SMTA International Conference Proceedings

The Importance of Conformal Coating Thickness and Edge Coverage

Authors: C.E Allen, A.Duffy, B.G Turner, P.J Kinner
Company: Electrolube Ltd
Date Published: 10/14/2018   Conference: SMTA International

Abstract: As electronics continue to become ever more densely populated, and expected to operate in ever more hostile environments, the use of conformal coating is becoming more and more essential to protect the assembly from its operating environment, and ensure acceptable reliability for the application intended.

Conformal coated assemblies are often exposed to harsh operating environments, including high humidity, high temperatures, corrosive gases, condensing environments and rapid changes in operating temperature.

It is important that the conformal coating can withstand its anticipated operating environment. In previous papers, populated SIR (Surface Insulation Resistance) test assemblies were subjected to a harsh sequential load and their ability to withstand corrosion was assessed by SIR. During this testing it was seen that most of the coatings tested failed to provide good protection during powered salt-spray testing. Further testing, performed under condensing conditions, confirmed the importance of, and difficulty in, achieving good coverage with liquid applied conformal coatings.

In this paper, we compare the performance of new silicone and urethane materials, designed for coverage and thickness, with a popular acrylic and ultra-thin material, in a variety of experiments designed to determine, how thick is thick enough?

Key Words: 

conformal coatings, salt-water, immersion, condensation, coating thickness, coating coverage, silicone, urethane, acrylic, ultra-thin, fluoro-polymer.

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