Evaluation Protocol
Electrical characterization of metallic junctions in printed circuit board testing relies on injecting a known current through a closed circuit to calculate the voltage drop across the mating surfaces. Performing a contact resistance measurement isolates the microscopic irregularities of the conductive path from the bulk resistivity of the trace materials. This evaluation identifies marginal joints, oxidation layers, or plating defects before the assembled board enters thermal cycling.
Metrology Configuration
Four-wire Kelvin sensing configurations eliminate the influence of test lead resistance during high-accuracy circuit board inspection. In a typical contact resistance measurement, current is driven through one pair of probes while a high-impedance voltmeter measures the potential drop across another pair. This separation prevents the resistance of the measurement cables from distorting the calculated value of the junction.
For circuit boards destined for high-reliability applications, current levels are kept low during testing to avoid puncturing thin oxide films that may break down at higher voltages, revealing the true mechanical contact quality.
Quality Criterion
Acceptable electrical boundaries for interface transitions require values to remain below a specified milliohm threshold during the final quality audit. If a contact resistance measurement exceeds these limits, the assembly undergoes immediate rejection or rework. Stable readings under repeated mating cycles indicate high-quality mechanical contact and durable plating.
