SOLDER JOINT FORMATION SIMULATION AND COMPONENT TOMBSTONING PREDICTION DURING REFLOW

The failure of electrical devices associated with solder joints has be come one of the most critical reliability issues for surface-mounted d evices. Solder joint reliability performance has been found to be high ly dependent on the solder joint configuration, which, in turn, is gov erned by bond pad size, alloy material, and leadframe structure, as we ll as solder reflow characteristics. To investigate tombstone effects causing solder joint failure during leadless component reflow process, this work has focused on (1) developing a numerical model for the sim ulations of the solder joint formation during the reflow process, and (2) determining possibility that a tombstone effect for the leadless c omponent may occur by analyzing the force and torque in the problem. U sing this methodology, the tombstone effect associated with different pad geometry configurations and solder paste amount has been analyzed through the application of the public domain software tool Surface Evo lver. Simulations show that the tombstoning is very sensitive to pad/c omponent geometry design, solder surface tension, solder paste volume, wetting area, and wetting angle. This model simulation call be used t o determine optimal solder paste volume, pad geometry configurations, and solder material for avoiding tombstone effects.