Method for compensating for CTE mismatch using phase change lead-free super plastic solders

摘要

Lead-free solders comprising 85-96% tin (Sn) and 4-15% Indium (In) by weight percentage (wt. %) and exemplary uses of the same are disclosed. The Sn—In solder undergoes a martensitic phase change when it is cooled from a reflow temperature to room temperature. As a result, residual stresses that would normally occur due to solder strain caused by relative movement between joined components are substantially reduced. Typically, the relative movement results from a coefficient of thermal expansion (CTE) mismatch between the joined components. The disclosed exemplary uses include flip-chip assembly and IC package to circuit board mounting, such as ball grid array packages.