Author Topic: Cleaning flux residue  (Read 8286 times)

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Offline Medo

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Cleaning flux residue
« on: February 12, 2011, 08:24:27 am »
What are risk involved if one does not clean water soluble flux residue?

If I have water soluble flux core and I have some residue after soldering, what is "the worst thing" that can happen?
 

Offline Chasm

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Re: Cleaning flux residue
« Reply #1 on: February 12, 2011, 09:48:56 am »
Water soluble flux is an aggressive flux, it will literally eat the PCB traces over time.
 

alm

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Re: Cleaning flux residue
« Reply #2 on: February 12, 2011, 01:38:01 pm »
Plus it can increase leakage current, especially if it attracts moisture. Bad for low-power or high-impedance circuits.
 

Offline Zero999

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Re: Cleaning flux residue
« Reply #3 on: February 12, 2011, 03:36:37 pm »
Not to mention high voltage circuits, especially creepage between mains and DC.
 

Offline Time

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Re: Cleaning flux residue
« Reply #4 on: February 12, 2011, 04:09:00 pm »
Pardon the digression but I remember when I was working on a board in the lab.  Someone placed a can of lubrication spray right next to a can of spray meant for flux removal.  I probably squirt lubrication spray on my board 5 times before I realized it wasn't working and left a terrible residue... thank god the board (also just a prototype) still worked and the normal flux remover could get the residue off.
-Time
 

Alex

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Re: Cleaning flux residue
« Reply #5 on: February 12, 2011, 04:53:23 pm »
Well at least the board will slide in the enclosure easily  ::)
 

Offline Frangible

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Re: Cleaning flux residue
« Reply #6 on: February 16, 2011, 09:59:01 pm »
Many grocery stores and pharmacies sell 99% isopropyl alcohol.  This is pretty close to the anhydrous (100%) isopropyl alcohol commonly used in industry to clean PC boards.  It's cheap and works well if you use an acid brush and sop up the flux with a paper towel as you go.  Do not use the 70% stuff - that stuff has mineral oil in it.  You can used denatured alcohol (ethanol) - but the poison they put in there to prevent people from drinking it leaves a residue.
 

Offline Zero999

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Re: Cleaning flux residue
« Reply #7 on: February 16, 2011, 11:04:01 pm »
Has anyone tried vodka?

If it's too expensive what about the cheap Russian stuff which is just moonshine?
 

Offline Time

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Re: Cleaning flux residue
« Reply #8 on: February 16, 2011, 11:35:14 pm »
I attempted to clean up a board with isopropyl alcohol (all that I had laying around) today and I did more scraping and wiping than I did actual dissolving.
-Time
 

Offline the_raptor

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Re: Cleaning flux residue
« Reply #9 on: February 17, 2011, 05:51:18 am »
I haven't been able to find 99% Isopropyl alcohol locally at chemists/grocery stores, everywhere I looked had the same low concentration stuff which was pretty much rubbish.
 

Offline ElektroQuark

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Re: Cleaning flux residue
« Reply #10 on: February 17, 2011, 06:02:54 am »
I use isopropyl alcohol in a cheap ultrasonic bath. It works very well.

Offline oPossum

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Re: Cleaning flux residue
« Reply #11 on: February 17, 2011, 06:19:29 am »
Get denatured alcohol (from a paint store), not isopropyl (from a drug store).
 

Offline Time

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Re: Cleaning flux residue
« Reply #12 on: February 17, 2011, 02:17:59 pm »
It was 99.9% laboratory grade isopropyl from the chemical cabinet at work.
-Time
 

Offline Frangible

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Re: Cleaning flux residue
« Reply #13 on: February 17, 2011, 04:51:42 pm »
Isopropyl does not instantly dissolve flux, especially if it has been sitting on the board for a while.  It takes a good soaking - but it does work well and was all we used for building flight hardware. 

The trick I learned to using it was to cover the spot to clean with a kimwipe (or good quality paper towel), then soak the paper with alcohol and then poke and scrub at it with an acid brush with the bristles cut down to 1/4" or so.  Keep adding alcohol and moving the towel to a fresh spot.  You'll be amazed at how much flux gets soaked up by the paper. Once the paper comes clean, you're done.

