Patent Publication Number: US-2021183736-A1

Title: Semiconductor device

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a semiconductor device including a resin case that accommodates a semiconductor element and a heat dissipation component to which the resin case is fixed. 
     Description of the Background Art 
     The resin case accommodating the semiconductor element is fixed to the heat dissipation component such as a heat sink, with the back surface of the base plate being in a contact state with the heat dissipation component, whereby the heat generated in the semiconductor element is efficiently emitted outside through the base plate and the heat dissipation component. 
     There has been a problem that when excessive stress is applied to the resin case at the time of fastening the bolts to fix the resin case to the heat dissipation component, cracks are formed around the attachment holes of the resin case. 
     In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. 2019-161129 discloses a configuration in which a protrusion is provided around a through hole (corresponding to an attachment hole) of a screwed pedestal in a resin case. When screwing the resin case to the heat dissipation component, an excessive increase in bending stress is suppressed by screwing the screw member into the heat dissipation component while crushing the protrusion. As a result, cracks are prevented from forming around the attachment holes of the resin case. 
     SUMMARY 
     However, in the technique described in Japanese Patent Application Laid-Open No. 2019-161129, stress relaxation is insufficient because the resin case is deformed only by the height of the protrusion. Therefore, stress may concentrate around the attachment hole of the resin case and the resin case may possibly crack. 
     An object of the present disclosure is to provide a technique capable of relaxing the stress to be applied around the attachment hole of the resin case at the time of fixing the resin case accommodating the semiconductor element to the heat dissipation component with a bolt. 
     The semiconductor device according to the present disclosure includes a base plate, a heat dissipation component, and a resin case being rectangular in plan view. The heat dissipation component is disposed on the lower surface of the base plate. The resin case is disposed on the upper surface of the base plate and accommodates a semiconductor element. In a state where the resin case is disposed on the heat dissipation component via the base plate, the resin case is attached to the heat dissipation component with a bolt. The resin case has a recess portion, an attachment hole, and at least one groove. The recess portion is formed at a corner and the head of the bolt is placed therein. The attachment hole is formed below the recess portion and into which the shaft portion of the bolt is inserted. The at least one groove is formed between a wall portion on the inner peripheral side forming the recess and the attachment hole. One end of the at least one groove reaches an outer peripheral end of the resin case. 
     The configuration facilitates the corners of the resin case to bend downward from the at least one groove of the resin case as a starting point at the time of fixing the resin case accommodating the semiconductor element to the heat dissipation component with the bolts, thus the relaxation of the stress to be applied around the attachment holes of the resin case is ensured. 
     These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a state before a resin case and a base plate included in a semiconductor device according to Embodiment 1 are attached to a heat dissipation component; 
         FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view illustrating the semiconductor device according to Embodiment 1; 
         FIG. 4  is a plan view illustrating a state before a resin case and a base plate included in a semiconductor device according to. Modification of Embodiment 1 are attached to a heat dissipation component; 
         FIG. 5  is a cross-sectional view taken along line B-B of  FIG. 4 ; 
         FIG. 6  is a plan view illustrating a state before a resin case and a base plate included in a semiconductor device according to Embodiment 2 are attached to a heat dissipation component; 
         FIG. 7  is a cross-sectional view taken along line C-C of  FIG. 6 ; 
         FIG. 8  is a cross-sectional view illustrating the semiconductor device according to Embodiment 2; 
         FIGS. 9A and 9B  are enlarged cross-sectional views around a groove before and after bolt fastening; 
         FIG. 10  is a plan view illustrating a state before a resin case and a base plate included in a semiconductor device according to Embodiment 3 are attached to a heat dissipation component; 
         FIG. 11  is a cross-sectional view taken along line D-D of  FIG. 10 ; 
         FIG. 12  is a cross-sectional view illustrating the semiconductor device according to Embodiment 3; 
         FIGS. 13A and 13B  are enlarged cross-sectional views around a groove before and after bolt fastening; 
         FIG. 14  is a plan view illustrating a state before a resin case and a base plate included in a semiconductor device according to Embodiment 4 are attached to a heat dissipation component; and 
         FIG. 15  is a cross-sectional view taken along line E-E of  FIG. 14 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiment 1 
     Embodiment 1 will be described with reference to the drawings.  FIG. 1  is a plan view illustrating a state before a resin case  2  and a base plate  1  included in a semiconductor device  100  according to Embodiment 1 are attached to a heat dissipation component  13 .  FIG. 2  is a cross-sectional view taken along line A-A of  FIG. 1 .  FIG. 3  is a cross-sectional view illustrating the semiconductor device  100 . 
