Collaborative Research: Solid-Liquid Interactions during Transient Liquid Phase Bonding

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The combination of advanced thermodynamic and phase-field models, coupled with experiments will allow the understanding of solid/liquid interactions during Transient Liquid Phase (TLP) bonding. Better understanding of the solid/liquid interfacial phenomena is expected to make TLP bonding viable and will provide an environmentally-friendly alternative for electronic soldering. This research will study new approaches to control interfacial interactions to reduce joint width, shorten the bonding time, and improve the TLP joint characteristics. These include improving the compositional wetting at low temperatures through the de-stabilization of non-wettable oxide layers and maintaining a planar solid/liquid interface by applying transient diffusion barrier layers. The precipitation of Intermetallic Compounds will be addressed through processing parameters and diffusion barriers. The explored phenomena apply also to solidification, liquid phase sintering and other capillary-driven joining processes. The successful attainment of the objectives of this proposal will contribute to the development of better, environmentally-friendly electronic manufacturing techniques. Lead-containing alloys are extensively used as soldering materials for electronics. Unfortunately, poor recyclability makes electronic waste a major source for soil/water lead contamination. There is thus a strong driving force for the utilization of more environmentally-friendly alternatives. Despite considerable progress, most Pb-free solders require higher bonding temperatures, resulting in increased residual thermal stresses that reduce interconnect reliability. It is expected that understanding gained from this study will contribute to the ultimate phase-out of hazardous, lead-containing microelectronics components.