Cleaning PCB after soldering

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I'm curious as to the best way to clean the flux off of a PCB after hand soldering. Tried some 70 isopropyl which just kind of left a white flim. Tried some flux off which actually worked pretty well but left its own somewhat sticky residue.

Ideas?

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I use 99% IPA. It works very well.

Leon Heller G1HSM

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IPA (Indian Pale Ale) will leave a sticky sugary mark.

Why dilute perfectly good beer?

David.

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Just went to CVS and picked up some 91% IPA. The pharmacist says they're not allow to sell 99% in Minnesota I guess. Not sure if I believe it so I'm going to check a few other stores.

Anyway I tried the 91% and I got the same result as the 70%. Sticky white residue left all over the board. This is so obnoxious!

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99% is essential!

Leon Heller G1HSM

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I see that, I guess I'll have to get some from amazon.

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Nail polish remover (diluted acetone) works generally just fine to remove flux and other sticky goo. Just make sure to clean it with isopropyl after so the acetone doesn't eat through whatever plastic you splash it on.

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leon_heller wrote:
99% is essential!

I haven't found that to be true.

The white residue, in my experience, is dried flux. The only contaminant (AFAIK) in less pure IPA is water.

My technique is to have a couple pans of IPA

Soak a PCB in the pan 1, scrub on it for a while, and then shake it mostly dry before plopping it down in pan 2. Scrub it a bit, shake it off, into pan 3. Soak, scrub, shake, clean PCB.

Periodically you need to change out the IPA - but you only need to replace pan 3's IPA. It's old IPA goes into pan 2, pan 2's old IPA goes into pan 1.

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Interesting idea... How long do you soak them? Are they completely submerged? Do you use water at all?

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GordonFreeman wrote:
Interesting idea... How long do you soak them? Are they completely submerged? Do you use water at all?

I typically leave them in for 10 minutes in pan 1. Same for 2 and 3, not at all if I'm feeling lazy though.

Completely submerged.

No water.

Compressed air works great to dry them off, but time or heat will also do the trick.

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I've heard of other people getting white deposits with non-99% IPA.

Leon Heller G1HSM

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What kind of flux? Rosin, no clean, ???

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dksmall wrote:
What kind of flux? Rosin, no clean, ???

Rosin core I believe.

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Alright so I went out and bought 2 liters of 91% IPA and some food containers and soaked a couple boards in three baths 10-15 minutes each.

The first one just finished drying and while it's not perfect, it's much much better. Still a few small whitish spots but it's acceptable.

Thanks for the suggestion. :)

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GordonFreeman wrote:
Alright so I went out and bought 2 liters of 91% IPA and some food containers and soaked a couple boards in three baths 10-15 minutes each.

The first one just finished drying and while it's not perfect, it's much much better. Still a few small whitish spots but it's acceptable.

Thanks for the suggestion. :)


Did you scrub on them in between the soakings? You should have a brush/container (as in, once a brush has been used in pan 1 never let it be used in pan 2). Also, scrubbing is best done under the IPA (so you don't get sprayed with grossness). I use something stiff but not metal (like the back of a toothbrush) to keep the PCB from sliding around while I scrub on it.

Also, while soaking, it is helpful to swirl around the IPA periodically.

Toothbrushes work well, as do q-tips, but I find acid brushes to be most effective (though you'll want to shorten the bristles to make them stiffer).

You should be able to get your board to look spotless.

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I recal using carbon tetrachloride... but you young whipper snappers wouldnt have the ba**s to use it.

Seriously however mineral terpentine ( and a tooth brush ) is extremely effective in removing a lot of fluxes, no white residue. While it may seem like an oily carbo hydron, it does evaporate leaving a dry surface.
Same caveat as with the above alcohol process applies .. soak in dirty end rinse in cean end of cycle.

Keep in mind that no matter what the chemistry is certain components can not be immersed in the cleaning fluid.

EDIT: PS in order to keep carbon tet consumption low, used to recover the consumed fluid by distilling it.

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Hi,

I too found Rosin a real pain to get off boards.

Someone suggested using water soluable flux and it works so great. I rinse the boards under hot water in a sink for a minute and then use an air compressor to blast off the water.

The water soluable stuff doesn't wet on the soldering tip as well, but it works fine. It is conductive though, clean off is mandatory!!

