Abstract: A process for forming an insulation underfill for soldering semiconductor die solder balls by a solder paste on conductive traces on a support surface. The process comprises the screen printing or deposition from a syringe of thermoplastic or thermosetting epoxy columns between the solder balls, to a height equal to the standoff height of the die from the support surface. The assembly is first heated to a temperature at which the plastic becomes semifluid and before the area over which it will spread becomes contaminated with flux residue; and is next heated to the solder paste reflow temperature.

Abstract: A chip scale package has a semiconductor MOSFET die which has a top electrode surface covered with a layer of a photosensitive liquid epoxy which is photolithographically patterned to expose portions of the electrode surface and to act as a passivation layer and as a solder mask. A solderable contact layer is then formed over the passivation layer. The individual die are mounted drain side down in a metal clip or can with the drain electrode disposed coplanar with a flange extending from the can bottom.