The depletion/wetting of the low melting point alloy in electrically conductive adhesives (ECAs)

With the driving force of “green” revolution in electronics industry, tremendous efforts have been put into looking for lead-free alternatives. Although lead-free alloys draw a lot of attention, their parasitic weaknesses, such as high processing temperature and surface tension, limit their application on thermally sensitive, flexible, nonsolderable substrates and ultra-fine pitch size flip chip interconnection. Conventional electrically conductive adhesives (ECAs) have been widely used in surface mount and die-attach technologies for electrical interconnection and heat dissipation. The low processing temperature of ECAs is one of the major advantages over lead-free solders, which brings low system stress, simple manufacturing processes, etc. In order to improve the contact resistance of ECAs, a low melting point alloy (LMA) incorporation technology has been developed by our group. In this paper, the research thrust was concentrated on the LMA depletion method, since re-melting LMA in ECAs can adversely affect the physical properties. A differential scanning calorimeter (DSC) was used for the basic examination of the depletion rate of LMAs in typical ECAs. Cross-sectional morphology, LMA distribution and intermetallic compounds were investigated by scanning electron microscopy