Multipath Soldered Thermal Interface Between a Chip and its Heat Sink

Abstract

The invention comprises a process for joining a first surface and a second surface where the first surface comprises an initially non-solderable surface which comprises coating the first surface with a solder-adhesion layer to produce a solder-adhesion layer on the first surface and providing a Thermal Interface Material (“TIM”) composition comprising solderable heat-conducting particles in a bondable resin matrix where at least some of the solderable heat-conducting particles comprise a solder surface. The TIM composition is placed between the first surface and the second surface to extend between and be contiguous with both the second surface and the solder-adhesion layer on the first surface. Sufficiently heating the TIM composition results in (a) soldering at least some of the solderable heat-conducting particles to one another; and (b) soldering at least some of the solderable heat-conducting particles to the solder-adhesion layer on the first surface. When the second surface comprises a solderable surface, the particles will also bond to it. When the second surface is not solderable, a solder adhesion layer can be placed on it. The process also includes adhesively bonding the resin matrix to the first surface and the second surface. The first surface can comprise an electronic device such as a semiconductor device and the second surface can comprise a heat sink, such as a solderable heat sink. The invention also comprises a process for improving the heat conductivity of a TIM, an article of manufacture made by the process, and a composition of matter comprising the TIM.

1 . A process comprising joining a first surface and a second surface where said first surface comprises an initially non-solderable surface which comprises;
 coating said first surface with a solder-adhesion layer to produce a solder-adhesion layer on said first surface;   providing a TIM composition comprising solderable heat-conducting particles in a bondable resin matrix, at least some of said solderable heat-conducting particles comprising a solder surface;   placing said TIM composition between said first surface and said second surface to extend between and be contiguous with both said second surface and said solder-adhesion layer on said first surface;   heating said TIM composition sufficiently to;
 (a) solder at least some of said solderable heat-conducting particles to one another; 
 (b) solder at least some of said solderable heat-conducting particles to said solder-adhesion layer on said first surface; and 
   adhesively bonding said resin matrix to said first surface and said second surface.   
     
     
         2 . The Process of  claim 1  wherein said second surface comprises a solderable surface and at least some of said solderable heat-conducting particles are soldered to said solderable-surface. 
     
     
         3 . The process of  claim 1  wherein said solderable heat-conducting particles comprise a first group of particles comprised of solderable heat-conducting metals, or nanotubes, or mixtures thereof, and a second group of particles comprised of solderable heat-conducting non-metallic materials or mixtures thereof, or mixtures comprising said first group and said second group. 
     
     
         4 . The process of  claim 1  wherein said solderable heat-conducting particles comprise a first group of particles comprised of solderable heat-conducting metals, or nanotubes, or mixtures thereof, and a second group of particles comprised of solderable heat-conducting non-metallic materials or mixtures thereof, or mixtures comprising said first group and said second group, and wherein said solderable heat-conducting particles comprise Cu, Ni, Au, Ag, Al, Pd, or Pt metal particles, and said particles of solderable heat-conducting non-metallic materials comprise diamond, carbon nanotubes, AlN, and BN particles, and said solder comprises a lead-free solder. 
     
     
         5 . The process of  claim 1  wherein at least some of said solderable heat-conducting particles are coated with a metal comprising Sn, In, Bi, Sb, or Zn, or mixtures thereof. 
     
     
         6 . The process of  claim 1  wherein said solder-adhesion layer on said first surface comprises an outer metal layer comprising Au, Cu. Sn, Ni, In. Pb, Pt, or Pd layer, or mixtures thereof. 
     
     
         7 . The process of  claim 6  wherein said solder-adhesion layer on said first surface comprises at least one under layer metal comprising a Group IB, IIIA, IVB, VA, VIB, or VIII layer, or mixtures thereof. 
     
     
         8 . The process of  claim 7  wherein said under layer metal comprises at least one layer of a metal comprising a Cu, Al, In, Ti, Bi, V, Cr, Mo, W, Ni, Rh, Pd, or Pt layer, or mixtures thereof. 
     
     
         9 . The process of  claim 1  wherein said first surface comprises an electronic device and said second surface comprises a heat sink and said heating produces a multipath soldered interface between said electronic device and said heat sink. 
     