     As illustrated in  FIGS. 1 to 3 , the semiconductor device  100  includes the base plate  1 , the resin case  2 , and the heat dissipation component  13 . 
     The base plate  1  is a rectangular metal plate in plan view. The heat dissipation component  13  is a metal heat sink disposed on the lower surface of the base plate  1 . The heat dissipation component  13  has a rectangular shape in plan view and is formed into a thick plate shape. 
     The resin case  2  is disposed on the upper surface of the base plate  1  and accommodates a semiconductor element. Specifically, an insulating substrate having a circuit pattern is disposed on the upper surface of the base plate  1 , the semiconductor element is mounted on the upper surface of the circuit pattern, and these mounted components are sealed with a sealing material such as epoxy resin to form the resin case  2  having a rectangular shape in plan view. Between the semiconductor element and the circuit pattern, and between the circuit pattern and terminal electrodes  11  provided on the upper surface of the resin case  2  are connected with wires. 
     In a state where the resin case  2  is disposed on the heat dissipation component  13  via the base plate  1 , the resin case  2  is attached to the heat dissipation component  13  with bolts  10 . 
     Next, details of the resin case  2  will be described. As illustrated in  FIGS. 1 to 3 , the resin case  2  has recess portions  3 , attachment holes  4 , and grooves  6 . The recess portions  3  are formed at four corners of the resin case  2 , and the heads of the bolts  10  are placed in the recess portions  3 . Specifically, the recessed portions  3  are formed by hollowing the four corners of the resin case  2  and each portion has a shape defined by a wall portion  5  in the inner peripheral side and a bottom portion  5   a  continuous with the lower end of the wall portion  5 . Here, the wall portion  5  has an arc shape in plan view. 
     The attachment hole  4  is formed below the central portion of the recess portion  3  so as to communicate with the recess portion  3 , and the shaft portion of the bolt  10  is inserted therein. In Embodiment 1, the contours of the base plate  1 , the resin case  2 , and the heat dissipation component  13  are the same in plan view; therefore, holes  12  communicating with the attachment holes  4  are formed at the four corners of the base plate  1 , and holes (not illustrated) communicating with the holes  12  are formed at the four corners of the heat dissipation component  13 . Accordingly, the resin case  2  is attached to the heat dissipation component  13  with the bolts  10  via the base plate  1 . 
     The groove  6  is formed on the upper surface side of the resin case  2 , that is, in the portion between the wall portion  5  and the attachment hole  4 . Specifically, the groove  6  is formed in an arc shape in plan view along the wall portion  5  on the bottom portion  5   a , and both ends of the groove  6  reach the outer peripheral end of the resin case  2 . 
     The groove  6  is a round groove or a square groove that is recessed from the upper surface side to the lower surface side of the resin case  2 . Accordingly, the broadening of the grooves  6  facilitates the corners of the resin case  2  to bend downward from the grooves  6  as a starting point at the time of fixing the resin case  2  to the heat dissipation component  13  with the bolts  10 , and the stress to be applied around the attachment holes  4  is relaxed. Further, according to the action of the bending moment, the stress is reduced by shortening the distance between the fastening point of the bolt  10  which is the power point and the groove  6  which is the fulcrum. 
     Although the description was made that both ends of the groove  6  reach the outer peripheral portion of the resin case  2 , the groove  6  is broadened also at the time of fixing the resin case  2  to the heat dissipation component  13  with the bolts  10  with at least one end of the groove  6  reaching the outer peripheral portion of the resin case  2 , and this facilitates the corner of the resin case  2  to bend downward from the groove  6  as a starting point. 
