Cheap Alternative Solvents For PCB Cleaning

If you’re in the habit of using isopropyl alcohol to clean your PCBs after soldering, you probably have a nice big jug of the stuff stashed away. If you don’t, you’re probably out of luck, since the COVID-19 pandemic has pretty much cleared IPA out of the retail market. But don’t fret: depending on where you live, alternative PCB cleaning solutions may be as close as your nearest auto parts store.

[Steven]’s search for a cheaper and perhaps more readily available substitute for his usual dedicated flux cleaner lead him to try automotive brake cleaner on a few test boards. He suspected that they might contain acetone, which is prone to yield unfortunate results with solder resist and silkscreen on PCBs, so some tests were in order. The brand he tried was Normfest Bremsenreiniger MC-1, a German brand that according to its Safety Data Sheet contains only hydrocarbons like alkanes, butane, and propane. It did a fine job cleaning all but the crustiest rosin flux without collateral damage.

In the video below, [Steven] goes through a few more brands with similar results, and we were encouraged enough by his results to check brake cleaners made for the US market. Alas, almost all of the cheap and readily available aerosols have acetone as the principle ingredient, mixed in with methanol, ethanol, and assorted ingredients that together will probably make for a bad day. About the only US-sold brand without acetone that we could find was Keller-Heartt, which lists only naptha and ethanol on its SDS. There may be others, but make sure you test whatever you find.

Aerosol solvents aren’t the only way to clean a PCB, of course. Ultrasonic cleaners do a great job, and as [Steven] discovered, they’re generally safe for most components.

82 thoughts on “Cheap Alternative Solvents For PCB Cleaning

      1. off-label use again. if you oftener clean pcb’s the first sentence should NOT be a problem. you can arrive on target with a bicycle or a ferrari or a big limo. the question is HOW will you arrive and WHEN. ;) when not in high demand times, isopropanol can be considered “cheap junk”. gambling with something NOT destined at cleaning PCBs might end in a mess. or even worse.

    1. I tried the following things:
      – Acetone: works great but sometimes hard to source and dissolves the silkscreen, but it’s a must-have for toner-transfer PCBs
      – IPA: can be hard to source
      – Brake cleaner: I’ve had decent results with the cheap ones that are mostly refined gasoline, works similar to spirits but doesn’t leave any residue. It can be sourced in any car parts store. Some brake-cleaners sold as “non-flammable” use chlorinated solvents, I have no experience with that (it’s not sold in Europe)
      – Burning spirits: contains mostly ethanol and methanol (usually >70%-20% mix + “others”), easy to source in grocery stores and sometimes sold as “barbecue starter”. I’ve had good results, but it sometimes leave a shiny residue that makes varnish or paint hard to stick

      1. Yes, the fondue fuel, liquid chafing stove fuel, or warming dish fuel is very hit and miss. I came across some that was listed as 99% methanol on the MSDS (needed methanol for something) and that brand went out of stock, then bought another brand that looked the exact same, and that stuff was not 99% methanol, at a guess it was 60% ethanol 20% methanol 20% water. Probably brands carried by major hardware stores you’ll be able to find out exactly what they have, but the rotating no-name or minor brand stuff in supermarkets and discount stores is really hard to nail down. Besides, it’ also has dye in it, which may make all your stuff blue.

        1. The funny thing is that the content of those things is not very clear, and sometimes regulated (in order to avoid “moonshine” and intoxications), but the regulations change from country to country.
          The variety of solvents you can find in hardware stores can also change a lot depending on the countries. But sometimes the hardware stores just label usual solvents with a fancy name, mix it with some stuff to give it a nice color/smell and sell it for 10 times the price :/.

      2. Paint aisle has denatured alcohol (ethanol with a bitter taste agent to prevent consumption) should work fine without risk to silk screens, may have to dilute it with water. That’s the easiest protic solvent to get right now, besides maybe good ol cheap vodka.

        As far as aprotic solvents:

        Mineral spirits might also be worth a try, kinder gentler cousin to acetone.

        Maybe xylene, but it can be pretty harsh, test a corner first.

        Coleman fuel or kerosene is a pretty good solvent too.

        1. Be freaking careful with denatured alcohol. The “stuff” used to denature it isn’t regulated, and while some combinations are fine, I know at least one case where using it corroded the exposed metal extremely bad, to the point where the board stopped functioning. You’re much better off finding a cleaner that has a known, constant formulation.

