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. 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