This invention is a simple and effective process of producing a plastic pin grid array package having an encapsulated device and a heat sink forming a unitary component of a main planar body of the package. The process includes fabrication of a laminated planar main body having outer plastic sheets provided with metallizations, a metal sheet of high thermal conductivity, and plastic sheets positioned intermediate the outer plastic sheets and the metal sheet, the metal sheet having clearance holes filled with plugs of the material of the intermediate plastic sheets, a plurality of plated-through holes (PTHs) formed in the main body and terminal pins secured in the PTHs. Some of the PTHs contacting the metal sheet and some passing through the plugs in the clearance holes out of contact with the metal sheet. The device, such as an integrated circuit chip, mounted in a recessed cavity in the main body, is in contact with the metal heat-sink. In this manner heat is conducted away from the device by the heat sink and dissipated through the back of the package and those of the terminal pins which are in PTHs contacting the heat sink.