Organic Substrate Trace Copper-to-copper Dendrite Growth Analysis

In one BGA package, short failure is been detected by electrical test after JEDEC Bias-HAST condition; after investigation, the BGA organic substrate solder mask to core material adhesion degraded by moisture during MSL, induced delamination, then during Bias-HAST, Cu dendrite formed and grew along delamination interface and touch another copper trace caused short finally.In this paper, the Copper trace dendrite growth condition & mechanism be introduced, also interacted design & material property of BGA organic substrate, to clarify the organic substrate material selection & design risk on Copper to copper dendrite grow to short risk.