Ground plane for plastic encapsulated integrated circuit die packages

Abstract

A plastic encapsulated integrated circuit package is disclosed which comprises a multilayer ground plane assembly bonded to a lead frame with an integrated circuit die bonded to the composite assembly. The multilayer ground plane assembly is first formed by bonding together a metal sheet, such as a copper sheet, and a thermally conductive insulating layer, such as a thermally conductive polyimide material, to which is also bonded a layer of a b-stage adhesive material. The ground plane assembly may be bonded to the lead frame by placing the b-stage adhesive layer of the ground plane assembly against the lead frame and heating the ground plane assembly and lead frame to a temperature of from about 120.degree. C. to just under 200.degree. C. for a time period not exceeding about 10 seconds to bond the b-stage adhesive layer to the lead frame without oxidizing the lead frame. An integrated circuit die is then attached to the composite assembly with an adhesive and the die attached assembly is then cured in a non-oxidizing atmosphere in an oven at approximately 150.degree. C. for about 90 minutes to cure the adhesive and the b-stage adhesive layer. The die may then be electrically connected to the lead frame. The bonded together ground plane/lead frame/die composite assembly may then be placed in a mold and encapsulated in plastic.