Cooler, semiconductor device, and vehicle

Abstract

The temperature of a heating element arranged along a refrigerant circulation direction is made uniform. A cooler (1) comprises: a top plate part (2) that has a first surface (201) facing a flow path (100) of a refrigerant and in which a heating element (5) is arranged on a rear surface (202) of the first surface; a bottom plate part (300) that has a second surface (301) facing the first surface of the top plate part; fins (240) that extend from the first surface of the top plate part toward the second surface of the bottom plate part; and a peripheral wall part (320) that is provided between the top plate part and the bottom plate part and surrounds the fins in a plan view of the first surface. The second surface of the bottom plate part is provided with a recess (360) that extends downstream from the upstream end of the refrigerant flow path and includes a region overlapping at least a part of the heating element in a plan view when the heating element is arranged on the back surface of the first surface of the top plate part. The recess has a section in which the dimension (Rx) in the width direction orthogonal to the refrigerant circulation direction narrows along the refrigerant circulation direction from an inflow port (120) of the refrigerant toward an outflow port (121) of the refrigerant in the refrigerant flow path.

Description

Cooler, semiconductor device, and vehicle

[0001] The present invention relates to a cooler, a semiconductor device, and a vehicle.

[0002] Some coolers for cooling electronic components such as semiconductor devices have a plurality of fins arranged in a coolant flow path through which a coolant flows, and some of these coolers have a cross-sectional area that varies from the inlet to the outlet in order to prevent a decrease in cooling efficiency from occurring as the coolant flows from the inlet to the outlet in the coolant flow path (see, for example, Patent Documents 1 to 4).

[0003] JP 2010-153785 A JP 2013-165096 A JP 2005-19904 A JP 2008-263137 A

[0004] In the above-described cooler, it is difficult to equalize the temperatures of the multiple heat generating elements arranged along the direction in which the refrigerant flows.

[0005] The present invention has been made in view of the above points, and has as its object to make the temperature of heating elements arranged along the flow direction of the refrigerant uniform.

[0006] According to one aspect of the present invention, a cooler includes a top plate having a first surface facing a refrigerant flow path and a heat generating element disposed on a backside of the first surface, a bottom plate having a second surface opposite the first surface of the top plate, fins extending from the first surface of the top plate toward the second surface of the bottom plate, and a peripheral wall disposed between the top plate and the bottom plate and surrounding the fins in a plan view of the first surface. The second surface of the bottom plate is provided with a recess extending from an upstream end of the refrigerant flow path toward a downstream end thereof, the recess including an area overlapping with at least a portion of the heat generating element in the plan view when the heat generating element is disposed on the backside of the first surface of the top plate, and the recess has a section whose dimension in a width direction perpendicular to the refrigerant flow direction narrows along the refrigerant flow direction from a refrigerant inlet to a refrigerant outlet in the refrigerant flow path.

[0007] According to the present invention, the temperatures of the heating elements arranged along the flow direction of the coolant can be made uniform.

[0008] 9A is a perspective view illustrating an example of the shape of a recess in a cooler according to a second embodiment, and FIG. 9B is a cross-sectional view of a cooler in which the recess is formed in the bottom surface of the bottom plate portion. FIG. 9B is a cross-sectional view of a cooler in which the recess is formed in the bottom surface of the bottom plate portion. FIG. 9A is a perspective view illustrating an example of the shape of a recess in a cooler according to a second embodiment, and FIG. 9B is a cross-sectional view of a cooler in which the recess is formed in the cooler according to the second embodiment. FIG. 9B is a cross-sectional view illustrating another example of the shape of a recess in a cooler according to the second embodiment. FIG. 9C is a cross-sectional view illustrating an example of the temperature of a heat generating element disposed in the cooler according to the second embodiment. FIG. 9D is a cross-sectional view illustrating an example of the pressure loss in a cooler according to the second embodiment. 14A is a graph showing an example of the relationship between the range of the recess in the refrigerant flow direction and thermal resistance, and FIG. 14B is a graph showing an example of the relationship between the range of the recess in the refrigerant flow direction and pressure loss. FIG. 16A is a graph showing an example of the relationship between the range of the recess in the flow path width direction and thermal resistance, and FIG. 16B is a graph showing an example of the relationship between the range of the recess in the flow path width direction and pressure loss. FIG. 16B is a cross-sectional view showing a modified example of the position of the recess in the flow path width direction in the bottom plate portion. FIG. 16A is a graph showing a first modified example of changes in the width and depth of the recess in the bottom surface of the bottom plate portion along the refrigerant flow direction. FIG. 16B is a graph showing a second modified example of changes in the width and depth of the recess in the bottom surface of the bottom plate portion along the refrigerant flow direction. FIG. 16B is a cross-sectional view showing a modified example of the cross-sectional shape of the recess in the bottom surface of the bottom plate portion. FIG. 16B is a schematic plan view showing an example of a vehicle equipped with the semiconductor device according to the embodiment.

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The X-axis, Y-axis, and Z-axis in each of the referenced figures are shown for the purpose of defining planes and directions in the illustrated coolers and the like. The X-axis, Y-axis, and Z-axis are orthogonal to each other and form a right-handed system. In the following description, the direction parallel to the X-axis will be referred to as the X-direction, the direction parallel to the Y-axis will be referred to as the Y-direction, and the direction parallel to the Z-axis will be referred to as the Z-direction. Furthermore, when the X-direction, Y-direction, and Z-direction are associated with the directions of the arrows (positive and negative) of the X-axis, Y-axis, and Z-axis shown in the drawings, they will be referred to as the "positive side" or "negative side."

[0010] In this specification, the Z direction may be referred to as the up-down direction. In this specification, "up" and "above" refer to the positive side of the Z direction relative to a reference surface, component, position, etc., and "down" and "below" refer to the negative side of the Z direction relative to a reference surface, component, position, etc. For example, when describing "component B is placed on component A," component B is placed on the positive side of component A in the Z direction. Furthermore, when describing "the top surface of component A," this surface is the surface located at the end of component A on the positive side of the Z direction and facing the positive side of the Z direction. These directions and surfaces are terms used for convenience of explanation, and their correspondence with the X-axis, Y-axis, and Z-axis directions may change depending on the installation posture of the cooler, etc. For example, the surface of the cooler on which the wiring board and semiconductor elements are placed is referred to as the top surface of the cooler in this specification, but may also be referred to as the bottom surface, side surface, etc. of the cooler.

[0011] The aspect ratios and relative sizes of components in each figure are merely schematic representations and do not necessarily correspond to the relationships in an actual cooler or the like. For convenience of explanation, it is assumed that the relative sizes of components may be exaggerated. Underlined symbols in the figures indicate symbols that refer to the entire component when a portion of the component referenced by that symbol is referenced by another symbol. The letters in symbols represented by numbers and their following letters are intended solely to distinguish between multiple components identified by the numbers. In the following description, the letters are omitted when multiple components are not distinguished by letters following the numbers. For example, when referring to a specific heating element among the three heating elements 5A-5C, the symbol will be followed by the letter; otherwise, it will simply be referred to as "heating element 5." Furthermore, terms such as "first" and "second" in the following description are intended solely to distinguish between multiple components with the same name. Furthermore, when the illustration on the printed page is an illustration of an actual object rotated 90 degrees (for example, Figure 1), descriptions such as "left side of the illustration" and "right side of the illustration" shall mean that on the printed page, "left side of the illustration" refers to the "bottom" and "right side of the illustration" refers to the "top."

[0012] In the following description, detailed descriptions of the configuration, function, operation, manufacturing method, etc. of the illustrated cooler that are the same as or similar to those of known coolers will be omitted.

