Abstract
As the electronic packaging technology moving to the CSP, wafer level packaging, fine pitch BGA (ball grid array) and high density interconnects etc., the wireability of the PCB/substrate and soldering technology are as important as reliability issues. In this work, a comparison of ellipse/round pads of area array type packages has been studied for soldering, reliability and wireability requirements. The objective of this research is to develop numerical models for predicting geometry shapes of solder joint under ellipse/round pad boundary conditions and also for analysis of the solder joint reliability characteristics. In addition, a three-dimensional solder liquid formation model is developed for predicting the geometry, the restoring force, the wireability as well as the reliability of solder joints in an area array type interconnects (e.g., ball grid array (BGA), flip chip) under ellipse and round pad configurations. In general, the reliability of the solder joints is highly depend on the thermal-mechanical behaviors of the solder, the geometry configuration of the solder ball such as standoff height/contact angle, and the geometry layout/material properties of the package. An optimized solder pad design could lead a good wireability and also could achieve a good reliability life of the solder joint. Furthermore, the solder reflow simulation in this paper is based on an energy minimization engine called Surface Evolver and the finite element software ABAQUS is used for thermal stress/strain nonlinear analysis.