A coupon or test coupon is a printed circuit board (PCB) used to test the quality of a printed wiring board (PWB) fabrication process. Test coupons are fabricated on the same panel as the PWBs, typically at the edges. Coupons are then inspected to ensure proper layer alignment, electrical connectivity, and cross sectioned to inspect internal structures. Coupons can be designed custom for a PWB or selected from a vendor library.
Overview
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A coupon is designed to include traces and vias with the same dimensions and structures as those of the main PWB. It is standard practice to locate coupons on the edges of a panel, from which multiple PWBs are fabricated, to verify the consistency of plating, etching, and lamination across the whole panel. The use of coupons for testing is a necessary step in accurately and reliably monitoring fabrication quality and consistency.
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Further reading
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During the PCB Manufacturing process, it is important to evaluate the quality of the boards being fabricated. A good way to do this is to fabricate a few extra boards called PCB Test Coupons which can be tested to evaluate the performance of the boards. PCB Test Coupons are designed to have the same spec (trace width, copper weight, via structure, etc.) as the original PCB board and are tested to identify manufacturing defects, material defects or other related defects.
During the PCB Fabrication process multiple PCBs are fabricated on a large board called a panel. The PCB Test Coupon is usually not a part of the core PCB panel, is built in section surrounding the PCBs. They are designed to represent actual board conditions for plating, etching and lamination. It's common to fabricate one coupon at each end of a board panel to verify performance across the entire panel. Any defect identified in the PCB Test Coupon would mean that other boards on the same panel would have the same issues.
Advantages of using PCB Test Coupon: