Transient Leakage Current as a Non-destructive Probe of Wire-bond Electrochemical Failures

The electrochemical failures observed in the accelerated stress test (e.g., HAST/ THB) are correlated to the sequential processes of spatial and transient ionic distribution in the Epoxy Molding compound (EMC)/underfill materials, redox reaction, and the formation of Intermetallic Compounds (IMCs). Unfortunately, HAST tests require fully assembled IC, and can only occur relatively late in the process development. Here, we provide a new prediction approach to quantify bondpad/EMC interfacial charge dynamics using thermally stimulated charging current (TSCC). TSCC also probes EMC ionic transport mechanisms. We assess the universal (dispersive) nature of ionic transport in the EMC using measured and simulated TSCC for industry-grade EMC samples with high halide concentrations (13200 ppm). Finally, our proposed ion-assisted corrosion failure model, along with the predicted TSCC, elucidates the impact of halide concentration on bond wire electrochemical failures and may be used as a non-destructive method for predicting electrochemical failures of ICs. Most importantly, our approach may serve as an early indicator of the corrosion challenges long before the packaged IC has actually been fabricated.