Thermally coupling an integrated heat spreader to a heat sink base

Abstract

The base of a heat sink may be selectively plated with a solder wetting material and soldered to an integral heat spreader also selectively plated with gold. In another embodiment, the solder may be applied in the form of an insert made up of an electrical heating wire sandwiched between indium foil which acts as solder when heated by the intervening wire.

1 . a heat sink comprising:
 a heat transfer surface;   a base having a first and second side, the heat transfer surface coupled to a first side of said base; and   a selectively plated solder wetting material on the second side of said base.   
   
   
       2 . The heat sink of  claim 1  wherein said selectively plated layer corresponds to the profile of an integral heat spreader. 
   
   
       3 . The heat sink of  claim 1  wherein said base is formed of a material that does not wet indium solder. 
   
   
       4 . The heat sink of  claim 3  wherein said material is selected from the group of gold, silver, tin, or indium. 
   
   
       5 . An integral heat spreader comprising:
 a body to receive an integrated circuit, said body including an external surface exposed when said body receives said circuit; and   a solder wetting layer on said body, said layer covering less than all of said external surface.   
   
   
       6 . The heat spreader of  claim 5  wherein said body includes a depression to receive an integrated circuit, an first surface having said depression, an opposite surface, and side surfaces. 
   
   
       7 . The heat spreader of  claim 6  wherein said gold layer covers said opposite surface. 
   
   
       8 . The heat spreader of  claim 5  wherein said layer includes gold.