distribution in the semiconductor device2. In addition, since the four junction flow paths7are disposed at equal intervals, the coolant provides an even cooling effect on the heat transfer plate31when the coolant strikes the second surface31bof the heat transfer plate31at positions close to the central part of the semiconductor device2as illustrated inFIG.9.

As illustrated inFIG.10, in the first embodiment, the junction flow paths7are placed on the root portions of the first fins13connected to the first partition walls12. Thus, the coolant that has flowed from the junction flow paths7into the first inter-fin flow paths16flows from the vicinities of the first partition walls12toward the first common header region52. That is, part of the coolant flowing through the first inter-fin flow paths16first comes into contact with portions of the heat transfer plate31close to the central part of the semiconductor device2, and then comes into contact with portions of the heat transfer plate31close to the outer peripheral part of the semiconductor device2. Consequently, more heat in the portions of the heat transfer plate31close to the central part of the semiconductor device2can be absorbed by the coolant, so that the unevenness of the temperature distribution in the semiconductor device2can be reduced. The coolant flowing through the first inter-fin flow paths16absorbs more heat toward the outer periphery of the first flow path-forming plate32, thus increasing in temperature. Consequently, the cooling effect by the coolant on the outer peripheral part of the semiconductor device2is relatively lower than the cooling effect by the coolant on the central part of the semiconductor device2, so that the unevenness of the temperature distribution in the semiconductor device2can be reduced.

In the first embodiment, since the cooling effect on the central part of the semiconductor device2is higher than that on the outer peripheral part of the semiconductor device2, even if the length of the first inter-fin flow paths16is shortened, for example, even if the length of the first inter-fin flow paths16is halved, the cooling effect by the coolant on the central part of the semiconductor device2can be sufficiently exerted. Further, by shortening the length of the first inter-fin flow paths16, the pressure loss of the coolant in the first inter-fin flow paths16can be reduced.

As illustrated inFIG.8, in the first embodiment, the four first divided regions51separated by the four first partition walls12are formed in the first flow path5. A position where part of the first divided regions51are projected onto the first surface31acoincide the semiconductor device2. When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, each junction flow path7coincides with the corresponding one of the plurality of first divided regions51. Consequently, the coolant flows from the junction flow paths7into the first divided regions51, and the coolant strikes the second surface31bof the heat transfer plate31in the first divided regions51. This increases the number of points where the coolant strikes the second surface31bof the heat transfer plate31, enhancing the cooling effect by the coolant on the semiconductor device2. Experiments conducted by the present inventors have revealed that when part of the first flow path5is divided into the plurality of first divided regions51, the cooling effect on the semiconductor device2by the coolant is enhanced as compared with a case where straight fins are arranged without providing the first partition walls12, that is, a case where part of the first flow path5is not divided into the plurality of first divided regions51. The experimental results are based on the condition that the average flow velocity of the coolant flowing through the first inter-fin flow paths16is the same between the case where part of the first flow path5is divided into the plurality of first divided regions51and the case where part of the first flow path5is not divided into the plurality of first divided regions51.

As illustrated inFIG.2, in the first embodiment, the first common header region52provided around the first divided regions51is formed in the first flow path5, and the first common header region52communicates with the first inter-fin flow paths16in the first divided regions51. This allows all the first inter-fin flow paths16in the first divided regions51and the first common header region52to be disposed in the same layer, thus thinning of the entire heat sink3and reducing of the size of the heat sink3can be achieved. As illustrated inFIG.3, in the first embodiment, the second common header region62, which is provided so as to surround the second divided regions61, is formed in the second flow path6, and the second common header region62communicates with the second inter-fin flow paths21in the second divided regions61. This allows all the second inter-fin flow paths21in the second divided regions61and the second common header region62to be disposed in the same layer, thus thinning the entire heat sink3and reducing the size of the heat sink3can be achieved.

The heat sink3and the semiconductor device2have different thermal expansion coefficients and Young's moduli. Thus, heat generated at the time of joining the heat sink3and the semiconductor device2increases warpage, stress, and distortion that occur between the heat sink3and the semiconductor device2. This causes adverse effects such as the destruction of the semiconductor device2and a poor joint between the heat sink3and the semiconductor device2. When the entire heat sink3can be made thin as in the first, warpage, stress, and strain that occur between the heat sink3and the semiconductor device2can be reduced, and the occurrence of adverse effects as described above can be suppressed.

The larger the number of the first divided regions51illustrated inFIG.1, the higher the cooling effect on the semiconductor device2. On the other hand, the larger the number of the first divided regions51, the higher the production cost of the heat sink3. In general, the heat sink3including the coolant flow path4is produced by joining and cutting a plurality of members. As the number of the first divided regions51increases, the number of junctions and the number of cutting points increase, thus increasing the production cost of the heat sink3. Therefore, when part of the first flow path5is divided into the four first divided regions51as in the first embodiment, both the improvement of the cooling effect on the semiconductor device2by the coolant and the suppression of the production cost increase of the heat sink3can be achieved in a balanced manner.

