Thank you Lloyd.
I agree on the definitions. The issue of what do you do when something
wanders into the DMZ is one that causes us fits here for manual coating. I
am curious as to what your customers use to define the areas you describe.
For us, we often use 60 mils (1.5 mm) as an exclusion zone around a
connector. Our auditors look at this as a hard and fast thing. If you
have coating that strays into the DMZ by even a mil, it is a defect and
has to be dispositioned. Then our designers also put components or
critical vias in the middle of the DMZ with instructions to coat. From a
process perspective, the DMZ is there to prevent coating from flooding
into a connector. If coating wanders into the DMZ, as long as it does not
get onto either the mechanical mating surface or the electrical mating
surface, no harm, no foul. Your thoughts? Is the DMZ a Rule or a
Guideline?
I agree with you about dip coating, but in seeing our designs and how
complex they are, I would anticipate a huge change in culture would have
to occur to do this. But something to consider. Maybe I can sweet-talk
Graham Naisbitt into letting me borrow one of his dip coaters to play
with.
Doug Pauls
From: lduso - Diamond-MT.com <[log in to unmask]>
To: <[log in to unmask]>
Date: 05/09/2013 07:58 AM
Subject: Re: [TN] Automating Conformal Coating
Sent by: TechNet <[log in to unmask]>
You need a "definitely coating free area", a "definitely coated area",
and in between them an internationally recognized DMZ, an area that can or
cannot have coating. That area should be large enough to allow the
inevitable "creep" of the liquid being sprayed. With automation you are
not
dealing with a straight, sharp separation line like masking provides.
With that in mind, on the design, components that with out a doubt need to
be coated, should not be placed adjacent to components that can not be
coated. Respect the DMZ!
Another question is the type of automation. If you want a 100% coating,
and
a extremely fast process time, then automated dipping is the way to go.
The
board just has to be designed properly; as many connectors, switches, etc.
as possible along a side edge so when dipped, no masking is required. Or
if
masking is being done, something that can be masked with a liquid mask for
sealing.
Lloyd Duso
Diamond-MT
Plant Manager
(814) 535-3505
www.Diamond-mt.com
On Thu, May 9, 2013 at 8:40 AM, Douglas Pauls
<[log in to unmask]>wrote:
> Good morning all,
>
> Another conformal coating related question. What, from an assembly
point
> of view, would you tell a board designer are good design practices to
make
> an assembly coatable from an automated standpoint.
>
> I think we would all agree that having an assembly with no keep out
zones
> and a constant height for components to be the ideal. The more holes we
> poke in the film and the farther we get from the ideal, the less we can
> automate coating.
>
> So, what would you tell a designer to do?
>
> Or, to put the shoe on the other hand, what kinds of things should they
> NOT do, or bad practices to avoid?
>
> And, yes, I know It Depends.
>
> Doug Pauls
>
>
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