Isopropanol vs Ethanol for Flux cleaning

[danny_d]

Hey guys!
So, I'm in need of purchasing new alcohol for flux cleaning, and I was wondering which one of the the above types would be best.
I can get either Isopropanol or Ethanol (both 95%) for the same amount of money, however the Isopropanol bottle only comes in 100ml, and the Ethanol in 1 Liter. Even a 100ml would last me for quite a while, still, I'd prefer going with the Ethanol (unless it's considered unsafe for my intended purpose of course). In terms of safety (PCB plastic dissolving) and leaving residue, which one would be better?
I've read somewhere that Ethanol often contains Methanol as well (which can be unsafe to some types of plastic, but whether that's relevant to PCB type plastic, or when the Methanol is in very small quantities I wasn't able to find an answer for)

[Ian.M]

It depends what the Ethanol is denatured with.  If its denatured with Bitrex (denatonium benzoate), that will leave behind an undesirable persistent ionic residue.  If its denatured with other solvents and volatiles its probably acceptable (and it cant have more than 5% and still meet 95% purity spec,)

Its unlikely to be  un-denatured at the same price as Isopropanol as the tax on potable alcohol in most countries is prohibitively high for most technical uses.  e.g. in the Netherlands, as of 2016, the duty on 1l of potable 95% Ethanol was 16 Euro, applied before other taxes. 

[ogden]

It depends what the Ethanol is denatured with.  If its denatured with Bitrex (denatonium benzoate), that will leave behind an undesirable persistent ionic residue.  If its denatured with other solvents and volatiles its probably acceptable (and it cant have more than 5% and still meet 95% purity spec,)

Right. Worst choice would be gambling with denaturated Ethanol. Anyway base of all PCB cleaning solutions is isopropanol which obviously shall be tried first. If do not like how it works, then get clean ethanol from chem store, mix isopropanol:ethanol 2:1. Thou Ethanol is more aggressive to some plastics than isopropanol.

[danny_d]

Thanks guys, and yeah, it's denatured ethanol.
However, after more searching, I've found a source of pure (medical grade) 95% ethanol (which is not denatured), this would be perfectly fine, correct?

[janoc]

Thanks guys, and yeah, it's denatured ethanol.
However, after more searching, I've found a source of pure (medical grade) 95% ethanol (which is not denatured), this would be perfectly fine, correct?

Yes, but expensive overkill.

Isopropanol is completely fine.

Denatured ethanol is fine as well if you have one that doesn't leave a residue. I have encountered this only once. It is also a lot easier to obtain than isopropanol - any drugstore carries it, isopropanol not so much. Not impossible to find but you will likely need to order it online.

[Nusa]

Thanks guys, and yeah, it's denatured ethanol.
However, after more searching, I've found a source of pure (medical grade) 95% ethanol (which is not denatured), this would be perfectly fine, correct?

Pure and 95% are contradictory terms. I bet it's still denatured, probably with other alcohols that are acceptable for laboratory use. Give us a link if you want an opinion on the actual product.

Nondenatured alcohol that's intended for medical injection goes by the name of Dehydrated Alcohol and is at least 98% ethanol (the rest being water). It's typically diluted to 40-50% in the syringe at the time of use.

[saturation]

Key reasons for choosing IPA over ethanol, or other low carbon alcohols are:

https://www.berkshire.com/learning-center/dyk_1408_why_ipa/

[danny_d]

Thanks guys, and yeah, it's denatured ethanol.
However, after more searching, I've found a source of pure (medical grade) 95% ethanol (which is not denatured), this would be perfectly fine, correct?

Pure and 95% are contradictory terms. I bet it's still denatured, probably with other alcohols that are acceptable for laboratory use. Give us a link if you want an opinion on the actual product.

Sure, here it is:
https://www.ebay.com/itm/500-ml-95-Not-Denatured-Absolutely-Pure-Wheaten-Ethyl-Alcohol-Ethanol/292275498329
It also appears to have some kind of certification (just check the pics)

Key reasons for choosing IPA over ethanol, or other low carbon alcohols are:
https://www.berkshire.com/learning-center/dyk_1408_why_ipa/

Thanks for the info, will look a bit later.

[janoc]

Key reasons for choosing IPA over ethanol, or other low carbon alcohols are:

https://www.berkshire.com/learning-center/dyk_1408_why_ipa/

That's actually a fairly crap website. They neglect to mention things like methylalcohol fumes (and the liquid itself) being severely toxic, causing blindness and even death if ingested.

