Cleaning flux with Alcohol - Page 1
Forum section: electronics / beginners

author: Manafont
author_rank: Newbie
timestamp: May 11, 2022, 10:19:47 am
content: Hi, first of all thank you in advance for sparing your precious time to read and/or reply to my question.I am in the middle of changing some components on some of my old PC mouse & using some flux to help me do it.After researching for a bit while I heard that I can use Isopropyl Alcohol to clean the flux leftover/residue from the PCB.Since I'm fairly new to repairing, I have a few question regarding this.1. How many percent of Isopropyl Alcohol solution is good to use ? 50%? 70%? 99%?2. There's a capacitor on my mouse PCB, is it safe to clean the flux residue using Alcohol ? Like, it won't short the capacitor? One is elco type, one is smd type.

author: Gyro
author_rank: Super Contributor
timestamp: May 11, 2022, 11:35:49 am
content: Welcome to the forum.The highrt the concentration of IPA the better, the lower concentrations (rubbing alcohol?) tend to contain oils and other stuff, not just water. Electronics distributors normally stock 99%, you should also be able to find it on Amazon.IPA is safe on most components, including Elcos, the only ones that don't like it are Polystyrene ones, but you're very unlikely to come across one of those.One important thing to remember - IPA puts the flux into solution, you can't just apply it and let it dry. Mop it off with a tissue and re-apply if still sticky (and until the tissue no longer has brown stains). The other specific thing it to prevent the flux+IPA solution getting into the optical sensors, pivots etc. in the mouse and contaminating them with dried flux.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 11, 2022, 11:50:53 am
content: For a simple digital circuit removing the flux may not be needed. It depends on the flux type: some is corrosive and must be cleaned off, others say no clean and is OK to stay on a circuit that is not super critical to leakage.Just for cleaning flux there is no real need for high purity IPA. The main difference between the 90 % and 99% version is just water and the little extra water may even help. Rubbing alcohol for skin cleaning may contain other parts, but the more cheap versions for workshop use should mainly have water and maybe other alcohols as contamination, that don't really matter. The problem is more that the flux may contain more than just rosin, but also things like grease that does not dissolve in IPA. So while IPA dissolved rosin quite well it can leave behind a residue from the flux.

author: Manafont
author_rank: Newbie
timestamp: May 11, 2022, 11:56:51 am
content: Quote from: Gyro on May 11, 2022, 11:35:49 amThank you for the reply, I'll get atleast 90% then.Thanks also for the warning about sensors.Quote from: Kleinstein on May 11, 2022, 11:50:53 amI don't clean flux often when repairing other stuffs, but since this mouse is the one I'm really comfortable with, and it's production discontinuedI'm just trying to make it last as long as I can, I guess.Finding the same model, brand new in box one costs like up to $200 due to the rarity.But thank you for the lesson.

author: SmallCog
author_rank: Frequent Contributor
timestamp: May 11, 2022, 11:29:01 pm
content: I use these to do the mopping upWork well and don't leave bits of tissue behindThe exact same product may not be available in your part of the world but I'd recommend finding something similarThis particular one varies wildly in price, worth shopping aroundhttps://www.winc.com.au/main-catalogue-productdetail/kimtech-34120a-science-kimwipe-delicate-task-wipers-21-x-11cm-280-sheets/18813156

author: tooki
author_rank: Super Contributor
timestamp: May 12, 2022, 12:39:13 am
content: As always, I recommend skipping IPA and instead buying proper flux cleaner. Many modern fluxes contain ingredients which simply do not dissolve in IPA, leaving chalky white residues. Flux cleaners remove these, but are also just plain more effective than IPA, such that even though it costs more, you need less of it to accomplish cleaning.

author: Manafont
author_rank: Newbie
timestamp: May 21, 2022, 12:34:50 am
content: Quote from: SmallCog on May 11, 2022, 11:29:01 pmI use that too for cleaning my PC parts actually, since it's available in my country for like $2, thanks for recommending it !Bought it out of curiosity back then, now I know I made the right judgment.Since, in my country, these kinda things isn't that popular to be used when repairing stuffs.Quote from: tooki on May 12, 2022, 12:39:13 amI do want to, but in my country it's hard to find a good one.And when there are someone selling it (a well known brand that isn't fake), the price isn't even funny.The cheap available ones usually DIY-ish made from i don't know what, and they never say what they made it from.https://www.tokopedia.com/indraculla/flux-cleaner-oil-cleaner-grease-cleaner-mechanic-530-cleaning-solvent?extParam=ivf%3Dfalse%26src%3DsearchThat's the closest one to well known branded one that says "cleans flux", but ... yeah... too many fake "Mechanic" brand in my country.

