I need a conformal coating that will protect a pcb in a saline atmosphere, maybe even the odd small drop of saline will land on the pcb. The temperature is room temp and the pcb dissipates only the odd mW (no hot components)
Potting is not an option but dipping is!! (odd I know but nevertheless)
Has ayone knowledge/experience of a suitable conformal coating?
Thanks
RHRRC wrote in news:e2352b8e-429a-4099-8a46- snipped-for-privacy@r34g2000vbp.googlegroups.com:
Nothing odd about dipping as opposed to potting, it's standard practise for things like SAB units for burglar alarm bell boxes, etc..
Try RS Components for a look at some. 155-8156 is a can, as opposed to a spray can, which is how most are supplied. Even a spray can will work if you have a near UV bright LED or other source to help inspect for flaws in coverage. There's a 5 litre can if you want lots and spend high.
How long do you need it to work for. A coating just slows the progress of the salt and water working its way towards the PCB. Potting is thicker so it works longer.
Put it in a sealed housing and drop the coating?
Does it travel to the destination by air? Does it get exposed to sun light.
I have lots and lots of experience of unsuitable ones. I gave up long ago and went the sealed housing route.
Dolph's
The AC-41 is the stuff you want.
These are aerosols. They also have it in 1 Gal pails or bigger as well.
Name one modern electronic conformal coating that is attacked by normal saline solution.
What a total bullshit declaration.
Jeez what a stupid remark.
He is looking for someone with favorable experience, not some dopey f*ck that gave up along the way.
The problem is not the coating, but there are always wires going towards a PCB. This is where most of the water creeps in. Even regular chips have this problem. Thats why chips need to be baked if they where stored in open air for more than a few hours. Otherwise the packages will split open due to boiling water.
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Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn\'t fit, use a bigger hammer!"
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Apples and oranges. Water contained in parts has nothing to do with a sealed assembly being attacked externally by moisture.
Of course the proper sealing method would be to bake the assembly and or apply vacuum to the assembly to remove ALL water from it BEFORE applying the coating.
I have experience with 3. Here they are, in order of effectiveness, most effective first: Parylene (Excellent) . Excellent performance, but requires expensive equipment to apply. . Can not be dipped or brushed. . There are companies that will coat boards using Parylene. Resiweld . Can be dipped or brushed. Humiseal . The worst of the bunch, but OK for repair of small areas. Regards, Jon
'Worst of the bunch'? YOU are the worst of the bunch.
If you're willing to gamble maybe try floor epoxy.. Example:
Pros Possibly in stock at your local paint store or hardware store. If so, no special order or delivery required. Possibly cheaper than official conformal coatings.
Cons Not an official conformal coating. You'll have to figure out if water based epoxy, solvent based epoxy or
100% solids epoxy is preferred for dipping.D from BC myrealaddress(at)comic(dot)com BC, Canada Posted to usenet sci.electronics.design
al
Name one that doesn't eventually let the saline through.
ck
This looks like another nym for Always Wrong. He seems to be supporting the idea that a coating will work.
ell.
I am fairly certain that the AC-46 from these guys is one of the ones I tried. It worked about the same as the others. ie: it failed to keep the salt out of the PCB.
We had it done by an outside company. It was about the best of the ones I tried.
I have used one that can be brushed. Brushing without making bubbles is a bit tricky. It is better to put multiple coats than to try to do it all in one go.
Where I work, we called Humiseal "circuit stop". It was worse than an unsprayed PCB.
Can you really be *that* stupid?
You're a goddamned idiot. OF COURSE it would work!
You are devoid of facts, ie therefore full of shit.
What you know about coatings would fit on the tip of a molecular probe.
A part is also a sealed assembly! So if a small sealed assembly can't keep the water out, a big one can't either. Ofcourse you can use better materials which slow down the ingress of moisture but eventually you'll have moisture inside.
That is standard procedure. Still, relying on the sealing is relying on false hope. Water molecules are fairly small so they can creep into very tiny openings.
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
"If it doesn\'t fit, use a bigger hammer!"
--------------------------------------------------------------
No shit, dumbfuck.
Ifsaid 'sealed assenbly' get BAKED in an oven, there will be NO water in it, and if said assembly is subsequently sealed further, there is going to be a greater NO water content level in it, THEREFORE, if an entire assembly get baked, as is the STANDARD procedure for assemblies prior to sealing operations, then there will be NO water INSIDE the seal.
AFTER the sealing operation, there will be no water getting in as well.
Where your brain went askew is unknown.
If only we could have kept your mother from getting any water, we would then not have to listen to your utter stupidity.
You're an idiot. There are coated assemblies out there in the harshest of environs that have lasted for decades.
That should be a hint for you, and your blatant Obama styled lies.
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