Via size depends on the coating viscosity. The biggest thing people forget
to call-out in addition to vias; alignment holes for connectors. RJ45 jacks
are usually huge holes that allow coating.

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


On Thu, May 9, 2013 at 11:02 AM, Douglas Pauls
<[log in to unmask]>wrote:

> Thank you Amol.  I would agree with the vias.  We have that happen on a
> number of our assemblies now where the wicking action causes problems.
> When you say "if the vias are too big" is there a general range you are
> talking about?  Something like vias less than 8 mil diameter are not a
> problem with wicking but 15+ mils are?
>
> Fortunately, we are only working presently with single component conformal
> coatings and have not had to go to two part coatings, which I agree would
> make things more difficult for process control, as Graham Collins said.
> Nothing quite like trying to get set/cured coating out of a complex spray
> valve.
>
> Doug Pauls
>
>
>
> From:   Amol Kane <[log in to unmask]>
> To:     <[log in to unmask]>
> Date:   05/09/2013 08:32 AM
> Subject:        Re: [TN] Automating Conformal Coating
> Sent by:        TechNet <[log in to unmask]>
>
>
>
> A couple of things come to mind:
>
> 1. Design of thru vias with regards to the size and location when the
> assembly is designed for an automated spray process. If the vias are too
> big or close to keep out areas on the other side of the board, then you
> will have coating related defects on that side (usually coated first)
> during spraying the opposite side. Depending upon the inspection sequence,
> they may or may not get identified and corrected. Even if they are
> identified, they may make the assembly unsuitable for automated spraying
> without significant manual masking!
>
> 2. with regards to coating material, while a longer pot life is important,
> stable viscosity over the pot life is equally important to be able to
> control coating thickness and coverage for a given recipe setting.
>
> Regards,
> Amol
>
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
> Sent: Thursday, May 09, 2013 8:03 AM
> To: [log in to unmask]
> Subject: Re: [TN] Automating Conformal Coating
>
> Hi Doug
> No keep-out areas is a bit difficult, the board presumably has to connect
> to something, but what I have asked for (but not gotten) is that
> connectors have clear areas around them so that the measurement tolerance
> on the coated area can be high, and that the connectors be easily masked -
> preferably something we could put a rubber boot on, next best is easily
> taped to cover pins and mating area, worst are open body connectors.
>
> Component height restrictions will depend on how versitile your coating
> machine is - the one I had was a 4.5 axis machine (x-y-z, theta, and
> nozzle tilt) and so for us height issues were a programming problem - not
> so much a running problem.
>
> I would also add to the wish list a coating material that is agreeable
> with an automated process.  At a previous employer we had a high volume
> product that was coated - so an automatic candidate for automated
> spraying.  But the customer specified a coating material that had a 4 hour
> pot life, after which we had to flush the machine with toluene or it would
> seize up and need a full overhaul.  With an in-house project I'm sure you
> have more control over that factor.
>
> regards,
>
> Graham Collins
> Senior Process Engineer
> Sunsel Systems
> (902) 444-7867 ext 211
>
> On 5/9/2013 9:40 AM, Douglas Pauls 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
> >
> >
> > ______________________________________________________________________
> > This email has been scanned by the Symantec Email Security.cloud
> service.
> > For more information please contact helpdesk at x2960 or
> > [log in to unmask]
> > ______________________________________________________________________
> >
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>
>
>
>
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> ______________________________________________________________________
>


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________