     
         10 . The process of  claim 1  wherein said first surface comprises a semiconductor chip and said second surface comprises a solderable heat sink and said heating produces a multipath soldered interface between said semiconductor chip and said solderable heat sink; wherein
 said solder-adhesion layer on said first surface comprising a semiconductor chip comprises an outer metal layer comprising Au, Cu, Sn, Pd, Pb, In, or Ni, or mixtures thereof;   said particles comprise;
 (a) particles comprising Cu, Ni, Au, Ag, Al, Pd, or Pt metal, or mixtures thereof and are coated with a metal comprising Sn, In, Bi, Sb, or Zn, or mixtures thereof; or 
 (b) particles comprising diamond, carbon nanotubes, AlN, or BN, or mixtures thereof coated with a solder adhesion layer; or 
 (c) mixtures comprising said (a) particles and (b) particles; 
   said resin matrix comprises polyimides, siloxanes, polyimide siloxanes, epoxies phenoxys, polystyrene allyl alcohol polymers, or bio-based resins made from lignin, cellulose, wood oils, or crop oils, or mixtures thereof.   
     
     
         11 . A process of increasing the heat conductivity of a TIM composition comprising solderable heat-conducting particles in a bondable resin matrix wherein at least some of said solderable heat-conducting particles comprise a solder surface comprising:
 placing said TIM composition between a heat emitting surface and a heat exchange surface so that said TIM composition extends between and is contiguous with said surfaces, said heat emitting surface comprising an initially non-solderable surface subsequently coated with a solder-adhesion layer;   heating said TIM composition sufficiently to;
 (a) solder at least some of said solderable heat-conducting particles to one another; 
 (b) solder at least some of said solderable heat-conducting particles to said solder adhesion layer on said heat emitting surface; 
   adhesively bonding said resin matrix to said first surface and said second surface.   
     
     
         12 . The Process of  claim 11  wherein said heat exchange surface comprises a solderable heat exchange surface and at least some of said solderable heat-conducting particles are soldered to said solderable heat exchange surface. 
     
     
         13 . The process of  claim 11  wherein said particles comprise a first group of particles comprised of solderable heat-conducting metals or nanotubes, or mixtures thereof and a second group of particles comprised of non-metallic solderable heat-conducting materials or mixtures thereof, or mixtures comprising said first group with said second group. 
     
     
         14 . The process of  claim 11  wherein said solderable heat-conducting particles comprise a first group of particles comprised of solderable heat-conducting metals or nanotubes, or mixtures thereof and a second group of particles comprised of non-metallic solderable heat-conducting materials or mixtures thereof, or mixtures comprising said first group with said second group, wherein said particles comprised of solderable heat-conducting metals comprise Cu, Ni, Au, Ag, Al, Pd, or Pt metal particles, and said particles comprised of non-metallic solderable heat conducting materials comprise diamond, carbon nanotubes, AlN, or BN particles, and said solder comprises a lead-free solder. 
     
     
         15 . The process of  claim 14  wherein at least some of said solderable heat-conducting particles are coated with at least one metal comprising Sn, Zn, In, Ni, or Sb, or mixtures thereof. 
     
     
         16 . The process of  claim 11  wherein said solder-adhesion layer on said heat emitting surface comprises an outer metal layer comprising a Au, Cu, Sn, Ni, In, Pb, Pt, or Pd layer, or mixtures thereof. 
     
     
         17 . The process of  claim 16  wherein said solder-adhesion layer on said heat emitting surface comprises at least one under layer metal comprising a Group IB, IIIA, IVB, VA, VIB, or VIII metal, or mixtures thereof. 
     
     
         18 . The process of  claim 17  wherein said under layer metal comprises at least one layer of a metal comprising Cu, Al, In, Ti, Bi, V, Cr, Mo, W, Ni, Rh, Pd, or Pt, or mixtures thereof. 
     
     
         19 . The process of  claim 11  wherein said heat emitting surface comprises an electronic device and said heat exchange surface comprises a heat sink and said heating produces a multipath soldered interface between said electronic device and said heat sink. 
     