As illustrated inFIG.1, in the first embodiment, the first fins13are formed in a flat plate shape, and the plurality of first fins13are arranged side by side in parallel to each other. Consequently, the first inter-fin flow paths16are easily designed and produced. In addition, in the first embodiment, the second fins18are formed in a flat plate shape, and the plurality of second fins18are arranged side by side in parallel to each other. Consequently, the second inter-fin flow paths21are easily designed and produced.

The object to be cooled is not limited to the semiconductor device2as long as it is an electronic device that generates heat, and may be, for example, a capacitor. The first embodiment uses diffusion bonding as a method of joining each of the plates31to35, but the joining of each of the plates31to35is not limited to a particular method, but for example, brazing may be used. Each of the heat transfer plate31, the first flow path-forming plate32, the junction flow path-forming plate33, and the second flow path-forming plate34is produced by performing processing to form openings in a flat plate. Processing methods for forming openings include blanking, cutting, wire cutting, and etching. For a method of producing the heat sink3, for example, a production method disclosed in Japanese Patent Application Laid-open No. 2007-205694 etc. may be used. That is, by stacking and joining a large number of thin plates, the heat sink3may be produced. When the heat sink3is produced in this way, for example, each of the first flow path-forming plate32, the junction flow path-forming plate33, and the second flow path-forming plate34is formed by a plurality of thin plates. In the first embodiment, the heat sink3is formed of the plurality of plates31to35, but the heat sink3may be integrally formed using a 3D printer or the like. When the heat sink3is integrally formed, the members are not actually separated, but a region having the first surface31aand the second surface31bis regarded as the first plate. When the heat sink3is integrally formed, a region having the third surface33aand the fourth surface33bis regarded as the second plate. When the heat sink3is integrally formed, a region that forms the second flow paths6with the second plate is regarded as the third plate. In the first embodiment, the four first divided regions51are provided, but a plurality of first divided regions51other than four may be provided. The numbers of the second divided regions61and the junction flow paths7may be appropriately changed according to the number of the first divided regions51. In the first embodiment, the plurality of first fins13are arranged side by side in parallel, but may not be arranged side by side in parallel. In the first embodiment, the plurality of second fins18are arranged side by side in parallel, but may not be arranged side by side in parallel. In the first embodiment, the heat sink3includes the second flow path-forming plate34and the bottom plate35, and the coolant flow path4includes the second flow path6and the plurality of junction flow paths7. However, the second flow path-forming plate34and the bottom plate35may be omitted so that the coolant flow path4does not include the second flow path6and the plurality of junction flow paths7. In this configuration, the junction flow path-forming plate33is made a flat plate without openings like the bottom plate35according to the first embodiment. Further, the third opening10of the first flow path-forming plate32is omitted. The first opening8is created at a position that coincides with the first divided regions51in a planar view. For example, a first opening8may be created at a position that coincides with the corresponding one of the plurality of first divided regions51. In the first embodiment, a single junction flow path7is arranged at a position that coincides with the corresponding one of the plurality of first divided regions51, but two or more may be placed there. A single junction flow path7may be formed in the junction flow path-forming plate33, and the single junction flow path7may be arranged at a position that coincides with all the first divided regions51. In the first embodiment, the junction flow paths7are placed on the root portions of the first fins13connected to the first partition walls12. However, the positions of the junction flow paths7relative to the first fins13may be appropriately changed as long as the junction flow paths7are placed at positions that coincide with the first fins13.

Next, the semiconductor module1according to a first modification of the first embodiment will be described with reference toFIG.11.FIG.11is a diagram illustrating the heat sink3of the semiconductor module1according to the first modification of the first embodiment, and is an explanatory diagram for explaining the flow of the coolant in the first flow path5of the heat sink3. In the first modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The first modification is different from the first embodiment in the flow of the coolant in the first flow path5.

As illustrated inFIG.11, in the heat sink3according to the first modification, part of the first flow path5is divided into the four first divided regions51by the four first partition walls12. The first fins13disposed in the adjacent first divided regions51cand51ddo not protrude from the different first partition walls12. That is, the first fins13disposed in the adjacent first divided regions51cand51dprotrude from the same first partition wall12din opposite directions. The length directions of the first fins13disposed in the first divided regions51a,51c, and51dare parallel to each other. When the junction flow paths7are placed on the root portions of the first fins13connected to the first partition walls12, the three junction flow paths7a,7c, and7dare parallel to each other. The four junction flow paths7are disposed at unequal intervals. The coolant in the first inter-fin flow paths16in the first divided regions51aand51dflows from the left to the right of the sheet ofFIG.11. The coolant in the first inter-fin flow paths16in the first divided region51bflows from the bottom to the top of the sheet ofFIG.11. The coolant in the first inter-fin flow paths16in the first divided region51cflows from the right to the left of the sheet ofFIG.11. In the first modification, the positions of part of the first partition walls12when projected onto the first surface31a(not illustrated) also coincide with the central part of the semiconductor device2. Positions of part of the first fins13when projected onto the first surface31acoincide with the periphery of the central part of the semiconductor device2. Thus, heat generated in the central part of the semiconductor device2is easily transferred to the first partition walls12and the first fins13through the heat transfer plate31. Since the heat transferred to the first partition walls12and the first fins13is absorbed by the coolant flowing through the first inter-fin flow paths16, the cooling effect on the central part of the semiconductor device2is enhanced.

