Probably yes. I have not really seen this kind of failure, at least edge
moisture absorption on any of our stuff. Our Service Centers are pretty
good are reporting that kind of "weird stuff". And the only time we see
green fuzzy growing stuff on assemblies is when pilots have spilled
sugared sodas or coffee with sugar / cream into our electronics and fungus
uses that as its food.
Doug Pauls
From: Steven Creswick <[log in to unmask]>
To: <[log in to unmask]>
Date: 05/16/2013 10:33 AM
Subject: Re: [TN] Conformal Coating Question
Sent by: TechNet <[log in to unmask]>
Doug,
In Pat's case, can it also be board age/vintage/resin technology related
as
well? That all ties in with your questions on Tg, doesn't it?
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Thursday, May 16, 2013 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coating Question
Pat,
For the boards you talk about delaminating from moisture, are the boards
made of a good FR4 and are the edges routed or punched? If FR-4, low Tg
or
high Tg?
In my experience, routing the board edges tends to seal the face of the
board side. Punching the board means the fibers are unsealed and so
moisture absorption can be greater?
Doug Pauls
From: "Goodyear, Patrick" <[log in to unmask]>
To: <[log in to unmask]>
Date: 05/15/2013 04:38 PM
Subject: Re: [TN] Conformal Coating Question
Sent by: TechNet <[log in to unmask]>
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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