[0013] [First embodiment] Fig. 1 is a plan view of a cooler according to a first embodiment. Fig. 2 is a plan view illustrating the shape of a water jacket. Fig. 3 is a longitudinal cross-sectional view illustrating a refrigerant flow path. Fig. 4 is a transverse cross-sectional view illustrating a refrigerant flow path. In this specification, a longitudinal cross-section refers to a cross-section parallel to the YZ plane, and a transverse cross-section refers to a cross-section parallel to the ZX plane. Fig. 3 illustrates the configuration of the YZ cross-section of the cooler 1 at the position of the dashed dotted line A-A' in Fig. 2, and Fig. 4 illustrates the configuration of the ZX cross-section of the cooler 1 at the position Y0 in the Y direction in Fig. 2.

[0014] The cooler 1 illustrated in FIGS. 1 to 4 includes a top plate 2 and a water jacket 3. The top plate 2 and the water jacket 3 are exemplary components that define a space (hereinafter referred to as the "refrigerant flow path 100") through which a refrigerant flows. The top plate 2 has fins 240 extending downward from a lower surface (first surface) 201. The water jacket 3 has a bottom plate portion 300 having a bottom surface (second surface) 301 that faces the lower surface 201 of the top plate 2 and forms the lower end of the refrigerant flow path 100, and a rectangular ring-shaped peripheral wall portion 320 that extends upward from the bottom plate portion 300 and surrounds the fins 240 of the top plate 2 when viewed from above (in the XY plane) of the bottom surface 310. The top plate 2 and the water jacket 3 are made of a metal or alloy with high thermal conductivity, such as aluminum or copper, and are manufactured by known methods such as casting, press processing, or a method using a 3D printer. The top plate 2 may be referred to as a "top plate portion" as one of the components of the cooler 1. In the following description, the term "planar view" may refer to a planar view parallel to any of the XY plane, the YZ plane, and the ZX plane, but when simply referred to as "planar view," it refers to a planar view parallel to the XY plane (XY planar view).

[0015] The top plate 2 has a heating element 5 arranged on its upper surface 202, which is the outer surface of the cooler 1. The illustrated top plate 2 is a rectangular plate-like member when viewed from above, with three heating elements 5A to 5C arranged along the longitudinal direction (Y direction). The heating element 5 may be, for example, a circuit component including a wiring board 6 and semiconductor elements (semiconductor chips) 7A and 7B arranged along the Y direction on the top surface of the wiring board 6. The wiring board 6 may be a laminated substrate in which conductive plates (conductive patterns) made of copper or the like are arranged on the top and bottom surfaces of an insulating substrate such as a ceramic substrate or an insulating resin substrate. The conductive plate arranged on the bottom surface of the insulating substrate is joined to the top surface 202 of the top plate 2 via a bonding material such as solder. The number of heating elements 5 arranged is not limited to three. The heating element 5 is not limited to the two semiconductor elements 7A and 7B arranged along the longitudinal direction of the top surface 202 of the top plate 2 as illustrated in FIG. 1. The semiconductor elements 7A and 7B may be arranged, for example, along the short side direction of the upper surface 202 of the top plate 2. Furthermore, the number of semiconductor elements 7 included in one heating element 5 is not limited to two. A plurality of heating elements 5 with different configurations (functions) may be arranged on the upper surface 202 of the top plate 2 via a bonding material such as solder.

[0016] A case 8 having a frame-shaped portion surrounding the heating element 5 in a planar view may be disposed on the upper surface 202 of the top plate 2. The case 8 may include an insulating resin portion having a frame-shaped portion surrounding the heating element 5 in a planar view, and terminals (not shown) electrically connected to electrodes of the semiconductor element 7A or 7B via wiring (conductor patterns) of the wiring board 6 in the heating element 5. The space surrounded by the case 8 may be sealed with epoxy resin or the like. The heating element 5 is not limited to the combination of the wiring board 6 and the semiconductor elements 7A and 7B illustrated above, but may also be a resin-sealed semiconductor device (semiconductor package) with an exposed heat sink, such as a DIP (Dual Inline Package) type. In this specification, the assembly of one wiring board 6 and the semiconductor elements 7A and 7B arranged on the wiring board 6 is referred to as the heating element 5, but the individual semiconductor elements 7A and 7B may also be referred to as heating elements.

[0017] The water jacket 3 is a member that is attached to the underside 201 of the top plate 2 to form the refrigerant flow path 100, and includes a bottom plate portion 300 and a peripheral wall portion 320. In the illustrated water jacket 3, the bottom plate portion 300 has a bottom surface 301 that faces the underside 201 of the top plate 2, and is a rectangular plate-shaped portion whose longitudinal direction is the Y direction in a plan view, similar to the top plate 2.

[0018] The peripheral wall portion 320 is a rectangular annular portion in a plan view located above the bottom plate portion 300. The peripheral wall portion 320 may be formed integrally with the bottom plate portion 300 or separately from the bottom plate portion 300. The separately formed bottom plate portion 300 and peripheral wall portion 320 may be joined with a bonding material, laser welding, ultrasonic welding, or fastened with bolts or the like. The referenced drawings illustrate a cooler 1 in which the outline of the top plate 2 is contained within the area surrounded by the outline of the water jacket 3 in a plan view. However, the outline of the top plate 2 and the outline of the water jacket 3 may be the same, or the outline of the water jacket 3 may be contained within the area surrounded by the outline of the top plate 2. The top plate 2 may have any shape as long as it can close (cover) the opening at the upper end of the peripheral wall portion 320 of the water jacket 3. The peripheral wall portion 320 of the cooler 1 may be formed integrally with the top plate 2.

[0019] The refrigerant flow path 100 of the cooler 1 may be a substantially rectangular parallelepiped space defined by a bottom surface 301 of the bottom plate portion 300, a lower surface 201 of the top plate 2, and inner circumferential wall surfaces 321A to 321D of the peripheral wall portion 320 that connect to the bottom surface 301 of the bottom plate portion 300 and the lower surface 201 of the top plate 2. The refrigerant flow path 100 communicates with the outside of the cooler 1 via a first through-hole 120 formed in the peripheral wall portion 320 so as to have one open end on a first inner circumferential wall surface 321A located at one end in the longitudinal direction, and a second through-hole 121 formed in the peripheral wall portion 320 so as to have one open end on a second inner circumferential wall surface 321B located at the other end in the longitudinal direction (see FIG. 3, etc.). In this specification, the refrigerant flow path 100 defined in the cooler 1 is defined such that the first through hole 120 is used as a refrigerant inlet into the refrigerant flow path 100 and the second through hole 121 is used as a refrigerant outlet from the refrigerant flow path 100. That is, the illustrated cooler 1 is connected to a cooling circuit that circulates the refrigerant so that the refrigerant in the refrigerant flow path 100 flows in the +Y direction as a whole. In the following description, the first through hole 120 is referred to as the refrigerant inlet 120, and the second through hole 121 is referred to as the refrigerant outlet 121. As illustrated in FIGS. 2 and 3 , the refrigerant flow path 100 of the cooler 1 may have an inlet header 131 at the end on the negative side of the Y direction connected to the refrigerant inlet 120, and an outlet header 132 at the end on the positive side of the Y direction connected to the refrigerant outlet 121. Note that the inlet header 131 and the outlet header 132 may have inclined surfaces that slope toward the bottom surface 301. In the following description, the direction along the Y direction in the refrigerant flow channel 100 will be referred to as the refrigerant flow direction. The directions along the X direction and Z direction in the refrigerant flow channel 100 will be referred to as the flow channel width direction and the flow channel height direction, respectively.

