Patent Publication Number: US-2023141875-A1

Title: Cooler and semiconductor device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a cooler and a semiconductor device. 
     BACKGROUND ART 
     Inverters and motors of electric vehicles such as an electric motor vehicle and a hybrid vehicle have been conventionally surrounded by separate metallic housings, but have been developed to be integrated with each other for the purpose of miniaturization and space saving. The inverters receive direct currents supplied from batteries and convert the direct currents into three-phase alternating currents to supply the three-phase alternating currents to the motors. The inverters generate heat due to loss of semiconductor elements when converting the direct currents into the three-phase alternating currents. When the semiconductor elements are used at a high temperature, the elements themselves, bonding materials, peripheries of bonding parts, and the like may be broken, and thus the semiconductor elements need to be used while being cooled. 
     For example, Patent Document 1 discloses a configuration of a cooler that cools multiple semiconductor elements used in an inverter. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     
         
         Patent Document 1: Japanese Patent No. 4708951 
       
    
     SUMMARY 
     Problem to be Solved by the Invention 
       FIG.  24    shown in Patent Document 1 illustrates the cooler in which coolant flows through a flow path while taking away heat generated by the multiple semiconductor elements. As the coolant flows through the flow path, the coolant rises in temperature due to the heat of the semiconductor elements, and thus cooling effect decreases. As described above, conventional coolers are likely to cause an uneven degree of cooling during cooling of multiple cooling targets. 
     The present disclosure is made to solve such a problem, and an object of the present disclosure is to provide a cooler that is less likely to cause an uneven degree of cooling during cooling of multiple cooling targets, and a semiconductor device using the cooler that is less likely to cause the uneven degree of cooling during cooling of the multiple cooling targets. 
     Means to Solve the Problem 
     A cooler according to the present disclosure has an annular shape in plan view from a first direction and is provided inside with a flow path of a refrigerant, the flow path including: an outer-peripheral-side header region that is provided on an outer peripheral side of the annular shape and extends in a circumferential direction of the annular shape; an inner-peripheral-side header region that is provided on an inner peripheral side of the annular shape across a separation region from the outer-peripheral-side header region and extends in the circumferential direction; and a fin region serving as the separation region in which a fin is disposed. 
     Additionally, a semiconductor device of the present disclosure includes the cooler of the present disclosure and multiple semiconductor modules, the multiple semiconductor modules being disposed on a module placement surface of the cooler extending in a second direction intersecting a first direction and a third direction intersecting the first direction and the second direction. 
     Effects of the Invention 
     In the cooler of the present disclosure, the flow path includes the outer-peripheral-side header region that is provided on the outer peripheral side of the annular shape and extends in the circumferential direction of the annular shape, the inner-peripheral-side header region that is provided on the inner peripheral side of the annular shape across the separation region from the outer-peripheral-side header region and extends in the circumferential direction, and the fin region serving as the separation region in which the fin is disposed. As a result, the cooler of the present disclosure is less likely to cause an uneven degree of cooling when cooling a plurality of cooling targets. 
     Additionally, a semiconductor device of the present disclosure includes the cooler of the present disclosure and multiple semiconductor modules, the multiple semiconductor modules being disposed on a module placement surface of the cooler extending in a second direction intersecting a first direction and a third direction intersecting the first direction and the second direction. As a result, the semiconductor device of the present disclosure uses the cooler that is less likely to cause an uneven degree of cooling during cooling of the multiple cooling targets. 
     Detailed description below and accompanying drawings will clarify features, aspects, and advantages of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a sectional view of a semiconductor device according to a first embodiment. 
         FIG.  2    is a sectional view of an inverter unit of the first embodiment. 
         FIG.  3    is a perspective view of the semiconductor device of the first embodiment. 
         FIG.  4    is a plan view of a cooler of the first embodiment as viewed from an axial direction of a shaft of the semiconductor device. 
         FIG.  5    is a sectional view of the cooler of the first embodiment taken along a plane perpendicular to an axis of the shaft of the semiconductor device. 
         FIG.  6    is a sectional view of the cooler of the first embodiment taken along a plane perpendicular to the axis of the shaft of the semiconductor device. 
         FIG.  7    is a sectional view of an inverter unit of a second embodiment. 
         FIG.  8    is a sectional view of a cooler of a third embodiment taken along a plane perpendicular to the axis of the shaft of the semiconductor device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. First Embodiment 
     A-1. Configuration 
       FIG.  1    is a sectional view of a semiconductor device  10  as an inverter device of a first embodiment, and  FIG.  3    is a perspective view illustrating an external appearance of the semiconductor device  10 . 
