edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 28 NO. 2 36 PHASE 1: ELECTRICAL SIGNATURE AND FAILURE VALIDATION The fault isolation flow began with fail signature validation to confirm the failure and establish an electrical baseline. The primary tool for this is the current-voltage (IV) curve. By plotting the relationship between applied voltage and current, engineers can distinguish between high-resistance paths, ohmic shorts, and nonlinear diode behaviors. For the failing H310 unit, DC parametric characterization was performed using a curve trace board, sweeping voltage from –100 to 100 mV (Fig. 5). Comparing the failing unit to a known-good reference revealed a definitive signature: • Data Line D– exhibited a 30 Ω resistive short. • Data Line D+ exhibited a significantly more severe 3 Ω resistive short. This parametric validation confirmed that the functional failure was tied to a permanent physical change in the electrical path, rather than a transient “soft failure” or system lock-up. FROM SYSTEM ZAP TO SILICON IMPROVEMENT (continued from page 34) Fig. 5 IV curve of failed unit vs. known good unit.[2] Data Line D- shown in red and Data Line D+ shown in yellow. Fig. 6 CSAM analysis of the failed unit.[2]
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