[0020] As described above, fins 240 are arranged within the refrigerant flow path 100 defined by the top plate 2 and the water jacket 3. While Figures 3 and 4 illustrate a plurality of pin fins 240 arranged in a staggered pattern in a plan view, the fins 240 may be flat or may be corrugated fins made by bending a metal plate into a wave shape. The pin fins 240 may be formed integrally with the top plate 2, or may be formed on a base plate separate from the top plate 2 and attached to the top plate 2 by, for example, joining the base plate to the underside 201 of the top plate 2.

[0021] 1 to 4 may be the surface of the section of the surface of the bottom plate portion 300 facing the refrigerant flow path 100 that is between the inlet header 131 and the outlet header 132 in the refrigerant flow direction, in other words, the surface facing the region where the fins 240 are arranged on the underside 201 of the top plate 2. The bottom surface 301 of the bottom plate portion 300 is composed of a main bottom surface 350 that is substantially parallel to the underside 201 of the top plate 2, and a recessed portion 360 that is recessed from the main bottom surface 350 toward the bottom side of the cooler 1 and has a bottom on the bottom side of the cooler 1 (the −Z direction side).

[0022] The recess 360 illustrated in FIGS. 2 to 4 has a rectangular cross section (FIG. 4). The dimension Rx in the flow path width direction (X direction) perpendicular to the refrigerant flow direction (Y direction) narrows from position Y0 to position Y3 in the refrigerant flow direction of the refrigerant flow path 100. Furthermore, the depth Rz from the main bottom surface 350 to the bottom of the recess 360 in the depth direction (Z direction) perpendicular to the refrigerant flow direction (Y direction) and the flow path width direction (X direction) narrows (shallows) from position Y0 to position Y3 in the refrigerant flow direction of the refrigerant flow path 100. Position Y0 is the upstream end of the bottom surface 301 (the boundary between the bottom surface 301 and the inlet header 131), which is upstream of the first heat exchange section 101A. Position Y3 is the downstream end of the bottom surface 301 (the boundary between the bottom surface 301 and the outlet header 132), which is downstream of the third heat exchange section 101C. The first heat exchange section 101A may be a section in which heat exchange occurs between the heat generating element 5A, which is closest to the upstream end of the refrigerant flow path 100, of the three heat generating elements 5A to 5C arranged along the longitudinal direction (Y direction) on the upper surface 202 of the top plate 2, and the refrigerant in the refrigerant flow path 100. The third heat exchange section 101C may be a section in which heat exchange occurs between the heat generating element 5C, which is closest to the downstream end of the refrigerant flow path 100, of the three heat generating elements 5A to 5C, and the refrigerant in the refrigerant flow path 100. The section in which heat exchange occurs between the heat generating element 5B, which is located in the center of the three heat generating elements 5A to 5C, and the refrigerant in the refrigerant flow path 100 is hereinafter referred to as the second heat exchange section 101B.

[0023] The dimension Rx of the recess 360 in the flow path width direction and the depth Rz from the main bottom surface 350 in the cooler 1 of this embodiment illustrated in FIGS. 2 to 4 will be described again with reference to FIG. 5 . FIG. 5 is a graph illustrating a first example of the shape of a recess provided in the bottom surface of the bottom plate portion. In the graph of FIG. 5 , the horizontal axis represents the position in the refrigerant flow direction, with positions Y0 and Y3 representing the upstream and downstream ends of the bottom surface 301, respectively (see FIG. 3 ). Positions Y1 and Y2 represent the positions between the first heat exchange section 101A and the second heat exchange section 101B, and the positions between the second heat exchange section 101B and the third heat exchange section 101C, respectively (see FIG. 3 ). In the graph of FIG. 5 , the width Rx of the recess 360 on the left vertical axis represents the dimension Rx of the recess 360 in the flow path width direction, and the depth Rz of the recess 360 on the right vertical axis represents the depth Rz of the recess 360 from the main bottom surface 350.

[0024] The recess 360 in the bottom surface 301 of the bottom plate portion 300 extends downstream from the upstream end of the refrigerant flow path 100 (the boundary between the bottom surface 301 and the inlet header 131) and is provided so as to include an area that overlaps with at least a portion of the heating element 5 in a plan view when the heating element 5 is disposed on the upper surface 202 of the top plate 2. The recess 360 illustrated in FIGS. 2 to 4 extends from position Y0 to position Y3, and the width Rx of the recess 360 continuously narrows from position Y0 to position Y3, as shown in FIG. 5, from width W at position Y0 to width 0 at position Y3. Meanwhile, the depth Rz of the recess 360 continuously narrows from position Y0 to position Y3, as shown in FIG. 5, from depth -Z0 at position Y0 to depth 0 at position Y3. In this specification, a narrowing of the depth Rz refers to a narrowing (smaller) dimension Rz in the depth direction, and may be interpreted as a shallowing of the depth Rz. The aspect ratio W / Z0 of the rectangular recess 360 in cross section is not limited to a specific value. Furthermore, the depth Rz of a recess such as recess 360 in this specification can be interpreted as the distance Rz from the lower surface (first surface) 201 of the top plate 2 to the bottom surface of the recess. That is, the distance Rz of recess 360 from the lower surface 201 of the top plate 2 decreases as the recess moves downstream from position Y0. In other words, the height Rz of the flow path in cross section of recess 360 decreases as the recess moves downstream from position Y0.

[0025] When such a recess 360 is provided on the bottom surface 301 of the bottom plate portion 300 located at the lower end of the refrigerant flow path 100, a portion of the refrigerant flowing into the refrigerant flow path 100 from the inlet 120 flows through the recess 360, which has a rectangular cross section, from position Y0 to position Y3. The width Rx and depth Rz of the recess 360 narrow toward position Y3 (i.e., downstream). That is, the cross-sectional area of ​​the recess 360 (flow path area Rx × Rz) decreases toward downstream, so the refrigerant flowing through the recess 360 is gradually pushed toward the underside 201 of the top plate 2. Of the refrigerant flowing through the refrigerant flow path 100, the refrigerant flowing near the underside 201 of the top plate 2 increases in temperature due to heat exchange with the fins 240. In contrast, the refrigerant flowing below the underside of the fins 240 does not come into contact with the fins 240 (does not exchange heat), and therefore flows downstream (to position Y3) at a low temperature. Moreover, in cooler 1 of the present embodiment, as described above, the refrigerant flowing within recess 360 is gradually pushed out in a direction toward underside 201 of top plate 2. When low-temperature refrigerant is pushed out from within recess 360 in a direction toward underside 201 of top plate 2, the pushed-out refrigerant collides with the relatively low-temperature refrigerant flowing between the underside of fin 240 and bottom surface 301 (main bottom surface 350) of bottom plate portion 300, generating turbulence and promoting mixing with the refrigerant with an increased temperature flowing near underside 201 of top plate 2.

[0026] FIG. 6 is a circuit diagram showing an example of the configuration of a circuit including a heating element formed in a semiconductor device. To investigate the cooling effect of the cooler 1 of this embodiment, the inventors simulated the temperatures of semiconductor elements 7A and 7B when the heating element 5 forming the inverter circuit 9 illustrated in FIG. 6 was placed and operated. In the inverter circuit 9 of FIG. 6, a switching element is connected in series between a first main terminal 901 and a second main terminal 902. Specifically, an IGBT (Insulated Gate Bipolar Transistor) element 711 of the semiconductor element 7A and an IGBT element 711 of the semiconductor element 7B are connected in series. The first main terminal 901 is connected to the collector of the IGBT element 711 of the semiconductor element 7A, and the second main terminal 902 is connected to the emitter of the IGBT element 711 of the semiconductor element 7B. The emitter of the IGBT element 711 of the semiconductor element 7A is connected to the collector of the IGBT element 711 of the semiconductor element 7B and the intermediate terminal 903 .