     The semiconductor device  10  includes a housing  20 , a motor unit  30 , and an inverter unit  40 . The semiconductor device  10  includes the motor unit  30  that operates as a motor, and is a motor-integrated semiconductor device. 
       FIG.  2    is a sectional view of the inverter unit  40  of the first embodiment, and is an enlarged view of a region surrounded by a broken line in  FIG.  1   . 
     The housing  20  is made of metal and has a cylindrical shape as illustrated in  FIG.  3   . 
     The motor unit  30  includes a stator  31 , a rotor  32 , and a shaft  33 . 
     The shaft  33  is rotatably supported by the housing  20  with a bearing, and is disposed passing through a central axis of the cylindrical shape of the housing  20 . The shaft  33  partly protrudes outward from the housing  20 . 
     The shaft  33  is fixed to the rotor  32  of a permanent magnet having one pair or multiple pairs of an S pole and an N pole. The rotor  32  is configured to be rotatable with respect to the housing  20  integrally with the shaft  33 . 
     The stator  31  fixed to the housing  20  is disposed outside the rotor  32 . The stator  31  includes an electromagnet including a stator core fixed to the housing  20  and a stator coil wound around the stator core. The number of electromagnets included in the stator  31  is three, six, or nine, which is a multiple of three and in accordance with torque or rotation speed required for the motor. The stator  31  receives a three-phase alternating current supplied from the inverter unit  40 . However, the stator  31  may use a multiphase alternating current other than the three-phase alternating current, and in this case, the number of electromagnets included in the stator  31  is not necessarily a multiple of three. 
     The inverter unit  40  includes multiple semiconductor modules  42 , a control board  41 , and a cooler  50 . The semiconductor modules  42  are each a cooling target for the cooler  50 . 
     The inverter unit  40  supplies a three-phase alternating current to the stator  31 . For example, the inverter unit  40  converts a direct current supplied from a battery outside the semiconductor device  10  into an alternating current to supply the alternating current to the stator  31 . The inverter unit  40  includes as many semiconductor modules  42  as necessary for generating an alternating current to be supplied to the stator  31 . The present embodiment is described in which six semiconductor modules  42  are provided. 
       FIG.  4    is a plan view of the cooler  50  as viewed from a first direction. The first direction is an axial direction of the shaft  33  in  FIG.  1   . As illustrated in  FIG.  4   , the cooler  50  has an annular shape in plan view as viewed from the first direction.  FIG.  4    also illustrates the semiconductor modules  42  disposed on a surface of the cooler  50 . The present disclosure is described in which a simple annular shape means an annular shape in plan view when each of coolers  50 ,  150 , and  250  of respective embodiments is viewed from the first direction. Additionally, a simply described circumferential direction or radial direction means the circumferential direction or the radial direction of the annular shape in plan view when each the coolers  50 ,  150 , and  250  of respective embodiments is viewed from the first direction. 
     The cooler  50  is provided inside with a flow path of a refrigerant. The refrigerant is cooling water, for example.  FIGS.  5  and  6    are each a sectional view of the cooler  50  taken along a plane perpendicular to the first direction and passing through the flow path of a refrigerant.  FIG.  6    illustrates a position of each of the semiconductor modules  42  with a broken line in plan view from the first direction. 
     The cooler  50  includes an outer-peripheral-side pipe  54  and an inner-peripheral-side pipe  55 .  FIGS.  5  and  6    each illustrate positions of an outer-peripheral-side pipe connection region  54   a  where the outer-peripheral-side pipe  54  is connected to a frame body of the cooler  50  and an inner-peripheral-side pipe connection region  55   a  where the inner-peripheral-side pipe  55  is connected to the frame body of the cooler  50  in plan view from the first direction. The inner-peripheral-side pipe  55  and the outer-peripheral-side pipe  54  are connected with a flow path inside the cooler  50 , the flow path including an outer-peripheral-side header region  51 , an inner-peripheral-side header region  52 , and a fin region  53 . 
     The outer-peripheral-side header region  51  is provided on the outer peripheral side of the annular shape and extends in the circumferential direction. 
     The inner-peripheral-side header region  52  is provided on the inner peripheral side of the annular shape across a separation region from the outer-peripheral-side header region  51  and extends in the circumferential direction. 
