RELIABILITY OF LEAD-FREE HIGH TEMPERATURE SURFACE MOUNT COMPONENT ATTACHES

Abstract

This work investigates the relative reliabilities of SAC305, eutectic Au-Sn, and Ag-In transient liquid phase sintered (TLPS) solder joints subjected to high temperature passive thermal cycling. These solder materials were monitored for electrical resistance, mechanical pull strength, and microstructural changes during cycling. In fabricating the test assemblies, SAC305 and eutectic Au-Sn manufacturing parameters were gathered from the paste distributors while fabrication with Ag-In TLPS required in-house development. Work with the Ag-In TLPS paste revealed that reducing the additive (In) particle size led to statistically significant improvements in the solid volume fraction of the joints. Successful attachment of ceramic quadflat packs (CQFPs) to polyimide circuit boards using Ag-In TLPS demonstrated that surface mount joints with mechanical and electrical integrity could be manufactured from the material. Au-Sn was found to be the strongest of the materials while cracking in the SAC305 and Ag-In samples during cycling resulted in weaker joints.