Cleaning flux with Alcohol

[Manafont]

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.

[Gyro]

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.

[Kleinstein]

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.

[Manafont]

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.

Thank you for the reply, I'll get atleast 90% then.
Thanks also for the warning about sensors.

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.

I 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 discontinued
I'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.

[SmallCog]

I use these to do the mopping up

Work well and don't leave bits of tissue behind

The exact same product may not be available in your part of the world but I'd recommend finding something similar

This particular one varies wildly in price, worth shopping around

https://www.winc.com.au/main-catalogue-productdetail/kimtech-34120a-science-kimwipe-delicate-task-wipers-21-x-11cm-280-sheets/18813156

[tooki]

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.

[Manafont]

I use these to do the mopping up

Work well and don't leave bits of tissue behind

The exact same product may not be available in your part of the world but I'd recommend finding something similar

This particular one varies wildly in price, worth shopping around

https://www.winc.com.au/main-catalogue-productdetail/kimtech-34120a-science-kimwipe-delicate-task-wipers-21-x-11cm-280-sheets/18813156

I 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.

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.

I 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%3Dsearch
That's the closest one to well known branded one that says "cleans flux", but ... yeah... too many fake "Mechanic" brand in my country.

[MikeK]

An old toothbrush helps with cleaning.  Dip it in the IPA, scrub, repeat, rinse, wipe.

[jpanhalt]

[With respect to commercial cleaners] I 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.

ZEP 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.

[Manafont]

[With respect to commercial cleaners] I 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.

ZEP 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.

Never 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:trouble
but 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 $89
IF, 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" list
Just in case it suddenly shows up somewhere in the local market.

An old toothbrush helps with cleaning.  Dip it in the IPA, scrub, repeat, rinse, wipe.

Thank 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.

[jpanhalt]

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.

[Manafont]

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.

Well, I'll try to look at hardware store near me.
Thanks for the lesson & info, I really appreciate it. 

[jpanhalt]

I'd be happy to take a look at any MSDS/SDS that you find confusing.
John

[tooki]

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.

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.

I 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%3Dsearch
That's the closest one to well known branded one that says "cleans flux", but ... yeah... too many fake "Mechanic" brand in my country.

I’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.

[jpanhalt]

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.

[IanB]

Presumably with water based cleaners you need to rinse with DI water afterwards, and then dry thoroughly?

[jpanhalt]

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.

[free_electron]

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.

[jpanhalt]

I used Kester 63/37 T3 solder paste with EP256 flux.  While it is "no clean," it is not considered water soluble.

[tepalia02]

Using isopropyl alcohol or acetone is the easiest way to perform this task.

[Gyro]

Be very careful of Acetone. It is much more likely to damage plastic components, even if just taking off their markings.

[tooki]

Using isopropyl alcohol or acetone is the easiest way to perform this task.

No, 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.

[Doctorandus_P]

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.

[janoc]

Using isopropyl alcohol or acetone is the easiest way to perform this task.

No, 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.

Commercial 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.

[pcprogrammer]

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-P02/13534650 but wonder if it is still good for flux.