Cu/Ag Leadframe-Finish Migration Phenomena in Stress-Induced Green Phosphorus Mold Epoxy: An Electrochemical and Material

The existence of P particle in mold compound poses new failure mechanism of product leakage and/or short under specific operating conditions. This study developed an 80ETQFP package-level understanding of the stress-induced Cu/Ag leadframe-finish migration phenomena when inorganic P particulates are present and compares the results to a hydrophobic nitrogen-based flame retardant mold. Grounded on the electrochemical and extensive failure analyses using active 90nm Cu/Low-k Si device, it is found that Cu/Ag lead-finish migration is induced by the stressed formation of phosphoric acids during specific biased and temperature/moisture stressing. Its dendritic extension reflects a non-coplanar pattern and a cathodic-anodic electrochemical cell characteristic through the epoxy matrix. A hydrophobic nitrogen-based flame retardant mold does not have such a failure mechanism though the results indicate die pad delaminations. A migration model was proposed to prevent failure recurrences in future materials introduced to the industry