Board Assembly Tech Topic Series: Mechanical Shock Drop Reliability of BiSn LTS

Raiyo Aspandiar and Jagadeesh Radhakrishnan (Intel)
September 21 & October 12, 2021

This webinar shared details from the iNEMI BiSn-Based Low-Temperature Soldering Process and Reliability project team’s report on their assessment of mechanical shock reliability of BiSn in BGA solder joints.

The team evaluated the effectiveness of several new solder alloy formulations in three separate mechanical shock tests, each using a different BGA package, PCB test vehicle, and shock drop test condition to assess mechanical shock reliability of BiSn in BGA solder joints. The webinar detailed parameters and findings from each of the experiments and concluded the following.

• Ductile BiSn solder pastes have similar performance to baseline
BiSn solder pastes, and the performance of both are significantly
lower than baseline SAC for SMD (solder mask defined) pad
designs

• Low-temperature solder (LTS) joints show better reliability on MD
(metal defined) pad than SMD pad design

• Failures on MD lands are due to pad cratering instead of solder joint
crack

• Resin reinforcement enables significant improvements in ductile LTS
alloys and has the potential for performance equivalent to baseline
SAC

• Comparing pad surface finishes, OSP surface finish is significantly
better than ENIG surface finish