     In the present embodiment, the separation region is the same as the fin region  53  as a region. The fin region  53  is provided in a region radially interposed between the inner-peripheral-side header region  52  and the outer-peripheral-side header region  51 , and extends in the circumferential direction. As illustrated in  FIG.  5   , fins  57  are disposed in the fin region  53 . The fin region  53  allows the refrigerant to flow between the outer-peripheral-side header region  51  and the inner-peripheral-side header region  52 .  FIGS.  1 ,  2 , and  6    each illustrate the fin region  53  in a dot pattern for clarity. 
     The fins  57  desirably pin fins or corrugated fins, have high cooling efficiency, for example.  FIG.  5    illustrates the fins  57  as pin fins. 
     Even when the outer-peripheral-side header region  51  and the inner-peripheral-side header region  52  are identical in width of angle in the circumferential direction, the outer-peripheral-side header region  51  is longer in circumferential length than the inner-peripheral-side header region  52 . This configuration causes a pressure difference in the circumferential direction of the refrigerant to be more likely to occur in the outer-peripheral-side header region  51  than in the inner-peripheral-side header region  52 . To reduce the pressure difference of the refrigerant in the circumferential direction in the outer-peripheral-side header region  51 , the outer-peripheral-side header region  51  desirably has a radial width W 1  larger than a radial width W 2  of the inner-peripheral-side header region  52 . The reduction in the pressure difference of the refrigerant in the circumferential direction in the outer-peripheral-side header region  51  causes the cooler  50  to be less likely to have an uneven degree of cooling during cooling of the multiple cooling targets.  FIG.  5    shows W 1  and W 2 . 
     Each of the outer-peripheral-side header region  51  and the inner-peripheral-side header region  52  desirably has almost no flow path resistance to the refrigerant. In particular, the outer-peripheral-side header region  51  and the inner-peripheral-side header region  52  each desirably have sufficiently smaller flow path resistance to the refrigerant than the fin region  53 . 
     Each semiconductor module  42  includes a semiconductor element  43 , a heat spreader  46 , a main terminal  45 , a signal terminal  44 , and a sealing resin  47 . The semiconductor element  43  is joined to the heat spreader  46  with a brazing material such as solder, and sealed with the sealing resin  47 . The semiconductor module  42  has a surface from which the heat spreader  46  is exposed. The main terminal  45  and the signal terminal  44  are each connected on one side to the semiconductor element  43 , and are out of the sealing resin  47  on the other side. However, the configuration of the semiconductor module  42  is not limited to such an example. For example, the semiconductor module  42  may not include the heat spreader  46 , and the semiconductor element  43  itself may serve as the semiconductor module  42 . 
     As illustrated in  FIG.  4   , the multiple semiconductor modules  42  are disposed on a module placement surface  58  of the cooler  50  extending in a second direction intersecting the first direction and a third direction intersecting the first direction and the second direction. The multiple semiconductor modules  42  are disposed side by side in the circumferential direction on the module placement surface  58 , and are uniformly cooled by the cooler  50 . Although in the present embodiment, the first direction illustrated is perpendicular to a plane defined by the second direction and the third direction, the first direction is not necessarily perpendicular to the plane defined by the second direction and the third direction. 
     Each of the semiconductor modules  42  is disposed with the heat spreader  46  in contact with the module placement surface  58  of the cooler  50 . The module placement surface  58  includes a part corresponding to the fin region  53 , the part having higher cooling capacity than another part, so that each of the semiconductor modules  42  is disposed on the module placement surface  58  of the cooler  50  while having the region of the heat spreader  46  overlapping the fin region  53  in plan view from the first direction. The term, “overlapping”, includes a case of partially overlapping. 
     To sufficiently utilize the cooling capacity of the fin region  53 , each of the semiconductor modules  42  is desirably disposed on the module placement surface  58  of the cooler  50  while having the region of the heat spreader  46  included in the fin region  53  in plan view from the first direction. In consideration of diffusion of heat transferred from the heat spreader  46  to the cooler  50  at an outer wall of the cooler  50 , the fin region  53  more desirably includes a part from the region of the heat spreader  46  of each semiconductor module  42  to the outside by a distance equal to or more than a thickness of the outer wall of the cooler  50 , in plan view from the first direction. 
     Between each semiconductor module  42  and the cooler  50 , filler-containing grease is filled to fill a minute gap to facilitate heat transfer, for example. Each of the semiconductor modules  42  is pressed against the cooler  50  with a spring or a screw (not illustrated). 
     Each of the semiconductor modules  42  and the stator coil of the stator  31  are connected with a bus bar or a lead wire (not illustrated) disposed inside the housing  20 , and a three-phase alternating current is supplied from the inverter unit  40  to the stator coil of the stator  31 . For example, a bus bar or a lead wire for inputting a direct current from a battery outside the housing  20  to each of the semiconductor modules  42  is required to operate the semiconductor device  10 , but is not illustrated in the drawing. 
