Bare Board Insulation Resistance Testing Thresholds
Bare board insulation resistance testing requires minimum 100MΩ thresholds at 100V DC under IPC-9252B Class 3 to prevent electrochemical migration escapes.
High-Voltage Screening
Insulation Stressing
Electrical testing protocols for multilayer printed circuit boards employ elevated potentials to verify dielectric integrity and conductor spacing. This process, referred to as high-voltage screening, applies a voltage significantly above the normal operating limit of the assembly to force breakdown in weak areas. The test uncovers resin voids and conductive contaminants within the fiberglass layers before the boards are populated with expensive active components.
It acts as a necessary gatekeeper for high-reliability boards used in power distribution and electric vehicles.
Defect Precipitation
Applying high electrical stresses triggers localized arcing or leakage currents at points of mechanical weakness or contamination. During high-voltage screening, micro-cracks in the epoxy or trace burrs left by etching are subjected to intense electric fields that lead to dielectric puncture. This dielectric breakdown produces a measurable current spike, prompting an automatic rejection of the affected board.
This test catches flaws that would survive low-voltage continuity tests but fail after a few thermal cycles in the field.
Test Integrity
Setting the voltage too high can degrade healthy dielectric material and introduce latent damage that shortens the life of the board. Therefore, high-voltage screening parameters must be carefully calibrated to balance defect detection against the risk of dielectric fatigue. Typical tests apply the voltage for a few seconds to ensure complete safety without inducing long-term laminate degradation.