Myth busting solder-flux cleaning with isopropanol alcohol

[boffin]

I always give boards a quick wipe with flux cleaner before starting.  makes your life so much easier

[grantb5]

Anyone using a dehydrator?  I make small boards (HASL hot air surface leveling, not PB free) and solder using no-clean Kester 245 but for mainly cosmetic reasons I like to clean the boards. Mainly I use IPA but sometimes reach for MG 4140 or similar.  I've noticed with the high humidity we have lately that it's like there is water forming or at least that dried water look on the boards. Someone mentioned a no-heat dehydrator on Amazon but no details so I was wondering if some kind of dehydrator would help.  Or blowing/heaing maybe? My heat shrink gun is too hot I think to use and probably a hair dryer is static central.  Anyone use a food dehydrator or is a PCB one available for $100 kind of range?

[IanB]

Anyone using a dehydrator?  I make small boards (HASL hot air surface leveling, not PB free) and solder using no-clean Kester 245 but for mainly cosmetic reasons I like to clean the boards. Mainly I use IPA but sometimes reach for MG 4140 or similar.  I've noticed with the high humidity we have lately that it's like there is water forming or at least that dried water look on the boards. Someone mentioned a no-heat dehydrator on Amazon but no details so I was wondering if some kind of dehydrator would help.  Or blowing/heaing maybe? My heat shrink gun is too hot I think to use and probably a hair dryer is static central.  Anyone use a food dehydrator or is a PCB one available for $100 kind of range?

How might a dehydrator help here? As soon as you take a board out of the dry atmosphere it will get humidified again.

If you have some kind of filmy appearance on the boards after cleaning, I think that means there is residue left behind and the board is not properly clean. You should try extra rinsing with very clean solvent, maybe even de-ionized water. Remember that solvent after cleaning must not be left to dry in place as it will not physically remove dirt that way. Dirt must be washed off and carried away with copious rinsing.

[alsetalokin4017]

Desiccator?

Put sodium hydroxide pellets in the bottom to absorb moisture. Evacuate for even better performance. Reactivate the moist NaOH by baking in oven.

https://i.ebayimg.com/images/g/~3sAAOxyxpxQ52RP/s-l300.jpg

[nanofrog]

Don't just use a solvent (IPA, acetone, ... or some sort of mixture as tends to be in aerosol flux cleaner cans), as all it will do is spread the flux around the board.

Instead, you need to mop it off using something like Kim Wipes or foam swabs (i.e. those sold for cleaning ink jet printers on eBay and the like) types of things to actually remove it from the PCB. Repeat until it's all gone, and voila, you're done. 

[IanB]

Desiccator?

Put sodium hydroxide pellets in the bottom to absorb moisture. Evacuate for even better performance. Reactivate the moist NaOH by baking in oven.

Sodium hydroxide is not very safe. However, every supermarket and hardware store in the USA sells calcium chloride drying products for dehumidifying enclosed spaces. These would be a more practical solution for desiccators.

Even so, I think the problem is with cleaning, not with drying. If you just spray flux cleaner onto your board from a spray can, it will not clean the flux off. It needs to be scrubbed with a soft brush after application, and then the residue needs to be rinsed off using a separate application of solvent and/or de-ionized water.

[grantb5]

Thanks folks. Most of these are PTH (through hole) so swabs and wipes will probably get shredded. I do use a toothbrush with the IPA and/or MG. I will try harder.   It seems to me the moisture or film appears later but I will experiment with a few things.

[ogden]

Thanks folks. Most of these are PTH (through hole) so swabs and wipes will probably get shredded. I do use a toothbrush with the IPA and/or MG. I will try harder.

I do use Kontakt PCC aerosol bottle which is mostly Isopropanol, with built-in swab together with cheap "air duster" bottle. Duster shall be flammable type. You just blow all the remains of cleaning fluid away, evaporate it as well. It helps in tight places and under SOIC/LQFP IC's (!).

[grantb5]

I see Flux-Off has a product like that, maybe I'll give that a whirl.

https://www.chemtronics.com/flux-off-no-clean-plus

[nanofrog]

I see Flux-Off has a product like that, maybe I'll give that a whirl.

https://www.chemtronics.com/flux-off-no-clean-plus

It's decent stuff, but it's a bit on the expensive side. Especially the 12oz. aerosol cans that are hobbyist friendly.

• Amazon has it for $18.37 per can
• Digikey for $20.58
• Newark for $25.51

Then it gets really ugly when looking at CDN pricing (i.e. $44.16 CDN from Amazon.ca). 

