Study on the interdependence of soldering profile, ageing conditions and intermetallic layer thickness in large area solder joints and its influence on reliability

摘要

This study was aimed at quantifying critically relevant topics about the influence of intermetallic compounds (IMC) within power electronics reliability such as the influence of soldering profile on the growth rate of IMC in large area solder joints, estimation of IMC thickness during non-isothermal ageing and the impact of IMC thickness on reliability. To this end, test samples were soldered using four different soldering profiles by varying hold time at peak temperature and cooling rate. Isothermal ageing was performed at 125°C, 150°C and 175°C. IMC thickness measurements were taken at ageing durations of 200h, 500h and 1000h respectively. Using linear regression on experimental data and the finite differences method, a differential equation was derived and applied to predict IMC thickness for any arbitrary thermal ageing profile, for example, active or passive temperature cycling. Additionally, finite element method (FEM) simulations were carried out to evaluate the influence of IMC thickness under three potential failure modes. These failure modes result from either substrate war page or in-plane shear deformation. The study has been able to show the effects of soldering profiles on the IMC growth rate and also the influence of IMC thickness on stress state near crack locations using FEM simulations.