BERKSHIRE, UK – A just-released NPL report describes developments using a surface insulation resistance test method to assess conformal coating protection performance on electronics assemblies.
 
In the report, authors Dr. Chris Hunt and L. Zou of the NPL maintain SIR is sensitive in detecting circuit reliability underneath coatings.
 
In the study, a test vehicle featuring a range of components was used to identify coating protection problems. The procedure on how to choose and apply contaminants to test coupons to simulate the contaminants effect from harsh environments on underlying circuit reliability is detailed, as well as the test parameter settings for SIR test and SO2 exposure testing. The method provides a measurement tool to discriminate between coatings.
 
The use of this method to investigate the protection performance of seven different types of coatings (two water-based acrylics, solvent-based acrylic, fluoroacrylate, silicone, polyurethane, and epoxy) against solvent-based flux, surfactant and SO2 gas, is included in the appendix.
 
For more information contact Hunt at chris.hunt@npl.co.uk.