Formation of a self-interconnected joint using a low-melting-point alloy adhesive

The self-interconnection process is one of the promising methodologies for joining novel materials and assembling micro-electronic devices. Basic experiments fabricating micro joints using conductive adhesives with low melting point solders, such as Sn-In eutectic alloy, were demonstrated as an alternative method to conventional soldering or using the usual adhesive joining used in electronic assembly. The joint morphology. the formation of electrical conduction interconnections, and the self-interconnection characteristics were examined by optical and X-ray transmission microscopy. The behaviors of melting fillers such as aggregation, coalescence, and wetting were found to occur during joint formation. Especially on the copper line patterns of a glass-epoxy substrate, selective adhesional wetting of the melting alloy, enhanced by the oxygen-reduction capability of resin and capillary phenomena, was the main driving forces of the self-interconnection of joints. The alignment, joint height, and volume fraction of the filler need to be set correctly for a successful adhesion to be achieved.