FWIW, the Kim Wipes and foam swabs will work with PTH components quite well (they're older than SMD components). You mop/absorb the solved flux residue with them, not scrub at it. Use a brush first as you have been if you need to scrub a heavy deposit prior to mopping the mess off, repeating as necessary. You can even use Q-tips*; just clear off any cotton fuzz that might be left behind.

* Rotate in the same direction it was wound on the stick to help keep the cotton on it rather than your board.

[microMANIAC]

Back before I was a greybeard I used commercial flux cleaners, but since recently getting back into the field I have been using 91% isopropyl alcohol to clean flux from my personal project boards, although I have been frustrated by the gummy residue left over no matter how hard I scrub with an old toothbrush. One of the earlier posts in this thread mentioned brake cleaner, and since I recently bought about a dozen cans on sale for less than $3 each CDN I thought I would experiment with it on an inexpensive project. Brake cleaner is amazing stuff... extremely effective dissolving anything gummy or oily, dries quickly with no residue, safe on most plastics, comes in easy-to-use spray cans, and is relatively cheap (especially on sale like I got mine). It is, however, hard on rubber, but you don't find much of that on most circuit boards.

For a test I used it to clean off the flux after soldering the legs and ICSP pins onto an Arduino Nano clone. Initially I wasn't comfortable spraying it directly on the board, so instead I applied it to the old toothbrush bristles and then scrubbed the lines of header pins I had just soldered. The results were perfect... no damage to neighboring components or silkscreening, not a trace of flux or gumminess left on the board, and it air dried in about 60 seconds (blowing on it speeds up drying dramatically). I will definitely be turning to brake cleaner as my go-to flux remover.

I can't speak for all brands or formulations, but the product I used was "emzone Non-Chlorinated Brake & Parts Cleaner". The side label claims it leaves no residue, is fast drying, and has low odour, all of which I can confirm. It suggests pretesting on plastic components, and warns to avoid overspray on rubber parts, but I have used it on all kinds of plastic stuff, and almost all of it is impervious. Like I said, try it on a few lower-risk projects first, but I think you will find it fantastic for flux cleaning.

[thm_w]

Back before I was a greybeard I used commercial flux cleaners, but since recently getting back into the field I have been using 91% isopropyl alcohol to clean flux from my personal project boards, although I have been frustrated by the gummy residue left over no matter how hard I scrub with an old toothbrush. One of the earlier posts in this thread mentioned brake cleaner, and since I recently bought about a dozen cans on sale for less than $3 each CDN I thought I would experiment with it on an inexpensive project. Brake cleaner is amazing stuff... extremely effective dissolving anything gummy or oily, dries quickly with no residue, safe on most plastics, comes in easy-to-use spray cans, and is relatively cheap (especially on sale like I got mine). It is, however, hard on rubber, but you don't find much of that on most circuit boards.

For a test I used it to clean off the flux after soldering the legs and ICSP pins onto an Arduino Nano clone. Initially I wasn't comfortable spraying it directly on the board, so instead I applied it to the old toothbrush bristles and then scrubbed the lines of header pins I had just soldered. The results were perfect... no damage to neighboring components or silkscreening, not a trace of flux or gumminess left on the board, and it air dried in about 60 seconds (blowing on it speeds up drying dramatically). I will definitely be turning to brake cleaner as my go-to flux remover.

I can't speak for all brands or formulations, but the product I used was "emzone Non-Chlorinated Brake & Parts Cleaner". The side label claims it leaves no residue, is fast drying, and has low odour, all of which I can confirm. It suggests pretesting on plastic components, and warns to avoid overspray on rubber parts, but I have used it on all kinds of plastic stuff, and almost all of it is impervious. Like I said, try it on a few lower-risk projects first, but I think you will find it fantastic for flux cleaning.

I think this is the MSDS: http://emzone.ca/media/141950/p6-045046___________emzone_brake___parts_cleaner_-_the_big_can_-_482g_en_5.pdf

Heptane (including isomers) 64742-49-0 60-100%
Isopropyl Alcohol 67-63-0 5-10%
Carbon Dioxide 124-38-9 1-5%

Just make sure you have good ventilation, even if it doesn't have a strong odor.

