Physical Mechanism
Localized intensification of voltage gradients occurs when conductor geometries feature sharp edges or micro-scale roughness rather than smooth curves. This localized phenomenon, known as electric field enhancement, accelerates the degradation of nearby epoxy resins and glass fibres during high-voltage operation. It occurs predominantly at the foil peaks of the inner copper layers or around the sharp borders of non-functional pads.
The resulting concentration of electrical stress initiates micro-cracking and chemical deterioration of the dielectric matrix.
Dielectric Consequence
High voltage gradients on thin laminate layers decrease the reliability of circuit boards by lowering the threshold for electric discharge. Under these conditions, electric field enhancement drives the development of conductive anodic filaments between closely spaced plated through-holes. The presence of microscopic voids or moisture at the resin-glass interface further exacerbates the deterioration process by concentrating the electrostatic lines of force.
Insulation resistance drops rapidly once these filaments bridge the gap between adjacent conductors, leading to catastrophic board failure.
Mitigation Strategy
Manufacturing standards specify minimum conductor spacing and dielectric thickness to control electrostatic gradients across the board area. Incorporating rounded traces and using smooth copper foils reduces the occurrence of electric field enhancement during high-voltage product design. Careful selection of resin systems with high tracking resistance provides an additional margin of safety against early board breakdown.