     Further, the groove  6  may be formed on the lower surface side of the resin case  2 , that is, in the portion between the wall portion  5  and the attachment hole  4  on the lower surface of the resin case  2 , from the lower surface side of the resin case  2  toward the upper surface side. Accordingly, the narrowing of the grooves  6  facilitates the corners of the resin case  2  to bend downward from the grooves  6  as a starting point at the time of fixing the resin case  2  to the heat dissipation component  13  with the bolts  10 , and the stress to be applied around the attachment holes  4  is relaxed. Also, the groove  6  may be formed on the upper surface side and the lower surface side of the resin case  2 . 
     Further, as illustrated in  FIGS. 4 and 5 , two grooves  6  may be formed on the upper surface side in each of four corners of the resin case  2 . Also, two grooves  6  may be formed on the lower surface side in each of four corners of the resin case  2 , or may be formed on the upper surface side and the lower surface side in each of four corners of the resin case  2 . As a result, the corners of the resin case  2  are more facilitated to bend compare with a case where one groove  6  is formed in each corner of the resin case  2 .  FIG. 4  is a plan view illustrating a state before the resin case  2  and the base plate  1  included in a semiconductor device according to Modification of Embodiment 1 are attached to a heat dissipation component  13 .  FIG. 5  is a cross-sectional view taken along line B-B of  FIG. 4 . 
     As described above, the semiconductor device  100  according to Embodiment 1 includes the base plate  1 , the heat dissipation component  13  disposed on the lower surface of the base plate  1 ,and the resin case  2  having a rectangular shape in plan view disposed on the upper surface of the base plate  2  and accommodating the semiconductor element, in which in a state where the resin case  2  is disposed on the heat dissipation component  13  via the base plate  1 , the resin case  2  is attached to the heat dissipation component  13  with the bolts  10 , the resin case  2  includes the recess portion  3  in which the head of the bolt  10  is placed, the attachment hole  4  formed below the recess portion  3  and into which the shaft portion of the bolt  10  is inserted, and at least one groove  6  formed between the wall portion  5  on the inner peripheral side forming the recess portion  3  and the attachment hole  4 , and one end of the groove  6  reaches the outer peripheral end of the resin case  2 . 
     Therefore, the corners of the resin case  2  are facilitated to bend downward from the grooves  6  of the resin case  2  as a starting point at the time of fixing the resin case  2  accommodating the semiconductor element to the heat dissipation component  13  with the bolts  10 , thus the relaxation of the stress to be applied around the attachment holes of the resin case  2  is ensured. 
     As illustrated in  FIGS. 4 and 5 , the semiconductor device includes two grooves  6  formed on at least one surface side of the resin case  2 ; therefore, the corner of the case  2  is further facilitated to bend compared with the case where one groove  6  is formed. As a result, the stress to be applied around the attachment holes  4  of the resin case  2  is further relaxed. 
     Embodiment 2 
     Next, a semiconductor device  100 A according to Embodiment 2 will be described.  FIG. 6  is a plan view illustrating a state before a resin case  2 A and a base plate  1 A included in the semiconductor device  100 A according to Embodiment 2 are attached to a heat dissipation component  13 A.  FIG. 7  is a cross-sectional view taken along line C-C of  FIG. 6 .  FIG. 8  is a cross-sectional view illustrating the semiconductor device  100 A.  FIG. 9A  is an enlarged cross-sectional view around a groove  6  before a bolt  10  is fastened.  FIG. 9B  is an enlarged cross-sectional view around the groove  6  after the bolt  10  is fastened. It should be noted that, in Embodiment 2, the same components as those described in Embodiment 1 are denoted by the same reference numerals, and the description thereof is omitted. 
     As illustrated in  FIGS. 6 to 8 , in Embodiment 2, the heat dissipation component  13 A has a shape in which the upper surface thereof is bulging in an arc shape, and the resin case  2 A is fixed to the heat dissipation component  13 A of which upper surface is an arc shape. 
     The contour of the base plate  1 A in plan view is formed smaller than the contour of the resin case  2 A in plan view, and the corners of the resin case  2 A project from the base plate  1 A toward the outer peripheral side. Therefore, the corners of the resin case  2 A are directly fixed to the heat dissipation component  13 A without interposing the base plate  1 A. 