          1. Yeah I’ve run into that but it seems to be flux residue. Some flux especially some of the water based ones are super corrosive worse than acid flux decades ago.

            The pros use weird detergents and hot water in commercial (sometimes residential) dishwashing machines, so I rinse afterwards with steamy hot water which dries very quickly.

            I don’t like the feeling of dried flux on skin and the alcohol is very drying to skin so cheap nitrile gloves work well enough for protection. Or maybe they’re latex. Anyway they’re solvent proof “long enough”.

            Denatured ethanol burns really well so I do this in a metal utility basement sink with the water running. Unlike petroleum solvents and greases, ethanol mixes perfectly with water so if I manage to ever set my board and hands on fire, there is a stream of cold water about two inches away.

            My experience is ethanol needs a good soak for about three minutes in a sealed tupperware and then some toothbrush scrubbing and a water rinse, repeat about twice for perfection. Ethanol can be reused many times for rough cleaning but the final clean should be with fresh stuff so figure two tupperwares one with lots of gross old solvent and one that only touches clean new solvent.

            I’ve been accused of running boards thru a wave soldering machine before; yet I do it all by hand. Quality level CAN be very high with this cleaning technique.

          2. The corrosion I’ve run into with denatured alcohol is definitely *not* flux residue. These were previously cleaned boards that were later reworked and cleaned again, and the areas that were cleaned with denatured alcohol corroded heavily. This was then confirmed by cleaning bare boards with the same alcohol, and the same corrosion happened there.

            Again, the problem is just that “denatured alcohol” isn’t some definite formulation, there’s a ton of variation in what’s allowed in it, and some of them are very bad for PCBs. If you’ve got a manufacturer/supplier that you know is safe and have tested out, that’s fine, although with each new container I’d test it again, as the manufacturer could easily change the formulation at any time. But grabbing “denatured alcohol” from Random Paint Store can be *very* dangerous to use for cleaning PCBs.

        2. Denaturing agents aren’t taste agents; they are poisons. The usual denaturing agent for ethanol is methanol, which will make you blind even in small quantities if it doesn’t outright kill you. The reason taste agents are also added is that you can’t detect methanol by taste, so they are added so that you won’t accidentally drink the toxic moonshine.

          1. I was told a long time back, that the purple stuff they put in UK “meths” which is an ethanol/methanol blend, is actually an emetic, to make you puke if you drink it.

          2. No. The traditional denaturing agent is Bitrex, an incredibly bitter compound that leaves a bad taste even in the tiniest amounts. This is the best kind of denatured alcohol to clean stuff with – no visible residues.
            Then there are the sloppy ones, which petroleum distillation products – this crap leaves oily residues. It’s good only for burning.
            Methanol is indistinguishable from ethanol by taste or smell, which is why it would make for a very bad denarurant.

      3. Wow. I have not used those kinds of aggressive solvents since the 1970’s! Not since I visited a PCB and circuit stuffing house and saw them running finished populated boards through dishwashers. You can always add alcohol to soap and water if you need it.

    2. Denatured alc (methanol and ethanol) from the big box store works, been using it for decades. Still working on the gallon I bought years ago . Don’t know if it’s been wiped from the shelves as well though.

      1. Methanol can be absorbed through the skin, so anybody washing their hands with denatured alcohol is playing with fire. A lot of commercial denatured alcohols have a surprisingly high percentage of methanol, not just a few percent as you might expect.

          1. Not poisons. Embitterment agents and nausea… aka you didn’t pay the tax to drink this, SO we will cause you mild suffering to teach you a lesson.

            Don’t forget, people and animals will do anything for a buzz or high. (Documentary on birds and other animals getting drunk from fermented fruit is great.)

            And people huff gasoline/petrol fumes (even drink it) .

            In normal times Isopropyl was cheaper this is no longer the normal times.

        1. Wood Alcohol and Antifreeze poisoning is Cured by Grain Alcohol.

          In fact it’s standard medical treatment unless you are some strange religion.

          A which point you shouldn’t even be working with cleaning electronics.

      2. If you’ve got a specific store or brand that you use, share that: denatured alcohol isn’t a controlled formulation by any stretch of the imagination. In fact, according to Wikipedia, that’s intentional, to prevent easy distillation. Denaturants vary wildly, with some of them being Very Bad. Denatured alcohol doesn’t really describe a product, it describes the result of a process, and you can *definitely* denature alcohol with additives that would destroy a PCB.

