Long Term Missile Aging Reliability Prediction for Lead-Free Solder Interconnects

Because lead is a toxic metal, uses of it that affect the environment are a health risk. Less widely known than paint, gasoline, and batteries is the significant concern associated with ground water leaching of lead-based solder from electronics disposed of in landfills. Although many states have legislation regarding becoming lead-free, the US aerospace industry is, to some extent, being swept along with the international lead-free movement. The AMRDEC is faced with the problem of reliability-over-time, because its missiles are stored for years. Its Stockpile Reliability Programs (SRP) have maintained the necessary levels of reliability at an affordable cost. Now, with the transition to lead-free connections, a whole new set of challenges arises because their reliability is unknown. AMRDEC, as part of the TCG for "Predictive Materials Aging and Reliability," is developing tools to help in the SRP process. Sandia is using finite element analysis to simulate the effects of input variables of the solder characteristics and the environmental stresses over time to identify damage to the lead-free solder joints. This Phase I effort will take the Sandia results and expand them into a reliability prediction tool that can be used in trading-off parameters in making SRP decisions for missiles.