[0027] A diode element 712 such as an FWD (Free Wheeling Diode) element is connected in anti-parallel to the IGBT element 711 of each of the semiconductor elements 7A and 7B. The gate of the IGBT element 711 of the semiconductor element 7A is connected to a control terminal 904, and the gate of the IGBT element 711 of the semiconductor element 7B is connected to a control terminal 905. The emitter of the IGBT element 711 of the semiconductor element 7A is also connected to an auxiliary control terminal 906, and the emitter of the IGBT element 711 of the semiconductor element 7B is also connected to an auxiliary control terminal 907.

[0028] FIG. 7 is a graph showing an example of the relationship between the presence or absence of a recess and the temperature of a heat-generating element disposed in a cooler. An example of a simulation result is shown in FIG. 7. The vertical axis of the graph in FIG. 7 can be any value associated with the temperature of the semiconductor element. For example, the scale on the vertical axis can be associated with any of the following: temperature, a temperature difference from a reference temperature, and a relative value when the reference temperature is set to 1. In the simulation, each of the heat-generating elements 5A-5C disposed along the longitudinal direction on the upper surface 202 of the top plate 2 of the cooler 1 forms the inverter circuit 9 illustrated in FIG. 6, and the temperatures of the semiconductor elements 7A and 7B were derived when each inverter circuit 9 and the cooler 1 were operated. Furthermore, as a comparative example, the inventors also derived the temperatures of the semiconductor elements 7A and 7B when a cooler without a recess 360 was used through simulation.

[0029] In the graph of FIG. 7 , the temperatures of the semiconductor elements 7A and 7B in the comparative example without the recess 360 are indicated by circles (◯) and dotted lines. In the comparative example, the bottom surface 301 of the bottom plate 300 is a flat surface without the recess 360, and the coolant flowing along the bottom surface 301 is less likely to be stirred up (toward the underside 201 of the top plate 2). Therefore, in the comparative example without the recess 360, turbulence is less likely to occur, which promotes mixing of the low-temperature coolant flowing between the underside of the fin 240 and the bottom surface 301 of the bottom plate 300 with the higher-temperature coolant flowing near the underside 201 of the top plate 2. Therefore, without the recess 360, the temperature of the coolant exchanging heat with the fin 240 increases downstream, resulting in a larger difference in temperature between the semiconductor elements 7A and 7B of the heating element 5A located at the most upstream side of the coolant flow path 100 and the semiconductor elements 7A and 7B of the heating element 5C located at the most downstream side, as illustrated in FIG. 7 . Such a difference in temperature between the semiconductor elements 7A and 7B for each heat generating element 5 causes a difference in the operation of each inverter circuit 9. That is, in the conventional coolers disclosed in Patent Documents 1 to 4, the mixing of the low-temperature refrigerant flowing below the underside of the fins 240 and the refrigerant whose temperature has increased as it flows near the underside 201 of the top plate 2 is insufficient, making it difficult to reduce the temperature difference between the heat generating element (semiconductor element) on the upstream side and the heat generating element (semiconductor element) on the downstream side.

[0030] On the other hand, the temperatures of the semiconductor elements 7A and 7B when the cooler 1 of this embodiment having the recess 360 is used are indicated by squares (□) and a solid line in the graph of Figure 7. In the cooler 1 of this embodiment, the cross-sectional area (flow path area Rx x Rz) of the recess 360 decreases downstream, and the refrigerant extruded from the recess 360 toward the underside 201 of the top plate 2 promotes mixing of the low-temperature refrigerant flowing between the underside of the fins 240 and the bottom surface 301 of the bottom plate 300 and the high-temperature refrigerant flowing near the underside 201 of the top plate 2. The recess 360 has an area overlapping with the heat-generating element 5C located furthest downstream in a plan view, promoting mixing of the refrigerant even in the third heat exchange section 101C that exchanges heat with the heat-generating element 5C. Therefore, when the cooler 1 of this embodiment having the recess 360 is used, as illustrated in Figure 7, the difference in temperature between the semiconductor elements 7A and 7B of the heating element 5A located at the most upstream side in the refrigerant flow path 100 and the semiconductor elements 7A and 7B of the heating element 5C located at the most downstream side can be reduced.

[0031] As described above, the cooler 1 according to this embodiment has a recess 360 formed in the bottom surface 301 of the bottom plate 300. The recess 360 extends from the upstream end of the refrigerant flow path 100 toward the downstream end, and has a width Rx that narrows from the upstream end toward the downstream end, and a depth Rz from the bottom surface 301 (main bottom surface 350). This gradually pushes the refrigerant flowing in the recess 360 toward the underside 201 of the top plate 2, promoting mixing of the relatively low-temperature refrigerant flowing near the bottom surface 301 of the bottom plate 300 and the high-temperature refrigerant flowing near the underside 201 of the top plate 2, thereby suppressing a rise in the temperature of the refrigerant downstream of the refrigerant flow path 100. Therefore, the cooler 1 according to this embodiment can uniformize the temperature of the heat-generating elements arranged along the refrigerant flow direction.

[0032] Furthermore, in the cooler 1 according to the present embodiment, the recess 360 divides the refrigerant flowing through the inlet 120 into a refrigerant flowing near the underside 201 of the top plate 2 and a refrigerant flowing through the recess 360, thereby reducing the flow velocity on the inlet 120 side. This reduces the pressure loss of the cooler 1 compared to a comparative example in which the recess 360 is not provided. An example of the relationship between the presence or absence of a recess and the pressure loss is shown in the graph of FIG. 8 . In the graph of FIG. 8 , the pressure loss values ​​for the "with recess" and "without recess" cases may be values ​​derived by simulation of the pressure loss in the cooler 1 according to the present embodiment and the comparative example cooler used in the simulation described above with reference to FIG. 7 . In the graph of FIG. 8 , each pressure loss value is shown as a relative value, with the pressure loss value for the "without recess" case set to 1. In the illustrated result, the pressure loss with the recess is approximately 0.8 times that of the cooler without the recess. In other words, the cooler 1 according to the present embodiment, which is provided with the recess 360, can reduce the pressure loss by approximately 20% compared to a cooler without the recess 360, for example.

[0033] [Second embodiment] Fig. 9A is a perspective view illustrating an example of the shape of a recess in a cooler according to a second embodiment, and Fig. 9B is a cross-sectional view of the cooler in which the recess illustrated in Fig. 9A is formed. Fig. 10 is a cross-sectional view illustrating another example of the shape of the recess in the cooler according to the second embodiment.

[0034] The cooler 1 according to the first embodiment has a recess 360 that is rectangular in cross section ( FIG. 4 ) on the bottom surface 301 of the bottom plate portion 300. That is, the recess 360 illustrated in the first embodiment has a constant depth Rz from the main bottom surface 350 in the flow channel width direction (X direction) at a certain position in the refrigerant flow direction (Y direction). In contrast, in the cooler 1 according to the second embodiment, the depth Rz from the main bottom surface 350 in the flow channel width direction (X direction) at a certain position in the refrigerant flow direction (Y direction) varies.