author: MikeK
author_rank: Super Contributor
timestamp: May 21, 2022, 01:45:08 am
content: An old toothbrush helps with cleaning. Dip it in the IPA, scrub, repeat, rinse, wipe.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 21, 2022, 09:24:53 am
content: Quote from: Manafont on May 21, 2022, 12:34:50 amZEP cleaning products are sold in Indonesia. Distributor is in Singapore and various ads for ubuy on Google (https://zep2.zep.com/contact-us). Zep Heavy Duty Floor Stripper has effectively the same active ingredients as some of the Kester products, e.g., 5768. Like the Kester product, it is water based. I have used it at 1:3 dilution for a two minutes in an ultrasonic cleaner and board was as clean as I have ever seen. Rinse with distilled/deionized water for an additional 2 minutes. It can also be used neat with a toothbrush, but must be rinsed.

author: Manafont
author_rank: Newbie
timestamp: May 21, 2022, 03:24:27 pm
content: Quote from: jpanhalt on May 21, 2022, 09:24:53 amNever heard of that brand in my entire life. Never seen it in big hardware store, not even in Indonesia's Ace Hardware.Buying from Ubuy is basically importing it, I don't really mind ordering stuffs from outside my country, as long it's a good ratio of price:safety:troublebut it gets really troublesome when importing fluid product as an individual without special company permit, and especially so if it's heavy duty cleaning product.[See Image Attached Below]That's around $71, add around 20-25% total import fee & tax = around $89IF, and it's a big IF, they don't confiscate it under "dangerous items", if they do, there goes the $71.A hint of how stupid the customs here : A friend in US sent me a used motherboard once, they held it for nearly 2 months thinking it's dangerous. Took awhile lobbying, explaining, and teaching.I'd probably okay with it if I am some sort of professional repair shop, but yeah... not gonna go that much trouble again for simply repairing a single desktop mouse.But I thank you for the recommendation, I will add the brand name to my "Brand & Product to keep looking out for" listJust in case it suddenly shows up somewhere in the local market.Quote from: MikeK on May 21, 2022, 01:45:08 amThank you for the info !, I always wondered whether it's safe to use it to clean a pcb.Afraid I'd destroy the mask or something.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 21, 2022, 03:50:32 pm
content: I don't sell ZEP. My point is that if you compare the SDS/MSDS for various products you may find something virtually identical that is produced locally. Heavy duty/commercial floor strippers is where to start. The polymers/polishes/waxes are not unlike flux residues in terms of solubilities. You are looking for something that has one or more Cellosolves (alkoxy alcohols) in it. 2-butoxy ethanol is a common one. Plus something to make it alkaline. Ethanolamine is used commonly. Kester recommends a cleaner that can "saponify." That is where keeping it alkaline fits in.

author: Manafont
author_rank: Newbie
timestamp: May 21, 2022, 11:49:50 pm
content: Quote from: jpanhalt on May 21, 2022, 03:50:32 pmWell, I'll try to look at hardware store near me.Thanks for the lesson & info, I really appreciate it.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 22, 2022, 12:04:41 am
content: I'd be happy to take a look at any MSDS/SDS that you find confusing.John

