Assessing the Impact of Lead-free Solders on the Long-term Reliability of Weapon System Electronics

Lead based solders were used for decades to make conductive and structural connections in electronic assemblies. Whole manufacturing technologies were based on the melt, flow and wetting characteristics of these materials and establishing new solder platforms required substantial and pervasive changes in the industry. As industry moved away from the use of lead in electronic assemblies, the development of qualification standards for lead free solders and conductive adhesives was needed to ensure continued performance reliability.

TRI Austin developed procedures that can be used as a “standard of evaluation” for lead free solders, making it possible to compare them with each other and with lead/tin solders. Leading lead free solder alloys and conductive adhesives suitable for military applications were cataloged. Standardized models to predict thermal-mechanical failure were developed, given a formulation and a specified geometry. A standardized stress test was designed to validate the above model and enhance failure prediction.

TRI’s expertise in accelerated life testing provided the basis for evaluating lead free solders using thermal models and in the simulation of actual exposures to various “real world” environmental conditions. The technology can enhance the reliability of future missile and other weapons systems, and is applicable to National Missile Defense initiatives. It also provides the commercial electronics industry with tools to increase the reliability of consumer electronic components that use lead free solder interconnects.