[0035] 9A and 9B, the bottom surface 301 of the bottom plate portion 300 is provided with a V-shaped recess 370 that defines a flow path with an inverted triangular cross section. Also, the bottom surface 301 of the bottom plate portion 300 shown in FIG. 10 is provided with an arc-shaped recess 372 that defines a flow path with a downwardly convex, arched cross section. The V-shaped recess 370 and the arc-shaped recess 372 have a valley line 375, where the depth Rz is greatest, located at the center of the flow path width direction, and have a section where the depth Rz narrows from the valley line 375 toward the inner circumferential wall surface 321C and the inner circumferential wall surface 321D of the peripheral wall portion 320. The width Rx and depth Rz of the V-shaped recess 370 and the arc-shaped recess 372 can vary as shown in the graph of FIG. 5. The aspect ratio Rx / Rz of the dimension Rx in the flow path width direction and the dimension Rz in the depth direction of the V-shaped recess 370 and the arc-shaped recess 372 is not limited to a specific value.

[0036] FIG. 11 is a graph showing an example of the temperature of a heat-generating element disposed in a cooler according to the second embodiment. The inventors also simulated the temperatures of the semiconductor elements 7A and 7B when the heat-generating element 5 forming the inverter circuit 9 illustrated in FIG. 6 was disposed in the cooler 1 according to the present embodiment and the inverter circuits 9 and the cooler 1 were operated. In the graph of FIG. 11 , circles (◯) represent the temperatures of the semiconductor elements 7A and 7B when the recess 360 of the first embodiment and the recesses 370 and 372 of the present embodiment are not provided, and squares (□) represent the temperatures of the semiconductor elements 7A and 7B when the recess 360 of the first embodiment is provided. Also in the graph of FIG. 11 , open diamonds (◇) represent the temperatures of the semiconductor elements 7A and 7B when the recess 370 having a V-shaped cross section is provided, and filled diamonds (♦) represent the temperatures of the semiconductor elements 7A and 7B when the recess 372 having an arc-shaped cross section is provided. The vertical axis of the graph of FIG. 11 may be any value associated with the temperature of the semiconductor element. For example, the scale of the vertical axis is associated with any one of temperature, temperature difference from a reference temperature, and relative value when the reference temperature is set to 1.

[0037] Even when the V-shaped recess 370 and the arc-shaped recess 372 illustrated in this embodiment are provided, the cross-sectional areas (flow path areas) of the recesses 370 and 372 decrease toward the downstream side, so that the refrigerant flowing downstream through the recesses 370 and 372 is gradually pushed upward. Therefore, similar to the case where the recess 360 illustrated in the first embodiment is provided, mixing of the low-temperature refrigerant pushed upward through the recesses 370 and 372 and the high-temperature refrigerant flowing near the underside 201 of the top plate 2 is promoted. Therefore, even when the V-shaped recess 370 and the arc-shaped recess 372 illustrated in this embodiment are provided, the difference in temperature between the semiconductor elements 7A and 7B of the heating element 5A arranged at the most upstream side in the refrigerant flow path 100 and the semiconductor elements 7A and 7B of the heating element 5C arranged at the most downstream side can be reduced compared to when no recesses are provided, as illustrated in FIG. 11 . Furthermore, by providing the V-shaped recess 370 or the arc-shaped recess 372, the refrigerant flowing through the inlet 120 is divided into refrigerant flowing near the underside 201 of the top plate 2 and refrigerant flowing through the recess 370 or 372, thereby reducing the flow velocity at the inlet 120 side. This reduces the pressure loss of the cooler 1 compared to a comparative example in which the recesses 370 and 372 are not provided. An example of the relationship between the presence or absence of a recess and the pressure loss is shown in the graph of FIG. 12. In the graph of FIG. 12, the pressure loss values ​​for the "V-shaped" and "arc-shaped" coolers may be values ​​derived by simulation of the pressure losses of the cooler 1 with the V-shaped recess 370 and the cooler 1 with the arc-shaped recess 372, respectively, used in the simulation described above with reference to FIG. 11. In the graph of FIG. 12, each pressure loss value is expressed as a relative value, where the pressure loss value of the comparative example cooler (without a recess) in which the bottom surface 301 of the bottom plate portion 300 is a flat surface without a recess is set to 1. In the illustrated results, the pressure loss in the cooler 1 of this embodiment is about 0.85 to 0.86 times the pressure loss without the recesses. In other words, the cooler 1 of this embodiment provided with the recesses 370, 372 can reduce the pressure loss by about 14% to 15% in one example compared to a cooler without the recesses.

[0038] Note that the surfaces of the V-shaped recess 370 and the arc-shaped recess 372 illustrated in this embodiment are connected to the bottom surface 301 (main bottom surface 350) at an obtuse angle at their ends in the flow path width direction. Therefore, a portion of the refrigerant pushed upward from the recess 370 or the recess 372 may be pushed in an oblique direction toward the inner circumferential wall surface 321C or the inner circumferential wall surface 321D of the peripheral wall portion 320, rather than the +Z direction toward the underside 201 of the top plate 2. Therefore, under certain conditions, as illustrated in FIG. 11 , the difference in temperature between the semiconductor elements 7A and 7B of the most upstream heating element 5A and the semiconductor elements 7A and 7B of the most downstream heating element 5C may be greater than when the rectangular recess 360 illustrated in the first embodiment is provided. Taking such phenomena into consideration, when a recess having a varying depth Rz from the main bottom surface 350 in the flow path width direction (X direction) at a certain position in the refrigerant flow direction (Y direction) is provided on the bottom surface 301 of the bottom plate portion 300, it is preferable that the shape of the recess in cross section has a surface that connects to the bottom surface 301 (main bottom surface 350) at an obtuse angle of 90 degrees or close to 90 degrees at the end in the flow path width direction.

[0039] [Modification] Fig. 13 is a longitudinal cross-sectional view illustrating the range of the refrigerant flow direction of the recess provided in the bottom surface of the bottom plate. The longitudinal cross-sectional view in Fig. 13 may be a cross-sectional configuration of a YZ plane passing through the center of the refrigerant flow path 100 in the flow path width direction (the position of the dashed dotted line A-A' in Fig. 2). The recess 360 illustrated in Fig. 13 may be other recesses 370, 372.

[0040] The recesses 360, 370, and 372 extend downstream from the upstream end of the refrigerant flow path 100 (position Y0, which corresponds to the downstream end of the inlet header 131 if the inlet header 131 is included). In the above-described embodiment, as illustrated in FIGS. 2 , 3 , 5 , and 9A , the downstream ends of the recesses 360, 370, and 372 extend to the downstream end of the refrigerant flow path 100 (position Y3, which corresponds to the upstream end of the outlet header 132 if the outlet header 132 is included). However, the positions of the downstream ends of the recesses 360, 370, and 372 in the refrigerant flow direction are not limited to such positions. As illustrated in FIG. 13 , the downstream ends of the recesses 360, 370, and 372 are preferably located anywhere between the center position YC of the second heat exchange section 101B in the refrigerant flow direction and the downstream end of the refrigerant flow path 100 (position Y3, which corresponds to the upstream end of the outlet header 132 if the outlet header 132 is included). The center position YC of the second heat exchange section 101B may be interpreted as the center of the refrigerant flow path 100 in the flow direction of the refrigerant (the center of the section from position Y0 to position Y3).

[0041] 14A is a graph showing an example of the relationship between the range of the recess in the direction of coolant flow and thermal resistance, and FIG. 14B is a graph showing an example of the relationship between the range of the recess in the direction of coolant flow and pressure loss. The vertical axis in the graph of FIG. 14A can be any value associated with the temperature of the semiconductor element. For example, the scale of the vertical axis can be associated with any of the temperature, the temperature difference from a reference temperature, and a relative value when the reference temperature is set to 1.