Good luck,

Alan

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When cleaning rosin from boards, I use a small wad of paper towel dunked in fresh toluene. I scrub the board with the towel, which shreds somewhat in the process, but the paper absorbs and removes the dissolved rosin. The result is a squeaky clean board. My normal process uses only water soluble fluxes, and I only use rosin for repairs or the odd part that has to be added "later".

Tom Pappano
Tulsa, Oklahoma

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I just use neat methylated spirits applied with a tooth brush followed my vigorous scrubbing with the tooth brush where required. Hold the board on an angle and just let the residue drain off. Give it a splash of methylated spirit straight from the bottle to get rid of any flux residue. Do not use a "used" tooth brush as it seems to exude a white residues for a long time. Then I hit the board with some PCB lacquer.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

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With thinner and aceton will OK.
Combining with tooth brush and tissue as medium resorb.

The(medium resorb) ear cotton stick and tooth stick with rolled thin tissue for cleaning between IC legs or hard to reach location.

Our problem below big ICs.I didn't know how's to remove the lux after solder which cause rust(homemade PCB).

Jeckson

נרגעת

.

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Anyone heard of "water soluble" flux? :wink:

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Yeah, so what's your question? ;)

I believe the water soluble flux residue is corrosive, so if I forget to remove it, I will be in trouble.

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steve17 wrote:
Yeah, so what's your question? ;)

I believe the water soluble flux residue is corrosive, so if I forget to remove it, I will be in trouble.


It is, very much so in fact. Water soluble flux has to be cleaned off. Being that there are all sorts of nooks and crannies on PCBs this makes me nervous and I tend not to use it.

I seem to remember a no clean water soluble flux being announced recently. Can't remember where I saw it though.

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LDEVRIES wrote:
Do not use a "used" tooth brush as it seems to exude a white residues for a long time.

Strongly agree! All too many people make this mistake and end up with whitish PCBs.

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I've seen the little white particles on the board after cleaning with a used toothbrush. I assumed the flux caused that after being cleaned. My theory was:
flux + IPA -> white specks

Your explanation makes more sense.

But anyway, what's the problem with a white PCB?

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Quote:
I seem to remember a no clean water soluble flux being announced recently. Can't remember where I saw it though.

I use this stuff, which is also available as cored wire solder. I do however, always clean the boards afterward.

http://www.solderandmore.com/servlet/the-59/4300-SN63-fdsh-PB37-Solder-Paste/Detail

Tom Pappano
Tulsa, Oklahoma

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Quote:
But anyway, what's the problem with a white PCB?

Probably nothing, except it looks crap! For the price of a new tooth brush, you can avoid that! In addition to my procedure, I keep some of the used metho/flux residue and use it on newly home made boards to prevent them oxidizing. Once again if it has to much titanium powder(?) from the tooth paste it looks crap.

Charles Darwin, Lord Kelvin & Murphy are always lurking about!
Lee -.-
Riddle me this...How did the serpent move around before the fall?

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Quote:
so if I forget to remove it,
Then DON'T forget to remove it. :-)

I have been using water cleanable solder for about 15 years and never had a board come back. The person who used to do our large assembly runs put me onto it and our current assembler still uses water cleanable solder afaik.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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js wrote:
Then DON'T forget to remove it. :-)
Thanks. I'll have to remember that.

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Go to your local auto parts supply (Pep Boys, etc.). There are
several products used to remove water that finds it's way into a
car's gas tank. In particular are the products called HEET and
ISO-HEET. HEET is simply dry methyl alcohol. The product
ISO-HEET is dry isopropyl alcohol. Both should be 99% alcohol and remove solder flux residue.

I recommend using ISO-HEET. HEET, being methyl alcohol is very
nasty, toxic stuff. Don't breath its fumes; it attacks the
optic nerves. ISO-HEET, however, is simply dry "rubbing
alcohol" and is reasonably innocuous so long as it is kept
_outside_ the body.

Oh, did I mention cheap? $2-$4 for 12 oz. or so.

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Thanks for reminding me. I have a pint of Snap Gas Line Antifreeze. I got it to pre-heat my Petromax kerosene lantern. I'll try it sometime.

I normally use MG Chemicals flux remover. It contains ethanol, isopropanol and ethyl acetate. I'm not particularly impressed with it, but then I'm not very particular about the appearance of my PCBs either.

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Asalco Brand Flux remover. This stuff works fantastic with any type of flux ive thrown it on to. Just wax on wax off. Even removes(dissolves) thermal paste from hard to clean features too.

Its more expensive than the IPA route but you dont need much because it works so well. A can in the lab lasts months easily.