Modified Semi Additive Process Yield Loss Recovery Contract Mechanics
Modified semi additive process contracts require clear yield baselines, defect attribution formulas, and flash-etch metrology to recover scrap costs cleanly.
Cross-Section Metrology
Microscopic Inspection
Destructive physical analysis methods reveal subsurface vertical interconnections and dielectric layer integrity within fabricated printed circuit boards. Through cross-section metrology, technicians mount board coupons in epoxy resin, grind the potted assembly to a target plane, and polish the exposed copper surface for optical or electron microscopic examination. IPC-TM-650 test methods govern coupon preparation protocols.
The microsection specimen exposes plated through-hole wall thickness, barrel copper integrity, and inner-layer interconnect junctions.
Structural Measurement
Precision optical measurement tools evaluate physical feature dimensions against IPC-6012 Class 3 acceptance criteria. Metallurgical microscopes equipped with calibrated reticles quantify copper plating thickness along the vertical axis of via walls, identifying thin spots or plating folds. Dimensional analysis measures etch factor, dielectric thickness, and solder mask registration accuracy relative to underlying copper traces.
Scanning electron microscopes perform high-magnification verification when micro-voids, sub-micron copper cracks, resin recessions, or interfacial separation fall below optical light resolution capabilities. Automated image analysis software calculates grain boundary structure and intermetallic compound thickness across reflowed solder joints, providing quantifiable quality records for aerospace panel acceptance.
Verification Boundary
Microsection inspection destroys the sampled test coupon, restricting evaluation to dedicated coupon strips located on panel margins. Microscopic evaluation confirms structural compliance along the polished plane but leaves unexamined features across the remaining board area unverified.