Test Sample
Sacrificial circuit patterns fabricated on the waste border of a production panel represent the electrical and physical properties of the active printed circuit boards on the same sheet. Using perimeter coupons allows manufacturers to conduct destructive testing and quality verification without damaging the actual customer boards. These patterns are designed to undergo the exact same etching, plating, and lamination cycles as the functional circuits.
By placing them on the outer margins, they experience the most extreme process conditions found across the panel surface.
Impedance Verification
High-frequency transmission lines fabricated on these test blocks are measured with time-domain reflectometers to verify that trace impedance sits within limits. If the test line on the coupon fails the impedance requirement, it indicates that the etching or dielectric thickness on that panel region is out of specification. This test provides a reliable, non-destructive way to verify the signal integrity performance of the entire panel.
Because the coupons share the same layer stackup, their measured impedance corresponds to the active boards.
Mechanical Sectioning
Quality control technicians cut the coupons from the panel border and mount them in plastic resin for microscopic analysis. This cross-sectioning process reveals internal plating thicknesses, copper wrap quality, and via registration. These measurements provide the hard data required to issue a certificate of compliance to the buyer.
