Reflow Process Simulation For BGA Package By FEA

In surface mount technology, reflow profile control is important to the reflow process. However, it is usually not detected since in common practice reflow profile is measured by a thermocouple attached onto package surface. Therefore, it is worthy to see the true temperature of solder balls.In this study, a comprehensive finite element model based on BGA package is built for reflow profiles prediction Inside reflow furnace, heat transfer convection coefficient is estimated based on impinging jet airflow model. Appropriate boundary conditions such as convection coefficient, heating section temperature and time have been applied in finite element model to simulate temperature distribution within a BGA package body. Phase change of solder balls at around 183.5℃has been included.Our FEA simulation results for BGA package's reflow process show that: (1) In reflow furnace, impinging jet airflow model gives good estimation of heat transfer convection coefficient; (2) Phase change of solder balls at 183.5℃has effect on reflow profiles; (3) Excluding the responding time effect, central solderball's profile is close to the measured profile; (4) Copper traces was found to have no difference in length; (5) SB array layout has a significant effect on temperature uniformity of solder balls. Our study would be beneficial to know the whole package's temperature distribution characteristic including SB array, so it is valuable for SMT process engineers.