Silver Blues
Well-known member
Historically I never bothered cleaning boards but recently I started doing so with DIY-ed IPA/heptane cleaner - really works (the heptane helps to better dissolve the more nonpolar flux relative to straight IPA).
How do you typically Clean flux from PCB
- Thread starter ThatDude
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darwin999
Well-known member
I use 99% IPA and an inexpensive low-power ultrasonic cleaner, works in 10 seconds, super clean. No brushing, no marks, no damage.
I put ~1/8" IPA in a small plastic container just larger than the PCB, to minimize the amount of IPA required - just enough to coat both sides of the PCB without immersing the components. The ultrasonic has a water bath, and the plastic container just floats on top. And I can reuse the IPA a few times before disposal - I just seal the container w/ an air tight top and store it for the next use.
I put ~1/8" IPA in a small plastic container just larger than the PCB, to minimize the amount of IPA required - just enough to coat both sides of the PCB without immersing the components. The ultrasonic has a water bath, and the plastic container just floats on top. And I can reuse the IPA a few times before disposal - I just seal the container w/ an air tight top and store it for the next use.
wintercept
Well-known member
Got a link to the ultrasonic cleaner you have? I am curious about this approach for new builds.
I usually use 99% IPA and a toothbrush over a normal paper towel. Soaks it right up.
darwin999
Well-known member
Unfortunately my ultrasonic is a discontinued model (BE1163) from Grizzly Tools, I bought 2 of them ~6 years ago for $12/ea on a final clearance sale. It's small and low powered (in pic below, that's a red 125B in front of it) - so while not usable for carburetor cleaning, it's great for small jobs like this. It's also great for cleaning small parts, tools, jewelry, etc.
If you do get an ultrasonic, fill the water bath fairly full (so the "wave action" isn't too aggressive) and then float the small container with the PCB and IPA on top, then turn the unit on for 5-10 seconds at a time and then inspect.
wintercept
Well-known member
Thanks! That makes me feel more confident about getting one for like $50. Do you seal the container you put the PCB in or is it more like a tray?
Erik S
Well-known member
I got one on ebay a few years ago. Something similar to the 6l version of this one.
I don't even remember what project I bought it for, but I've used it for all kinds of stuff and it's great. I think the last time I used it was to clean 57 grimy synthesizer knobs. There's been at least once that I wished I had bought the next size up. You can clean little stuff in a big one, but you can't clean big stuff in a little one.
Ultrasonic Cleaner with Timer Heating Machine Digital Sonic Cleaner SUS304 | eBay
Tank Material: Stainless Steel SUS304. Profound Cleaning Power: Featuring two industrial-grade ultrasonic transducers, this ultrasonic parts cleaner features 61W/79W/139W/183W/409W/512W/300W ultrasonic cleaning power.
www.ebay.com
darwin999
Well-known member
I've done both, actually, and both work fine. Covered is probably safer, may reduce amount of IPA that's vaporized (which I don't need to breathe). I only put enough IPA to reach both sides of the PCB (so maybe 1/8 to 3/16"), to avoid immersing the soldered components. And I put the PCB in the ultrasonic before soldering the pots and switches, so those don't get immersed either. Even though I use 99% IPA, as the IPA evaporates it cools the PCB. When the humidity is high, I often see a little water condensation afterwards - kind of a light fog can briefly appears on the surface. Most resistors, diodes, and caps are sealed - but pots and water seem like a bad combo. I don't want corrosion issues down the road. I'm likely being over-anal here, lol, so strike your own balance with it...
But in summary, it works very well - quick and very clean, no abrasion marks. And once you have the ultrasonic, odds are you'll use it for cleaning all sorts of things. Hard water deposits in the coffee maker line? Ultrasonic + vinegar clears it fast. My wife drops an earring and gets sticky road tar on it, ultrasonic and strong soap does the job in no time. Etc.
Good luck!
* Note added afterwards: Lo and behold, immersing pots in solvents may not be a good idea for an entirely different reason - look at https://forum.pedalpcb.com/threads/lost-friction-in-potentiometer-after-cleaning.25188/
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darwin999
Well-known member
View attachment IMG_1716_H.264.mov
Here's a few second video, showing an unsoldered PCB because that's just what was handy.
Water bath, and just a little IPA in the small plastic container (w/ the PCB) floating on the bath.
Here's a few second video, showing an unsoldered PCB because that's just what was handy.
Water bath, and just a little IPA in the small plastic container (w/ the PCB) floating on the bath.
wintercept
Well-known member
Ah I see now, I was trying to imagine how it would work with the lid closed but I see you leave it open and use a deep container for the IPA. Thanks for all the info!
darwin999
Well-known member
I see some folks in earlier posts are using heptane. Wow, that seems like overkill when IPA does the job fine, kind of like using grenades to kill mosquitos before a BBQ... Jokes aside, I used to be a materials physicist and all my labs had fume hoods to limit how much stuff we breathed in. But home use is very different. I urge you younger folks to limit your exposure to high-powered solvents, they can lead to all sorts of ugly health issues by the time you get old (like I am). Take care of yourselves!
