Cross Sectional Analysis
Plated through holes in printed circuit boards require physical dissection to expose internal copper barrels and dielectric interfaces for microscopic verification. Destructive microsectioning transforms a mounted coupon into a polished plane by grinding through the center axis of a barrel using progressively finer abrasives. Technicians mount the sample in thermosetting resin to edge support fragile copper features during mechanical removal of surrounding material.
Final colloidal silica suspensions polish the exposed metallic surface until grain structures and plating anomalies become visible under metallurgical illumination.
Interconnect Verification
Barrel cracking, resin recession, and plating voids demand cross sectional examination because optical inspection misses buried defects inside multilayer boards. Standards mandate specific minimum copper thicknesses on barrel walls to prevent open circuits during thermal expansion cycles. Excessive drilling roughness leaves voids in electroless copper deposits, which standard electrical continuity tests fail to catch until thermal stress induces field failures.
Chemical etching highlights grain boundaries within the copper deposit to reveal structural defects from contaminated plating baths.
Coupon Destruction
Production panels carry sacrificial test strips alongside operational circuits specifically designed for sacrifice during quality audits. Cutting these coupons from the panel destroys the test vehicle permanently, rendering the sampled board unusable for further electrical testing. Destructive microsectioning provides the definitive physical evidence required to accept or reject a high reliability manufacturing lot based on internal workmanship compliance.
