Quality Specimen
Standardized test patterns etched onto the periphery of a production panel allow manufacturers to evaluate the integrity of plated through holes and vias without destroying functional circuits. The coupon d specifically focuses on the thermal stress resistance and electrical continuity of the vertical interconnects.
Structural Evaluation
Multiple layers of copper and dielectric are connected by the drill holes represented in this representative block. Subjecting the coupon d to repeated temperature swings simulates the harsh environments of reflow soldering and operational heat. Resistance is measured before and after the thermal cycles to detect any hairline fractures or barrel cracking that would indicate a failure in the plating process.
Micro-sectioning of this specimen reveals the internal grain structure of the copper.
Batch Approval
Acceptance of a whole production lot often hinges on the performance of these sacrificial strips. Because the coupon d undergoes the exact same plating and etching steps as the main boards, it acts as a reliable proxy for the quality of the entire batch. Failure in this specific pattern results in the rejection of the panel to prevent unreliable hardware from reaching the end user.
Documentation of these results forms a part of the permanent quality record for aerospace or medical electronics.
