Manufacturability and Reliability Screening of Lower Melting Point Pb-Free Alloys Containing Bi

摘要

This paper is the first of two papers discussing the Celestica/Honeywell Lower Melt Alloy program. The program explores the manufacturability and reliability for Pb-freethree Bi-containing alloys in comparison with conventional SAC305 and SnPb assemblies. The first alloy included in the study is a Sn-based alloy with 3.4%Ag and 4.8%Bi which showed promising results in the National Center for Manufacturing Sciences (NCMS) and German Joint (GJP) projects. The other two alloy variations have reduced Ag content, with and without Cu. BGA and leaded components were assembled on medium complexity test vehicles using these alloys, as well as SAC305 and SnPb as base line alloys for comparison. Test vehicles were manufactured using two board materials, 170°C glass transition temperature (Tg) and 150°C Tg, with three surface finishes: ENIG, ENEPIG, and OSP. The ATC testing was done at -55°C to 125°C with 30 minute dwells and lOC/min ramps. Vibration at two G-Force test conditions with resistance monitoring was performed. In this paper, the detailed microstructure examination before testing and after 1500 cycles of-55°C to 125°C, together with failure analysis, is described. These results allow preliminary recommendations of proper combinations of the solder alloys, board materials, and surface finishes for high reliability applications.