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Humiseal 1A33 conformal coating using automated atomized spray

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Humiseal 1A33 conformal coating using automated atomized spray | 3 July, 2018

Reaching out to all conformal coating experts, please help!

While setting up conformal coating using the automated atomized spray, we observing issues associated with conformal coating wetting on the following regions:

1) Component edges 2) Metallic surfaces

We are conducting a wash with Kyzen Aquanox A4241 liquid to clean flux residues and using Oxygen only plasma to deal with surface energy issues. Visibly, we don't see flux residue under the microscope. Should we consider using other gases that would affect the contact angle of metal surfaces (Maybe, argon????) Are there any detrimental effect of oxygen-based plasma cleaning on metallic surfaces.

The material that we are utilizing for this purpose is Humiseal 1A33 Urethane based conformal coating compound mixed with the recommended thinner in a ratio of 1:4 (as supported by the material TDS). Should we consider increasing viscosity?

Are there any ways to improve metal wetting such as soldered areas, gull wings, traces and exposed BGA pads? (Hard limits: Can not use coupling compound interfaces such as organosilanes, cannot change coating material)

How can we avoid shadowing in areas of high density/complexity?

We have enough leeway to vary atomizing air pressure, tank pressure, spray pressure, dwell time, cure method, number of coats, a volume of material dispensed.

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