Standard Microsection Inspection Procedures for Class Two and Class Three Annular Rings
Class 3 microsections require zero inner layer breakout and 0.050 mm minimum ring width, whereas Class 2 permits 90-degree breakout if conductor spacing holds.
Coupon Grinding
Sample Preparation
Destructive physical analysis of printed circuit boards requires the extraction and mounting of small representative test specimens in rigid resin blocks. To expose the internal copper layers, coupon grinding uses progressively finer abrasive paper to wear away the surrounding polymer matrix. This mechanical action prepares the cross section of multi-layer structures for detailed inspection of plating thickness and via integrity.
Operators execute the process using automated rotating platens that ensure a perfectly perpendicular face is presented to the abrasive surface. Consistent pressure is maintained to prevent uneven wear or rounded edges on the metal boundaries.
Microscopic Exposure
Abrasive scratching must be minimized to avoid smearing soft copper across the dielectric boundaries. By employing coupon grinding with silicon carbide disks, technicians can control the rate of material removal to reach the exact center of drilled holes. The technique prevents the deformation of thin metal walls during sectioning, ensuring that measurement of plating thickness is true to the actual fabricated state.
Structural Evaluation
Polished cross sections reveal internal defects that are hidden from external automated optical inspection tools. Through the use of coupon grinding, laboratories verify compliance with standards for copper thickness and laminate voids. The resulting microsection remains the definitive reference for quality audit reports.