PC board coatings

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Bear
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PC board coatings

Post by Bear » Sun Jan 15, 2012 2:41 pm

Good day all! Does anyone know how to dissolve the (conformal?) coating on the bottom of pc boards. I have tried all sorts of chemicals I.E. lacquer thinner, rust remover (naval jelly), brake parts cleaner, rubbing alcohol and nail polish remover, all to no avail. Seems like there should be something short of a low yield nuclear device. Any suggestions would be appreciated.

Thanks

Dennis

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Janitor Tzap
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Re: PC board coatings

Post by Janitor Tzap » Sun Jan 15, 2012 4:55 pm

Well....
The only stuff I know of that will possibly get that off would be Acetone.

But that would be going so called nuclear on it, because it will also eat away most plastics,
paints, and silk screening on the board.

If this an epoxy of some sort.
Try using a heat gun too soften it.
Use a plastic flat blade screw driver,
or plastic putty knife to scrape it off.

Good Luck!


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jwax
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Re: PC board coatings

Post by jwax » Tue Jan 17, 2012 9:59 am

There are literaly hundreds of conformal coatings for electronics, all designed to prevent you from doing what you're trying to do. Even with the manufacturer and part number of that coating, chances are slim to none that you will be able to dissolve it.
(Nail polish remover is mostly acetone)

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Janitor Tzap
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Re: PC board coatings

Post by Janitor Tzap » Tue Jan 17, 2012 10:40 am

jwax wrote:(Nail polish remover is mostly acetone)
Yes, but it is not pure Acetone. :wink:

This is also why I suggested using a heat gun to soften the coating.
But this can get tricky.
You want to get the coating just to it's melting point.
So you can scrape it off.
If you have a temperature adjustable heat gun,
this makes it a bit easier, and less of a chance of burning the board.
Though, I've come across some coatings that have a melting point close
to the melting point of solder.
Thus, if you get it too hot, and you have SMD's in the area of the coating.
You could end up taking off the coating with SMD's as well. :(


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Edd
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Re: PC board coatings

Post by Edd » Wed Jan 18, 2012 2:53 pm

Bear . . .



I have tried all sorts of chemicals I.E. lacquer thinner, rust remover (naval jelly), brake parts cleaner, rubbing alcohol and nail polish remover.

Heh . .heh . .heh . . . I see that you have certainly run the gamut in the agressiveness of mentioned solvents above, possibly excepting xylene, toluene and my favorite, most agressive one that even "takes the balls off a pool table". . . that being MEK.
Now at NASA we had some beautiful, glass clear, conformally coated PCB's with a finish hard as a rock that you could only surfactally scratch.
In order to spot troubleshoot / test and prepare a small problem area for rework by the "repair ladies" , I would build up a circular dam SURROUNDING the small work area with layered up candle wax drippings.
My magic solution was to then don a respirator and the use of a concocted witches brew of methyl chloride and carbolic acid . . . . no . .NO ! . I didn't say CARBONIC acid . .thats 'jes . . .plain 'ole sodie wawter. . . . Its CARBOLIC acid.
Now you might come up with less than reagent strength by obtaining your ersatz carbolic acid element via the use of olde tyme Lysol, in its darkened glass bottle (now acetate plastic packaging ?) . Which pours out as a darkened reddish brown. Plus you NEVER can forget its signature distinctive odor.
Its Methyl Phenol content is about 50 % dilution and for obtaining the methyl chloride aspect, peruse the labels of the strength of content of the MC in several Paint Strippers at the Homeless Despot / Lowes.
I would then fill the dam with the solution and initially check for any leaks and then leave time for the chemicals to work on the area inside. the end effect was the making of the area of epoxy brittle such, that multiple press/forcing my Starrett pocket scribes Image point into a surface would then micro crack and break the epoxy into small removable shards.
For any stubborn areas, just set aside and then let the solution then do its work on the extra exposed surface areas that were opened previously.
After rework and the need for re coating, the board is spot degreased and a 2 part epoxy mix made and drip deposited across the reworked area and on into the surface abraded area about 1/8 in around the adjutting original pottings coating.
Sooooo . . . if you are repairing spot areas, the procedure is possible, but if wanting to strip a big board for all of its parts, only select hi-valued parts are worth the trouble.
Whenever I see one of these surplus boards being available somewhere . . . I just cringe, smile and pass it up.


