INVESTIGATION OF SNPBAG SOLDER FOR DIE ATTACH OF GAAS DEVICES

Solder-based die-attach processes used to affix GaAs devices to heat s preading carriers were investigated. The microstructures of the solder materials were assessed, with a focus on void formation, and the resp onse of the solder and backsurface metallization and carrier plating t o the temperature cycles of die attachment and reflow processes. Voide d regions were found in all solder joints, with a dramatic sensitivity to temperature cycles. Gold-tin alloy phases were found to dominate t he microstructure of the solder for all configurations evaluated. The total thermal budget was a critical issue in the formation and transfo rmation of various phases, as expected for low melting point alloys. N iVAu and TiPtAu backmetal systems were investigated to determine their suitability for die attachment.