|About this Abstract
||Materials Science & Technology 2019
||Advanced Microelectronic Packaging, Emerging Interconnection Technology, and Pb-free Solder
||A Model Study of Microstructure Evolution and Bi Diffusion in Sn-Bi Low Temperature Soldering Systems
||Yaohui Fan, John E. Blendell, Carol A. Handwerker
|On-Site Speaker (Planned)
A new low temperature interconnect technology based on Sn-Bi alloys is being considered for attaching Sn-Ag-Cu (SAC) solder BGAs to circuit boards at temperatures significantly lower than for homogeneous SAC joints. Microstructure development studies of reflow and annealing, including Bi diffusion and precipitation, are important in understanding mechanical reliability and failures paths in the resulting heterogeneous joints. Experiments in several SAC-SnBi geometries revealed that Bi concentration profiles deviate from local equilibrium expected from the phase diagram, with much higher local concentrations and lower volume fractions of liquid than expected during short-time high temperature anneals in the two-phase region. As annealing time increased and Sn grain coarsening occured, the compositions and fractions revert to the phase diagram, suggesting an “anti-Scheil” effect.
||Definite: At-meeting proceedings