73's de Edd
[email protected] . . . . . . . . (Interstellar~~~~Warp~~~Speed)
[email protected]. . . . . . . . (Firewalled*Spam*Cookies*Crumbs)


Education . . . Learning what you didn't even know that you didn't know. . . .( How's that again ? )




.

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jwax
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Re: PC board coatings

Post by jwax » Wed Jan 18, 2012 3:50 pm

Yikes Ed! Talk about a witches brew!
Where do you procure methyl chloride? I thought it was a gas. Or, is it Methylene Chloride, that funny smelling liquid that's not easy to purchase?
Big caution with those chemicals, to those who can find them.

(I resisted suggesting dripping hot sulfuric acid on the epoxy blob because I thought it was too nasty to suggest!) Edd- I think yours is nastier. :smile:

Robert Reed
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Re: PC board coatings

Post by Robert Reed » Wed Jan 18, 2012 6:30 pm

Isn't Edds "Meth" compound the base for many common Paint strippers (at least the ones that actually work). If so, have used this product many times with no after affects (YET :smile: ) Just common sense precautions are all that were needed.

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Edd
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Re: PC board coatings

Post by Edd » Wed Jan 18, 2012 10:01 pm

.


Sir J-wax . . . .

Sir Robert . . . . . aka : . . . ." the Reedster ". . . . easily caught it . . . so possibly
you didn't read the fine print in the contract above with its:

. . . " and for obtaining the methyl chloride aspect, peruse the labels of the strength of content of the Methyl Chloride in several Paint Strippers at the Homeless Despot / Lowes. ".

And then . . . the resultant brew is potentially a toss up between it and the lesser of "Grandma's Lye soap" . . . . .

Now get your eyes fully well focused and your ears perked up and . . . then visually and aurally check out:

http://www.youtube.com/watch?v=qQA6tBYAvms

Thassitt . . . .

73's de Edd
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[email protected]. . . . . . . . (Firewalled*Spam*Cookies*Crumbs)


. . . Perhaps your whole purpose in life is simply to serve as an ample warning to others . . .

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jwax
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Re: PC board coatings

Post by jwax » Thu Jan 19, 2012 12:24 pm

Sorry for the nit-picking, but you must be referring to Methylene Chloride (Dichloromethane), and not Methyl Chloride (Chloromethane). Very different animals.
Yes, find the Methylene Chloride in various concentrations in the solvent aisle at Home Despot, but please be cautious.

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reloadron
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Re: PC board coatings

Post by reloadron » Wed Jan 25, 2012 2:18 am

Depending on the exact type of coating I have used products like this one additionally in a can products like this one have worked out well. Really depends on the coating to be removed.

Ron

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haklesup
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Re: PC board coatings

Post by haklesup » Wed Jan 25, 2012 6:28 pm

a lot of the suggested alternatives will leave a residue, be sure to wash in at least water followed by alcohol but maybe acetone also before repowering the cleaned board. If you have a coating that won't come off with acetone, chances are that anything stronger may damage a component package, be very cautious. Acetone may yet work if you wait long enough. Do not heat any solvents even though it would accelerate the action. ultrasonic action will help but don't use it if you have any relays or similar mechanical components.

Bygar
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Re: PC board coatings

Post by Bygar » Sun Jan 29, 2012 10:18 am

Here is my two cents worth.
Conformal coatings are usually:
Epoxy based,
Urethane based.
Epoxy can be be dissolved by paint remover, none wax version is preferred.
Will probably affect many components.
Urethane will respond to methyl ethyl keytone, MEK.
BYGAR.

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Re: PC board coatings

Post by Bear » Thu Feb 02, 2012 1:30 pm

Gentlemen...Thank you one and all for your kind responses. Sorry I haven't got back sooner. I, and the computer have been feeling under the weather lately, so have not got around to trying any of the remedies that all of you have kindly recommend. Feeling a little better, so I will try some if not all suggestions and report back.

Again, Thank You

Dennis (AKA Bear)

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