     The control board  41  is configured to detect an input signal, a current, and a temperature to the semiconductor module  42  through the signal terminal  44 , and protects the semiconductor element  43 . 
     The control board  41  and the cooler  50  each have an annular shape with a hole in the center when viewed from the axial direction of the shaft  33 , the annular shape having an outer peripheral part attached and fixed to the housing  20 . The control board  41  and the cooler  50  are fixed to the housing  20  with the shaft  33  passing through the hole of the annular shape of each of the control board  41  and the cooler  50 . 
     A-2. Operation 
     The inverter unit  40  converts a direct current into an alternating current by causing the multiple semiconductor elements  43  to sequentially switch, and then Joule heat is generated by resistance and a current of each of the semiconductor elements  43 . Each semiconductor element  43  and its peripheral components individually have a heat-resistant temperature unique to material, and are individually required to be maintained at the heat-resistant temperature or lower. Joined materials each have a different linear expansion coefficient, and thus have a different amount of expansion and contraction in accordance with change in temperature. The materials are joined at a part where distortion occurs due to the different amount of expansion and contraction, so that the part cracks or peels. Thus, the cooler  50  cools the semiconductor module  42  to keep the temperature of the semiconductor module  42  at a certain temperature or lower. The multiple semiconductor modules  42  are desirably cooled uniformly. 
     The refrigerant flows in a direction that depends on a direction in which a pump, which is not illustrated and is not included in the cooler  50 , is connected to the outer-peripheral-side pipe  54  and the inner-peripheral-side pipe  55 . In the present embodiment, the refrigerant flows in a direction in which the refrigerant is taken into the cooler  50  from the inner-peripheral-side pipe  55  and discharged to the outside of the cooler  50  from the outer-peripheral-side pipe  54 . That is, the cooler  50  takes in the refrigerant through the inner-peripheral-side pipe  55  to cause the refrigerant to flow from the inner-peripheral-side header region  52  toward the outer-peripheral-side header region  51  through the fin region  53 , and discharges the refrigerant from the outer-peripheral-side pipe  54  to the outside of the cooler  50 . When the pump is inversely connected to the outer-peripheral-side pipe  54  and the inner-peripheral-side pipe  55 , the refrigerant can flow in a direction opposite to the above direction. The cooler  50  may also include a pump. 
     The inner-peripheral-side header region  52  and the outer-peripheral-side header region  51  each have the sufficiently smaller flow path resistance than the fin region  53 . Thus, when the refrigerant flows through the flow path of the cooler  50 , the inner-peripheral-side header region  52  and the outer-peripheral-side header region  51  are each under substantially uniform pressure. This causes a pressure gradient to be generated in the fin region  53  in the radial direction. For example, a pressure difference between first and second ends of the inner-peripheral-side header region  52 , the first end being close to the inner-peripheral-side pipe connection region  55   a , and the second end being close to the outer-peripheral-side pipe connection region  54   a , and a pressure difference between third and fourth ends of the outer-peripheral-side header region  51 , the third end being close to inner-peripheral-side pipe connection region  55   a , and the fourth end being close to the outer-peripheral-side pipe connection region  54   a , are smaller than a pressure difference between the first end of the inner-peripheral-side header region  52 , the first end being close to the inner-peripheral-side pipe connection region  55   a , and the third end of the outer-peripheral-side header region  51 , the third end close to the inner-peripheral-side pipe connection region  55   a , and a pressure difference between the second end of the inner-peripheral-side header region  52 , the second end being close to the outer-peripheral-side pipe connection region  54   a , and the fourth end of the outer-peripheral-side header region  51 , the fourth end being close to the outer-peripheral-side pipe connection region  54   a . Here, the pressure difference is an absolute value. 
     The semiconductor modules  42  each generate heat that is transferred to the refrigerant through the outer wall of the cooler  50  or to the refrigerant through the outer wall of the cooler  50  and the fins  57 . As a result, the semiconductor modules  42  are cooled. 
     The refrigerant is under substantially uniform pressure in each of the inner-peripheral-side header region  52  and the outer-peripheral-side header region  51 , so that the refrigerant flows in the fin region  53  in parallel in the circumferential direction from the inner-peripheral-side header region  52  toward the outer-peripheral-side header region  51  at a substantially uniform flow rate, and thus the fin region  53  has cooling capacity that is substantially uniform in the circumferential direction. Thus, the multiple semiconductor modules  42  disposed side by side in the circumferential direction on the module placement surface  58  is cooled substantially uniformly. 
