Overcoming The Challenges Presented With Automated Selective Conformal Coating Of Advanced Electronic Assemblies By Employing Plasma Treatment TechnologyAuthor: David Foote
Company: Nordson March
Date Published: 10/13/2013 Conference: SMTA International
Additional challenges for conformal coating adhesion are contaminants such as mold release compounds and residual flux. The effects of residual mold release on various surface mount components, quad flat packs, dip packages and the like. Visually these devices appear to be clean and void of contaminants and although the packages have passed various levels of outgoing QC metrics as well as incoming inspection metrics, they often times display the effects of residual mold release when conformal coating is applied via select coating equipment. To a similar extent, manufacturers of printed circuit board assemblies have dealt with excess flux residues, both traditional and no-clean chemistries. With high lead count devices, minimal lead spacing, thus correspondingly high aspect ratios, often time’s residual flux can be left behind even after extensive aqueous cleaning and/or not sufficiently consumed in either the soldering or reflow processes. Given this reality, often selectively applied conformal coatings can be inhibited from sufficiently adhering to the critical junction points at the device body to lead and lead to pad.
Plasma surface treatment, conformal coating adhesion, plasma surface cleaning
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