NASA DoD Phase 2: SAC305 and Sn100C Copper Dissolution Testing
Authors: Jeff Kennedy, Dave Hillman, and Ross Wilcoxon Company: Celestica and Rockwell Collins Date Published: 5/14/2013
ICSR (Soldering and Reliability)
Abstract: Copper dissolution is a concern for products making the conversion to lead-free solder alloys. In these alloys, the more rapid reaction of tin/copper in lead-free solder alloys compared to tin-lead solder alloys, can accelerate the degradation of the plated copper connections. No copper dissolution testing was conducted during Phase 1 of the JCAA/JGPP program testing, which focused on the reliability of solder joints. The Phase 2 effort included testing to validate copper dissolution measurements reported by the commercial electronics industry. Copper dissolution is of particular concern when components are reworked, which is much more commonly used on highreliability electronics than in consumer electronics. Reworking product that has lead-free solder joints may impact the repair depot operations as the copper dissolution may remove over half of the Plated Through Hole (PTH) copper in a single rework cycle. This paper describes copper dissolution measurements of two lead-free solder alloys, for both plated through holes and surface mount pads, to better define allowable rework process windows. These results showed that due to the higher copper dissolution rates, lead-free assembles may require design changes such as PTH copper thickness to ensure that they can be reworked.