edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 28 NO.4 14 to a recurring equipment error that made fault isolation challenging. To address this, various OBIRCH settings and bench setups were explored. The lowest possible voltage setting, where the failure could still be observed, was used while performing the fastest OBIRCH scan mode to capture the failure before the temperature returned to ambient levels. Fortunately, an anomalous resistance change was observed on the unit (Fig. 4). Fig. 4 Fault isolation results of the returned unit at cold temperatures. Fig. 5 Transformer driver die layout and bias circuitry schematics showing the suspected anomalous site.
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