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From:
"Goodyear, Patrick" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Goodyear, Patrick
Date:
Wed, 15 May 2013 21:34:07 +0000
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Dale, 

Based on my experience as an end user who works at a facility on the Pacific Coast 85 feet above the ocean, the use of edge coating is almost a requirement.    Over time I have noted more than one instance of moisture intrusion on the edge of a circuit card, in some instances causing the traces to un-bond and in some instances causing the board to swell, I have seen numerous boards that have had the edges of circuit cards, green stuff along the edge of the traces.   Rusty component leads are also a problem, areas uncoated and areas where the plating was damaged.    

Pat Goodyear
Control Technician 
Diablo Canyon Power Plant

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of lduso - Diamond-MT.com
Sent: Wednesday, May 15, 2013 12:35 PM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating Question

Dale, this was just brought up about a month ago but it was not the main topic. I think it was part of the large discussion about coating that Doug started. Here at Diamond-MT we are a conformal coating application house, that's all we do. We coat for everyone from the big guys to the small mom and pop shops. They send us the boards with a spec and we coat them in whatever they want. That being said, of the thousands of different part numbers we have coated over the years, I'd say less than ten required coating on the edge. As a matter of fact, we have more part-numbers that require us to leave the edges coating-free than be coated. Unless you have something conductive exposed on the edge, there really isn't a reason to coat it. (Of course we are talking about all liquids, parylene is a different matter.)

Lloyd Duso
Diamond-MT
Plant Manager
(814) 535-3505
www.Diamond-mt.com


On Wed, May 15, 2013 at 3:08 PM, Dale Ritzen <[log in to unmask]> wrote:

> Hello Technetters,
> Don't know if this has come up before or not (nothing in the 
> archives), but we are researching any conformal coating requirements 
> specifying that the edges - not just the surfaces - of the boards be 
> covered. With the emergence of automated coating equipment, i.e. 
> moving away from the spray or dunk coating processes, we are finding 
> it hard to identify a coating machine that can do board edges. So...
>
> 1. Is there a valid need to coat the board edges, or is this simply a 
> customer driven requirement? (I'm waiting for an "It depends..." on 
> this
> one.)
> 2. Are there any IPC standards that address this specific question?
> J-STD-001E, section 10, covers coating to "all areas designated for 
> coverage on the assembly drawing/documentation", and does not 
> specifically mention board edges. I don't have copies of HDBK-830 or 
> CC-830B for reference, so am relying on your inputs and experience with this question.
> I would be glad to do some reading up on this if anyone has any 
> suggestions for white papers or other documents that cover this (pun intended).
>
> We'd really like to understand what the industry-wide requirements are 
> for conformal coat in this regard. Might be a lost cause already as we 
> have been getting the boards sprayed for years, so the customer is 
> used to seeing every surface coated, including edges. But, the only 
> spec they've quoted so far is the old Mil-I-46058C which was removed 
> from service back in the 1990's. After reading through it though, I 
> don't find anything that specifically addresses this question.
>
> Any feedback would be appreciated!
>
> Dale Ritzen, ASQ CQA
> Manager | Quality Group and ISO Management Representative 
> _____________________________________________
> Austin Manufacturing Services
>
>
>
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