A Correlation between Surface Insulation Resistance and Solvent Extract Conductivity Cleanliness Tests

Bellcore has two generic physical design criteria for telecommunications product cleanliness. Residual insoluble contamination levels are monitored by surface insulation testing, and soluble ionic species by solvent extract conductivity testing. The previously undefined relationship between the two has been elucidated and is reported in this paper. Contamination of insulation resistance test pattern surfaces with LiBr at the criterion limit of 1 μg NaCl equivalent per cm2 results in surface insulation resistance levels in the 109 to 1010 ohm range, which is the criterion level. A discussion correlates the Bellcore cleanliness criteria with satisfactory performance of today's leakage sensitive ICs. Contamination levels at or above 5 μg NaCl equivalent per cm2 result in significant circuit corrosion and migration at 85°C/85% relative humidity stress, clearly indicating unsatisfactory field performance for a product with such contamination levels.