ANALYSIS OF WETTING AND TENSILE STRENGTH OF SOLDER ALLOYS

摘要

The move to lead free solder alloys has created a major concern for reliability engineers who are responsible for the mechanical reliability of interconnections on electronic assemblies. Lead free solders introduce a number of different material constituents that have not had long term-term reliability testing performed at the material interface of the interconnections. Testing of electronic assemblies in their final configuration is the main reliability test method used to determine acceptability and compliance for making a change from 63/37 solder alloy to a lead free solder alloy. The question asked by reliability and process engineers is which lead free solder alloys should I use in which flux configuration and is there a difference in performance between flux types and vendor brands. To answer these questions and understand the difference in tensile strength between 63/37 and lead free solder alloys, the following test protocol was created to correlate tensile strength to wetting angle via wetting force capability (Capillary Attraction). This unusual comparison of tensile strength and wetting force capability has a defined objective to correlate wetting angle and wetting force (capillary attraction) to overall tensile strength of a solder joint by correlating common measure points from different solder alloys and their specific flux configuration. This solder joint or interconnection and its corresponding wetting force capability have a direct correlation to mechanical strength and integrity.