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conformal coating PCBs with onboard connectors

Last year I hand coated the first 15 circuit boards of my 60-sensor bee-hive monitor, but for the next 15 boards I'd like to use a conformal coating house. I faced two problems in coating the boards, first, about 20 pcb-mounting connectors (through-hole, not that it matters), and second, a host of test points that I didn't want to seal over.

I solved the first problem with specially-made plugs and the second with shrouded pins to keep holes dry. This meant mounting the board with plugs and pins, spraying, let dry, dismount, and repeat, one board at a time. Painful and time consuming.

I dunno how to approach the conformal coating house, will they have magical tricks to solve the problems?

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 Thanks, 
    - Win
Reply to
Winfield Hill
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Win, I don't know (so maybe I should just shut up.) But I'm going to suggest calling/emailing/ some places and see what they say. If you are doing a small run ~100 or less then you want to find a small guy who will work with you a bit. Maybe you can have connectors waxed or covered.. Are you in a hurry? Of course the small guy may cost more.

George H.

Reply to
George Herold

I'm sure they must have tricks; I've seen conformal coatings on boards with edge connectors, after all.

One approach I've used, is to get a latex molding compound (TAP plastics sells it in tubs)

and blob it over the parts you want protected. After it dries, it's easy to pull off (and it's water-based, most hydrophobic coatings won't attack it).

Another old solution is 'washable solder mask', but that's a ... different kind of coating.

Reply to
whit3rd

We used to use that to keep solder off. Put it on with a nozzled bottle. It just rubs off with fingers after processing.

NT

Reply to
tabbypurr

The assembly house I use a lot does selective conformal coating. The machine they're using is Dima HC-200 dispenser, which can selectively spray the coating and leave holes for test points and connectors.

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mikko OH2HVJ
Reply to
Mikko OH2HVJ

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

Yeah... That was the pink stuff sometimes powder blue. But we masked off any through holes or via that were needed downstream of the wave or reflow step. If the connectors are through hole, then mask the holes and solder the connectors on by hand after the wave or reflow, Or douse the whole thing in the mask, cause it peels right off like you said.

I would worry about small for factor high pin count connectors as the pink stuff could get under the pins and alter connector function / continuity integrity., even if it wipes clean from their surfaces.

Reply to
DecadentLinuxUserNumeroUno

I just probe through the coating. Today's coatings are invariably self- healing IME.

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Reply to
Cursitor Doom

Cursitor Doom wrote in news:q9vdus$2u4$ snipped-for-privacy@dont-email.me:

Absolutely not. Any breech means that water can then invade the very thing you were sealing against. And no, regardless of how you think the material 'feels', it does not 'self heal'. Erroneous 'estimation'.

Repair work on coated mil PCB assemblies requires the worked areas be resealed. So, since they know what they are doing/talking about, I am pretty sure commercial work follows. If it needed conformal coating to start with the reason is almost always moisture barrier related.

Reply to
DecadentLinuxUserNumeroUno

We use Techspray's WonderMASK (the pink kind). I find it very easy to work with. Goes on easy, comes off easy, does a brilliant job.

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Reply to
DemonicTubes

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