By Richard Coyle, Ph.D.
Free for Everyone
Innovations in Pb-free solder alloy development are being driven by evolving application requirements. One key area for Pb-free solder alloy development is the need for alloys that can resist thermal fatigue damage in increasingly aggressive product use environments, while providing acceptable performance under drop, shock and vibration loading conditions. Pb-free solder alloys based on the SnAgCu system (SAC) typically have better fatigue life than traditional eutectic SnPb solder, but their thermal fatigue reliability is limited at higher operating temperatures. In response to the need for higher temperature performance, numerous new commercial Pb-free solder alloys are being developed and introduced. These alloys are based on the SAC system, but have significant solute additions to promote solid solution, dispersion, or additional precipitate strengthening at higher operating temperatures. This presentation addresses requirements, alloy evolution, and alloy metallurgy, along with the initial results from a major industrial consortia project that is evaluating thermal fatigue reliability of multiple high reliability solder alloys.