[langwadt]

It depends what the Ethanol is denatured with.  If its denatured with Bitrex (denatonium benzoate), that will leave behind an undesirable persistent ionic residue.  If its denatured with other solvents and volatiles its probably acceptable (and it cant have more than 5% and still meet 95% purity spec,)

Its unlikely to be  un-denatured at the same price as Isopropanol as the tax on potable alcohol in most countries is prohibitively high for most technical uses.  e.g. in the Netherlands, as of 2016, the duty on 1l of potable 95% Ethanol was 16 Euro, applied before other taxes.

there's an EU standard for denatured alcohol:

100 L of absolute ethanol: 3 litres of isopropyl alcohol, 3 litres of methyl ethyl ketone and 1 gram denatonium benzoate.
 
does that minute amount of denatonium benzoate really matter?

[Nusa]

It depends what the Ethanol is denatured with.  If its denatured with Bitrex (denatonium benzoate), that will leave behind an undesirable persistent ionic residue.  If its denatured with other solvents and volatiles its probably acceptable (and it cant have more than 5% and still meet 95% purity spec,)

Its unlikely to be  un-denatured at the same price as Isopropanol as the tax on potable alcohol in most countries is prohibitively high for most technical uses.  e.g. in the Netherlands, as of 2016, the duty on 1l of potable 95% Ethanol was 16 Euro, applied before other taxes.

there's an EU standard for denatured alcohol:

100 L of absolute ethanol: 3 litres of isopropyl alcohol, 3 litres of methyl ethyl ketone and 1 gram denatonium benzoate.
 
does that minute amount of denatonium benzoate really matter?

Yes. Denatonium benzoate isn't considered toxic, but it's called the most bitter substance known to man. Even that low dose is detectable and highly objectionable to most humans. It's added to all sorts of poisonous products to discourage ingestion. There are even nail polish products designed to stop nail-biting or thumb-sucking.

[Ian.M]

there's an EU standard for denatured alcohol:

100 L of absolute ethanol: 3 litres of isopropyl alcohol, 3 litres of methyl ethyl ketone and 1 gram denatonium benzoate.
 
does that minute amount of denatonium benzoate really matter?

That is one combination of denaturants that meet the minimum requirements for Ethanol to be sold without Excise duty in the E.U.   Member states are free to make more stringent specifications for denatured alcohol produced within their borders, and some, that have problems with home production of illegal distilled spirits do so, to increase the concentration of denaturant that will be carried over in a simple distillation process.   

[janoc]

Yes. Denatonium benzoate isn't considered toxic, but it's called the most bitter substance known to man. Even that low dose is detectable and highly objectionable to most humans. It's added to all sorts of poisonous products to discourage ingestion. There are even nail polish products designed to stop nail-biting or thumb-sucking.

Isn't this the chemical Nintendo added to their Switch game cartridges to prevent people from chewing on them (for whatever reason)?

Of course, Ben Heckendorn wouldn't be Ben Heckendorn if he didn't test that:
https://youtu.be/hpSPyW5v8r0?t=653 

[kalel]

Is there a requirement to say what the other 5% is (declared on the bottle)? Or some kind of statement about being denatured and toxic / cannot be used for drinking, for safety.

[Nusa]

Is there a requirement to say what the other 5% is (declared on the bottle)? Or some kind of statement about being denatured and toxic / cannot be used for drinking, for safety.

Given that this is an international forum and you don't have a country tag listed, that's an unknown answer in your case. Government rules that apply depend on which combination of country, state, and/or local governments we're talking about. Whether the rules are actually enforced also may vary.

[langwadt]

It depends what the Ethanol is denatured with.  If its denatured with Bitrex (denatonium benzoate), that will leave behind an undesirable persistent ionic residue.  If its denatured with other solvents and volatiles its probably acceptable (and it cant have more than 5% and still meet 95% purity spec,)

Its unlikely to be  un-denatured at the same price as Isopropanol as the tax on potable alcohol in most countries is prohibitively high for most technical uses.  e.g. in the Netherlands, as of 2016, the duty on 1l of potable 95% Ethanol was 16 Euro, applied before other taxes.

there's an EU standard for denatured alcohol:

100 L of absolute ethanol: 3 litres of isopropyl alcohol, 3 litres of methyl ethyl ketone and 1 gram denatonium benzoate.
 
does that minute amount of denatonium benzoate really matter?

Yes. Denatonium benzoate isn't considered toxic, but it's called the most bitter substance known to man. Even that low dose is detectable and highly objectionable to most humans. It's added to all sorts of poisonous products to discourage ingestion. There are even nail polish products designed to stop nail-biting or thumb-sucking.

I know it is enough that no one want to drink it, but when used for cleaning is it really enough to leave a residue that makes a difference?

[JacquesBBB]

You can find isopropanol from reputable source at low price on amazon.

https://www.amazon.fr/ISOPROPANOL-alcool-isopropylique-99-9/dp/B01HJOCKEI/ref=sr_1_5?s=hpc&ie=UTF8&qid=1513151772&sr=1-5&keywords=Isopropanol

https://www.amazon.fr/H%C3%B6fer-Chemie-GmbH-6-l-disopropanol/dp/B005J4B4LG/ref=pd_sbs_328_1?_encoding=UTF8&psc=1&refRID=EMFSZ3M9DRHHWK0B8QEJ

[IanMacdonald]

Isopropanol is probably the better choice for PCBs but be aware that it causes rubber to swell up so keep it off grommets or the like.

