Removing old flux when desoldering?

I use a proprietary aerosol defluxer made by Electrolube, applied with an old toothbrush. Has worked well for me for years.

Arfa

I brush the area lightly with a soft toothbrush dipped in isoproyl alcohol to remove the flux and then dab with a Q tip or lint free cloth to dry out the area. The toothbrush tends to spatter if you brush too hard so cover the surrounding area if the flux build up is large arunwad

Flux remover and cotton swabs. If it's in a spray can, I wouldn't recommend spraying it - it can make a tacky mess.

Flux stripper and a toothbrush.

circuit

fine, but

method.

what % isopropyl do you use ? if it is greater than 90% drug store variety where does one fidn such isopropyl ?

i have use the 90% variety and it seems to leave a residue .

robb

I've used paint thinner or laquer thinner...alcohol sometimes leaves a white residue

I use naptha with good results.

The IPA that I use is 99.7% and is called "Electronics Grade". I just get it from my normal trade electronic components supplier. It leaves no discernable residue in itself, although any will leave a residue if it is used to dissolve a 'contaminant', and then not fully flushed off the board.

Arfa

You're brave ! Do you ever have any trouble with the solder mask or silk screen overlay dissolving away ?

Arfa

Thanks to all for the suggestions. I didn't have anything mentioned at home so I tried some "Goo Gone" which seemed to work quite well.

sometimes leaves a

mask or silk

I was thinking same thing.

maybe now i can try my *brake cleaner* spray it has a (tolulene, xylene, naptha, acetone) mix that should blast just about any residue off ? (just joking) i would not try it on any useful board probably melt the components off

robb

A few years back we were TRYING to remove silk screen from boards. Obviously _something_ will dissolve it but we never found what it might be.

I prefer MG Chemicals 4140 flux remover in 1 litre bottles. Just bought 4 more today from MarVac for $16 each. It's a mixture of alcohols that work better that isopropyl and causes no damage to the components - including styrenes.

GG

some newer flux will wash away with water solvent based cleaners

rubbing alcohol is fine too

flux is non-conductive, residue wont affect anything, except if you constantly obsess about it and gaze affectionately at your work

i mostly just leave it on, just like the asian mass produced junk we keep seeing.

aesthetics really dont affect electrical performance!

;-)).

using those other solvents often softens insulatons and migrates into components. BAD BAD BAD!

is it fun to see your handy work light up in flames?

breath deeply, you might get a rush too!

Now you see, I just can't do that ! It's ingrained in me. Many years ago, I was taught as an apprentice, to have a tidy mind, and to leave things as you found them. My apprentice mentor was one of the best service engineers that I ever came across - then or now - and he taught me many things that have served me well throughout my professional career in electronic service work.

One of those things was that the only way anyone should be able to see where you've replaced a component on a PCB, is if your soldering is *better* than the factory original, and that involves removing flux residue.

There is a practical side to it as well. When flux is left on a board for any length of time, something happens to it (so it must still be reacting in some way ??) such that it becomes a brilliant resister of a soldering iron tip. I repair some commercial boards that used to be done by a company that did thoroughly scruffy work, and always left all of the flux on the board, from where they had replaced components which regularly fail. When I now see these same boards, the rework vacuum iron, really struggles to remelt the joints which are covered in flux, against those that are not. It also clogs up the vacuum tip much more regularly than when I am working on boards that are flux-free. Perhaps I'm just a sad old pedant on this sort of thing, but it pleases me to look on good workmanship and practices, and I'm far too long in the tooth to change now ... d;~}

Arfa

In the old days (late-60's / early 70s for me), we used MEK and a short-bristled brush (a plumber's acid/flux brush with the bristles cut down). Yes, we used it indoors, and yes, we used it all day, and no, to my knowledge no one suffered any effects from it. Every tech and every engineer had a small pot of it on his bench with a self-closing lid, which reduced the exposure, and he opened the pot, dipped the brush, and cleaned each solder joint as he made it. Later, when we started using small wave-soldered boards, each board was cleaned in the same way after it came out of the solder bath / trimmer station. It was the only way that inspection of the board could happen. By the way, this was not Joe's Garage shop - this was Motorola, and we were inventing/building the HT-220 Handie-Talkie.

MEK is still available over-the-counter at Sherwin-Williams paint stores, for example.

Bill

If you are covering a large area, use a paint brush thats about an inch wide, cut the bristles about an inch long (till they feel stiff, maybe shorter), dip in alcohol and it will scrub it till its like new.

yes, i do appreciate your position. looking back to gear i fixed, (if it still even exists, most long gone to the recycle ) it wasnt any trouble as i used basic needle point 10/20/30 watt irons and loupes. nothing really commercial, just fix-it immediately and get it into service. i usually never saw the same gadget twice again!

if somethng/device is so prone to failure, then the design was poor and we got soemthing that failed less or never again

quality in the workmanship is key to success as the units get brutally handled and .criticized by the end users. & some people expect laptops to survive being run over by a car, its just crazy!

cleanliness is indeed closer to godliness, it is easier to verify work done, good/bad joints and just for prettiness too

i have often used the onboard left over flux to assist the new solder work, yep, u can call me cheeep, i dont care.

i do admire the slick screen printed masks, fully labelled component, location grids, section function layot delineators and so forth too. but thats for those companies the have 5000 designers, techs and worldwide distribution networks to play with. along with millions of buks to squander!

the end result is, do good , reliable , and safe work. that will keep u your job ( maybe) and reinforce your self -respect too.

keep

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that

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but

he he, you just dont remember the effects now do you!! :-))

xylene and tri-chlorethylene were our favorite whiffers, we used it for god knows what.

if the alcohol didnt do it, out came that stuff. egads!

keep

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work.

where

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iron

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board,

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