Method of making chip package with grease heat sink

Abstract

The present invention relates to enhanced protection of the active surface and the bond wires or ball array of a microelectronic device, and to thermal management of the microelectronic device as it is packaged with a printed circuit board (PCB) or other substrate. The enhanced protection and thermal management are accomplished with a high-temperature thermal grease that is glob topped or encapsulated over the bond wires or ball array, and the active surface of the microelectronic device. The high-temperature thermal grease exchanges heat, particularly by conduction, away from the active surface of the microelectronic device as well as away from the bond wires.

1 . A method of making an IC chip package, comprising: 
 providing a first IC chip with an active surface having extending therefrom an electrical connector in electrical communication with circuitry of the first IC chip;    providing a board-on-chip (BOC) substrate having a first side;    mounting the first IC chip to the first side of the BOC substrate;    disposing a second IC chip having an active surface over the first side of the BOC substrate;    disposing a third IC chip having an active surface over the first side of the BOC substrate and over the second IC chip;    disposing a container upon the BOC substrate and in contact with the active surface of the first IC chip; and    injecting a grease between the BOC substrate and the container in contact with the electrical connector and with the active surfaces of each of the first, second and third IC chips and enclosed within the container and the BOC substrate.    
     
     
         2 . The method of  claim 1 , further comprising: 
 operating the first, second, and third IC chips to generate heat therefrom; and    conducting the heat from the electrical connector and from the first, second, and third IC chips to the grease, to the container, and to the ambient.    
     
     
         3 . The method of  claim 1 , further comprising selecting the grease to have: 
 a thermal conductivity in a range from about 2 Watts/m·K to about 5 Watts/m·K;    a dielectric constant in a range from less than about 6 to about 9; and    a melting point in a range from about 190° C. to about 220° C.    
     
     
         4 . The method of  claim 1 , further comprising: 
 generating heat from at least one of the first, second and third IC chips by operating the at least one of the first, second and third IC chips; and    allowing the heat to propagate to the grease and to the container.    
     
     
         5 . The method of  claim 1 , further comprising: 
 securing the container to the BOC substrate with a dam structure that contacts the grease.    
     
     
         6 . The method of  claim 1 , further comprising selecting the grease to have a thermal conductivity that is less than a thermal conductivity of the container.  
     
     
         7 . The method of  claim 1 , wherein: 
 disposing the container upon the BOC substrate encloses a volume external to the first, second, and third IC chips, and wherein the injecting a grease comprises filling with the grease the external volume enclosed by the container.    
     
     
         8 . The method of  claim 1 , further comprising selecting the container to comprise a metal that has a thermal conductivity greater than the thermal conductivity of the grease.