Case 134 ยท Public preview
Improved Solder-Mask Coverage Cannot Compensate for Drill Misregistration
A module built with an improved two-layer solder-mask structure failed high-potential testing despite excellent mask coverage over its vias.
Optical microscopyElectrical fault localizationAssembly dissectionMetallographic microsectioningBackscattered-electron SEM
What the evidence preview establishes
Drill misregistration and severe hole breakout reduced conductor clearance to approximately 7.7 mils at the electrical-breakdown site. The improved mask structure covered the vias well and reduced the reported failure rate, but it could not compensate for the localized loss of PWB spacing.
Why this case matters
Solder-mask improvement and drill registration control solve different parts of the insulation problem. Verify both via coverage and minimum finished conductor spacing, because a robust coating cannot restore clearance already lost through hole breakout.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.