     As described above, the flow path of the cooler  50  includes the outer-peripheral-side header region  51  provided on the outer peripheral side of the annular shape and extending in the circumferential direction, the inner-peripheral-side header region  52  provided on the inner peripheral side of the annular shape across the separation region from the outer-peripheral-side header region  51  and extending in the circumferential direction, and the fin region  53  serving as the separation region in which the fins  57  are disposed, thereby causing the cooler  50  to be less likely to cause an uneven degree of cooling during cooling of the multiple cooling targets. 
     The motor unit  30  is configured such that a three-phase alternating current is applied to the stator  31  to generate a magnetic field, and the rotor  32  is rotated to convert electric energy into kinetic energy. However, the conversion efficiency is not 100%, and a part of the energy is lost. Then, most of the loss is converted into heat. Thus, the motor unit  30  also needs to be cooled as necessary, but the cooling of the motor unit  30  is eliminated in the drawing of the present embodiment. 
     When the motor unit  30  generates heat, the heat is transferred to the inverter unit  40  through the housing  20  made of metal. The cooler  50  is fixed to the housing  20  on the outer peripheral side, so that the cooler  50  may rise in temperature on its outer peripheral side, and thus the refrigerant in the outer-peripheral-side header region  51  may also rise in temperature. However, the refrigerant flows through the inner-peripheral-side header region  52 , the fin region  53 , and the outer-peripheral-side header region  51  in this order. Thus, the refrigerant flows in the outer-peripheral-side header region  51  after cooling the semiconductor modules  42 , so that the cooling of the semiconductor modules  42  with the fin region  53  can be less likely to be affected by heat generated by the motor unit  30 . 
     A-3. Effect 
     The flow path of the cooler  50  includes the outer-peripheral-side header region  51  provided on the outer peripheral side of the annular shape and extending in the circumferential direction, the inner-peripheral-side header region  52  provided on the inner peripheral side of the annular shape across the separation region from the outer-peripheral-side header region  51  and extending in the circumferential direction, and the fin region  53  serving as the separation region in which the fin  57  is disposed. As a result, the cooler  50  is less likely to cause an uneven degree of cooling during cooling of multiple cooling targets. 
     The cooler  50  causes the refrigerant to flow from the inner-peripheral-side header region  52  toward the outer-peripheral-side header region  51  through the fin region  53 . As a result, the cooling with the fin region  53  can be less likely to be affected by heat transferred from the housing  20  fixing the cooler  50  on the outer peripheral side to the cooler  50 . 
     The cooler  50  includes the outer-peripheral-side header region  51  that desirably has a wider radial width than the inner-peripheral-side header region  52 . As a result, the cooler  50  is lesser likely to cause an uneven degree of cooling during cooling of multiple cooling targets. 
     The multiple semiconductor modules  42  in the semiconductor device  10  are disposed on the module placement surface  58  of the cooler  50 . This configuration enables the multiple semiconductor modules  42  to be cooled by the cooler  50 . 
     The multiple semiconductor modules  42  in the semiconductor device  10  are disposed side by side in the circumferential direction on the module placement surface  58  of the cooler  50 . This configuration enables the multiple semiconductor modules  42  to be cooled more uniformly by the cooler  50 . 
     The multiple semiconductor modules  42  in the semiconductor device  10  are each disposed on the module placement surface  58  of the cooler  50  with the heat spreader  46  in the region overlapping the fin region  53  in plan view from the first direction. This configuration enables the multiple semiconductor modules  42  to be cooled by the fin region  53 . 
     The multiple semiconductor modules  42  in the semiconductor device  10  are each desirably disposed on the module placement surface  58  of the cooler  50  with the heat spreader  46  in a region included in the fin region  53  in plan view from the first direction. This configuration enables the multiple semiconductor modules  42  to be efficiently cooled by the fin region  53 . 
     The fin region  53  in the semiconductor device  10  desirably includes a part from the region of the heat spreader  46  of each of the multiple semiconductor modules  42  to the outside by a distance equal to or more than a thickness of the outer wall of the cooler  50 , in plan view from the first direction. This configuration enables the multiple semiconductor modules  42  to be more efficiently cooled by the fin region  53 . 
     The semiconductor device  10  is a motor-integrated semiconductor device. As a result, a motor-integrated semiconductor device capable of cooling the multiple semiconductor modules  42  with the cooler  50  is fabricated. 