  1. Not sure what I do wrong, but cleaning with IPA always leaves a white residue.

    The last couple of years I have used a 3 stage approach: quick clean with Carburettor Cleaner, then a quick scrub with Clean Green (Some water based cleaner found here in ZA), and finally a rinse with Distilled Water.

    Obviously this isn’t a process for production boards, but for my client-prototypes it works wonders.

    1. Hmmm – I found that methylated spirits (aka methanol, sold for cheap here mixed with a bitter purple dye so kids don’t drink it) works great. Seems to dissolve flux as well. ‘n Boer maak ‘n plan.

      Never thought of carb cleaner – will try it next time!

      Greets from Krugersdorp, ZA

      1. The purple stuff is a dye. Pyridine, added to UK methylated spirits to make it undrinkable. Pyridine is harmful if inhaled, swallowed or absorbed through the skin. The smell of it would preventing you getting that far.

  2. Im an autospark, I often repair ECU’s to the component level, or at the very least get them to live long enough to extract data/coding. Owning a garage I have brake clean by the gallon, I’ve never used isopropyl alcohol to clean a circuit board lol

    That said, be careful, brake clean comes in many flavors, check the msds. the hydrogenated naptha stuff is what you want, usually labled, “non chlorinated”. its a superb solvent to have around.

      1. Never bought it, I used 99% IPA. When we get it back… get one clean dry gatorade bottle, put a pinkie worth of IPA in the bottom, jam MAF in the top (After removal from intake housing) shake like mad. Well, gatorade bottle fits Ford MAFs.

  3. I just use isopropyl alcohol and a brush. There is a cleaning fluid for PCBs, which is basically isopropyl alcohol and some soap. A friend of mine used denatured alcohol because it’s cheaper…

  4. On PCBs, I use Kester 33 solder which uses water soluble flux core (lanlolin-based) and it cleans up with hot water and a little bristle brush. No need for any solvents at all. I only use rosin core on non-PCB assemblies (wire harnesses, connectors, RF cans) which are not cleaned. Bear in mind this is RMA (rosin, mildly activated) which does not aggressively corrode as badly as some other rosin-cored solders. If I have to solder wires directly to PCBs, I’ll use RMA solder, but when it has cooled for at least an hour or so, I’ll come back with a dental pick and scrape away any visible rosin and brush away any visible residue. No solvent required. Been doing it like this since 1971, no problems and no brain cells lost from solvent fumes.

  5. I used to use fluxclene and isopropyl alcohol, but this seemed to always result in some white residue. For the past couple of years however, in a production setting I’ve moves to using Qualitek Everkleen 1005 https://www.somersetsolders.com/pcb-flux-cleaner-for-ultrasonic-and-in-line-systems/p317. This sapnifies the flux, making it water soluble. A 3% heated to 40-50°C in the ultrasonic cleaner, or just scrubbed with a toothbrush does the job very nicely. Rinse well with deionised water using a wash bottle and then dry in the oven at 60°C. Granted this was in a small production environment and so we have access to things not normally found at home, but a home oven would suffice (so long as it is clean!).

  6. Sure, there’s not a drop of isopropyl alcohol in the pharmacy or grocery store, but my auto parts shore has a shelf full. It is labeled dry gas or gas line antifreeze. Check the label, available in 99% and 99.9%

    1. Iso-heet is one brand. However, around here it’s usually a couple of bucks for a hundred ml or so. Some places sell it by the case, which is a bit cheaper. It could also be labelled octane booster, in which case it’s $10 for a couple of hundred ml. Okay I guess if you absolutely must have IPA for something. But in the past I just used drug store 99% for these purposes due to being $2 for 500ml

    2. I picked up a couple of bottles of iso-heet from Home Depot after running out of IPA.

      I don’t think it’s pure IPA. MSDS says there’s additives in it. I found it makes things sticky after it dried, it smells a bit different, and is amber in color. IPA is clear and doesn’t have these properties.