Next, the semiconductor module1according to a second modification of the first embodiment will be described with reference toFIGS.12and13.FIG.12is an exploded perspective view illustrating the semiconductor module1according to the second modification of the first embodiment.FIG.13is a partially enlarged cross-sectional view of the semiconductor module1according to the second modification of the first embodiment. In the second modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The second modification is different from the first embodiment in the flow of the coolant.

As illustrated inFIG.12, in the first modification, the coolant is caused to flow from the second opening9into the heat sink3. The coolant that has flowed from the second opening9into the heat sink3flows into the first common header region52. Then, the coolant flows from the first common header region52into the first inter-fin flow paths16in the first divided regions51. Next, the coolant flows from the first inter-fin flow paths16into the second inter-fin flow paths21in the second divided regions61through the junction flow paths7. At this time, the coolant in the first inter-fin flow paths16in the first divided region51aflows into the second inter-fin flow paths21in the second divided region61athrough the junction flow path7a. The coolant in the first inter-fin flow paths16in the first divided region51bflows into the second inter-fin flow paths21in the second divided region61bthrough the junction flow path7b. The coolant in the first inter-fin flow paths16in the first divided region51cflows into the second inter-fin flow paths21in the second divided region61cthrough the junction flow path7c. The coolant in the first inter-fin flow paths16in the first divided region51dflows into the second inter-fin flow paths21in the second divided region61dthrough the junction flow path7d. After that, the coolant flows from the second inter-fin flow paths21in the second divided regions61into the second common header region62. Then, the coolant flows from the second common header region62to the outside of the heat sink3through the fourth opening11, the third opening10, and the first opening8.

Next, the flow of the coolant in the first inter-fin flow paths16and the junction flow paths7will be described with reference toFIG.13. The coolant flowing into the first inter-fin flow paths16flows toward the first partition walls12. The coolant illustrated inFIG.13flows through the first inter-fin flow path16from the left to the right of the sheet ofFIG.13and strikes the first partition wall12. The coolant is changed in flow downward of the sheet ofFIG.13by the first partition wall12and flows into the junction flow path7. At this time, a vortex23is generated near the joint22between the heat transfer plate31and the first partition wall12. The faster the flow velocity of the coolant flowing through the first inter-fin flow path16, the smaller the scale of the vortex23. Thus, the effect of the vortex23on the temperature rise of the heat transfer plate31and the first partition wall12is suppressed. When the coolant strikes the first partition wall12, the boundary layer of the coolant becomes thinner, so that the first partition wall12can be efficiently cooled. The first partition walls12, which are disposed near the central part of the semiconductor device2, are portions to which heat from the central part of the semiconductor device2is easily transferred through the heat transfer plate31. By the coolant striking the first partition walls12, the first partition walls12can be intensively cooled, so that the temperature of the central part of the semiconductor device2can be efficiently lowered. Heat generated in the semiconductor device2is transferred to the coolant through the heat transfer plate31, the first partition walls12, and the first fins13. Passing a sufficient amount of the coolant for the amount of heat generated by the semiconductor device2through the coolant flow path4can suppress the rise of the coolant temperature caused by heat transferred from the semiconductor device2. Thus, the larger the amount of the coolant flow, the more efficiently the central part of the semiconductor device2can be cooled, so that the unevenness of the temperature distribution in the semiconductor device2can be reduced.

Next, the semiconductor module1according to a third modification of the first embodiment will be described with reference toFIG.14.FIG.14is a diagram illustrating the semiconductor module1according to the third modification of the first embodiment, and is a plan view illustrating the first partition walls12, the first fins13, and the junction flow paths7projected onto the first surface31a. InFIG.14, for ease of explanation, the first partition walls12and the first fins13are illustrated by solid lines, and the junction flow paths7and the semiconductor device2are illustrated by broken lines. InFIG.14, for ease of explanation, the heat transfer plate31is drawn extremely small. In the third modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The third modification is different from the first embodiment in that the flow path width of the first inter-fin flow paths16is unequalized.

Each first divided region51is provided with the plurality of first inter-fin flow paths16. In each first divided region51, the flow path width of the first inter-fin flow paths16is unequal. The flow path width of the first inter-fin flow paths16is small in a position close to the central part of the semiconductor device2and is large in a position close to the outer peripheral part of the semiconductor device2. In the first modification, six first inter-fin flow paths16are provided in each first divided region51. The first four first inter-fin flow paths16on the side close to the central part of the semiconductor device2have the same flow path width. Hereinafter, these four first inter-fin flow paths16may sometimes be referred to as center-side inter-fin flow paths16A. The remaining two first inter-fin flow paths16have the same flow path width. Hereinafter, these two first inter-fin flow paths16may sometimes be referred to as outer-peripheral-side inter-fin flow paths16B. The flow path width of the outer-peripheral-side inter-fin flow paths16B is larger than the flow path width of the center-side inter-fin flow paths16A. In each first divided region51, the first inter-fin flow paths16have the same flow path length.

