A COMPLIENT SOLDER MATERIAL PROCESS CAPABLE OF CUSTOMIZING AN ELECTRICAL INTERCONNECTION'S MECHANICAL AND COMPOSITIONAL END-USE PROPERTIES

摘要

This study develops a solder technology that can be used to tailor a solder joint's desired end-use properties. The technology platform can form joints "with a regular distribution of free surfaces that are highly compliant and capable of relieving damaging stresses within thin surface mount joints. The technology can also be used to engineer a solder that is low-flow in nature to limit both slumping and bridging. The solder system is formed from the usual components, tin and lead. Small lead or tin particles are coated with a thin film of the other component, mixed with flux paste, and the temperature is raised to just above the eutectic temperature. Solid state diffusion occurs across the lead-tin interface until its composition reaches the melting point. The lead-tin interface melts eutecticly and the particles are then interconnected by a thin near eutectic liquid film. Additional metal from the solid particle dissolves into the liquid increasing its composition and thus its melting point. Diffusion into the liquid continues until it solidifies isothermally. In a powder formulation this forms an interconnecting network of solder "mini-elements" that can be fashioned into highly compliant, low-flow, or specifically customized to compositional and mechanical end-use requirements.