     B. Second Embodiment 
     B-1. Configuration and Operation 
     A semiconductor device (referred to below as a semiconductor device  110 ) of the present embodiment includes an inverter unit  140  instead of the inverter unit  40  as compared with the semiconductor device  10 . The semiconductor device  110  is identical to the semiconductor device  10  in other points. 
       FIG.  7    is a diagram illustrating a half of a section of the inverter unit  140 , and is a diagram corresponding to  FIG.  2    illustrating the inverter unit  40  of the first embodiment. 
     The inverter unit  140  includes a cooler  150  instead of the cooler  50  as compared with the inverter unit  40 . The cooler  150  in the inverter unit  140  cools a main terminal  45  of a semiconductor module  42 . The inverter unit  140  is similar to the inverter unit  40  in other points. 
     The cooler  150  is provided inside with a flow path of a refrigerant, the flow path including: an outer-peripheral-side header region  51  that is provided on an outer peripheral side of an annular shape and extends in the circumferential direction of the annular shape; an inner-peripheral-side header region  152  that is provided on an inner peripheral side of the annular shape across a separation region from the outer-peripheral-side header region  51  and extends in the circumferential direction; and a fin region  53  serving as the separation region in which a fin  57  is disposed. The outer-peripheral-side header region  51  and the fin region  53  are similar to those of the cooler  50  of the first embodiment. 
     The inner-peripheral-side header region  152  has a wider width in a first direction than the fin region  53 . This configuration enables increase in sectional area of the flow path of the inner-peripheral-side header region  152 , so that flow path resistance of the inner-peripheral-side header region  152  can be lowered to uniform internal pressure of the inner-peripheral-side header region  152 , and thus the fin region  53  has cooling capacity that is more uniform in the circumferential direction.  FIG.  7    illustrates the fin region  53  in a dot pattern for clarity. 
     A module placement surface  158  of the cooler  150  extending in a second direction intersecting the first direction and a third direction intersecting the first direction and the second direction includes a part corresponding to the inner-peripheral-side header region  152 , the part protruding from a part corresponding to the fin region  53 . This configuration can easily achieve a configuration in which the inner-peripheral-side header region  152  has a wider width in the first direction than the fin region  53 . 
     The inverter unit  140  is configured such that the main terminal  45  of each semiconductor module  42  is in contact with the protruding part of the module placement surface  158  with an insulating material  60  interposed therebetween. The insulating material  60  is a glass coat, for example. The main terminal  45  may be heated to a high temperature due to heat generated by a large current flowing to drive a motor unit  30  or heat transferred from the semiconductor element  43  because of being joined to the semiconductor element  43 . The main terminal  45  is cooled by being in contact with the protruding part of the module placement surface  158  with the insulating material  60  interposed therebetween. The main terminal  45  has a smaller heating value than the semiconductor element  43 , so that cooling with a part corresponding to the inner-peripheral-side header region  152  instead of the fin region  53  is sufficient. The main terminal  45  is in contact with the part of the module placement surface  158  of the cooler  150 , the part protruding from the part corresponding to the fin region  53 , and thus facilitating wiring for cooling the main terminal  45  with the cooler  150 . 
     Although the above description shows that the inner-peripheral-side header region  152  has the wider width in the first direction than the fin region  53 , at least one of the outer-peripheral-side header region  51  and the inner-peripheral-side header region  152  may have a wider width in the first direction than the fin region  53 . This configuration also enables increase in sectional area of the flow path in the at least one region, so that flow path resistance in the at least one region can be lowered to uniform internal pressure in the at least one region, and thus the fin region  53  has cooling capacity that is more uniform in the circumferential direction. That is, the cooler  150  is lesser likely to cause an uneven degree of cooling during cooling of multiple cooling targets. 
     When a part of the module placement surface  158  of the cooler  150 , the part corresponding to the one region, protrudes from the part corresponding to the fin region  53 , a configuration in which the at least one region has a wider width in the first direction than the fin region  53  can be easily achieved. When the main terminal  45  of each of the multiple semiconductor modules  42  is disposed in contact with the protruding part corresponding to the at least one region with the insulating material  60  interposed therebetween, the main terminal  45  can be cooled. 
     B-2. Effect 
     The cooler  150  may be configured such that at least one of the outer-peripheral-side header region  51  and the inner-peripheral-side header region  152  has a wider width in the first direction than the fin region  53 . This configuration causes the cooler  150  to be lesser likely to cause an uneven degree of cooling during cooling of multiple cooling targets. 
