Cooling Rates in Lead-free and Tin/lead Reflow

摘要

The impact of a fully controlled and robust reflow process on solder-joint quality has been the topic of many studies, and is well understood for processes using eutectic tin/lead as the interconnect alloy. However, many questions remain unanswered regarding lead-free alloys. Current forced convection reflow ovens are designed to control the heating process with great stability and uniformity. The impact of controlled cooling on joint quality and yield typically is not evaluated. Traditionally, cooling of electronic assembly emphasized the board's exit temperature and board handling post-reflow. Studies have shown that cooling rates influence the formation of joint mi-crostructure and consequently, joint quality.