Insights into the Solder Non-wetting Failure due to Flux Inactivation and Degradation

The occurrence of solder non-wetting after the attach process is a critical failure mode as it poses concerns on the package’s electrical, mechanical and reliability robustness. Herein, we report the failure analysis done to address the non-wetting failure observed at the customer side. Systematic comparative analyses of the retained and returned samples revealed that the non-wetting is induced by the formation of an organic barrier separating the solder area from the non-wetting area, preventing the wetting and the metallurgical weld formation between the solder and the surface finish. The organic barrier is a by-product of the flux inactivation and degradation due to the incorrect reflow profile used by the customer. Moreover, imaging analysis showed foreign materials in the solder, identified as Fe
2
O
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, leading to the recommendation of improved handling and processing at the customer side.