In the first modification, three junction flow paths7are placed on each of the plurality of first divided regions51. In each first divided region51, the flow path area of the junction flow path7in the position close to the central part of the semiconductor device2is large, and the flow path area of the junction flow paths7in the position close to the outer peripheral part of the semiconductor device2is small. The flow path area of the junction flow path7closest to the central part of the semiconductor device2is larger than the flow path area of the remaining two junction flow paths7. Hereinafter, the junction flow path7closest to the central part of the semiconductor device2may sometimes be referred to as a center-side junction flow path7A, and the remaining two junction flow paths7may sometimes be referred to as outer-peripheral-side junction flow paths7B. The two outer-peripheral-side junction flow paths7B have the same flow path area. Each outer-peripheral-side junction flow path7B communicates with the corresponding one of the outer-peripheral-side inter-fin flow paths16B. Although not illustrated, the second inter-fin flow paths21have the same configuration as the first inter-fin flow paths16. That is, the second inter-fin flow paths21having a small flow path width are provided in a position close to the central part of the semiconductor device2, and the second inter-fin flow paths21having a large flow path width are provided in a position close to the outer peripheral part of the semiconductor device2.

In the first modification, by making the flow path width of the first inter-fin flow paths16small in the position close to the central part of the semiconductor device2and large in the position close to the outer peripheral part of the semiconductor device2, the first fins13can be densely disposed to dispose more first fins13in the position close to the central part of the semiconductor device2. Consequently, the area of heat dissipation by the first fins13can be increased, and the number of points where the coolant strikes the second surface31bof the heat transfer plate31can be increased in the position close to the central part of the semiconductor device2as compared with those at the outer peripheral part of the semiconductor device2. This can further lower the temperature of the central part of the semiconductor device2, reducing the unevenness of the temperature distribution in the semiconductor device2. The flow path width of the first inter-fin flow paths16may be equalized as in the first embodiment, and, as in the first modification, the junction flow paths7having a large flow path area may be disposed in positions close to the central part of the semiconductor device2, and the junction flow paths7having a small flow path area may be disposed in positions close to the outer peripheral part of the semiconductor device2. This increases the amount of the coolant flow in the positions close to the central part of the semiconductor device2compared to that at the outer peripheral part of the semiconductor device2. Consequently, the temperature of the central part of the semiconductor device2is lowered more than that of the outer peripheral part of the semiconductor device2, and the unevenness of the temperature distribution in the semiconductor device2can be reduced.

When the flow path width of the first inter-fin flow paths16is narrowed in the positions close to the central part of the semiconductor device2, and is widened in the positions close to the outer peripheral part of the semiconductor device2, the pressure loss of the coolant differs between the first inter-fin flow paths16of the small flow path width and the first inter-fin flow paths16of the large flow path width, and an uneven flow may occur. In this regard, in the first modification, by increasing the flow path area of the junction flow paths7in the positions close to the central part of the semiconductor device2and reducing that in the positions close to the outer peripheral part of the semiconductor device2, the pressure loss of the coolant can be adjusted to be equal between the first inter-fin flow paths16of the small flow path width and the first inter-fin flow paths16of the large flow path width. This allows adjustment to equalize the amount of the coolant flowing through the first inter-fin flow paths16of the small flow path width and the amount of the coolant flowing through the first inter-fin flow paths16of the large flow path width.

Next, the semiconductor module1according to a fourth modification of the first embodiment will be described with reference toFIGS.1,9, and15.FIG.15is a plan view illustrating the first flow path-forming plate32of the semiconductor module1according to the fourth modification of the first embodiment. In the fourth modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The fourth modification is different from the first embodiment in that the width of the first partition walls12is smaller than the width of the first fins13.

The width of the first partition walls12is smaller than the width of the first fins13. As described above, when the coolant flows into the heat sink3from the first opening8illustrated inFIG.1, the coolant strikes the second surface31bof the heat transfer plate31as illustrated inFIG.9, and vortices23are generated near the joints22between the first partition walls12and the heat transfer plate31. When such vortices23are generated, the heat exchange efficiency of the first partition walls12may become lower than the heat exchange efficiency of the first fins13, decreasing the cooling effect on the central part of the semiconductor device2. Thus, in the first modification, as illustrated inFIG.15, by making the width of the first partition walls12smaller than the width of the first fins13, the second surface31bof the heat transfer plate31illustrated inFIG.9can be brought closer to the central part of the semiconductor device2, and the contact area of the coolant coming into contact with the second surface31bof the heat transfer plate31can be increased. Consequently, even when the vortices23are generated, the cooling effect on the central part of the semiconductor device2is enhanced.

Next, the semiconductor module1according to a fifth modification of the first embodiment will be described with reference toFIGS.12,13, and16.FIG.16is a plan view illustrating the first flow path-forming plate32of the semiconductor module1according to the fifth modification of the first embodiment. In the fifth modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The fifth modification is different from the first embodiment in that the width of the first partition walls12is larger than the width of the first fins13.

