The SRI are currently leading a collaborative research project on the reliability of lead-free solder. This work involves carrying out accelerated temperature cycling tests to measure the mean time to failure of ball grid array solder joints. Comparisons are then made with numerical predictions based on finite element analysis and complex fatigue life models of the solder joints. Work is also under way to develop a small-scale fatigue test fixture to examine the complex relationship between creep and fatigue in thermal cycling of solder joints.