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ESD considerations during Conformal Coating?

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#58932

ESD considerations during Conformal Coating? | 28 May, 2009

How does one keep a pcb safe from ESD when applying an aerosol conformal coating on a flat surface? Even if you had an ESD mat to place the pcb on it would quickly be coated. The only thing I can think of is an ionizer. Does not the aerosol create a static charge as it moves through the air on its way to the pcb? Are there any methods or specialized products with this in mind?

Thanks B

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#58937

ESD considerations during Conformal Coating? | 28 May, 2009

A grounded operator spraying conformal coating from an aerosol can will generate >10kv on the surface of the board. To avoid this charge: * Use an electric paint sprayer to apply liquid -base conformal coating * Purchase a metal nozzle for an electric spray gun so that it can be connected to ground * Use a nuclear ionizer where the coating process is done

We have heard of grounders manufactured specifically for aerolsol cans, but are unaware of sources for or the effectiveness of such devices.

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#58938

ESD considerations during Conformal Coating? | 29 May, 2009

Thank you Dave. I have searched the internet and cannot find any literature to the fact. Do you have knowledge of of any articles, whitepapers, etc...

Thanks again, B

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#58943

ESD considerations during Conformal Coating? | 29 May, 2009

Duno. Google => esd "conformal coating"

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#58951

ESD considerations during Conformal Coating? | 29 May, 2009

I too have heard of the ESD problem when using aerosol spray conformal coating, but I haven't found any documentation. I have been spraying SR conformal coating for ~ 10,000 boards with no failures due to the coating. The person spraying is grounded and the boards are placed on aluminum foil, which is replaced to prevent coating build-up. This probably isn't best, but so far it has worked for me.

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#58955

ESD considerations during Conformal Coating? | 1 June, 2009

If the operator has zero charge and the board has a 10kv charge, when the operator pulls the shorting strip from the edge connector after the coating has cured, there is a large potential for ESD induced damage.

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#58957

ESD considerations during Conformal Coating? | 1 June, 2009

shorting strip?

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#58958

ESD considerations during Conformal Coating? | 1 June, 2009

So would the proper technique be as follows:

1. Grounded operator picks up PCB from ESD rack and attaches a 1meg(wrist strap cord)shunt to ground to a grounding surface on the pcb.

2. operator sprays conformal coating onto pcb using a sprayer that has nozzle grounded.

3. After cured, the operator blasts the PCB with inonizer, (including work surface).

4. Grounded operator picks up pcb and places in ESD rack.

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