     As illustrated in  FIG. 9A , the groove  6  is a round groove that is recessed from the upper surface side to the lower surface side of the resin case  2 A. As illustrated in  FIGS. 8 and 9B , the groove  6  broadens and the corner of the resin case  2 A is allowed to bend downward from the groove  6  as a starting point at the time of fixing the resin case  2 A to heat dissipation component  13 A with the bolts  10 ; therefore, fixing the resin case  2 A along the shape of the upper surface of the heat dissipation component  13 A is ensured. 
     As described above, in the semiconductor device  100 A according to Embodiment 2, the heat dissipation component  13 A has a shape in which the upper surface thereof is bulging in an arc shape, the groove  6  is a round groove that is recessed from the upper surface side to the lower surface side of the resin case  2 A, the corners of the resin case  2 A project from the base plate  1 A toward the outer peripheral side, and, in a state where the grooves  6  are broadened, the corners of the resin case  2 A are bent downward. 
     Accordingly, the base plate  1 A is not disposed on the back side of the corners of the resin case  2 A; therefore, the corners of the resin case  2 A is facilitated to bend downward at the time of fixing the resin case  2 A to the heat dissipation component  13 A with the bolts  10 ; therefore, the stress to be applied around the attachment holes  4  of the resin case  2 A can be further relaxed. At this point, the groove  6  broadens and the corner of the resin case  2 A is allowed to bend downward, and fixing the resin case  2 A along the shape of the upper surface of the heat dissipation component  13 A is ensured. 
     Embodiment 3 
     Next, a semiconductor device  100 B according to Embodiment 3 will be described.  FIG. 10  is a plan view illustrating a state before a resin case  2 B and a base plate  1 A included in the semiconductor device  100 B are attached to a heat dissipation component  13 A.  FIG. 11  is a cross-sectional view taken along line D-D of  FIG. 10 .  FIG. 12  is a cross-sectional view illustrating the semiconductor device  100 B.  FIG. 13A  is an enlarged cross-sectional view around a groove  6  before a bolt  10  is fastened.  FIG. 13B  is an enlarged cross-sectional view around the groove  6  after the bolt  10  is fastened. It should be noted that, in Embodiment 3, the same components as those described in Embodiments 1 and 2 are denoted by the same reference numerals, and the description thereof is omitted. 
     As illustrated in  FIGS. 10 to 12 , Embodiment 3 is different from Embodiment 2 in the position where the groove  6  is formed. 
     As illustrated in  FIG. 13A , the groove  6  is a round groove that is recessed from the lower surface side to the upper surface side of the resin case  2 B. As illustrated in  FIGS. 12 and 13B , the groove  6  narrows and the corner of the resin case  2 B is allowed to bend downward from the groove  6  as a starting point at the time of fixing the resin case  2 B to heat dissipation component  13 A with the bolts  10 ; therefore, fixing the resin case  2 B along the shape of the upper surface of the heat dissipation component  13 A is ensured 
     As described above, in the semiconductor device  100 B according to Embodiment 3, the heat dissipation component  13 A has a shape in which the upper surface thereof is bulging in an arc shape, the groove  6  is a round groove that is recessed from the lower surface side to the upper surface side of the resin case  2 B, the corners of the resin case  2 B project from the base plate  1 A toward the outer peripheral side, and, in a state where the grooves  6  are narrowed, the corners of the resin case  2 B are bent downward. 
     Accordingly, the base plate  1 A is not disposed on the back side of the corners of the resin case  2 B; therefore, the corners of the resin case  2 B is facilitated to bend downward at the time of fixing the resin case  2 B to the heat dissipation component  13 A with the bolts  10 ; therefore, the stress to be applied around the attachment holes  4  of the resin case  2 B can be further relaxed. At this point, the groove  6  narrows and the corner of the resin case  2 B is allowed to bend downward, and fixing the resin case  2 B along the shape of the upper surface of the heat dissipation component  13 A is ensured. Further, as illustrated in  FIG. 13B , the groove  6  is narrowed after the bolt  10  is fastened; therefore, the corner of the resin case  2 B is prevented from bending further downward. 
