Application of numerical analysis to the optimisation of electronic component reliability screening and assembly processes

Abstract

This study investigates the prediction of transient board-mounted electronic component heat transfer in environments representative of reliability screening and surface-mount assembly processes using computational fluid dynamics (CFD) analysis. The test cases are based on a board-mounted 160-lead Plastic Quad Flat Pack (PQFP) component, analysed in still-air and a range of forced airflows. For reliability screening, three types of transient operating conditions are considered, namely (i) component dynamic power dissipation in fixed ambient conditions, (ii) passive component operation in dynamic ambient conditions, and (iii) combined component dynamic power dissipation in varying ambient conditions. For surface-mount assembly, the test vehicle is exposed to a typical solder reflow thermal profile. Benchmark criteria are based on component junction temperature and component-printed circuit board (PCB) surface temperature, measured using thermal test dies and infrared thermography, respectively. Component/PCB numerical modelling is based on nominal geometry dimensions and material properties. Overall, component transient thermal behaviour is found to be accurately predicted, suggesting that CFD analysis could play an important role in providing critical boundary conditions to determine accelerated life testing parameters and optimise new assembly processes.