QFN Solder Joints Research Articles

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.

Solder joint formation simulation and reliability study of quad flat no lead package

Abstract Based on the minimal energy principle, the shape prediction models of the 0·5 mm pitch, 16 pin quad flat no lead (QFN) package solder joints were developed. The influence of the process parameters including the pad length, the pad width and the stand-off on the solder joint shape of QFN was studied. Utilising the surface coordinate exported from the QFN solder joint shape prediction models, finite element analysis (FEA) models were set up and then the non-linear FEA of the QFN solder joints under thermal cycles was performed by ANSYS. The stress–strain distribution within the solder joints and the maximum strain range of the solder joint were determined. The thermal fatigue life of the QFN solder joint was calculated based on the maximum strain range and the Coffin–Manson equation. The results show that the process parameters influence the QFN solder joint shape distinctly, and the QFN solder joint with different pad lengths, pad widths and stand-offs has various stress–strain distributions and f...