Heat spreading layer with high thermal conductivity

Abstract

Embodiments of the invention comprise a homogeneous heat spreading cap element in chip packages to facilitate better heat spreading and dissipation. The heat spreading cap comprises a single high-K graphite layer supported by a copper frame for increased stability and reduced thermal warpage during handling and operation while minimizing thermal penalty by reducing the amount of material having a relatively low heat conductivity that is needed in conventional heat spreading caps.

We claim: 
     
         1 . A cooling system for a semiconductor package comprising:
 a heat spreading layer partially encased in a supporting frame, the heat spreading layer including a perimeter, the supporting frame being configured to encase the perimeter and an adjacent portion of the heat spreading layer, defining centrally exposed top and bottom portions of the heat spreading layer; and   a heat generating element thermally connected to the centrally exposed bottom portion of the heat spreading layer.   
     
     
         2 . The system of  claim 1 , wherein the semiconductor package is a flip chip ball grid array package, a flip chip land grid array package, or a flip chip pin grid array package. 
     
     
         3 . The system of  claim 1 , wherein the semiconductor package is a wire bonding assembly package. 
     
     
         4 . The system of  claim 3 , wherein the centrally exposed bottom portion of the heat spreading layer further comprises a centrally protruding portion connected to a central portion of a top surface of the heat generating element. 
     
     
         5 . The system of  claim 1 , wherein the heat spreading layer is made from graphite. 
     
     
         6 . The system of  claim 5  wherein the heat spreading layer is positioned to have high thermal conductivity in a first direction being substantially perpendicular relative to the substrate, and relatively high thermal conductivity in at least a second direction substantially parallel relative to the substrate. 
     
     
         7 . The system of  claim 1 , wherein the heat spreading layer is made from pyrolytic graphite. 
     
     
         8 . The system of  claim 1 , wherein the heat spreading layer is attached to the supporting frame using an adhesive material. 
     
     
         9 . The system of  claim 1 , wherein the supporting frame is a single piece having a cavity for encasing the heat spreading layer. 
     
     
         10 . The system of  claim 1 , wherein the supporting frame comprises at least a first piece and a second piece. 
     
     
         11 . The system of  claim 10 , wherein the first piece and the second piece of the supporting frame are joined mechanically, by an adhesive material, and/or by a thermally conductive adhesive material. 
     
     
         12 . The system of  claim 1 , wherein the supporting frame is made from a polymer. 
     
     
         13 . The system of  claim 1 , wherein the supporting frame is made from a metal. 
     
     
         14 . The system of  claim 13 , wherein the supporting frame is made from copper. 
     
     
         15 . The system of  claim 1 , wherein a top surface of the supporting frame is flush relative to a top surface of the heat spreading layer. 
     
     
         16 . The system of  claim 1 , wherein at least a portion of a top surface of the supporting frame is raised relative to a top surface of the heat spreading layer. 
     
     
         17 . The system of  claim 1 , wherein an inner perimeter of a top portion of the supporting frame surrounds the centrally exposed top portion of the heat spreading layer, and the inner perimeter is beveled. 
     
     
         18 . The system of  claim 1 , wherein a portion of the top surface of the supporting frame extends over a portion of the top surface of the heat spreading layer. 
     
     
         19 . The system of  claim 1 , further comprising a heat dissipating element thermally connected to a top surface of the heat spreading layer, the heat dissipating element having a centrally protruding portion on a bottom surface thereof, wherein the centrally protruding portion is beveled. 
     
     
         20 . The system of  claim 1 , wherein a top surface and/or a bottom surface of the heat spreading layer is chamfered. 
     
     
         21 . The system of  claim 1 , wherein a top surface and/or a bottom surface of the heat spreading layer has rabbet edges. 
     
     
         22 . A semiconductor package, comprising:
 a substrate;   a chip electrically connected to the substrate;   a thermal module having a heat spreading layer partially encased in a supporting frame, the heat spreading layer including a perimeter, the supporting frame being configured to encase the perimeter and an adjacent portion of the heat spreading layer, defining centrally exposed top and bottom portions of the heat spreading layer, wherein the chip is thermally connected to the centrally exposed bottom portion of the heat spreading layer; and   a circuit board electrically connected to the substrate and the chip.   
     
     
         23 . The semiconductor package of  claim 22 , further comprising:
 a plurality of the chips electrically connected to the substrate; and   a plurality of the thermal modules corresponding to each of the chips, wherein each chip is thermally connected to the centrally exposed bottom portion of each of a plurality of the heat spreading layers, respectively, of each of the thermal modules.   
     
     
         24 . A method for cooling a heat generating element in a semiconductor package, comprising:
 partially encasing a heat spreading layer in a supporting frame, the heat spreading layer including a perimeter, the supporting frame being configured to encase the perimeter and an adjacent portion of the heat spreading layer, defining centrally exposed top and bottom portions of the heat spreading layer; and   thermally connecting a heat generating element to the centrally exposed bottom surface of the heat spreading layer.   
     
     
         25 . The method of  claim 23 , wherein the semiconductor package operates under a hygrothermal condition with a temperature between approximately −40° C. and 125° C. and relative humidity of up to 85%.