author: tooki
author_rank: Super Contributor
timestamp: May 22, 2022, 06:00:55 pm
content: Quote from: Manafont on May 21, 2022, 12:34:50 amI’m sure real flux remover is available from the right sources.FWIW, I’m talking about solvent-based flux cleaners, not the alkaline water-based cleaners jpanhalt is referring to. Look at the MSDSs: solvent based flux removers are typically a blend of alcohols and hydrocarbon solvents, sometimes also acetone (which makes it more effective, but attacks more plastics). Some also use citrus terpenes. If you’re thinking that this sounds a lot like brake cleaner, you’re not wrong.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 22, 2022, 06:51:35 pm
content: My training in chemistry was in the 1960's. Our labs smelled like real organic chemistry labs were supposed to smell. They were named after Ira Remsen who discovered saccharin, not just by being brilliant, but because he tasted and smelled stuff. We still smelled and occasionally tasted stuff (egads!). It is important to note that Remsen did not have the analytical instruments we had even then. Given that, it took a lot convincing for me to go to water-based chemistry.For cleaning all of the gunk off a freshly prepared, reflowed PCB, I was amazed at how well the water chemistries surpassed absolute ethanol and ethanol+acetone, which were my go to's for cleaning. I still keep two bottles around for spot cleaning, but they require physical scrubbing to remove "white residue."* With the water-based saponifier cleaner, there was not speck of white residue even between the pins of a TQFP chip. The second attachment is a picture of a TSSOP (0.65mm pitch device) on the same board with a better camera. If you want to spend a little more, buy the Kester 5768 water-based cleaner or similar. If you are a cheapskate, go with a similar floor stripper.*The reason I tried the water based cleaner was that the ethanol-acetone cleaner left white residue.

author: IanB
author_rank: Super Contributor
timestamp: May 22, 2022, 06:55:38 pm
content: Presumably with water based cleaners you need to rinse with DI water afterwards, and then dry thoroughly?

author: jpanhalt
author_rank: Super Contributor
timestamp: May 22, 2022, 07:35:51 pm
content: Of course there is a mandatory rinse. As for drying? The boards were so hydrophobic (Oshpark) that very little was needed. Basically, the water just didn't stick. I used clean air to blow out from under parts. I saw negligible mist -- some of which may have been from my air.As for parts? I did not install any parts that were not liquid proof. In that design, those were the 6 button switches and the Omega TC socket. In the future, I may be more daring.This experience with hydrophobicity may not apply to boards without solder resist. Although, I have no reservations using water-based flux removers for such DIY boards.

author: free_electron
author_rank: Super Contributor
timestamp: May 23, 2022, 12:52:32 am
content: careful with water soluble fluxes. you need to get every last bit of that stuff off the board. That white residue will absorb moisture from the air , becomes conductive in the 100 k ohm range between 0.5mm pins and will eat the copper ! (electromigration , go above 10 volt between pins and you will get dendrite formation after a couple of hours.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 23, 2022, 06:02:33 am
content: I used Kester 63/37 T3 solder paste with EP256 flux. While it is "no clean," it is not considered water soluble.

author: tepalia02
author_rank: Regular Contributor
timestamp: June 17, 2022, 12:03:29 pm
content: Using isopropyl alcohol or acetone is the easiest way to perform this task.

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2022, 12:25:47 pm
content: Be very careful of Acetone. It is much more likely to damage plastic components, even if just taking off their markings.

author: tooki
author_rank: Super Contributor
timestamp: June 17, 2022, 09:14:54 pm
content: Quote from: tepalia02 on June 17, 2022, 12:03:29 pmNo, it is not. As I’ve said repeatedly, many fluxes DO NOT fully dissolve in alcohol, resulting in white residue later on. Commercial flux removers not only clean more thoroughly, they also work faster (especially on burnt flux), and you also need less of it.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 17, 2022, 09:46:48 pm
content: I occasionally clean flux of a PCB with isopropanol but it does leave a residue quite easily.To mitigate this I've adopted the following workflow:1. Use isopropanol and a brush to loosen most of the flux.2. When there are thicker pieces of flux residue, I treat them with a screwdriver to break them loose.3. Wash the with soapy water (and also a brush).4. Use more isopropanol to wash away most of the water.5. Tie a string to it (approx 80cm) and swing it around. Both the centrifugal force and the wind dry the PCB quickly.6. Optionally, dry it for a few hours in a warm place or let it dry further overnight.

author: janoc
author_rank: Super Contributor
timestamp: June 17, 2022, 10:22:12 pm
content: Quote from: tooki on June 17, 2022, 09:14:54 pmCommercial flux cleaners are often mostly IPA, e.g. Kontakt-LR from Kontakt Chemie that I have here - contains IPA + 15-30% of aliphatic hydrocarbons (possibly just the propane gas in the spray can). The white residue is the flux after the alcohol has evaporated because you didn't wash/wipe it off completely, not because the flux didn't dissolve.Also even normal alcohol (ethanol) will work for flux cleaning, especially for rosin based fluxes.The key is to use enough of it and make sure the dissolved flux is actually washed/wiped off and not left to dry on the board.