[0042] 13 is set as described above. One of the reasons for this is that if the downstream ends of the recesses 360, 370, and 372 were located anywhere between the center position YC of the second heat exchange section 101B and the upstream end of the refrigerant flow path 100 (the boundary between the bottom surface 301 and the inlet header 131), all of the refrigerant flowing through the recesses 360, 370, and 372 would be pushed upward near the second heat exchange section 101B. That is, the refrigerant would not be stirred due to being pushed upward from the recesses 360, 370, and 372 downstream of the center position YC of the second heat exchange section 101B, and the temperature of the refrigerant flowing through the third heat exchange section 101C exchanging heat with the downstream heating element 5 would rise, resulting in a decrease in cooling performance. As an example, a graph comparing the thermal resistance of a cooler 1 having a V-shaped recess 370 extending from position Y0 to position Y3 with the thermal resistance of a cooler 1 having a V-shaped recess 370 extending from position Y0 to position YC is shown in Figure 14A. When the V-shaped recess 370 is provided from position Y0 to position YC, the thermal resistance is higher downstream in the flow direction than in the cooler 1 having the V-shaped recess 370 extending from position Y0 to position YC, resulting in reduced cooling performance. Taking this into consideration, when the downstream ends of the recesses 360, 370, and 372 are positioned upstream of position YC, it can be expected that the thermal resistance downstream in the refrigerant flow direction will be even higher than in the cooler 1 having the V-shaped recess 370 extending from position Y0 to position YC. Therefore, the downstream ends of the recesses 360, 370, and 372 are preferably located downstream of the position YC in the flow direction, and more preferably located further downstream than the position of the most downstream heating element 5C. By setting the downstream ends of the recesses 360, 370, and 372 to be located anywhere between the center position YC of the second heat exchange section 101B and the downstream end of the refrigerant flow path 100, it is possible to suppress a temperature rise of the refrigerant downstream and to uniformize the temperature of the heating elements 5 arranged along the flow direction of the refrigerant.

[0043] Furthermore, when the downstream ends of the recesses 360, 370, and 372 are positioned upstream of the center position YC in the refrigerant flow path 100, the pressure loss increases compared to when the downstream ends of the recesses 360, 370, and 372 are positioned from the center position YC to the downstream end of the refrigerant flow path 100. An example of the relationship between the range of the recess 370 in the refrigerant flow direction and the pressure loss is shown in the graph of FIG. 14B. The graph of FIG. 14B shows the pressure loss values ​​of the cooler 1 in which the recess 370 is provided from position Y0 to position Y3 and the cooler 1 in which the recess 370 is provided from position Y0 to position YC, relative to the pressure loss value of a comparative cooler (without recesses) in which the bottom surface 301 of the bottom plate portion 300 is a flat surface with no recesses formed. In the illustrated results, the cooler 1 in which the recess 370 is provided from position Y0 to position YC has a higher pressure loss. In consideration of this phenomenon, it can be expected that the pressure loss will be even higher if the downstream ends of the recesses 360, 370, and 372 are positioned upstream of position YC. Therefore, by setting the downstream ends of the recesses 360, 370, and 372 to any position between the center position YC of the second heat exchange section 101B and the downstream end of the refrigerant flow path 100, it is possible to achieve both uniform temperature distribution of the heating elements 5 arranged along the refrigerant flow direction and reduced pressure loss.

[0044] Fig. 15 is a partially enlarged plan view illustrating the range in the flow path width direction of the recess provided in the bottom surface of the bottom plate portion. Fig. 15 shows an enlarged view of the end portion on the refrigerant inlet 120 side of the plan view of the water jacket 3 illustrated in Fig. 2. The recess 360 illustrated in Fig. 15 may be other recesses 370, 372.

[0045] The maximum value W ( FIG. 5 ) of the width Rx of the upstream end of each of the recesses 360, 370, and 372 may be the dimension in the flow path width direction of the refrigerant flow path 100, in other words, the distance between the inner circumferential wall surface 321C and the inner circumferential wall surface 321D that face each other in the short direction (X direction). On the other hand, if the width Rx of the upstream end of each of the recesses 360, 370, and 372 is small, the change in the cross-sectional area (flow path area) of the recess in the flow direction of the refrigerant becomes small. This reduces the amount of refrigerant pushed upward from the recesses 360, 370, and 372, which may weaken the effect of stirring the refrigerant. Furthermore, the reduced amount of refrigerant flowing into the recesses 360, 370, and 372 increases pressure loss. 15, it is preferable that the width Rx of the upstream end of each of the recesses 360, 370, and 372 is such that one end E1 of the recess in the flow path width direction is between position X0 of the inner circumferential wall surface 321C and the first threshold position X1, and the other end E2 is between the inner circumferential wall surface 321D and the second threshold position X3. The first threshold position X1 is the center position in the flow path width direction between position X0 of the inner circumferential wall surface 321C and position X2 of the recess center 380, and the second threshold position X3 is the center position in the flow path width direction between position X4 of the inner circumferential wall surface 321D and position X2 of the recess center 380. As will be described later with reference to Figure 17, if the center (recess center 380) of recesses 360, 370, and 372 in the flow path width direction is biased toward inner wall surface 321C or inner wall surface 321D, the recess may be formed so that only one end E1 of the recess in the flow path width direction or the other position E2 satisfies the above-mentioned condition, depending on the direction of bias.

[0046] 16A is a graph showing an example of the relationship between the range of the recess in the flow path width direction and thermal resistance, and FIG. 16B is a graph showing an example of the relationship between the range of the recess in the flow path width direction and pressure loss. The vertical axis in the graph of FIG. 16A can be any value associated with the temperature of the semiconductor device. For example, the scale of the vertical axis can be associated with any of the temperature, the temperature difference from a reference temperature, and a relative value when the reference temperature is set to 1.

[0047] 15 , one of the reasons for setting the range of the dimension (recess width Rx) in the flow path width direction at the upstream ends of the recesses 360, 370, and 372 is that when the width Rx at the upstream end is narrower than the width corresponding to the distance X3-X1 from position X3 to position X1, the area of ​​the heat generating element 5 that overlaps with the recesses 360, 370, and 372 in a plan view becomes narrower. In other words, the area of ​​the heat generating element 5 that exchanges heat with the refrigerant whose temperature has been reduced due to the mixing of the relatively low-temperature refrigerant pushed upward from the recesses 360, 370, and 372 and the relatively high-temperature refrigerant flowing near the underside 201 of the top plate 2 becomes narrower, and the temperature of the refrigerant flowing through the third heat exchange section 101C that exchanges heat with the downstream heat generating element 5 increases, thereby reducing cooling performance. As an example, FIG. 16A shows a graph comparing the thermal resistance of a cooler 1 in which the width Rx = W of the upstream end of the V-shaped recess 370 is wider than the width corresponding to the distance from position X3 to position X1 (i.e., W > X3 - X1) with the thermal resistance of a cooler 1 in which the width Rx corresponds to the distance from position X3 to position X1. When the width Rx of the upstream ends of the recesses 360, 370, and 372 is narrowed, the thermal resistance downstream in the flow direction is higher than that of a cooler 1 with a wider width Rx, resulting in reduced cooling performance. Given this, it can be predicted that if the width Rx = W of the upstream ends of the recesses 360, 370, and 372 is set to W < X3 - X1, the thermal resistance downstream in the refrigerant flow direction will be even higher. Therefore, it is preferable that the width Rx = W of the upstream ends of the recesses 360, 370, and 372 be W > X3 - X1, and more preferably W = X4 - X0. This makes it possible to suppress a rise in the temperature of the coolant on the downstream side, and to make the temperature of the heating element 5 arranged along the flow direction of the coolant uniform.

