Case 670 ยท Public preview
A Plausible Contributing Defect May Not Predict Which Devices Fail
Three stressed diodes became shorted or severely degraded, while comparison devices retained normal forward voltage and high resistance.
Electrical testingMicrofocus X-rayChemical decapsulationSEMEDSControl comparison
What the evidence preview establishes
The failures were caused by overheating through localized hot-spot formation or generalized junction diffusion. Die-attach voids could impede cooling or concentrate current, but voiding did not correlate strongly with failure because a functional comparison device contained extensive porosity.
Why this case matters
Do not equate a plausible defect with a discriminator. Compare failed and passing hardware, then correlate void location and area with thermal resistance, current density, and the actual damage site.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.