The width of the first partition walls12is larger than the width of the first fins13. When the coolant flows into the heat sink3from the second opening9illustrated inFIG.12, the coolant strikes the first partition walls12as illustrated inFIG.13. When the coolant strikes the first partition walls12in this way, the heat exchange efficiency of the first partition walls12can become higher than the heat exchange efficiency of the first fins13, and the first partition walls12may be eroded by the coolant striking them. Thus, in the first modification, as illustrated inFIG.16, by making the width of the first partition walls12larger than the width of the first fins13, the heat dissipation area of the first partition walls12can be increased, enhancing the cooling effect on the central part of the semiconductor device2, and the life of the first partition walls12can be extended.

Next, the semiconductor module1according to a sixth modification of the first embodiment will be described with reference toFIGS.1,17, and18.FIG.17is a plan view illustrating the first partition walls12and the first fins13of the semiconductor module1according to the sixth modification of the first embodiment.FIG.18is a plan view illustrating the second partition walls17and the second fins18of the semiconductor module1according to the sixth modification of the first embodiment. In the sixth modification, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The sixth modification is different from the first embodiment in that the flow path width of the second inter-fin flow paths21is larger than the flow path width of the first inter-fin flow paths16, and the width of the second fins18is larger than the width of the first fins13.

The flow path width of the second inter-fin flow paths21illustrated inFIG.18is larger than the flow path width of the first inter-fin flow paths16illustrated inFIG.17. In other words, the installation interval between the second fins18is larger than the installation interval between the first fins13. The width of the second fins18illustrated inFIG.18is larger than the width of the first fins13illustrated inFIG.17.

As illustrated inFIG.1, the second inter-fin flow paths21are placed farther from the semiconductor device2than the first inter-fin flow paths16, and thus less contribute to the cooling of the semiconductor device2than the first inter-fin flow paths16. On the other hand, the smaller the flow path width of the second inter-fin flow paths21is made, the larger the pressure loss of the coolant in the second inter-fin flow paths21becomes. Therefore, in the first modification, as illustrated inFIGS.17and18, by making the flow path width of the second inter-fin flow paths21larger than the flow path width of the first inter-fin flow paths16, the pressure loss of the coolant in the second inter-fin flow paths21can be reduced.

Here, the functions and effects of the first modification will be further described. For example, an insulating material that interrupts electric conduction may be disposed between the semiconductor device2and the heat transfer plate31illustrated inFIG.1to provide insulation between the semiconductor device2and the heat transfer plate31. The material of the heat transfer plate31is, for example, copper. On the other hand, the material of the insulating material is, for example, aluminum nitride or silicon carbide. Since the heat transfer plate31and the insulating material are formed of different types of materials, there is a difference in thermal expansion coefficient between the heat transfer plate31and the insulating material. Therefore, warpage occurs in the heat transfer plate31when the heat transfer plate31and the insulating material are cooled after the heat transfer plate31and the insulating material have risen in temperature at the time of joining of the heat transfer plate31and the insulating material. When warpage occurs in the heat transfer plate31, warpage also occurs in the other plates32to35, and the entire heat sink3warps.

As a way to reduce such warpage of the heat sink3, a possible way is not only join an insulating material to the heat transfer plate31but also join an insulating material to the bottom plate35so that the heat transfer plate31and the bottom plate35have almost the same configuration. As another way to reduce the warpage of the heat sink3, a possible way is to configure the first flow path-forming plate32and the second flow path-forming plate34almost the same. In the first embodiment, the latter way is adopted, and the configuration of the first fins13in the first flow path-forming plate32and the configuration of the second fins18in the second flow path-forming plate34are made the same. That is, the installation interval between the first fins13and the installation interval between the second fins18are made equal, and the width of the first fins13and the width of the second fins18are made equal.

On the other hand, when the installation interval between the second fins18is made larger than the installation interval between the first fins13with emphasis on reducing the pressure loss of the coolant in the second inter-fin flow paths21as in the first modification illustrated inFIGS.17and18, the warpage of the heat sink3cannot be reduced. In this regard, in the first modification, by making the width of the second fins18larger than the width of the first fins13, the rigidity of the second fins18can be increased to suppress the warpage of the heat sink3. That is, in the first modification, by making the flow path width of the second inter-fin flow paths21larger than the flow path width of the first inter-fin flow paths16, the pressure loss of the coolant in the second inter-fin flow paths21can be reduced, and by making the width of the second fins18larger than the width of the first fins13, the warpage of the heat sink3can be suppressed. The warpage of the heat sink3may be reduced by increasing not only the width of the second fins18but also the width of the first fins13. The warpage of the heat sink3may be reduced by increasing only the width of the first fins13.

Second Embodiment

Next, a semiconductor module1A according to a second embodiment of the present invention will be described with reference toFIG.19.FIG.19is a diagram illustrating the semiconductor module1A according to the second embodiment of the present invention, and is a plan view illustrating the first partition walls12, the first fins13, and the junction flow paths7projected onto the first surface31a. InFIG.19, for ease of explanation, the first partition walls12and the first fins13are illustrated by solid lines, and the junction flow paths7and the semiconductor device2are illustrated by broken lines. InFIG.19, for ease of explanation, the heat transfer plate31is drawn extremely small. In the second embodiment, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The second embodiment is different from the first embodiment in that six first divided regions51are provided.

