Method for removing flux?
Oldbitcollector (Jeff)
Posts: 8,091
What is the best way to remove the flux (from solder) from the board itself when finished with my project? I've learned from experience not to ignore
this problem. What's the preferred removal method without damage?
Thanks
OBC
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this problem. What's the preferred removal method without damage?
Thanks
OBC
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Brian
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Post Edited (parts-man73) : 5/4/2009 12:51:56 PM GMT
OBC
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-Phil
Then the "used" alcohol can light the lamps you'll need after that kid in your avatar gets done blowing out your electrical service!
(smiles)
DJ
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Instead of:
"Those who can, do.· Those who can't, teach." (Shaw)
I prefer:
"Those who know, do.· Those who understand, teach." (Aristotle)
·
Yes, I agree. I got my 99% isopropyl from Walmart, very cheap. I use a Q-tip and scrub it off. Make sure nobody in the house uses the alcohol for anything else, though, since solder flux and possibly solder lead, etc. could get into the bottle if you are re-using the same Q-tip or whatever.
One hazard of using a toothbrush is that the flick of the bristles might flick some of the alcohol into your face.
Post Edited (ElectricAye) : 5/4/2009 3:32:41 PM GMT
-Phil
Depending upon the flux you may have to try different cleaners. From past experience there doesn't seem to be a one size fits all cleaner. I usually start out with the cheapest solution and use the inexpensive isopropyl alcohol from the local drug store (not a fan of WalMart) with a tooth brush to help loosen stubborn flux, etc. From there I'll try some of the electronic cleaners and the flux sprays. Recently I tend to avoid the flux sprays since it seems the formulas have changed and don't seem to work nearly as well as they used to. Whatever cleaner you try be careful where you spray it. Most of the parts seem fine but one notable example are older relays with clear plastic covers. Some of the flux sprays can react with the plastic and melt them. Not to mention what it may do to the person using it.
If the boards are dusty, etc there are some instances where I have actually washed them off (yes, with water) and used a dish soap to act as a degreaser and cleaner. The results can be fantastic. I don't submerge the board but rinse and scrub them with a soft brush. Once done I make sure they are thoroughly dry and use compressed air to blow them off and get any water out from under parts and out of sockets. A hair dryer on warm helps finish the job. The key is to make sure you dry them right after they are cleaned to remove the excess moisture. After that I let them sit for a while before even thinking of powering them back up.
Anyone else have good methods for cleaning boards?
-Phil
It can cause problems with high-impedance circuits as it can absorb moisture and become conducting. Normally, it doesn't matter.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Yes, that is one of the reasons I prefer to avoid all the Flux sprays. I'd like to stay around long enough to watch the kids grow up and take care of some more projects on my wish list!
Finding alternate methods for cleaning boards is definitely an interesting topic and I hope others will chime in with what they have been successful with.
On that note I have heard of one method that I have seen used but am not a fan of. One particular repair shop used to clean the back of their boards with lighter fluid. This removed the flux but ends up leaving a shinny coating over the back of the board once it evaporates. I have seen boards that this was done to and wondered what had happened to them. Didn't seem to cause any problems but I don't ever plan on trying it. Whenever I have repaired one I try to clean them again to get rid of it.
Robert
That residue was probably the flux left after the solvent has evaporated.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
That's why no serious master of soldering ever goes anywhere without his or her boll weevil.
en.wikipedia.org/wiki/Boll_weevil
Get with the times, Phil.
-Phil
Now you've got me thinking along the lines of engineering a bacterium to do the job. It might eat your face, though.
If that's too difficult to source, just use 91% Isopropyl Alcohol (available at every walmart). Typically used with a plain old acid flux brush with shortened bristles for stiffness (already mentioned). The ideal brush is one made of hog bristle as they clean better with less force. Also, they last much longer because it is easier to clean the residue out of the bristles.
If you are using no-clean flux, removal is dependent on your circuit, but typically only "excessive" flux residue is removed and usually only for cosmetic reasons. Removal of no-clean flux is performed with IPA or flux remover.
RF and high speed circuitry can be affected by no clean flux residue, but it is not a common problem for most circuits discussed on these forums. Most of the electronics in your house probably have no-clean flux residue on their PCBs.
In volume manufacturing, organic flux (commonly referred to as "water soluble" or "aqueous" flux) is usually removed by an inline cleaner. Hot (140F), treated, de-ionized water is sprayed at high pressure on the PCB to remove the flux. Basically the machine is a large dishwasher with a conveyor running through it.
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Andrew Williams
WBA Consulting
IT / Web / PCB / Audio
This might sound wierd, But it works for Me.
____________$WMc%____________
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The Truth is out there············································ BoogerWoods, FL. USA
I don't suppose they used the same dishwasher to wash the company coffee pot.
"Sugar? Cream? Splenda? How about a little Lead Oxide?"
I doubt that isopropyl alcohol alone could cause a short. Even though it's conductive as a liquid, the pure form evaporates vey quickly. There may have been other contaminants that got moved around but not eliminated during the cleaning process. Or you didn't wait long enough before powering up the board.
BTW, there are much better protectants than WD40, which can get gummy with age. I sometimes use a polystyrene conformal coat, which seals a PCB against moisture, salt, and other environmental nasties.
-Phil
Also, as a note, a while back I was having trouble with SMT resonators (the 20MHz ones that Parallax sells) on boards I was having reflow soldered.· The conclusion was that they were affected by the wash.· Since then, I solder them on the boards myself with the no-clean solder and have had no further problems.
Chris I.
91% strikes me as not being pure enough for this use?
OBC
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New to the Propeller?
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Whit+
"We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
You need 99% IPA.
Starman:
Denatured alcohol is mainly ethanol with some methanol and other stuff to make it undrinkable. It isn't much use for removing flux. Cellulose paint thinners (xylene) works quite well and is easy to obtain, but isn't very pleasant to use.
Leon
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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle
Post Edited (Leon) : 5/5/2009 2:52:56 PM GMT
At all of my jobs in electronics manufacturing, we use >99% in 1 gallon jugs from typical distributors. My current company uses "Techspray 1610" which is "Isopropanol (67-63-0) 100%". Data sheet states: "99.8+% pure, anhydrous isopropanol for all-purpose cleaning. Excellent for tape head cleaning, removal of fluxes, light oils, polar soils, and white mineral residue. Can be used as a thinner for most fluxes."
The lower percentage of alcohol just means there is a higher percentage of water. The greater the dilution, the lower the ability of the alcohol to dissolve the flux. So, the alcohol will still remove the flux, just at a slower rate and more may have to be used.
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~~ dRu ~~
Okay, I'm bowing down in respect for Phil, here. My Q-tip suggestion sucks in light of the toothbrush method. I just got through soldering a VGA connection, and I had forgotten what a mess all that loose cotton creates.
That, and my boll weevil just up and died.