     Embodiment 4 
     Next, a semiconductor device according to Embodiment 4 will be described.  FIG. 14  is a plan view illustrating a state before a resin case  2 C and a base plate  1 A included in the semiconductor device according to Embodiment 4 are attached to a heat dissipation component  13 A.  FIG. 15  is a cross-sectional view taken along line E-E of  FIG. 14 . It should be noted that, in Embodiment 4, the same components as those described in Embodiments 1 to 3 are denoted by the same reference numerals, and the description thereof is omitted. 
     As illustrated in  FIGS. 14 and 15 , in Embodiment 4, the groove  6  is constructed with an upper groove  6   a  and a lower groove  6   b , and the upper groove  6   a  and the lower groove  6   b  are formed on the upper surface side and the lower surface side of the resin case  2 C, respectively. Specifically, the upper groove  6   a  is a round groove recessed from the upper surface side to the lower surface side of the resin case  2 C as in the case of Embodiment 2. And, the lower groove  6   b  is a round groove recessed from the lower surface side to the upper surface side of the resin case  2 C as in the case of Embodiment 3. 
     As in the case of Embodiments 2 and 3, consider a case where the resin case  2 C is fixed to the heat dissipation component  13 A with the bolts  10 . At this point, the upper grooves  6   a  broaden and the lower grooves  6   b  narrow and the corners of the resin case  2 C are allowed to bend downward from the upper grooves  6   a  and the lower grooves  6   b  as a starting point; therefore, fixing the resin case  2 C along the shape of the upper surface of the heat dissipation component  13 A is ensured. 
     The positions of the upper groove  6   a  and the lower groove  6   b  in the lateral direction may or may not be aligned. When the position of the upper groove  6   a  is aligned with the position of the lower groove  6   b  in the lateral direction, the corner of the resin case  2 C is further facilitated to bend. 
     As described above, in the semiconductor device according to Embodiment 4, the heat dissipation component  13 A has a shape in which the upper surface is bulging in an arc shape, the upper groove  6   a  is a round groove recessed from the upper surface side to the lower surface side of the resin case  2 C, the lower groove  6   b  is a round groove recessed from the lower surface side to the upper surface side of the resin case  2 C, and the corners of the resin case  2 C project from the base plate toward the outer peripheral side, and, in a state, as the upper groove  6   a  that is recessed from the upper surface side to the lower surface side of the resin case  2 C broadens and the lower groove  6   b  that is recessed from the lower surface side to the upper surface side narrows, the corner of the resin case  2 C is bent downward. 
     Accordingly, the base plate  1 A is not disposed on the back side of the corners of the resin case  2 C; therefore, the corners of the resin case  2 C is facilitated to bend downward at the time of fixing the resin case  2 C to the heat dissipation component  13 A with the bolts  10 ; therefore, the stress to be applied around the attachment holes  4  of the resin case  2 C can be further relaxed. At this point, the upper grooves  6   a  broaden and the lower grooves  6   b  narrow and the corners of the resin case  2 C is allowed to bend downward; therefore, the amount of bending of the corners of the resin case  2 C can be adjusted. As a result, the fixing of the resin case  2 C along the shape of the upper surface of the heat dissipation component regardless of the shape of the heat dissipation component is ensured. 
     Other Modification 
     Although the grooves  6  are preferably formed around the attachment holes  4  formed at the four corners of the resin case, the grooves  6  may formed around some of the attachment holes  4 . For example, in a state where a heat dissipation component having a shape in which the upper surface is bulging in an arc shape, such as a heat dissipation component  13 A, is attached, even when the grooves  6  are provided around the attachment hole  4  on one side of the resin case in plan view, and no groove  6  is provided around the attachment holes  4  on the opposite side, the same effect as each Embodiment can be obtained. 
     If the resin case does not need to be bent too much, for example, if the heat dissipation component  13 A has a relatively small degree of bulging, by providing the groove  6  only around the at least one attachment hole  4 , the same effect as each Embodiment can be obtained. 
     Further, also in Embodiments 2 to 4, two grooves  6  may be formed for each attachment hole. This makes the corners of the resin case be further facilitated to bend compare with the case where one groove is formed for each attachment hole. As a result, the stress applied around the attachment holes  4  of the resin case is further relaxed. 
     It should be noted that Embodiments of the present invention can be arbitrarily combined and can be appropriately modified or omitted without departing from the scope of the invention. 
     While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised without departing from the scope of the invention.