Silver Blues
Well-known member
You might be surprised how much better the heptane/IPA mixture works than straight IPA, seeing as fluxes are mostly nonpolar stuff. I've found that straight IPA has a tendency to smear the flux around before removing it, where the heptane/IPA mixture clears it right out - may just be the solder I'm using, YMMV.
IPA is really not very toxic and heptane is only moderately toxic with significant exposure. Don't bathe in either one, but sage advice above: in the relatively small quantities electronics hobbyists will use them, and used with reasonable precautions (e.g. even a fume extractor with a carbon filter will do it), you shouldn't have any issues. Not like we're cleaning our boards with benzene
IPA is really not very toxic and heptane is only moderately toxic with significant exposure. Don't bathe in either one, but sage advice above: in the relatively small quantities electronics hobbyists will use them, and used with reasonable precautions (e.g. even a fume extractor with a carbon filter will do it), you shouldn't have any issues. Not like we're cleaning our boards with benzene
darwin999
Well-known member
@Silver Blues - I fully believe you that adding heptane works better, I also have seen that IPA + Q-tips leaves residue.
My concern is about the additional health risk you might be taking, which likely has not been fully identified and/or quantified.**
E.g., if you're using heptane indoors at home, you're likely well above the recommended exposure threshold of 500ppm.
Above I was only noting that IPA + light ultrasonic agitation also yields very clean results, without any added health risk.
And @Kanshin may be the safest of all with his Kester 331 w/ water soluble flux!
** It's hard to quantify the health risks to humans from various chemicals, because it's simply unethical to intentionally harm people. And studies on lab rats don't always accurately translate over to humans. Hence many risks are largely unknown, and will likely stay so.
My concern is about the additional health risk you might be taking, which likely has not been fully identified and/or quantified.**
E.g., if you're using heptane indoors at home, you're likely well above the recommended exposure threshold of 500ppm.
Above I was only noting that IPA + light ultrasonic agitation also yields very clean results, without any added health risk.
And @Kanshin may be the safest of all with his Kester 331 w/ water soluble flux!
** It's hard to quantify the health risks to humans from various chemicals, because it's simply unethical to intentionally harm people. And studies on lab rats don't always accurately translate over to humans. Hence many risks are largely unknown, and will likely stay so.
Silver Blues
Well-known member
That's fair. Goodness knows many homes don't have the greatest ventilation, unlike our labs. Though the existing toxicological data on heptane aren't very condemning, I do agree with you that limiting exposure is the best strategy.
EDIT I should clarify that I don't think that anything you said above is wrong and I don't mean to argue or distract from your very valid point. I only say this because people tend to be broadly afraid of "chemicals" when they don't need to be, so it helps to know what's truly dangerous and what poses less risk. Everything is chemicals - if it's made of matter, it's made of chemicals. I work with chemicals day in and day out so have pretty good hazard awareness, but sometimes it can be hard to find important information, too. SDSs tend to overblow the risks of relatively benign things and can vastly underrepresent the risks of heinously dangerous things (e.g. HF). n-Hexane is an insidious one, for example, as it gets metabolized to 2,5-hexanedione, which has rather significant neurotoxicity; this mechanism of toxicity is not of concern in n-pentane or n-heptane, for example (and if you ask me, both have better working properties, so that's a win-win). Heptane is also not that volatile, so unless you're using tons of it or really not being careful, I would say the risk is not extreme. As far as hardware-store chemicals go, for example, I'd be much more concerned about methanol than heptane, as this can cause a lot more damage with a lot less exposure. Not to say that you shouldn't be careful with it, you always should, but I don't think one needs to be afraid of it.
EDIT I should clarify that I don't think that anything you said above is wrong and I don't mean to argue or distract from your very valid point. I only say this because people tend to be broadly afraid of "chemicals" when they don't need to be, so it helps to know what's truly dangerous and what poses less risk. Everything is chemicals - if it's made of matter, it's made of chemicals. I work with chemicals day in and day out so have pretty good hazard awareness, but sometimes it can be hard to find important information, too. SDSs tend to overblow the risks of relatively benign things and can vastly underrepresent the risks of heinously dangerous things (e.g. HF). n-Hexane is an insidious one, for example, as it gets metabolized to 2,5-hexanedione, which has rather significant neurotoxicity; this mechanism of toxicity is not of concern in n-pentane or n-heptane, for example (and if you ask me, both have better working properties, so that's a win-win). Heptane is also not that volatile, so unless you're using tons of it or really not being careful, I would say the risk is not extreme. As far as hardware-store chemicals go, for example, I'd be much more concerned about methanol than heptane, as this can cause a lot more damage with a lot less exposure. Not to say that you shouldn't be careful with it, you always should, but I don't think one needs to be afraid of it.
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