     The module placement surface  158  of the cooler  150  may be configured such that a part corresponding to at least one region protrudes from a part corresponding to the fin region  53 . This configuration can facilitate achieving the configuration of the cooler  150  in which at least one of the outer-peripheral-side header region  51  and the inner-peripheral-side header region  152  has a wider width in the first direction than the fin region  53 . 
     The semiconductor device  110  is configured such that the main terminal  45  of each of the multiple semiconductor modules  42  is in contact with the protruding part of the module placement surface  158  with the insulating material  60  interposed therebetween. This configuration enables the main terminal  45  to be cooled. The main terminal  45  is in contact with the part of the module placement surface  158  of the cooler  150 , the part protruding from the part corresponding to the fin region  53 , and thus facilitating wiring for cooling the main terminal  45  with the cooler  150 . 
     C. Third Embodiment 
     C-1 Configuration and Operation 
     As illustrated in  FIGS.  5  and  6   , the cooler  50  of the first embodiment includes the fin region  53  that extends in the circumferential direction, and the multiple semiconductor modules  42  that are disposed at intervals in a region corresponding to the fin region  53  of the module placement surface  58 . Although the semiconductor modules  42  can be cooled by the fin region  53  in the configuration of the first embodiment, the refrigerant also flows in a part corresponding to the intervals between the semiconductor modules  42  in the fin region  53 . Even when the refrigerant flows in a part in the fin region  53 , the part corresponding to a part provided with no semiconductor module  42 , the refrigerant is less likely to contribute to cooling of the semiconductor modules  42 . 
     An inverter unit (referred to below as an inverter unit  240 ) provided in a semiconductor device (referred to below as a semiconductor device  210 ) of the present embodiment includes a cooler  250  instead of the cooler  50  as compared with the inverter unit  40  provided in the semiconductor device  10  of the first embodiment. The inverter unit  240  is identical to the inverter unit  40  in other points. The semiconductor device  210  is identical to the semiconductor device  10  except that the inverter unit  240  is provided instead of the inverter unit  40 . A sectional view of the semiconductor device  210  is illustrated in  FIG.  1    as in the first embodiment. An enlarged view of a region surrounded by a broken line in  FIG.  1    of the inverter unit  240  is illustrated in  FIG.  2   . Then, a reference numeral of a component different in a reference numeral between the present embodiment and the first embodiment is indicated in parentheses in  FIGS.  1  and  2   . 
       FIG.  8    is a sectional view of the cooler  250  taken along a plane perpendicular to a first direction and passing through a flow path of the refrigerant.  FIG.  8    illustrates a position of each of the semiconductor modules  42  with a broken line in plan view from the first direction. 
     As illustrated in  FIGS.  1  and  8   , the flow path inside the cooler  250 , as with the flow path inside the cooler  50 , includes an outer-peripheral-side header region  51  provided on an outer peripheral side of an annular shape and extending in the circumferential direction, and an inner-peripheral-side header region  52  provided on an inner peripheral side of the annular shape across a separation region from the outer-peripheral-side header region  51  and extending in the circumferential direction. 
     The cooler  250  includes a fin region  253  in which fins are disposed. The fin region  253  is provided in a separation region radially interposed between the inner-peripheral-side header region  52  and the outer-peripheral-side header region  51  to cause the refrigerant to flow between the inner-peripheral-side header region  52  and the outer-peripheral-side header region  51 . The fin region  253  is intermittently provided in the circumferential direction. As a result, when the semiconductor modules  42  are each disposed in a region corresponding to the fin region  253  in the module placement surface  58 , the semiconductor modules  42  can be efficiently cooled. The separation region in the present embodiment is obtained by combining the fin region  253  and a region occupied by metal blocks  56  described later, illustrated in  FIG.  8   .  FIG.  8    illustrates the fin region  253  in a dot pattern for clarity. Although the fins disposed in the fin region  253  are each a pin fin or a corrugated fin, for example, as with the fins  57  disposed in the fin region  53  in the first embodiment, the fins are not illustrated. 
     As illustrated in  FIG.  8   , the semiconductor device  210  includes the multiple semiconductor modules  42  that are disposed overlapping respective fin regions  253  intermittently provided in the circumferential direction one by one, in plan view from the first direction. This configuration does not cause the refrigerant to flow to regions having low efficiency for cooling the respective multiple semiconductor modules  42  in the separation region, and thus each of the semiconductor modules  42  can be efficiently cooled. 
