Dielectric Limit
Maximum electrical potential represents the point at which an insulating material fails and allows current to flow through a non-conductive path. Reaching the breakdown voltage causes a sudden, permanent rupture of the molecular structure within a PCB laminate or solder mask. This value is measured in volts per unit of thickness and determines the safety margins for high-voltage circuits.
Designers must calculate this limit to prevent catastrophic arcing that destroys components and traces.
Stress Protocol
Standardized tests apply an increasing potential across the dielectric until a rapid rise in leakage current indicates failure. Determining the breakdown voltage involves submerging the sample in oil to prevent surface flashover during the procedure. Rapidly increasing the voltage provides a short-term rating, while a stepped approach identifies the endurance of the material under prolonged stress.
Humidity and temperature influence the results because moisture absorption lowers the resistance of the epoxy matrix. Most laboratories report the average of multiple points across a single panel to account for local variations in resin density or glass weave.
Safety Margin
Derating factors ensure the assembly remains functional under environmental extremes or transient surges. While the breakdown voltage specifies the absolute failure point, the working voltage is kept much lower to account for aging and chemical degradation. Exposure to corrosive gases or repeated thermal cycling creates micro-cracks that compromise the insulation over time.
Engineers select materials with higher ratings for aerospace or industrial power supplies where reliability is mandatory.
