Adhesion/reliability/reworkability study on underfill material from free radical polymerization system and its hybrid composite with epoxy resin

The application-of the underfill materials has been to enhance the solder joint fatigue life in the flip chip assembly, typically by up to an order of magnitude, as compared to the non-underfilled devices. Most of the current underfills, however, are mainly thermosetting epoxy resin curing system based materials, which would be transformed into infusible three dimensional network structure, and thus would exhibit appreciable adhesion and reliability capability but would be lacking desired reworkability after curing. From the standpoint of polymeric material chemistry, other thermoplastic or thermosetting polymer materials could be of great economic/cost interest as underfill for some microelectronic packaging applications. In this paper, the experimental focus was devoted to the study of adhesion, reliability and reworkability for the free radical polymerization (FRP) system as well as its hybrid composites or blends with phenoxy resin or epoxy resin (EPR), which could be potential underfill material candidates. The study covered formulation screening based on adhesion measurement, and assessment on reliability and reworkability performance for selected compositions developed so far