edfas.org 13 ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 28 NO. 4 Fig. 2 Oscilloscope plots of the customer-returned unit (CRU) showing the failing cold temperature condition. Fig. 3 Oscilloscope plots of the customer-returned unit (CRU) showing the passing cold temperature condition. Additionally, cold testing can cause moisture to form through condensation, which may result in electrical leakage, corrosion, or false signal readings. These effects can damage the unit or mask the actual fault signatures. With this, die backside analysis using light emission microscopy (LEM) and optical beam induced resistance change (OBIRCH) was performed under controlled cold temperature conditions to minimize moisture-related interference. Die backside analysis is a failure analysis technique in semiconductor engineering where the silicon substrate from the side opposite the active circuitry is accessed to inspect for electrical defects such as opens, shorts, leakage paths, or abnormal device behavior, all while preserving the integrity of the top side metal layers. LEM AND OBIRCH OBSERVATIONS LEM analysis—which identifies electrically active regions by capturing low level infrared emissions—showed an absence of normal emissions on some circuit blocks responsible for oscillation in the internal circuitry of the transformer driver die, indicating that these blocks were unpowered. During OBIRCH analysis—a laser‑based technique that detects resistance changes caused by localized heating to pinpoint opens or high‑resistance defects—fluctuations in the power supply during temperature changes (from cold to ambient temperatures) may have affected the accuracy of the resistance measurements, leading
RkJQdWJsaXNoZXIy MTYyMzk3NQ==