The study of self-alignment capability of electrically conductive adhesives (ECAs) using low melting point alloy for flip-chip application

A feasibility study of the self-alignment capability of electrically conductive adhesives (ECAs) for a flip-chip interconnection application was carried out. The effect of the low melting alloy (LMA) filler on the self-alignment capability of ECAs was investigated. The surface energy of the epoxy resin was studied in terms of the various additives and their loading level using a goniometer with a built-in environmental chamber. The curing profile of the epoxy resin and the melting point of the LMA filler were measured using a differential scanning calorimeter (DSC). The ECAs filled with the LMA over 85 wt% showed self-alignment during the heating process. However, when silver flakes were added to the ECA formulation, self-alignment did not take place. We concluded that the LMA filler depleted into the silver flakes can adversely affect the self-alignment of ECAs. The key parameters required for ECA self-alignment capability are presented. This paper discusses the feasibility of the application of ECA with self-alignment capability for flip-chip interconnection. Initial results from these series studies indicate that incorporation of the LMA into ECAs is an efficient way to make ECAs with self-alignment capability.