Investigation of SnPbAg solder for die attach of GaAs devices

Solder-based die-attach processes used to affix GaAs devices to heat spreading carriers were investigated. The microstructures of the solder materials were assessed, with a focus on void formation, and the response of the solder and backsurface metallization and carrier plating to the temperature cycles of die attachment and reflow processes. Voided regions were found in all solder joints, with a dramatic sensitivity to temperature cycles. Gold-tin alloy phases were found to dominate the microstructure of the solder for all configurations evaluated. The total thermal budget was a critical issue in the formation and transformation of various phases, as expected for low melting point alloys. NiVAu and TiPtAu backmetal systems were investigated to determine their suitability for die attachment. [PUBLICATION ABSTRACT]