      1. I’ve seen two MSDS for it, one said 99% IPA and 1% inert proprietary ingredient, which I think was a fancy way of saying the remaining water. The other was 87% and other ingredients, which might be some kind of STP/Redex type stuff, which is oily/mineral-spiritsy/detergenty

  7. I’ve had great results with Detergent 8. It’s a cleaner concentrate that is not solvent-based, you dilute it with water and wash your boards with it. Works great with a brush or in a heated ultrasonic cleaner. It leaves no residue, doesn’t smell, and isn’t a huge health risk.

    The only downside is the gallon jug is expensive–you can request a small sample bottle that will probably last you a lifetime though!

  8. If you can get your hands on weaksauce 50% Isopropyl, which theoretically nobody wants, an interesting fact. IPA and salt water don’t mix, the IPA will float on top of brine. Ergo, to make 50% stronger, stick a couple of spoons of salt in the bottle and shake it hard, then decant the now stronger IPA from the salt water at the bottom. If you’re doing anything that’s likely to be sensitive to the salt though be aware of the possibility that a small amount may remain in the IPA.

    1. I always forget the obvious to me stuff… let it stand for a while after shaking.

      Also filtration will get out any undissolved salt dust that might be still suspended in the IPA.

      1. Since he mentioned it worked due to salt ions being more polar than the isopropyl, I’m wondering if another more polar salt would do the same to ethyl. However, most of them would make it poisonous to drink. CuSO4 for example… might be fine for hand cleaner though… Igor, bring me the “root clear” and some cheap wine!

  9. I have a problem with the expression “like alkanes, butane and propane” because butane and propane are alkanes ! but that maybe just me. And I’d rather write naphtha like that, sounds better too… :rollseyes:

  10. I used some Walmart Carb Cleaner to clean off the adhesive and prep prior to toner transfer on some LED TV LED pcb’s I re-used for another project. Still have more than half of the 99% IPA jug stashed… though have tapped into for my homebrew essential oil bug spray unfortunately. Article makes me wonder about refrigerants also as I’ve read before they’re, or at least one of them specifically was popularly, used for cleaning electronics.

    1. Yes, a decade or so back I got some brake cleaner cheap and as I used the last of it, I started to get the suspicion it was some sort of refrigerant. It had chlorinated hydrocarbons in. Filed it mentally to look into next time I was messing with heat pipes or something, but I’ve never seen that brand again. Possibly it was a sell off as it was phased out.

      1. Just looked on my shelf and have an engine degreaser that has a “detergent” and looks similar to the chlorinated brake cleaner ingredients. I’ll have to ask around next time I’m around the parts and auto network to see if they used anything flourinated. Get’s me thinking about some of the fuel additives might be useful also for cleaning, after thinking about the newer flourinated polymer lined gas lines.

    1. That’s usually heavy on the ether or chloroform type stuff.

      There was a “dry cleaner” type of home stain removing solvent on the market, brand name I remember was “thawpit” which was also made of that sort of stuff, maybe carbon tetrachloride too.

  11. One of the main types of brake cleaner, like CRC Brakleen (red can) is tetrachloroethylene, which is also the ingredient in some electrical cleaners. It’s usually in every auto parts store. (might not be in California anymore). Iso-Heet fuel line water remover or store brand in the red bottle is 99+% IPA

  12. Coming from a manufacturing environment, you need to check the component datasheets to see what solvents they are compatible with and what if any measures you need to observe. In the old days a lot of things got hand soldered on after the boards were ran through the wave. Some parts would go through but have seals put over them to keep the defluxing solvents out. Using random solvents may work to remove the flux, but they may also get into parts and cause damage or even attack the plastic some parts are constructed out of and not cause problems for a long time until say, a miniature toggle switch body becomes brittle and cracks because it was exposed to an incompatible solvent. Surface mount parts also lack a lot of the “body” protection that larger thru hole parts had. Again, the issues may not pop up right away, but it would not surprise me if surface mount caps, years down the road had issues stemming from absorbing the wrong solvent.

  13. Be careful when using ultrasonic cleaners (often used to clean jewelery). They can permanently damage crystals & crystal oscillators. Back in the day, I used to work for Spectrum Technology (later sold to Dale), which made both crystal oscillators & TCXOs. Our Production department was forbidden to use ultrasonic cleaners after the crystal was installed.