     
         20 . The process of  claim 11  wherein said heat emitting surface comprises a semiconductor chip and said heat exchange surface comprises a solderable heat sink and said heating produces a multipath soldered interface between said semiconductor chip and said heat sink, wherein;
 said solder-adhesion layer on said semiconductor chip is comprised of an outer metal layer comprising Au, Cu, Sn, Pd, Pb, In, or Ni metal layer, or mixtures thereof;   said solderable heat-conducting particles comprise;
 (a) particles comprising Cu, Ni, Au, Ag, Al, Pd, or Pt metal, or mixtures thereof, and are coated with a metal comprising Sn, In, Bi, Sb, or Zn, or mixtures thereof; or 
 (b) particles comprising diamond, carbon nanotubes, AlN, or BN, or mixtures thereof, or 
 (c) mixtures comprising said (a) particles and (b) particles; 
   said resin matrix comprises polyimides, siloxanes, polyimide siloxanes, epoxies phenoxys, polystyrene allyl alcohol polymers, or bio-based resins made from lignin, cellulose, wood oils, or crop oils, or mixtures thereof.   
     
     
         21 . An article of manufacture comprising a TIM comprising solderable heat-conducting particles in a bondable resin matrix, at least some of said solderable heat-conducting particles having a solder surface, said TIM positioned between a heat emitting surface and a heat exchange surface so that said TIM extends between and is contiguous with said surfaces, said heat emitting surface comprising an initially non-solderable surface coated with a solder-adhesion layer, said TIM having;
 (a) at least some of said solderable heat-conducting particles soldered to one another;   (b) at least some of said solderable heat-conducting particles soldered to said heat emitting surface; and   
       said resin matrix adhesively bonded to said heat emitting surface and said heat exchange surface. 
     
     
         22 . The article of manufacture of  claim 21  wherein said heat exchange surface comprises a solderable surface and at least some of said solderable heat-conducting particles are soldered to said heat exchange surface. 
     
     
         23 . The article of manufacture of  claim 21  wherein said heat emitting surface comprises an electronic device and said heat exchange surface comprises a heat sink wherein said article of manufacture has a multipath soldered interface between said electronic device and said heat sink. 
     
     
         24 . The article of manufacture of  claim 21  wherein said heat emitting surface comprises a semiconductor chip and said heat exchange surface comprises a solderable heat sink wherein said article of manufacture has a multipath soldered interface between said semiconductor chip and said solderable heat sink, and wherein,
 said solder-adhesion layer on said semiconductor chip is comprised of an outer metal layer comprising Au, Cu, Sn, Pd, Pb, In, or Ni metal layer, or mixtures thereof;   said particles comprise;
 (a) particles comprising Cu, Ni, Au, Ag, Al, Pd, or Pt metal, or mixtures thereof, and are coated with a metal comprising Sn, In, Bi, Sb, or Zn, or mixtures thereof; or 
 (b) particles comprising diamond, carbon nanotubes, AlN, or BN, or mixtures thereof coated with a metal comprising Cu, Ni, or Pd, or mixtures thereof; or 
 (c) mixtures comprising said (a) particles and (b) particles; said resin matrix comprises polyimides, siloxanes, polyimide siloxanes, epoxies phenoxys, polystyrene allyl alcohol polymers, or bio-based resins made from lignin, cellulose, wood oils, or crop oils, or mixtures thereof. 
   
     
     
         25 . The article of manufacture of  claim 21  wherein said heat exchange surface comprises a solderable surface and at least some of said solderable heat-conducting particles are soldered to said heat exchange surface, and wherein:
 said solder-adhesion layer on said heat emitting surface is comprised of an outer metal layer comprising Au, Cu, Sn, Pd, Pb, In, or Ni metal layer, or mixtures thereof;   said particles comprise;
 (a) particles comprising Cu, Ni, Au, Ag, Al, Pd, or Pt metal, or mixtures thereof, and are coated with a metal comprising Sn, In, Bi, Sb, or Zn, or mixtures thereof; or 
 (b) particles comprising diamond, carbon nanotubes, AlN, or BN, or mixtures thereof; or 
 (c) mixtures comprising said (a) particles and (b) particles; 
   said resin matrix comprises polyimides, siloxanes, polyimide siloxanes, epoxies phenoxys, polystyrene allyl alcohol polymers, or bio-based resins made from lignin, cellulose, wood oils, or crop oils, or mixtures thereof.