Circuit board and method for producing the same

Abstract

A method for producing a circuit board having a metal circuit pattern on an insulating substrate is provided, including the steps of joining a metal plate onto a surface of the insulating substrate using a hard brazing member containing an active element and removing unnecessary conductive layer portions adjacent a metal circuit pattern of the metal plate to at least partially expose a portion of the surface of the insulating substrate.

1 . A circuit board having a circuit on an insulating substrate, wherein 
 said circuit is formed by a sandblast treatment for a metal plate which is joined onto said insulating substrate and which has a circuit pattern.    
   
   
       2 . The circuit board according to  claim 1 , wherein said circuit pattern is formed by etching said metal plate after said metal plate is joined onto said insulating substrate.  
   
   
       3 . The circuit board according to  claim 1 , wherein said circuit pattern is formed before joining said metal plate onto said insulating substrate.  
   
   
       4 . The circuit board according to  claim 1 , wherein said circuit of said metal is joined onto said insulating substrate using a hard brazing member containing an active element.  
   
   
       5 . The circuit board according to  claim 4 , wherein said hard brazing member has a thickness of not more than 10 μm when said circuit of said metal is joined onto said insulating substrate.  
   
   
       6 . The circuit board according to  claim 4 , wherein a conductive reactive layer is generated by a reaction between said insulating substrate and said active element in said hard brazing member, and a part of said conductive reactive layer, which corresponds to a metal-removed portion of said circuit, is removed by said sandblast treatment.  
   
   
       7 . The circuit board according to  claim 4 , wherein said active element is at lease one of elements belonging to any one of Group 2A, Group 3A, Group 4A, Group 5A, and Group 4B in the periodic table.  
   
   
       8 . The circuit board according to claims  1 , wherein a plating layer is stacked on said circuit of said metal.  
   
   
       9 . The circuit board according to claims  1 , wherein a surface roughness of said circuit of said metal or a surface roughness of said plating layer on said circuit is not more than Ra=1.0 μm.  
   
   
       10 . The circuit board according to  claim 1 , wherein a heat spreader member or a heat sink member is joined to a lower portion of said insulating substrate.  
   
   
       11 . The circuit board according to  claim 10 , wherein 
 a buffer plate of metal is joined between said insulating substrate and said heat spreader member or said heat sink member using a hard brazing member containing an active element; and    a first joined unit is provided, which comprises said circuit of said metal, said insulating substrate, said buffer plate, and said heat spreader member or said heat sink member.    
   
   
       12 . The circuit board according to  claim 11 , wherein said heat sink member has a shape of fin.  
   
   
       13 . The circuit board according to  claim 11 , wherein 
 a metal plate is joined to a lower surface of said heat spreader member or said heat sink member using a hard brazing member containing an active element; and    a second joined unit is provided, which comprises said circuit of said metal, said insulating substrate, said buffer plate, said heat spreader member or said heat sink member, and said metal plate.    
   
   
       14 . The circuit board according to  claim 13 , wherein a ratio between a thickness of said circuit of said metal and a total thickness of said buffer plate and said heat spreader member or said heat sink member is 1:0.5 to 1:3 when a coefficient of thermal expansion of said insulating substrate in said second joined unit is smaller than a coefficient of thermal expansion of a material used for said heat spreader member or said heat sink member.  
   
   
       15 . The circuit board according to  claim 13 , wherein said second joined unit is warped so that a lower surface of said metal plate is convex-shaped toward the outside.  
   
   
       16 . The circuit board according to  claim 13 , wherein said metal plate has a shape of fin.  
   
   
       17 . The circuit board according to  claim 11 , wherein said buffer plate has a thickness of 0.03 to 0.5 mm.  
   
   
       18 . The circuit board according to  claim 11 , wherein said insulating substrate has a thickness of not more than 0.6 mm when said insulating substrate is composed of Si 3 N 4 .  
   
   
       19 . The circuit board according to  claim 11 , wherein said first or second joined unit has a coefficient of thermal conductivity of not less than 200 W/m.  
   
   
       20 . The circuit board according to  claim 11 , wherein said hard brazing member has a melting point of not more than 700° C.  
   
   
       21 . The circuit board according to  claim 11 , wherein said hard brazing member is composed of Ag—Cu—In—Ti.  
   
   
       22 . The circuit board according to  claim 11 , wherein an amount of said active element in said hard brazing member for joining at least said circuit of said metal and said insulating substrate is 0.05 to 2%.  
   
   
       23 . The circuit board according to  claim 11 , wherein an amount of said active element in said hard brazing member for joining said buffer plate and said heat spreader member or said heat sink member is 0.5 to 10%.  
   
   
       24 . The circuit board according to  claim 11 , wherein a thickness of said hard brazing member for joining said heat spreader member or said heat sink member and said buffer plate, or a thickness of said hard brazing member for joining said heat spreader member or said heat sink member and said metal plate is not more than 25% of a thickness of said buffer plate.  
   
   
       25 . The circuit board according to  claim 11 , wherein a thickness of said hard brazing member for joining said insulating substrate and said circuit of said metal, or a thickness of said hard brazing member for joining said insulating substrate and said buffer plate is not more than 10% of a thickness of said buffer plate.  
   
   
       26 . The circuit board according to  claim 25 , wherein said thickness of said hard brazing member is not more than 30 μm.  
   
   
       27 . The circuit board according to  claim 10 , wherein said heat spreader member or said heat sink member contains at least one selected from the group consisting of SiC, AlN, Si 3 N 4 , BeO, Al 2 O 3 , Be 2 C, C, Cu, Cu alloy, Al, Al alloy, Ag, Ag alloy, and Si.  
   
   
       28 . The circuit board according to  claim 27 , wherein said heat sink member is composed of a composite material in which an SiC base material is impregnated with Cu or Cu alloy.  
   
   
       29 . The circuit board according to  claim 28 , wherein said heat sink member is composed of a composite material in which a C base material is impregnated with Cu or Cu alloy.  
   
   
       30 . The circuit board according to  claim 1 , wherein said insulating substrate is composed of AlN or Si 3 N 4 .