Insulating sheet and method for producing it, and power module comprising the insulating sheet

Abstract

An insulating sheet includes an adhesive component of essentially a thermosetting resin and a filler member infiltrated into the component. Heat conductivity of an adhesive face region of the insulating sheet is smaller than heat conductivity of an inner region, other than the adhesive face region of the insulating sheet.

1 . An insulating sheet comprising: 
 an adhesive component of essentially a thermosetting resin and a filler member infiltrated into the component, wherein heat conductivity of an adhesive face region of the insulating sheet is smaller than heat conductivity of an inner region, except for the adhesive face region of the insulating sheet.    
   
   
       2 . The insulating sheet as claimed in  claim 1 , wherein the heat conductivity of the adhesive face region of the insulating sheet is from 0.2 to 10 W/mK and the heat conductivity of the inner region of the insulating sheet is from 10 to 16 W/mK.  
   
   
       3 . The insulating sheet as claimed in  claim 1 , wherein 
 filler content of the adhesive face region is smaller than filler content of the inner region, and    the heat conductivities of the adhesive face region and of the inner region are controlled by the filler content of each region.    
   
   
       4 . The insulating sheet as claimed in  claim 1 , wherein the heat conductivity sequentially increases in a direction from the adhesive face of the insulating sheet inside the insulating sheet.  
   
   
       5 . The insulating sheet as claimed in  claim 1 , wherein the heat conductivity of the adhesive face region of the insulating sheet stepwise differs from the heat conductivity of the inner region, except for the adhesive face region of the insulating sheet.  
   
   
       6 . The insulating sheet as claimed in  claim 1 , wherein the filler member is a flattened or granular filler, and is at least one of aluminum oxide (alumina), boron nitride, and silicon carbide.  
   
   
       7 . The insulating sheet as claimed in  claim 1 , including one of a ceramic sheet with a through-hole, a ceramic sheet with a metal-coated through-hole, and a glass laminate with a metal-coated through-hole infiltrated in the inner region of the insulating sheet as the filler member.  
   
   
       8 . The insulating sheet as claimed in  claim 1 , wherein a core region of a center part region in a thickness direction of the inner region of the insulating sheet is filled with a conductive filler member.  
   
   
       9 . The insulating sheet as claimed in  claim 8 , wherein the conductive filler member is a conductive metal sheet with a through-hole.  
   
   
       10 . The insulating sheet as claimed in  claim 1 , wherein the adhesive component is in an A or B stage condition.  
   
   
       11 . A method for producing an insulating sheet, comprising: 
 obtaining an A-stage or B-stage laminate that includes a first layer of a first insulating sheet composition and a second layer of a second insulating sheet composition on the first layer; and    pressing the A-stage or B-stage laminate so that adhesive components in the first and second layers mix together, wherein 
 the first insulating sheet composition includes an adhesive component of essentially a thermosetting resin and a filler member and thermosetting to have a heat conductivity of from 0.2 to 10 W/mK, and  
 the second insulating sheet composition includes an adhesive component of essentially a thermosetting resin and a filler member and thermosetting to have a heat conductivity of from 10 to 16 W/mK.  
   
   
   
       12 . The method for producing an insulating sheet as claimed in  claim 11 , further comprising laminating a first A-stage or B-stage laminate and a second A-stage or B-stage laminate with respective second layers of the laminates facing each other.  
   
   
       13 . A power module comprising: 
 a power semiconductor device;    a conductive member with the power semiconductor device mounted thereon;    a cured insulating sheet fitted to a face of the conductive member, opposite to a face of the conductive member having the power semiconductive device mounted thereon; and    a heat sink member fitted to the cured insulating sheet, wherein the insulating sheet includes: 
 an adhesive component of essentially a thermosetting resin and a filler member infiltrated into the component, and  
 heat conductivity of an adhesive face region of the insulating sheet is smaller than heat conductivity of an inner region, except for the adhesive face region of the insulating sheet.  
   
   
   
       14 . A power module comprising: 
 a power semiconductor device;    a circuit board with the power semiconductor device mounted thereon;    a heat sink member having the circuit board located thereon;    a case attached to a peripheral part of the heat sink member;    a molding resin in the case sealing the circuit board and the power semiconductor device in the case;    a cured insulating sheet fitted to a face of the heat sink member, opposite a face of the heat sink member having the circuit board mounted thereon; and    a heat spreader fitted to the cured insulating sheet, wherein the insulating sheet includes: 
 an adhesive component of essentially a thermosetting resin and a filler member infiltrated into the component, and  
 heat conductivity of an adhesive face region of the insulating sheet is smaller than heat conductivity of an inner region, except for the adhesive face region of the insulating sheet.