Low Temperature Soldering: Reflow Optimization for Enhanced Mechanical Reliability
Authors: Morgana Ribas, Ph.D., Bhaskar Vangapandu, Raghu Raj Rangaraju, Suresh Telu, Ph.D., Laxminarayana Pai, Ramesh Kumar, Vikas Patil, H. V. Ramakrishna, Ph.D., Traian Cucu, Ph.D., Siuli Sarkar, Ph.D. Company: Alpha Assembly Solutions, a MacDermid Performance Solutions Business Date Published: 10/14/2018
Abstract: There is a growing interest surrounding use of Sn-Bi solder alloys for lowering reflow soldering temperature. Among the many benefits enabled by that are: Reduced dynamic warpage, more complex assemblies, reduced energy costs and increased production yields. Recently, low temperature solder alloys with micro-additives have been introduced as an alternative for replacing Sn-Ag-Cu solders while maintaining its mechanical (drop) shock performance. In this work, we further discuss solderability and mechanical reliability of a novel low temperature proprietary alloy (generically called as X46). Its drop shock performance evaluation is extended to include the effect of various reflow profiles, including the effect of time above liquidus (TAL) and peak reflow temperatures. Analysis of soldering performance, including voids measurements, and failure analysis are also included in the discussion. Based on these results, the following reflow conditions are recommended: (i) For BGA, peak temperature of 190-200oC (?3oC) and TAL between 30 and 90s, (ii) For the LGA, 180-200oC (?3oC) peak temperature and TAL between 30 and 90s.
Lead-free, low temperature soldering, Sn-Bi alloys, drop shock, voids, reflow optimization.