MIXED ASSEMBLY PROCESS DEVELOPMENT & RELIABILITY QUALIFICATION
Authors: L. Pymento, W.T. Davis, and T. Godown Company: IBM Corporation Date Published: 1/17/2006
Pan Pacific Symposium
Abstract: The transition from Sn-Pb to Pb-free assembly as directed by the EU implies that all components are available in a Pb-free finish and can withstand the higher temperature profiles required to reflow Pb-free solder. However, during this transition, it is possible that certain designs will be required to accommodate components that are RoHS (Restriction of Hazardous Substances) compliant with a limitation on peak temperature, or a ball grid array (BGA) package may only be available in a SAC finish forcing a solution using leaded paste and an optimized reflow profile that allows for dissolution of the SAC (SnAgCu) ball composition, and at the same time does not violate the peak temperature specifications. This approach is referred to as a Mixed Assembly solution and is the focus of this study. Mixed Assembly requires significant process development and reliability studies to prove it as a viable option on a given product. Though these studies demonstrated that Mixed Assembly with an optimized reflow profile is a viable solution for a specific planar, one cannot conclude that this specific solution can be generically applied to all Mixed Assembly applications.