Determining conformal coating protection
Abstract
Purpose
This work sets out to characterise the protective properties of conformal coatings and how they degrade.
Design/methodology/approach
The approach dosed several commercial coatings with two different contaminants, a synthetic generic flux mixture of dibasic acids in both a solvent‐ and water‐based carrier, and sodium chloride. The protective properties were monitored using three complementary techniques: surface insulation resistance measurements, sequential electrochemical reduction analysis, and diffusion measurements.
Findings
The experimental approach was verified and the SIR measurements were shown to be the most valuable. Coatings offered varying levels of resistance to the contaminants, with the silicone coating being the most resistant. The flux variants generally proved more harmful to the coatings, suggesting that flux diffusion through the coating exceeded that of NaCl and hence led to greater electrochemical corrosion. Flux transmission through the coatings was verified by the diffusion measurements.
Research limitations/implications
The project only investigated a limited number of contaminates on simple single sided boards. Future work will investigate coverage effects and a wider range of contaminants.
Practical implications
The work shows that coatings can allow diffusion of contaminates, particularly organics, which can lead to corrosion. The test methodology described here can be used to characterise coating susceptibility.
Originality/value
This work starts to develop for the first time a test methodology to characterise the protective properties of conformal coatings, and shows that flux, and hence other similar organic contaminants, may represent a protection challenge for some coating chemistries.
Keywords
Citation
Hunt, C., Mensah, A., Buxton, A. and Holman, R. (2006), "Determining conformal coating protection", Soldering & Surface Mount Technology, Vol. 18 No. 4, pp. 38-47. https://doi.org/10.1108/09540910610717893
Publisher
:Emerald Group Publishing Limited
Copyright © 2006, Emerald Group Publishing Limited