Microstructural Analysis of Binary Alloys

University Of New Mexico, Albuquerque NM

Investigators

Abstract

Tin-Lead (Sn-Pb) solders are widely used as soldering materials in semiconductor devices. The as-solidified structure can naturally change over time; however, the evolution can also be driven by thermal or mechanical loads. Changes in microstructure, in particular, locally coarsened regions, have been observed as precursors to the formation of cracks, and ultimately of failure. Time-dependent, microstructural changes, coupled to mechanical straining and damage evolution, must be considered for realistic mathematical models and numerical simulations. The investigator and her colleague study, through mathematical modeling and numerical simulation, the fundamentals of microstructure evolution and its influence on material failure in Sn-Pb solder joints. In the process, they develop the mathematical model and numerical capability more generally to treat the many coupled processes that influence the overall strength and integrity of a binary alloy. Microelectronic components are generally attached to printed circuit boards using solder. The solder joint can serve as the mechanical as well as the electrical connection. It has been estimated that on the order of 10,000,000,000,000 solder joints are produced each year. Damage to solder joints is a primary failure mechanism in electronic components. Even on the shelf, daily or yearly temperature cycles, physical handling, occasional bumps, chemical reactions or radiation can cause damage. Under operating conditions, thermal fluctuations or mechanical vibration can be even more severe. For expensive devices, in critical applications, improved joint integrity can have enormously beneficial consequences, both economically and in terms of reliability of components. The modeling undertaken here can play a crucial role in providing guidance for maintenance of critical components because it is practically impossible to examine microscopically individual, in-service joints for potential failure. The theoretical framework developed here will also be readily applicable to analyzing self-assembling behavior and degradation in some nano-scale materials and devices.