Influence of Reflow Profile on Thermal Fatigue Behaviors of Solder Ball Joints

Abstract

In electronic package design, solder joints are critical in providing electrical connections and mechanical support. The mechanical reliability of interconnection is dependent on the microstructure evolution that occurs within the solder due to the temperature changes primarily from transportation, storage, and device usage. In this study, two solder alloys, eutectic 63Sn37Pb and lead-free 95.5Sn4.0Ag0.5Cu, were tested for their thermal fatigue reliability and were observed for changes in microstructure. The different microstructures of each sample were created by controlling the cooling rate, fast or slow, during reflow. To characterize reliability, the samples endured thermal cycling − 40-125 °C until electrical failure. Finite element analysis was used to predict the primary deformation mechanism. The microstructure was inspected by cross-sectioning the solder samples using scanning electron microscopy with energy-dispersive x-ray spectroscopy. It was found that by controlling the microstructure development through the reflow rate, the solder joint’s thermal fatigue life can be extended, and concurrently, the reliability of the electronic package can be enhanced.