In the second embodiment, part of the first flow path5is divided into the six first divided regions51by six first partition walls12. The six first partition walls12extend radially from a center point. The six first partition walls12are disposed at 60 degree intervals along a circumferential direction around the center point. When the six first partition walls12are distinguished, they are referred to as first partition walls12e,12f,12g,12h,12i, and12j. When the six first divided regions51are distinguished, they are referred to as first divided regions51e,51f,51g,51h,51i, and51j. Although not illustrated, part of the second flow path6is also divided into six second divided regions61by six second partition walls17.

Six junction flow paths7are disposed at 60 degree intervals along a circumferential direction around a center point. When the six junction flow paths7are distinguished, they are referred to as junction flow paths7e,7f,7g,7h,7i, and7j. In a planar view, the first divided region51eand the junction flow path7ecoincide with each other. In a planar view, the first divided region51fand the junction flow path7fcoincide with each other. In a planar view, the first divided region51gand the junction flow path7gcoincide with each other. In a planar view, the first divided region51hand the junction flow path7hcoincide with each other. In a planar view, the first divided region51iand the junction flow path7icoincide with each other. In a planar view, the first divided region51jand the junction flow path7jcoincide with each other.

Positions when part of the first partition walls12, part of the first fins13, and part of the first inter-fin flow paths16are projected onto the first surface31acoincide with the semiconductor device2. In the second embodiment, the center point of the six first partition walls12coincides with the central part of the semiconductor device2. A position where a part of the first partition walls12is projected onto the first surface31acoincides with the central part of the semiconductor device2and the periphery of the central part of the semiconductor device2. Positions when part of the first fins13and part of the first inter-fin flow paths16are projected onto the first surface31acoincide with the periphery of the central part of the semiconductor device2. Although the position when part of the first partition walls12are projected onto the first surface31acoincide with the central part of the semiconductor device2in the second embodiment, the position when part of the first fins13are projected onto the first surface31amay coincide with the central part of the semiconductor device2.

When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, each junction flow path7is disposed at a position that coincides with the corresponding one of the plurality of first divided regions51, and is formed elongatedly across the plurality of first fins13. The length direction of each junction flow path7is orthogonal to the length direction of the first fins13. Each junction flow path7is disposed at a position that coincides with root portions of the first fins13connected to the first partition wall12.

In the second embodiment, part of the first flow path5is divided into the six first divided regions51by the six first partition walls12. When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, each junction flow path7coincides with the corresponding one of the plurality of first divided regions51. Consequently, the coolant flows from the junction flow paths7into the first divided regions51, and the coolant strikes the second surface31bof the heat transfer plate31in the first divided regions51. As a result, compared to the heat sink3according to the first embodiment in which the four first divided regions51are provided, the number of points where the coolant strikes the second surface31bof the heat transfer plate31is increased, enhancing the cooling effect on the central part of the semiconductor device2. In the second embodiment, to approximately equalize the pressure loss of the coolant in the first inter-fin flow paths16, the lengths of the first fins13in the first divided regions51are made approximately equal. However, the first fins13in the first divided regions51may have different lengths.

Third Embodiment

Next, a semiconductor module1B according to a third embodiment of the present invention will be described with reference toFIGS.20to23.FIG.20is an exploded perspective view illustrating the semiconductor module1B according to the third embodiment of the present invention.FIG.21is a plan view illustrating the first flow path-forming plate32of the semiconductor module1B according to the third embodiment.FIG.22is a cross-sectional view of the semiconductor module1B taken along line XXII-XXII illustrated inFIG.21.FIG.23is a cross-sectional view of the semiconductor module1B taken along line XXIII-XXIII illustrated inFIG.21. InFIG.21, for explanatory convenience, the semiconductor device2and the junction flow paths7are illustrated by broken lines. InFIG.21, for explanatory convenience, only the first flow path-forming plate32of the heat sink3is illustrated, and the positions of the cross sections of the semiconductor module1B illustrated inFIGS.22and23are indicated using the first flow path-forming plate32. In the third embodiment, the same reference numerals are assigned to portions corresponding to those in the above-described first embodiment to omit explanation. The third embodiment is different from the first embodiment in that the first opening8and the second opening9are provided in the bottom plate35, the third opening10is provided in the second flow path-forming plate34, and two first divided regions51are provided.

As illustrated inFIG.20, the heat sink3is formed by stacking the heat transfer plate31, the first flow path-forming plate32, the junction flow path-forming plate33, the second flow path-forming plate34, and the bottom plate35. From the side closer to the semiconductor device2, the heat transfer plate31, the first flow path-forming plate32, the junction flow path-forming plate33, the second flow path-forming plate34, and the bottom plate35are arranged in this order. The heat transfer plate31is a flat plate without openings. In the third embodiment, the first opening8and the second opening9are formed in the bottom plate35. The first opening8and the second opening9are provided in positions away from each other. The first opening8and the second opening9pass through the bottom plate35in the thickness direction of the bottom plate35. One of the first opening8and the second opening9serves as a coolant inlet. The other of the first opening8and the second opening9serves as a coolant outlet.