[microMANIAC]

Heptane (including isomers) 64742-49-0 60-100%
Isopropyl Alcohol 67-63-0 5-10%
Carbon Dioxide 124-38-9 1-5%

Somebody didn't check their math there... the Heptane can be up to 100%, but the other two can't be lower than 5% and 1% respectively. If the Heptane is at its maximum of 100% and the others are at their minimums... that adds up to 106%. Surely the maximum Heptane component should be 94%.

 

BTW, I used this cleaner on a couple more PCBs since my original post and the results were stellar.

[helius]

Somebody didn't check their math there...

You don't understand. They know exactly what their product contains, not a range of possibilities. Those aren't error bars.
What they aren't doing is telling you exactly what is in their product. They take the precise proportion of each hazardous ingredient (non-hazardous ingredients are not listed at all) and add sufficient "fuzz" on either side to obscure the content. Summing to 100% is nowhere in the procedure and would not improve anything from their perspective (the minimum possible information disclosure within the law).

[Fleetz]

Been looking into the best way for a hobbyist like myself to clean PCBs that I design. IPA was one method I explored however seems it can be somewhat problematic with residue unless follow up cleaning is implemented.

In the next day or so I will be trying out a water based flux cleaner in a ultrasonic bath cleaner I recent purchased on eBay for $100. The flux cleaner I am trying is https://www.shesto.co.uk/precision-engineering/ultrasonics-1/shesto-ultrasonic-cleaner-solution-for-flux-remover-pcb/

The flux cleaning solution needs to be elevated to around 50-60C which is no problem as the ultrasonic cleaner I purchased has an adjustable heater. Once it goes through the ultrasonic bath the PCB is rinsed in demineralised water then dried. Hopefully leaving a relatively clean streak free PCB.

I have seen a YouTube video of a user of using a flux cleaner solution similiar to what I am about to use where he uses a toothbrush once the board is in the ultrasonic bath to gently brush more heavily fluxed areas on the PCB to assist in the moving of the flux into solution so I will be using that technic to.

Then I intend using a IPA bath after the ultrasonic to displace the water based cleaner then dry the PCB. Hopefully finish with a very clean board.

[helius]

Many are leery of putting themselves in contact with ultrasonic cleaners, due to their known capability for tissue disruption.

[Fleetz]

Many are leery of putting themselves in contact with ultrasonic cleaners, due to their known capability for tissue disruption.

No intention of putting my fingers into an active ultrasonic bath, the ultrasonics will be switched off for any spot cleaning or any action that requires direct human intervention.

[floobydust]

Ultrasonic cleaning is very hard on electronics, IC bonding wires can fail and I've seen metals get etched as the solder fillets look roughed up. Keep the intensity and time as low as possible.

[microMANIAC]

You don't understand.

Ummm... yes, I do. It's you that doesn't understand.

They clearly state that the IPA is at least 5%, and CO2 is at least 1%. They can't then claim that the Heptane can be up to 100%. The Heptane can't be more than 94%... it's simple math.

[helius]

Looks like you still don't get it. It is not a "claim that heptane can be up to 100%". The only "claim" is that the exact, known, amount of heptane is somewhere between the figures given. "Simple math" is not involved at all, only legal requirements.

[Brumby]

"Simple math" is not involved at all, only legal requirements.

.... and obfuscation of the real formula.

[boffin]

I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)

[microMANIAC]

Ok, the last thing I want to do is get into a flame war with a longtime contributor, so this will be my last comment on this topic, but your argument is just semantics, and it's still wrong.

"the exact, known, amount of heptane is somewhere between the figures given"

Exactly!!! But that is ALSO true for the other listed components.

The amount of CO2 is somewhere between one and five percent (but not LESS than 1%). Isopropyl alcohol makes up five to ten percent of the product (but not LESS than 5%). That means that somewhere between six and fifteen percent of this brake cleaner is NOT heptane. There is absolutely no way the heptane can contribute more than 94% of the total. I'm not sure why this is so difficult to understand. Heptane is a distinct component in its own right, it is not itself made up of CO2 or IPA. If the product is indeed at least 1% CO2 and 5% IPA, it is IMPOSSIBLE for it to simultaneously be 100% heptane.

If your argument is that the numbers are correct because it is strictly true that a 94% heptane concentration is "between 60 and 100%", well that is just ludicrous. Nobody says a peanut butter cup is 20% chocolate and somewhere between 60% and 100% peanut butter. The most logical explanation is my original one, that the manufacturer made a simple mistake when listing the ingredients.

[microMANIAC]

I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)

You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.

[boffin]

I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)

You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.

Not something I had at hand, but I'll give it a try sometime.