A Study of the Effects of Infra‐red Reflow Profile on Solder Joint Strength and Structure

Abstract

The effects of varying reflow profiles on the tensile pull strength and structure of solder joints of components with tin plated and nickel‐palladium plated leads were studied. It was found that, in the case of tin plated leads, the structure and the tensile pull strength of the resultant solder joints were not significantly affected by varying the reflow conditions from Profile 1 (peak temperature range: 174°C to 195°C, reflow time 24 seconds) and Profile 2 (peak temperature range: 198°C to 218°C, reflow time 30 seconds). On the other hand, the mean pull strength of solder joints of nickel‐palladium plated lead was found to be significantly higher for joints reflowed with profile 2 than that of joints reflowed with Profile 1. Also, for both reflow profiles, the pull strengths of joints of nickel‐palladium plated leads were significantly higher than those of tin plated leads. This higher average pull strength may be due to the dissolution of palladium in the solder and/or the increased density of intermetallic precipitates in the solder fillet, and the increased intermetallic layer thickness at the lead/solder interface.