Destructive Micro-Sectioning Protocols for Detecting Hyper Corrosion Spikes in ENIG
Destructive micro-sectioning with nitric acid etching isolates ENIG hyper-corrosion spikes under SEM to reject defective PCB lots before assembly.
Polishing Artifacts
Meaning
Surface anomalies introduced during the preparation of metallographic specimens can easily be mistaken for genuine material defects under microscopic inspection. These artificial features, classified as polishing artifacts, include scratches, smeared metal, or edge rounding caused by improper grinding and polishing techniques. They are addressed in test guidelines like GB/T 13298, which emphasizes the need to distinguish preparation errors from real microstructural features.
The definition of this category is limited to defects created during specimen preparation, excluding pre-existing manufacturing flaws.
Defect Identification
Distinguishing these artificial flaws from real material failures requires analyzing their shape and orientation across the specimen. Real cracks typically follow grain boundaries or thermal stress lines, whereas preparation scratches often run parallel to each other or across several different materials. Smeared metal can hide micro-cracks, leading to a false sense of security during quality checks.
Quality Enforcement
Under administrative auditing procedures for certified testing laboratories in China, technicians must demonstrate their ability to prepare damage-free specimens before receiving official credentials. Verification agencies routinely inspect sample specimens to ensure that analytical reports are based on clear images.
Process Improvement
Eliminating these anomalies requires using cleaner polishing clothes and transitioning to finer diamond abrasives in a step-by-step sequence. Using the correct pressure and lubricant prevents the metal from flowing across the boundary lines.