[0048] Furthermore, when the width Rx=W of the upstream ends of the recesses 360, 370, and 372 is narrowed, the pressure loss increases as described above. An example of the relationship between the range of the recess 370 in the flow path width direction and the pressure loss is shown in the graph of FIG. 16B. The graph of FIG. 16B shows the pressure loss values ​​of the cooler 1 in which the width Rx=W of the upstream end of the recess 370 is set to W>X3-X1 and the cooler 1 in which W=X3-X1, relative to the pressure loss value of the comparative cooler (without recesses) in which the bottom surface 301 of the bottom plate portion 300 is a flat surface with no recesses formed. In the illustrated results, the cooler 1 in which the width Rx-W of the recess 370 is set to W=X3-X1 has a higher pressure loss. Taking these phenomena into consideration, it can be expected that the pressure loss will be even higher when the width Rx=W of the upstream ends of the recesses 360, 370, and 372 is set to W<X3-X1. Therefore, by setting the width Rx = W of the upstream ends of the recesses 360, 370, and 372 to W > X3 - X1, it is possible to achieve both uniform temperature distribution of the heating element 5 arranged along the flow direction of the refrigerant and reduced pressure loss.

[0049] FIG. 17 is a cross-sectional view illustrating a modification of the position of the recess in the flow path width direction provided on the bottom surface of the bottom plate portion. The recess 360 illustrated in FIG. 17 may be replaced by other recesses 370 and 372. The center (recess center 380) of the recesses 360, 370, and 372 in the flow path width direction does not have to be the center position X2 (see FIG. 15 ) of the refrigerant flow path 100 in the flow path width direction. For example, as shown in FIG. 17 , the position of the recess center 380 in the flow path width direction may be changed depending on the position of the semiconductor elements 7A and 7B of the heating element 5 arranged on the upper surface 202 of the top plate 2 in the flow path width direction. For example, if the area where the semiconductor elements 7A and 7B are arranged in a plan view is biased toward the inner circumferential wall surface 321D, the position of the recess center 380 and the width of the upstream end of the recesses 360, 370, and 372 may be set according to that bias. Furthermore, the planar shape and / or cross-sectional shape of the recesses 360, 370, and 372 do not have to be line-symmetrical.

[0050] 18 and 19 are graphs illustrating a first and second modified example of changes in width and depth of recesses provided in the bottom surface of the bottom plate along the refrigerant flow direction, respectively.

[0051] The dimension Rx of the recesses 360, 370, and 372 in the flow path width direction in the cooler 1 according to the embodiment described above may have a section in which the dimension Rx is constant regardless of the distance from the upstream end (position Y0), as illustrated in FIG. 18 . Furthermore, the width Rx of the downstream end of the recesses 360, 370, and 372 is not limited to the width 0 illustrated in FIGS. 5 and 18 , but may have a finite, predetermined value (i.e., the shape of the recesses 360, 370, and 372 in plan view may be a trapezoid with the upstream end at the bottom and the downstream end at the top). In the graph of FIG. 18 , the width Rx is constant from position Y0 to position Y1 between the first heat exchange section 101A and the second heat exchange section 101B. However, the section (range) in which the width Rx is constant is not limited to a specific section. Furthermore, the section in which the width Rx is constant may be located between two sections in which the width Rx narrows depending on the position in the flow direction.

[0052] Furthermore, the depth Rz of the recesses 360, 370, and 372 may have a section in which it remains constant regardless of the distance from the upstream end (position Y0), as illustrated by the dotted line in Figure 18. In the graph of Figure 18, the width Rx is constant from position Y0 to position Y1 between the first heat exchange section 101A and the second heat exchange section 101B, but the section (range) in which the depth Rz remains constant is not limited to a specific section. That is, the section in which the depth Rz of the recesses 360, 370, and 372 remains constant may or may not correspond to a section in which the width Rx remains constant. Furthermore, the section in which the depth Rz remains constant may be located between two sections in which the depth Rz changes depending on the position in the flow direction.

[0053] Furthermore, the width Rx and depth Rz of the recesses 360, 370, and 372 may change stepwise, as illustrated in FIG. 19 . That is, the side surfaces and bottoms of the recesses 360, 370, and 372 may be formed in a stepwise manner so that the width Rx and depth Rz gradually narrow along the refrigerant flow direction. When the width Rx and depth Rz change stepwise, the number of steps is not limited to a specific number. Furthermore, when the width Rx or depth Rz changes stepwise, the amount of change in the width Rx or depth Rz per step is not limited to a specific amount of change. The amount of change in each step may or may not be constant. Furthermore, each of the width Rx and depth Rz may have a section where the width Rx changes stepwise and a section where the width Rx and depth Rz change continuously.

[0054] FIG. 20 is a cross-sectional view illustrating a modified example of the cross-sectional shape of the recess provided on the bottom surface of the bottom plate portion. As illustrated in FIG. 20 , the recess provided on the bottom surface 301 of the bottom plate portion 300 may have a multi-stage structure in which a second recess 361 is further provided on the bottom surface of a first recess 360. The second recess 361 is not limited to the rectangular recess in cross section illustrated in FIG. 20 , but may also be the V-shaped recess 370 ( FIG. 9B ) or the arch-shaped recess 372 ( FIG. 10 ) illustrated in the second embodiment. The downstream end of the second recess 361 in the refrigerant flow direction may be the same as the downstream end of the first recess 360, or may be located upstream of the downstream end of the first recess 360 (e.g., between the downstream end of the first recess 360 and the center YC of the second heat exchange section 101B).

[0055] In the above-described embodiment, an example was shown in which the depth Rz of the recesses 360, 370, and 372 narrows (shallows) toward the downstream side. However, the depth Rz of the recesses 360, 370, and 372 may be constant throughout the entire refrigerant flow direction. Although not illustrated, the refrigerant inlet 120 and outlet 121 in the cooler 1 according to the above-described embodiment do not have to be through-holes penetrating the peripheral wall portion 320. The refrigerant inlet 120 and outlet 121 may be, for example, through-holes formed in the top plate 2 or through-holes formed in the bottom plate portion 300. The cooler 1 may be formed by integrating the top plate 2, bottom plate portion 300, and peripheral wall portion 320, which are manufactured separately, or by integrating the top plate 2 with the peripheral wall portion 320 integrally formed therewith and the bottom plate portion 300. Furthermore, the cooler 1 manufactured using a 3D printer may have the top plate 2 having the fins 240, the bottom plate portion 300, and the peripheral wall portion 320 all integrally formed.

[0056] The cooler 1 of the above-described embodiment is not limited to a specific application, but is suitable for cooling a semiconductor device in which the inverter circuit 9 described above with reference to FIG. 6 is formed. In particular, the cooler 1 of the embodiment is suitable for cooling a semiconductor device in which the heat generating element 5 generates a large amount of heat during operation, or a semiconductor device in which it is desired to suppress differences in operating characteristics (output) due to temperature differences between multiple heat generating elements 5. For example, the cooler 1 of the above-described embodiment can be applied to a power conversion device such as an on-vehicle inverter device. With reference to FIG. 21 , a vehicle equipped with a semiconductor device 10 to which the cooler 1 according to the present invention is applied will be described.

