Underfill material selection for flip chip technology

Abstract

Six underfill materials were examined for the selection of an appropriate underfill material for Digital Equipment Corporation's flip chip development project. Several tests were performed to determine the material properties, process properties, and the reliability of each underfill material. A material with a fast flow rate, uniform and void free flow pattern, fast curing schedule, good thermal and mechanical properties, and good reliability results is needed to satisfy the requirements for this project. Materials F and E exhibited all the above requirements and were concluded as the two best underfill materials for the flip chip process. Important material properties which contributed to the desired results of these materials include a filler particle content of about 65%, a weight loss percentage during cure of less than 1%, and a Tg of 140°C.