The Optimization of Reflow Soldering Temperature Profile Based on Simulation

Generally, the thermal profile created for the reflow furnaces contains several distinct regions, namely the initial ramp, a dwell at elevated temperature, a ramp to the maximum temperature, and a cool down region. Because of the mismatch in coefficient of thermal expansion (CTE) of the components interconnected, the thermal strain and associated thermal stress are produced during reflow, which may lead to delamination in interfacial materials and nucleating of micro crack. Reducing the maximum thermal stress has a significant improvement on the reliability of solder joints. In this paper, a finite element model of a specific BGA contained electronic assembly was built and the thermal mechanic behavior of eutectic SnPb solder joint was simulated during reflow. Further, several critical reflow profile parameters, namely the peak reflow temperature, dwell time above liquids, soak time, ramp rate, conveyor speed, were optimized in order to minimize the maximum thermal stress in the whole electronic assembly. The simulation results shows that the maximum thermal stress can be reduced by the optimization of the several critical reflow profile parameters.