[0057] FIG. 21 is a plan view schematic diagram showing an example of a vehicle equipped with a semiconductor device according to an embodiment. The vehicle 1501 shown in FIG. 21 is, for example, a four-wheeled vehicle equipped with four wheels 1502. The vehicle 1501 may be, for example, an electric vehicle in which the wheels are driven by a motor or the like, or a hybrid vehicle that uses power from an internal combustion engine in addition to a motor. Furthermore, the vehicle to which the semiconductor device 10 is applied is not limited to a four-wheeled vehicle, but may also be a two-wheeled vehicle, a railcar, or the like. The power conversion device to which the semiconductor device 10 is applied may be a device that supplies power to a motor that rotates the wheels 1502 of the vehicle 1501, but may also include a device that supplies power to other electronic devices (electrical components) in the vehicle 1501.

[0058] Vehicle 1501 includes a drive unit 1503 that applies power to wheels 1502, and a control device 1504 that controls drive unit 1503. Drive unit 1503 may be configured with at least one of a motor and a hybrid of an engine and a motor, for example.

[0059] The control device 1504 controls (e.g., controls power) the drive unit 1503. The control device 1504 includes a semiconductor device 10 including the cooler 1 according to the above-described embodiment. The semiconductor device 10 can be configured to control power to the drive unit 1503.

[0060] The semiconductor device 10 according to the above-described embodiment may be applied to industrial power conversion devices, such as inverter devices for driving motors in elevators, escalators, building air conditioning systems, etc. Furthermore, the circuit formed in the semiconductor device 10 is not limited to the half-bridge inverter circuit 9 illustrated in FIG. 6 . The switching elements of the inverter circuit 9 are not limited to IGBT elements 711, but may also be power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) elements, BJT (Bipolar Junction Transistor) elements, etc. The diode elements 712 of the inverter circuit 9 may be, for example, SBD (Schottky Barrier Diode) elements, JBS (Junction Barrier Schottky) diode elements, MPS (Merged PN Schottky) diode elements, PN diode elements, etc. The semiconductor elements used to form the inverter circuit 9 are not limited to semiconductor elements formed with switching elements and diode elements, such as RC (Reverse Conducting)-IGBT elements. The inverter circuit 9 may be formed by connecting a semiconductor element having a switching element formed therein and a semiconductor element having a diode element formed therein by wiring members such as wires and leads. The semiconductor substrate used to form the semiconductor elements is not limited to a silicon (Si) substrate, but may also be a wide bandgap semiconductor substrate such as a silicon carbide (SiC) substrate or a gallium nitride (GaN) substrate. The circuit formed in the semiconductor device 10 may be, for example, a full-bridge inverter circuit. Furthermore, the circuit formed in the semiconductor device 10 is not limited to a power conversion circuit that converts direct current to alternating current, but may be another circuit, or may include a power conversion circuit and another circuit.

[0061] The embodiments of the cooler and semiconductor module according to the present invention are not limited to the above-described embodiments, and may be variously changed, substituted, or modified without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea.

[0062] The following summarizes the characteristics of the above-described embodiment. The cooler according to the above-described embodiment includes a top plate portion having a first surface facing a refrigerant flow path and a heat generating element disposed on a backside of the first surface, a bottom plate portion having a second surface opposite the first surface of the top plate portion, fins extending from the first surface of the top plate portion toward the second surface of the bottom plate portion, and a peripheral wall portion provided between the top plate portion and the bottom plate portion and surrounding the fins in a plan view of the first surface, wherein the second surface of the bottom plate portion is provided with a recessed portion extending from an upstream end toward a downstream end of the refrigerant flow path and including an area overlapping with at least a portion of the heat generating element in the plan view when the heat generating element is disposed on the backside of the first surface of the top plate portion, and the recessed portion has a section whose dimension in a width direction perpendicular to the refrigerant flow direction narrows along the refrigerant flow direction from a refrigerant inlet to a refrigerant outlet in the refrigerant flow path.

[0063] In the cooler according to the above embodiment, the downstream end of the recess is located between the center of the upstream end and downstream end of the refrigerant flow path and the downstream end of the refrigerant flow path.

[0064] In the cooler according to the above embodiment, at least one of the widthwise ends at the upstream end of the recess is located between the center of the recess, the center of the peripheral wall end, and the peripheral wall.

[0065] In the cooler according to the above embodiment, the recess has a section in which the depth dimension perpendicular to the refrigerant flow direction and the width direction narrows along the refrigerant flow direction from the refrigerant inlet to the refrigerant outlet in the refrigerant flow path.

[0066] In the cooler according to the above embodiment, the recess has a rectangular cross section perpendicular to the flow direction of the refrigerant.

[0067] In the cooler according to the above embodiment, the recess has a section in which the dimension in the depth direction narrows along a direction from the recess toward the peripheral wall portion.

[0068] The semiconductor device according to the above-described embodiment includes the cooler according to the above-described embodiment and the heat generating element disposed on the top plate portion of the cooler, and the heat generating element includes a semiconductor element.

[0069] In the semiconductor device according to the above embodiment, the heating element at least partially overlaps with the recess in the plan view.

[0070] The vehicle according to the above-described embodiment includes the semiconductor device according to the above-described embodiment.

[0071] As described above, the present invention has the effect of making the temperature of heating elements arranged along the flow direction of the refrigerant of a cooler applied to a semiconductor device, etc., uniform, and is particularly useful for application to semiconductor devices that generate a large amount of heat during operation, such as industrial or electrical devices, and semiconductor devices in which it is desirable to suppress differences in operating characteristics (output) due to temperature differences between multiple heating elements 5.

[0072] This application is based on Japanese Patent Application No. 2024-148290, filed on August 30, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A cooler comprising: a top plate portion having a first surface facing a refrigerant flow path and a heating element disposed on the reverse side of the first surface; a bottom plate portion having a second surface opposite the first surface of the top plate portion; fins extending from the first surface of the top plate portion toward the second surface of the bottom plate portion; and a peripheral wall portion provided between the top plate portion and the bottom plate portion and surrounding the fins in a plan view of the first surface, wherein the second surface of the bottom plate portion is provided with a recess portion extending from the upstream end toward the downstream end of the refrigerant flow path and including an area that overlaps with at least a portion of the heating element in the plan view when the heating element is disposed on the reverse side of the first surface of the top plate portion, and the recess portion has a section whose dimension in a width direction perpendicular to the flow direction of the refrigerant narrows along the flow direction of the refrigerant from the refrigerant inlet to the refrigerant outlet in the refrigerant flow path.

2. The cooler according to claim 1, wherein the downstream end of the recess is located between the center of the upstream end and downstream end of the refrigerant flow path and the downstream end of the refrigerant flow path.

3. A cooler as described in claim 1, wherein at least one of the widthwise ends at the upstream end of the recess is located between the center of the recess, the center of the peripheral wall portion, and the peripheral wall portion.

4. A cooler as described in claim 1, wherein the recess has a section in which the dimension in the depth direction perpendicular to the refrigerant flow direction and the width direction narrows along the refrigerant flow direction from the refrigerant inlet to the refrigerant outlet in the refrigerant flow path.

5. The cooler according to claim 1, wherein the recess has a rectangular cross section perpendicular to the flow direction of the refrigerant.

6. A cooler according to claim 1, wherein the recess has a section in which the dimension in the depth direction narrows along a direction from the recess toward the peripheral wall portion.

7. A semiconductor device comprising the cooler according to any one of claims 1 to 6 and the heat generating element disposed on the top plate of the cooler, wherein the heat generating element includes a semiconductor element.

8. The semiconductor device according to claim 7, wherein the heating element at least partially overlaps with the recess in the plan view.

9. A vehicle comprising the semiconductor device according to claim 7.

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