Impact of Board Pad Finish of the SnPb and Lead-free Solder Interconnect Reliability for Leadless Chip Resistors Under Random Vibration Loading

Abstract

The results from a step-stress random vibration tests are used to assess the interconnect reliability of various solder, component terminal and printed wiring board pad finishes. The durability assessment of leadless chip resistors attached with tin-lead and tin-silver-copper is examined. Component terminal finish, tin and tin-lead, in tin-lead soldered assemblies are examined. The board pad finishes used in the assemblies tested included immersion tin, immersion silver, electroless or electrolytic nickel immersed in gold, and organic solderability preservative, while tin-lead hot air solder leveling pad finish assembled with tin-lead solder served as a baseline. Destructive failure analysis is used to assess failure locations. Although the results obtained from the test indicate that under the vibration regimen studied no significant difference was found between the durability of tin-lead and tin-silver-copper assemblies, the lead-free components did outperform the tin-lead assemblies. Pad finish is found to have a greater influence on tin-lead as compared to tin-silver-copper soldered assemblies. Immersion silver and electroless or electrolytic nickel immersed in gold showed the best durability results.