This is the technique used by all of the assemblers who build satellite hardware at the place I used to work.  There may be chemicals that work faster, but at least isopropyl isn't known to cause cancer...
 

Offline Bored@Work

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Re: Cleaning flux residue
« Reply #14 on: February 17, 2011, 06:34:23 pm »
I use isopropyl alcohol in a cheap ultrasonic bath. It works very well.

You know that is really risky? The ultrasonic vibration can create an explosive air / alcohol vapor on the surface and around the bath. It doesn't take much to ignite such a vapor, e.g. by a spark from the electromechanics in the bath.

The right stuff to use in an ultrasonic bath to clean flux is a specific flux cleaner. They contain Ammonia, which reacts with the flux to create a kind of soap (saponification), which is then washed away.
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Offline ElektroQuark

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Re: Cleaning flux residue
« Reply #15 on: February 17, 2011, 06:41:13 pm »
Yes, I know. It is a matter of knowing what are you working with.
« Last Edit: February 18, 2011, 07:47:26 am by EdoNork »
 

Offline metalphreak

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Re: Cleaning flux residue
« Reply #16 on: February 17, 2011, 06:46:29 pm »
Those in Perth can grab isopropyl alcohol from Altronics:

http://www.altronics.com.au/index.asp?area=item&id=T3035
http://www.altronics.com.au/index.asp?area=item&id=T3038 <--- Comes in a 2L plastic container now not steel

They've got dealers all around Australia that might stock it too. It's actually produced by Richard Foot Pty Ltd which is in NSW I think.

http://www.rfoot.com.au/chemicals/distributors.html

Offline tsmith35

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Re: Cleaning flux residue
« Reply #17 on: June 10, 2013, 02:16:30 pm »
Yes, this is an old thread, but this will be helpful to others regardless of the age of the thread....

After looking far and wide (every store I could think of) for 99% isopropyl alcohol (IPA), I found it by the gallon at a farm supply store, and dirt cheap at that. It's commonly used for veterinary procedures. I have several gallons of it now.

Vodka is typically 80 proof, or 40% alcohol. The water in vodka mixes with flux, leaving a milky-white residue that looks terrible. I have used Everclear in the past (190 proof or 95% pure), but it's expensive and still has 5% water in it. Okay, that's it for now... ;)
 

Offline Mr Smiley

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Re: Cleaning flux residue
« Reply #18 on: June 10, 2013, 03:50:49 pm »
Put your bottle of vodka in the freezer, only the water content freezes, filter out the ice and you have some wicked vodka  :-+

 :)
There is enough on this planet to sustain mans needs. There will never be enough on this planet to sustain mans greed.
 

Offline nanofrog

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Re: Cleaning flux residue
« Reply #19 on: June 10, 2013, 07:28:45 pm »
Put your bottle of vodka in the freezer, only the water content freezes, filter out the ice and you have some wicked vodka  :-+

 :)
Or build a still, and make your own.  :-DD
 

Offline dr_p

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Re: Cleaning flux residue
« Reply #20 on: June 11, 2013, 09:37:02 am »
Put your bottle of vodka in the freezer, only the water content freezes, filter out the ice and you have some wicked vodka  :-+

my vodka doesn't freeze at -20C. It just thickens to an typical oil consistency.
 

Offline Dave

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Re: Cleaning flux residue
« Reply #21 on: June 11, 2013, 09:46:43 am »
What kind of a terrible person would use vodka to clean his circuit boards?! :wtf:
Use isopropanol, that stuff's for cleaning. Vodka is for drinking.
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Offline Mr Smiley

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Re: Cleaning flux residue
« Reply #22 on: June 11, 2013, 01:45:37 pm »
A glass for me  :P

A cotton but dipped for you

A glass for me  :o

A cotton bud dipped for you

Even after a few hours, that board is gonna look sparkling clean, till morning  :-DD

 :)
There is enough on this planet to sustain mans needs. There will never be enough on this planet to sustain mans greed.
 


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