In the third embodiment, the third opening10is formed in the second flow path-forming plate34. The third opening10passes through the second flow path-forming plate34in the thickness direction of the second flow path-forming plate34. A second dividing wall19eis provided around the third opening10. The third opening10is separated from the second divided regions61and the second common header region62by the second dividing wall19e. This prevents the coolant flowing through the third opening10from meeting the coolant flowing through the second divided regions61and the second common header region62. In a planar view, the first opening8, the third opening10, the fourth opening11, and the first common header region52are disposed at a position that coincides with each other. The first opening8, the third opening10, the fourth opening11, and the first common header region52communicate with each other.

As illustrated inFIG.21, in the third embodiment, part of the first flow path5is divided into the two first divided regions51by one first partition wall12. The first partition wall12extends linearly along the left-right direction of the sheet ofFIG.21. When the two first divided regions51are distinguished, they are referred to as first divided regions51kand51m. The first partition wall12protrudes inward from a side of the first outer peripheral wall15in a rectangular annular shape. The distal end of the first partition wall12is connected to a first dividing wall14ein a rectangular shape. One of two spaces partitioned off by the first partition wall12, the side of the first outer peripheral wall15, and the first dividing wall14eis the first divided region51k. The other of the two spaces partitioned off by the first partition wall12, the side of the first outer peripheral wall15, and the first dividing wall14eis the first divided region51m.

The plurality of first fins13are disposed in each first divided regions51. The plurality of first fins13are arranged by being spaced side by side in parallel. The first fins13in all the first divided regions51are installed at equal intervals. The first fins13protrude from the first partition wall12toward the first divided regions51. One end of each first fin13along the length direction is connected to the first partition wall12. The other end of each first fin13along the length direction faces the first common header region52. The first fins13disposed in the adjacent first divided regions51protrude in opposite directions from the same first partition wall12. The first fins13protrude from one end face of the first partition wall12along the width direction and the other end face of the first partition wall12along the width direction. The first inter-fin flow paths16are formed between the adjacent first fins13and13, between the first fins13and the side of the first outer peripheral wall15adjacent to each other, and between the first fins13and the first dividing wall14eadjacent to each other.

As illustrated inFIG.20, in the third embodiment, part of the second flow path6is divided into two second divided regions61by one second partition wall17. The second partition wall17extends linearly along the left-right direction of the sheet ofFIG.20. When the two second divided regions61are distinguished, they are referred to as second divided regions61kand61m. In a planar view, the second common header region62is disposed at a position that coincides with the second opening9. The second common header region62communicates with the second opening9.

The second partition wall17protrudes inward from a side of the second outer peripheral wall20in a rectangular annular shape. The distal end of the second partition wall17is connected to the second dividing wall19ein a rectangular shape. One of two spaces partitioned off by the second partition wall17, the side of the second outer peripheral wall20, and the second dividing wall19eis the second divided region61k. The other of the two spaces partitioned off by the second partition wall17, the side of the second outer peripheral wall20, and the second dividing wall19eis the second divided region61m.

The plurality of second fins18are disposed in each second divided region61. The plurality of second fins18are arranged by being spaced side by side in parallel. The second fins18in all the second divided regions61are installed at equal intervals. The second fins18protrude from the second partition wall17toward the second divided regions61. One end of each second fin18along the length direction is connected to the second partition wall17. The other end of each second fin18along the length direction faces the second common header region62. The second fins18disposed in the adjacent second divided regions61protrude in opposite directions from the same second partition wall17. The second fins18protrude from one end face of the second partition wall17along the width direction and the other end face of the second partition wall17along the width direction. The second inter-fin flow paths21are formed between the adjacent second fins18and18, between the second fins18and the side of the second outer peripheral wall20adjacent to each other, and between the second fins18and the second dividing wall19eadjacent to each other. The length direction of the first fins13in the first divided region51kand the length direction of the second fins18in the second divided region61kare parallel to each other. The length direction of the first fins13in the first divided region51mand the length direction of the second fins18in the second divided region61mare parallel to each other.

As illustrated inFIG.22, the first fins13are provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The second fins18are provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35.

As illustrated inFIG.23, the first partition wall12is provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The first outer peripheral wall15is provided in contact with the second surface31bof the heat transfer plate31and the third surface33aof the junction flow path-forming plate33. The second partition wall17is provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35. The second outer peripheral wall20is provided in contact with the fourth surface33bof the junction flow path-forming plate33and the bottom plate35. The first inter-fin flow paths16and the second inter-fin flow paths21communicate with each other through the junction flow paths7. The width of the first partition wall12and the width of the second partition wall17are equal. The width of the first fins13and the width of the second fins18are equal. The installation interval between the first fins13is equal to the installation interval between the second fins18.

As illustrated inFIG.20, two junction flow paths7are placed at a distance from each other. When the two junction flow paths7are distinguished, they are referred to as junction flow paths7kand7m. In a planar view, the first divided region51k, the second divided region61k, and the junction flow path7kare disposed at a position that coincides with each other. In a planar view, the first divided region51m, the second divided region61m, and the junction flow path7mare disposed at a position that coincides with each other.

