Mechanical Adhesion
A standardized mechanical test measures the force required to separate a conductive metal foil from its dielectric substrate under specified conditions. Conducting peel strength testing ensures that the laminate can withstand the thermal and mechanical stresses of circuit board fabrication and assembly. This test pulls a copper trace of a specific width from the board surface.
Measurement Protocol
A test specimen is prepared by etching a straight copper trace of standardized width, usually one millimeter, onto the test laminate. During peel strength testing, the trace is clamped to a tensile testing machine that pulls the copper strip away from the dielectric substrate at a constant speed of fifty millimeters per minute. The force required to peel the trace is continuously recorded and divided by the trace width to express the result in Newtons per millimeter.
This quantitative data allows manufacturers to verify that the copper-dielectric bond meets the minimum peel requirements of IPC standards.
Failure Mechanism
Lower than expected values can indicate either inadequate oxide treatment on the copper foil or incomplete curing of the resin system. Thermal stress during soldering can degrade the adhesive bond, so boards are often tested both before and after thermal shock exposure. When the copper pulls away too easily, it poses a risk of trace lifting during component rework or field operation.
High-temperature laminates are formulated to maintain high strength even when subjected to temperatures of two hundred and eighty degrees Celsius.