author: pcprogrammer
author_rank: Super Contributor
timestamp: June 18, 2022, 05:27:29 am
content: Do they still sell this in Europe. A while back I searched the net, but did not find a supplier.I got it very long ago on a electronics fair and it works very well.Edit: I found this:https://www.digikey.fr/en/products/detail/microcare-corporation/MCC-P02/13534650but wonder if it is still good for flux.

author: tooki
author_rank: Super Contributor
timestamp: June 18, 2022, 11:27:21 am
content: Quote from: janoc on June 17, 2022, 10:22:12 pmWhile I agree that proper wiping is essential, it’s not as simple as you say.The white residues, which are most common with no-clean fluxes, are metal salts that are insoluble in alcohol. It’s not because of poor cleaning technique.Yes, commercial flux removers contain IPA, but it’s thecombinationof solvents that makes them work so much better. On the one hand, they can dissolve the constituents that aren’t soluble in alcohol alone. Second, these combinations dissolve everythingfasterthan IPA alone.Kontakt LR is actually one cleaner I use. The hydrocarbons are not the propellant. (It uses carbon dioxide as the propellant.)Yes, IPA and ethanol work fine for most old-school rosin fluxes, but they’re still not the best thing out there.

author: janoc
author_rank: Super Contributor
timestamp: June 18, 2022, 02:31:39 pm
content: Quote from: Doctorandus_P on June 17, 2022, 09:46:48 pmI think I wouldn't want to be near during one of your flux cleaning sessions! Drying the board with a paper towel and a small fan will do the same service, without the risk of anything getting hit/destroyed.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 18, 2022, 07:11:15 pm
content: For those who are safety conscience or worried about breathing a little alcohol vapor, you could put the PCB in a dish towel and fling it around your head really fast.My serious response is "it depends." If there is a large amount of soldering or re-soldering, I use a water-based cleaner similar to the Kester ones (i.e., a cellosolve + ethanol amine + water) in an ultrasonic cleaner and rinse with DI water. The resist is so hydrophobic, the boards come out almost dry. A quick blast with compressed air finishes the job.For just a few joints, I use ethanol (absolute) and a brush. A quick flick of the wrist gets rid of most of the liquid. A second or third wash removes everything, followed by compressed air for a final drying. You want to blow residual off, not evaporate it in situ.

author: tepalia02
author_rank: Regular Contributor
timestamp: June 19, 2022, 02:23:44 pm
content: Thanks a lot to everyone who replied to my previous comment. This is what I appreciate about this forum. I was going through this blog earlier.https://pcbtracks.com/how-to-manufacture-pcb-at-home/It is regarding how to make a PCB at home. It has a few tips about cleaning. It does not mention alcohol. It only mentions water and using a hose to clear the PCB. Is it a good idea dear friend? Am I missing something?

author: janoc
author_rank: Super Contributor
timestamp: June 19, 2022, 07:25:02 pm
content: Quote from: tepalia02 on June 19, 2022, 02:23:44 pmThat website offers some pretty dubious advice, such as the etching with the hydrochloric ("muriatic") acid and peroxide combo. Which is about the worst etchant available. Along with this gobbledygook:"Ferric chloride is normally used in the making of the acid. But, in our process, we shall be using another method because ferric acid is not easily found and if the ferric acid is available the purchase procedure is very tiring due to the documentation that is required."The hose comment he has there is not about flux cleaning but about washing the etchant off after the etching. Terrible idea to do it like that because that guarantees splashing the acid around and the toxic waste getting in the soil and sewers.As usual, that something is posted on the internet doesn't mean that it is correct, works or a good idea.Flux cleaning discussed here is something different - that's what you need to do after soldering, to clean up the flux residue. Spraying a board with a hose with no cleaning agent (alcohol, flux cleaner, etc.) will only make the board wet but not really clean the flux residues properly.

author: tepalia02
author_rank: Regular Contributor
timestamp: June 20, 2022, 08:22:19 am
content: Quote from: janoc on June 19, 2022, 07:25:02 pm