Structural health monitoring of solder joints in QFN package

QFN is very attractive package especially when it is used for power components. Its electrical and thermal performance turned this package to a very desirable for high speed and high power components. However the drawback of QFN package is its low reliability in applications that experience thermal cycles such as automotive and aerospace. A novel technique presented in this paper suggests a quantitative measurement tool for crack propagation in QFN solder-joints that could predict end-of-life of monitored joints. The technique that has been developed is based on serial ohmic resistance changes in solder joints as a function of crack propagation. A combination of mathematical model and measured data of solder-joints' ohmic resistance provides a structural health monitoring tool of QFN solder-joints. This could be used as a prognostic tool to remaining useful life of QFN package.