Destructive Coupon Microsection Preparation and Optical Feature Extraction
Precision destructive microsection preparation and calibrated optical extraction establish compliance for barrel plating, wrap copper, and internal layer interfaces.
Grain Boundary Delineation
Microstructural Contrast
A chemical processing step used to reveal the crystalline structure of copper deposits on printed circuit boards exposes the microstructural boundaries between copper grains. Executing grain boundary delineation allows quality engineers to inspect the size and orientation of copper crystals in plated through-holes.
Etching Action
Specially formulated acid solutions, such as acidified ammonium persulfate or a mixture of ammonium hydroxide and hydrogen peroxide, are applied to the polished copper cross-section for several seconds. These etchants react preferentially at the high-energy grain boundaries rather than on the flat crystal faces, which creates microscopic grooves. The grooved regions scatter light differently under a microscope, which produces clear contrast between individual grains.
This localized chemical attack must be carefully timed to avoid over-etching, which can obliterate the fine details of the metal structure.
Feature Evaluation
Evaluating the size of copper grains is necessary to assess the mechanical reliability and ductility of the plating. Electrodeposited copper with a fine, equiaxed grain structure resists thermal cracking during subsequent soldering cycles better than coarse-grained copper. In contrast, large, columnar grain structures often indicate improper bath chemistry or low additive levels during the electroplating process, which increases the risk of board failure.
Visualizing these features helps laboratories adjust bath parameters before production runs suffer from reliability issues.