Comparing various test environments for conformal coating evaluation

Flowers of sulfur testing of conformal coatings is well researched and established. However, the electronics industry has a long history of testing based on mixed-flowing gas environments. This work compares the results of testing three commonly available conformal coatings using the flowers of sulfur, the mixed flowing gas and the iodine vapor tests. Serpentine thin films of copper and silver were coated with the conformal coatings under test and the corrosion rates of the underlying thin films were measured by electrical means in the flowers of sulfur and the mixed-flowing gas environments. In the iodine vapor test the extent of thin film corrosion was visually evaluated. The extent of corrosion of the metal films was used as a measure of the conformal coating performance. The three test results were in qualitative agreement.