Influence of Copper Pad Dimension on Thermal Fatigue Life Performance of BGA Packages

As electronic packages continue to get smaller, designing reliable solder joints is becoming an increasingly important part of the design process. The shape and height of the solder joint are major factors that can be optimized to improve the reliability of flip chip (FC) and ball grid array (BGA) packages. Optimizing the dimensions of the underlying copper pad, which influences solder height and shape, can lead to a longer time to failure for packages undergoing cyclic temperature loads. In this study, the influence of the copper pad design on the thermal fatigue life performance of an off-the-shelf BGA package is investigated. Printed circuit boards (PCBs) with different pad dimensions are employed to analyze the difference in the performance in accelerated thermal cycling (ATC) tests on a BGA package. In this article, Surface Evolver is used to predict the shape of the solder joint for different combinations of copper pad diameters on the component and PCB side, and its influence on fatigue life test performance is compared. The accumulated plastic work is used to predict the thermo-fatigue life of different solder geometries.