Thermally conducting foam interface materials

Abstract

In one aspect, the invention provides a foam thermal interface material comprising a foamed film, the film comprising a blend of polymeric hot melt pressure sensitive adhesive having a number average molecular weight of greater than 25,000 and at least 25 percent by weight of thermally conductive filler, said film having a void volume of at least 5 percent of the volume of said foamed film.

1 . A foam thermal interface material comprising a foamed film, the foamed film comprising a blend of polymeric hot melt PSA having a number average molecular weight of greater than 25,000, individual microfibers which are unbroken for at least 0.5 cm in the machine direction, and at least 25 percent by weight of thermally conductive filler, said film having a void volume of at least 5 percent of the volume of said foamed film. 
   
   
       2 . The foam thermal interface material of  claim 1  wherein the foamed film further comprises a fire retardant. 
   
   
       3 . The foam thermal interface material of  claim 1  wherein the material has stretch release properties. 
   
   
       4 . The foam thermal interface material of  claim 1  wherein the microfibers imparting stretch release properties have been formed in situ. 
   
   
       5 . The foam thermal interface material of  claim 2  wherein the material will pass UL 94 V-2 rating. 
   
   
       6 . The foam thermal interface material of  claim 1  wherein the void volume ranges from 5 to 75 volume percent of the material. 
   
   
       7 . The foam thermal interface material of  claim 1  wherein the thermally conductive filler is selected from the group consisting of ceramics, metal oxides, metal hydroxides, and combinations thereof. 
   
   
       8 . The foam thermal interface material of  claim 1  wherein the polymeric hot melt PSA is selected from acrylic polymer, thermoplastic elastomer, rubber, block copolymer, poly-alpha-olefins, and blends thereof. 
   
   
       9 . The foam thermal interface material of  claim 1  wherein the thermally conductive filler is selected from the group consisting of boron nitride, silicon nitride, aluminum nitride, titanium nitride, aluminum oxide, beryllia, zirconia, silicon carbide, boron carbide, magnesium hydroxide, magnesium oxide, aluminum hydroxide, and combinations thereof. 
   
   
       10 . The foam thermal interface material of  claim 1  wherein the thermally conductive filler is present in the foamed film in an amount of at least 40 weight percent. 
   
   
       11 . The foam thermal interface material of  claim 1  further having a backing adjacent to said foamed film. 
   
   
       12 . The foam thermal interface material of  claim 11  wherein the backing is thermally conductive. 
   
   
       13 . The foam thermal interface material of  claim 1  further having at least one adhesive skin layer attached to at least a portion of said foamed film. 
   
   
       14 . The foam thermal interface material of  claim 13  wherein the at least one adhesive skin layer contains thermally conductive filler. 
   
   
       15 . The foam thermal interface material of  claim 1  having a bulk conductivity of at least 0.5 Watts/meter-K. 
   
   
       16 . A method of conducting heat from an electrical component to a heat sink material comprising the steps of: providing a foam thermal interface material of  claim 1 ; and contacting the foam thermal interface material with an electrical component and a heat sink material such that the foam thermal interface material is between the electrical component and the heat sink material. 
   
   
       17 . A thermal interface composition comprising polymeric hot melt PSA having a number average molecular weight of greater than 25,000, individual microfibers which are unbroken for at least 0.5 cm in the machine direction and at least 25 percent by weight of thermally conductive filler, and an effective amount of a foaming agent. 
   
   
       18 . The thermal interface composition of  claim 17 , wherein the thermally conductive filler is selected from the group consisting of ceramics, metal oxides, metal hydroxides, and combinations thereof. 
   
   
       19 . The thermal interface composition of  claim 17  wherein the polymeric hot melt PSA is selected from acrylic polymer, thermoplastic elastomer, rubber, block copolymer, poly-alpha-olefin, and blends thereof. 
   
   
       20 . The thermal interface material of  claim 17 , wherein the foaming agent is selected from the group consisting of expandable microspheres, physical blowing agents, chemical blowing agents, and combinations thereof.