    IPA is probably the best solvent, as it won’t destroy the PCB, won’t cause health issues (unless you stupidly try to drink it), and won’t harm the environment. Prolonged exposure to gasoline-based solvents (even kerosene) can cause the PCB to de-laminate. We used to use acetone on military & satellite projects, and it works well on almost all fluxes (even acid-core flux), as others have said, acetone can dissolve some silkscreens, the glue used on labels, and some plastics. I dare you: try to fill a styrofoam cup with acetone, and see what happens! I’ve also worked with 1,1,1-trichloroethane & freon-113 for cleaning flux. They worked very well, but are now considered to be either toxic or bad for the environment.

    Once the virus crisis passes, IPA will be available again. Just be patient. I have roughly 2 quarts of IPA remaining in my home-loan, but I’m saving it to make hand sanitizer (3:1 ratio of alcohol to Aloe vera gel).

  14. I’ll stick with my 3M Novec. Quite expensive, but you only need a tiny bit, penetrates between the tiniest SMD legs, doesn’t contaminate your workspace and evaporates fast enough to power up the board in about a minute. It’s the closest thing to Freon TF that used to be used for production board cleaning back before environmental concerns.

  15. What’s the problem? Use acetone, acetone-based cleaners (if you are a male, ask your girlfriend for nail polish remover, if you are a girl, you probably already have it) or just simple gas or diesel, whatever your car like. IPA is definitely not the best cleaner for PCB at all. IPA is slow and you need a lot.

    1. There are non-acetone hail polish removers these days… Not sure if they are as effective.
      The problem with acetone is that it can be a bit aggressive on some component packaging .e.g. those PVC heat shrink labels on electrolytic caps.

        1. The less than sign messes with the text.

          45-50 % low vapour pressure aliphatic hydrocarbon (kerosene)
          less than 35% petroleum base oil (non hazardous heavy paraffins)
          less than 25% aliphatic hydrocarbons (same CAS number as the first item, but flammable)
          2-3% carbon dioxide (propellant)

          You might not want the petroleum base oil as that would stick around and may attack rubber e.g. electrolytic cap rubber seal. The kerosene and the lighter hydrocarbons would evaporate in tens of minutes, so you should be okay.

          >Petroleum-based hydraulic oils and greases contain a variety of long chain hydrocarbon components. These chemicals have extremely adverse effects on EPDM rubber seals and can actually dissolve the material.

  16. Citrus Limonene based solvent cleaners are quite effective followed by hot water wash off and slow oven dry. There are usually Limonene based general cleaners which are readily available at supermarket & hardware stores. We bought in bulk for a small manufacturing firm and so had a good grip on any issues with additives but for at home it doesn’t cost much to buy a few brands and test for effects on plastics and such.

  17. When IBM CE’s stopped using the old tape drive cleaner for everything (MEK I think) they used a LOT of Limonene. Another non HAZMAT solution might be Everclear. 95% ethanol to the rescue.

    1. Reading these replies here… especially with people saying washing machines, dish washers and deterrents, water, salt, etc, etc and random nonsense they have sitting on there shelves.

      Is driving me to drink. Lemme be honest THIS is actually the best post and response.

      Everclear and Golden Grain. 95% or 190 proof are best cleaners.

      Also, it is important to note for the OSHA crazed and scared that the cure to “Methanol” aka Wood Alcohol AND Glycol (aka “Green Anti-freeze”) …

      Medically! Is Ethanol aka Grain Alcohol.

      If 90% Isopropyl is unavailable use Triple Distilled Moonshine of 94% or better.

      If you use tap water and soap you will destroy ROHS based soldering tech.

      -=-=-=-=-=–=-=–=-

      Rest in pieces my Corsair Keyboard with mechanical switches, LEDs and micro-controller. (I even used Dawn non-concentrate and distilled water. )

  18. Folks. Please could I urge people to add their country or region to these posts. There are huge differences between the EU and US in the make up of these solvents.

    As an example, here in the UK “methylated spirits” is the purple colour solvent sold in the paint isle.
    You’d think from the name it would have methanol in it right ?
    Well, not any more.
    The EU has declared that methanol is a big NO NO for any domestic sales. As mentioned above it causes blindness and nerve damage.

    While the purple stuff retains the name, it hasn’t actually contained methanol for more than a decade now ( at least over here ) it’s now most likely to be 98% ethanol with colouring and bittering agents.

    I strongly suspect though this ingredient list varies hugely from region to region.

    Please, if you can, post your geographic region with these tips.

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