Investigation of electrochemical migration on fine pitch BGA package

Electrochemical migration (ECM) is proved from electrochemical phenomenon involving the transport of metal ions under voltage and an electrolyte. We studied metal migration phenomenon, generation mechanism and root cause on fine pitch BGA package product. Electrical detection failures caused by excessive leakage current phenomenon after HAST stress. The leakage current result caused by electrochemical migration between two solder bumps that are with respect to surface of package substrate from ionic contamination. We considered that moisture combined with particular ion impurities causing electrochemical migration phenomenon during HAST stress. Both failure analyses and repeatability experiment results of HAST are reported.