As illustrated inFIG.21, a position where part of the first partition wall12, part of the first fins13, and part of the first inter-fin flow paths16are projected onto the first surface31a(not illustrated) coincides with the semiconductor device2. In the third embodiment, the center point of the first partition wall12coincides with the central part of the semiconductor device2. A position where a part of the first partition wall12is projected onto the first surface31acoincides with the central part of the semiconductor device2and the periphery of the central part of the semiconductor device2. A position where part of the first fins13and part of the first inter-fin flow paths16are projected onto the first surface31acoincides with the periphery of the central part of the semiconductor device2. Although a position where a part of the first partition wall12is projected onto the first surface31acoincides with the central part of the semiconductor device2in the third embodiment, a position where a part of the first fins13is projected onto the first surface31amay coincide with the central part of the semiconductor device2.

When the junction flow paths7, the first divided regions51, and the first fins13are projected onto the first surface31a, each junction flow path7coincides with the corresponding one of the plurality of first divided regions51and is formed elongatedly across the plurality of first fins13. The length direction of each junction flow path7is orthogonal to the length direction of the first fins13. Each junction flow path7coincides with root portions of the first fins13connected to the first partition wall12.

Next, the flow of the coolant will be described with reference toFIG.20. First, a case where the coolant is caused to flow in from the first opening8will be described. The coolant that has flowed from the first opening8into the heat sink3flows into the first common header region52through the third opening10and the fourth opening11. Then, the coolant flows from the first common header region52into the first inter-fin flow paths16in the first divided regions51. Next, the coolant flows from the first inter-fin flow paths16into the second inter-fin flow paths21in the second divided regions61through the junction flow paths7. At this time, the coolant in the first inter-fin flow paths16in the first divided region51kflows into the second inter-fin flow paths21in the second divided region61kthrough the junction flow path7k. The coolant in the first inter-fin flow paths16in the first divided region51mflows into the second inter-fin flow paths21in the second divided region61mthrough the junction flow path7m. After that, the coolant flows from the second inter-fin flow paths21in the second divided regions61into the second common header region62. Then, the coolant flows from the second common header region62to the outside of the heat sink3through the second opening9.

Next, a case where the coolant is caused to flow in from the second opening9will be described. The coolant that has flowed from the second opening9into the heat sink3flows into the second common header region62. Then, the coolant flows from the second common header region62into the second inter-fin flow paths21in the second divided regions61. Then, the coolant flows from the second inter-fin flow paths21into the first inter-fin flow paths16in the first divided regions51through the junction flow paths7. At this time, the coolant in the second inter-fin flow paths21in the second divided region61kflows into the first inter-fin flow paths16in the first divided region51kthrough the junction flow path7k. The coolant in the second inter-fin flow paths21in the second divided region61mflows into the first inter-fin flow paths16in the first divided region51mthrough the junction flow path7m. After that, the coolant flows from the first inter-fin flow paths16in the first divided regions51into the first common header region52. Then, the coolant flows from the first common header region52to the outside of the heat sink3through the fourth opening11, the third opening10, and the first opening8.

In the third embodiment, part of the first flow path5is divided into the two first divided regions51by the first partition wall12. Part of the second flow path6is divided into the two second divided regions61by the second partition wall17. The two junction flow paths7are formed in the junction flow path-forming plate33. Therefore, compared to the heat sink3according to the first embodiment in which the four first divided regions51, the four second divided regions61, and the four junction flow paths7are formed, the configuration of the first flow path5, the second flow path6, and the junction flow paths7is simpler, so that the production cost of the heat sink3can be reduced.

The first opening8and the second opening9may be provided in the heat transfer plate31or the bottom plate35, depending on the use conditions of the heat sink3. In the third embodiment, the number of plates forming the heat sink3is five, but the number of plates forming the heat sink3may be six or more. In the third embodiment, the heat sink3is formed of the plurality of plates31to35, but the heat sink3may be integrally formed using a 3D printer or the like.

The configurations shown in the above embodiments show an example of the subject matter of the present invention, and can be combined with another known art, and can be partly omitted or changed without departing from the scope of the present invention.

REFERENCE SIGNS LIST

1,1A,1B semiconductor module;2semiconductor device;3heat sink;4coolant flow path;5first flow path;6second flow path;7,7a,7b,7c,7d,7e,7f,7g,7h,7i,7j,7k,7mjunction flow path;7A center-side junction flow path;7B outer-peripheral-side junction flow path;8first opening;9second opening;10third opening;11fourth opening;12,12a,12b,12c,12d,12e,12f,12g,12h,12i,12jfirst partition wall;13first fin;14a,14b,14c,14efirst dividing wall;15first outer peripheral wall;16first inter-fin flow path;16A center-side inter-fin flow path;16B outer-peripheral-side inter-fin flow path;17,17a,17b,17c,17dsecond partition wall;18second fin;19a,19b,19c,19esecond dividing wall;20second outer peripheral wall;21second inter-fin flow path;22joint;23vortex;24central partition wall;31heat transfer plate;31afirst surface;31bsecond surface;32first flow path-forming plate;33junction flow path-forming plate;33athird surface;33bfourth surface;34second flow path-forming plate;35bottom plate;51,51a,51b,51c,51d,51e,51f,51g,51h,51i,51j,51k,51mfirst divided region;52first common header region;61,61a,61b,61c,61d,61k,61msecond divided region;62second common header region.