Adhesion Failure
A physical defect in printed circuit boards involves the separation of the conductive copper foil from the underlying resin-impregnated glass-fiber substrate. The occurrence of trace delamination destroys the mechanical bond between the copper and the board, leaving the trace vulnerable to physical damage and heat. It is a critical failure that compromises both the electrical and mechanical integrity of the circuit.
Moisture Influence
Adhesion loss typically begins at the interface where the copper trace meets the epoxy-glass laminate during thermal cycles or assembly soldering. This separation is driven by the mismatch in thermal expansion between the copper foil and the organic resin. During soldering processes like reflow or wave soldering, temperatures exceeding two hundred degrees Celsius can weaken the adhesive bond of the resin.
If the bond strength falls below the internal stress of the board, the copper trace lifts away from the surface. In multi-layer boards, this separation can also occur on internal layers, creating air gaps that alter the impedance of high-frequency traces.
Quality Inspection
Laminate selection and surface treatment of the copper foil are the primary controls used to prevent this defect. Copper surfaces are chemically roughened to create a mechanical interlock with the resin during the lamination process. Automated optical inspection or cross-sectional analysis is used to identify lifted traces during manufacturing quality audits.
