Integrated circuit package

Method of mounting an integrated circuit chip having an active face having outer edges, a back face and a plurality of input/output terminals on the active face thereof with a plurality of flexibe beam leads, each of said leads having an inner and an outer lead site, with the inner lead site of each lead being bonded respectively to an input/output terminal of the integrated circuit chip, on a substrate having a top surface with a chip pad formed on the top surface and a plurality of outer lead pads associated with the chip pad comprising the steps of:

• preheating the substrate to a first temperature range at which a given thermosetting plastic becomes tacky;
• placing a preform comprised of a segment of the web coated with the thermosetting plastic which plastic is electrically insulating and thermally conductive on the chip pad to cause the preform to adhere to the pad, said preform substantially covering the chip pad;
• placing the integrated circuit chip on the preform, active face down, and applying a force to the back of the chip to initiate encapsulation of the active face, and portions of the leads proximate the input/output terminals of the chip in the thermosetting plastic of the preform;
• heating the substrate, chip and preform to a second temperature for a first predetermined period of time to partially cure the thermosetting plastic of the preform to cause the plastic to flow around the inner portions of the leads between the active face of the chip and the chip pad;
• positioning the chip while the plastic is partially cured so that the outer lead bonding site of each beam lead substantially overlies the outer lead pad to which it to be bonded;
• thermocompressively bonding the outer lead bonding sites of the leads to the outer lead pads to place the leads under compression;
• and
• heating the thermoplastic material to a third temperature for a second predetermined period of time to substantially cure the thermosetting plastic.