     As illustrated in  FIG.  8   , the multiple semiconductor modules  42  are each disposed on the module placement surface  58  of the cooler  250  with a heat spreader  46  in a region overlapping the fin region  253  in plan view from the first direction. The semiconductor modules  42  are each desirably disposed on the module placement surface  58  of the cooler  250  with the heat spreader  46  in a region included in the fin region  253  in plan view from the first direction. The fin region  253  desirably includes a part from the region of the heat spreader  46  of each of the semiconductor modules  42  to the outside by a distance equal to or more than a thickness of an outer wall of the cooler  250 , in plan view from the first direction. 
     The cooler  250  further includes the metal blocks  56 , and the metal blocks  56  are disposed in a region provided with no fin region  253  in the separation region. The metal blocks  56  are disposed in each of the intervening portions of the fin regions  253  provided intermittently. When a heating value of the semiconductor modules  42  temporarily increases, such as when a motor unit  30  is locked or when a high load is suddenly applied to the semiconductor modules  42  due to sudden acceleration of an electric vehicle using the semiconductor device  10 , cooling with the fins  57  and a buffer due to heat capacity of metal blocks  56  can suppress a temperature rise. Thus, output of a pump (not illustrated) that causes the refrigerant to flow into the cooler  250  can be reduced. 
     Although aluminum is often used as material of a cooler, copper having a large heat capacity per volume is preferably used as material of the metal blocks  56  because effect of the metal blocks  56  increases as its heat capacity increases. In that case, the copper needs to be subjected to surface treatment such as plating to prevent corrosion. Copper is also suitable as a thermal buffer against a sudden increase in the heating value of the semiconductor modules  42 , due to its higher thermal conductivity than aluminum. 
     Placement of the metal blocks  56  and the fins  57  in the cooler  250  can be changed in accordance with estimated placement of the semiconductor modules  42  on the cooler  250 . 
     C-2. Effect 
     The cooler  250  includes the fin regions  253  that are intermittently provided in the circumferential direction. This configuration enables the semiconductor modules  42  to be efficiently cooled. 
     The cooler  250  further includes the metal blocks  56 , and the metal blocks  56  are disposed in regions provided with no fin region  253  in the separation region. This configuration enables a temperature rise to be suppressed when the heating value of the semiconductor modules  42  temporarily increases. 
     The semiconductor device  210  includes the multiple semiconductor modules  42  that are disposed overlapping respective fin regions  253  intermittently provided in the circumferential direction one by one, in plan view from the first direction. This configuration enables each of the semiconductor modules  42  to be efficiently cooled. 
     D. Fourth Embodiment 
     The first to third embodiments each have no limitation on a type of semiconductor used for each of the semiconductor elements  43  built in the semiconductor module  42 . The present embodiment uses any one of the coolers according to the first to third embodiments, and the semiconductor elements  43  include a wide band gap semiconductor. The wide band gap semiconductor has a larger band gap than silicon semiconductor and is, for example, a silicon carbide semiconductor. When the wide band gap semiconductor is included, a loss in normal operation decreases and a heat-resistant temperature increases. 
     The decrease in the loss in the normal operation and the increase in the heat-resistant temperature enables the metal block  56  to absorb the amount of heat during increase in temperature from temperature in the normal operation to the heat-resistant temperature when the cooler  250  of the third embodiment is used as a cooler, the amount of heat being more than that when the semiconductor elements  43  do not include the wide band gap semiconductor, and thus the metal block  56  is further improved in function as a thermal buffer. 
     Although the present disclosure has been described in detail, the above description is illustrative and not restrictive in all aspects. Thus, it is perceived that countless modifications being not shown by way of example can be assumed. 
     EXPLANATION OF REFERENCE SIGNS 
     
         
         
           
               10 ,  110 ,  210 : semiconductor device 
               20 : housing 
               30 : motor unit 
               31 : stator 
               32 : rotor 
               33 : shaft 
               40 ,  140 ,  240 : inverter unit 
               41 : control board 
               42 : semiconductor module 
               43 : semiconductor element 
               44 : signal terminal 
               45 : main terminal 
               46 : heat spreader 
               47 : sealing resin 
               50 ,  150 ,  250 : cooler 
               51 : outer-peripheral-side header region 
               52 ,  152 : inner-peripheral-side header region 
               53 ,  253 : fin region 
               54 : outer-peripheral-side pipe 
               54   a : outer-peripheral-side pipe connection region 
               55 : inner-peripheral-side pipe 
               55   a : inner-peripheral-side pipe connection region 
               56 : metal block 
               57 : fin 
               58 ,  158 : module placement surface 
               60 : insulating material