Developing A Pb-Free Solder Through Micro-Alloying
Authors: Srinivas Chada, Ph.D., Mark Currie, Ph.D., and Brian Toleno, Ph.D., and Hector Steen, Ph.D. and Richard Boyle Company: Henkel Electronic Materials, LLC Date Published: 10/16/2011
Abstract: Legislative regulations such as End-of-life vehicles (ELV) and Restriction of Hazardous Substances (RoHS) directive are aimed at reducing the environmental impact of automobiles at the end of their viable life and by banning the use of four regulated heavy metals (lead, mercury, cadmium and hexavalent chromium). These directives have lead to substitution efforts and ongoing adaptation to replace lead in solders systems. The commonly used and accepted replacement for lead bearing Sn-Pb solder alloys is the Sn-Ag-Cu (tin-silver-copper, also known as SAC) alloy system. SAC alloys have been suitable solder alloy materials for the production of many Electric and Electronic (E&E) devices, but for applications that dictate extremely high reliability current SAC formulations are not ideal. Specifically, devices that will be used in automotive products require lead-free materials that can tolerate higher temperatures during operation in the under-the-hood environments. Also, these materials need to provide high temperature (>125° C) thermal cycling reliability levels better than prevailing SAC materials, and offer vibration resistance equal to or better than traditional SAC alloys. Although hand-held application does not demand high temperature functionality, drop shock and vibration requirements are similar to that required in automotive industry. Drawing from micro-alloying methodologies, this investigation focuses on development and understanding of the properties for a lead-free solder alloy based on SAC, but enhanced with varying levels of dopants to improve the performance of E&E used in automotive and other high reliability devices.
Pb-free solder, micro-alloying, creep resistance, Coffin-Manson, high temperature reliability, Innolot