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January 23, 2012

Exposed Leads on Conformally Coated Boards

If you clip the leads of a component on a PCB that has been conformally coated, is it necessary to recoat these exposed leads?

S. F.

Experts Comments

I would recommend that you recoat the leads. When clipping the leads you could have damaged the conformal coating thereby leaving voids in your coating. As the coating is applied as a protective barrier it should be contiguous.

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Steve Cook
Director of Product Technology
Techspray
Steve Cook is the Director of Product Technology at Techspray, a division of Illinois Tool Works (ITW) and a leading manufacturer of chemical products for the electronics industry.

I presume that you are clipping them to test them and therefore making contact to the lead.

You are effectively removing the coating and producing a site for moisture and or chemicals to access the board.

Once an area is exposed it is possible, for example with salt mist, that corrosion will travel under the coating causing de-lamination and ultimately an electrical failure.

I would suggest that you do re-coat the exposed areas.

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Chris Palin
European Manager
HumiSeal
Chris Palin is currently managing European sales and support for HumiSeal Conformal Coatings. His expertise is in test & reliability, solder technology, power die attach and conformal coating.

Yes, it is recommended. The exposed area may not be as sensitive as other areas in the board however they will become the weakest spot in the board if not coated.

However you may have the alternative to use a faster, easier to apply, faster cure, higher viscosity product as long as the two materials are compatible and show good adhesion.

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Wayne Wagner
President
Krayden Inc.
Wayne Wagner has over 25 years in the conformal coating industry and is the president of Krayden Inc., a leading distributor of engineered materials.
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