Solder Joint Formation Simulation and Reliability Study of Quad Flat No-lead Package

摘要

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 were studied. Utilizing the surface coordinate exported from the QFN solder joint shape prediction models, the finite element analysis models were set up and then the nonlinear finite element analysis of the QFN solder joints under thermal cycles was performed by using 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 Coffin-Manson equation. The results show that the process parameters influence the QFN solder joint shape distinctly, the QFN solder joint with the different pad length, pad width and stand-off has the different stress/strain distribution and fatigue life, the QFN solder joint with the pad length of 0.7mm, the pad width of 0.28mm and the stand-off of 0.125 has the fatigue life of 252 cycles under thermal cycles.