[TheUnnamedNewbie]

Depending on the flux I've found that ethanol doesn't do all that well in regards to cleaning things. Isopropyl works better (I actually like to use disinfecting swabs, I can get 100 or such for a few euros, and use cotton swabs to clean up after wetting the board with the swab).

[janoc]

Depending on the flux I've found that ethanol doesn't do all that well in regards to cleaning things. Isopropyl works better (I actually like to use disinfecting swabs, I can get 100 or such for a few euros, and use cotton swabs to clean up after wetting the board with the swab).

Yep, ethanol tends to leave a white residue if cleaning some gel and rosin-based fluxes and you don't use enough of it to wash it off. IPA doesn't do that. However, for normal water-based fluxes it is not a problem.

[plazma]

Depending where you live you may find pure IPA sold as anti-freeze agent for diesel engines or truck air brakes. I bought 1 liter bottle for 4€ in Finland.

[KL27x]

I use 95% ethanol. There is no PCB component/plastic that I have encountered which is noticeably degraded or dissolve in short exposure to ACTEONE, let alone ethanol. Housings are a different story. But even here, I have never encountered any problem with ethanol.

The benefits of ethanol, to me:

1. smell is much less noticeable/objectionable to me
2. 95% will STAY 95%. Isopropyl will slowly absorb water from the air that you let into the container; it stabilizes at 91%
3. Hardware store sells it in big tin containers which are a convenient size/shape to sit on a shelf along with all my other solvents and finishes which I conveniently buy at the same store.

Bitrex, smitrex.
I don't really care if there's a little trace of bitrex in there. If it wasn't soluble in the 5% water, it would just settle to the bottom of the container and wouldn't serve it's purpose, no? The 5% water also has to dissolve the ionic contamination from the board you're cleaning. Or the ethanol has to at least suspend it while you brush it off.
If you just leave the ethanol to dry on the board, of course the bitrex will remain on the board. Along with all the flux residue you were trying to clean off.

Pure isopropyl would be useful for final rinse, if you needed it. For basic cleaning, it doesn't matter if there's a trace of something else in there. It will still get the board much cleaner than it was before. There will be plenty more contamination in the bathwater just from the smelly guy sitting in the tub.

[MrAl]

Hi,

I use isopropyl usually 70 percent.  Seems good enough and easy to get at almost any store.
Have to watch out though as some places are selling 50 percent now, and i would not use that stuff.  90 percent yes even better.
I use 70 percent for other general cleaning too though so i always have it on hand.

[Ian.M]

I've used denatured Ethanol and Isopropanol (IPA).    95% denatured Ethanol is great for getting the crud off really dirty boards - wave soldered or reflowed with no defluxing then used in a poorly ventilated room by chain-smokers till a crust of gooey cigarette tar has built up on every surface. 

However, before using denatured Ethanol on anything sensitive, its advisable to evaporate about a ml to dryness on a watchglass (or similar concave glass surface) using warm air or other gentle heat source, and note if there is any objectionable residue^*.  Also observe the last of the liquid closely as it evaporates to see if it is oily.    On sensitive high impedance circuits its only the first stage of a cleaning process and needs to be followed by an aqueous phase to remove ionic contamination and then by a good technical grade of 95% (or purer) IPA to quickly remove the residual water from the aqueous cleaning phase + any detergent residue.  The board can then be dried with no risk of iron component leads and other parts rusting, or heat damage due to prolonged and excessive drying temperatures.

On less sensitive circuits, you can probably skip the aqueous cleaning phase unless a water soluble flux was used, or objectionable streaking was left after drying.  Blotting off as much denatured Ethanol as possible followed by an IPA rinse (without drying in between) is usually adequate.

As IPA forms an azeotrope with water, (87.7% IPA by weight), and absorbs moisture from the air, if you ever need to use it for rapid water removal,  you need drier IPA than that, so that traces of moisture aren't left behind as it evaporates.   Keep all bulk IPA containers tightly stoppered,  and only dispense enough for a few days use.

* If you are intending to use denatured Ethanol as a single cleaning stage, you will probably want to test the conductivity of the residue if there was any apparent.  Add a drop of deionised water and see if the residue is water soluble then compare conductivity  with a control drop of the deionised water, taking care to use clean electrodes and immerse them the same distance with the same separation.

[ogden]

I've used Kontakt PCC bottle which mostly is IPA + some Ethanol & Methanol. Brush is very, very important part of this "tool". Such bottle is always ready to use, too. For surface mount boards additional "air duster" bottle (which indeed is not "canned air" but butane+propane) will be useful as well. It does two things - blows away mix of flux+cleaner from tight places and helps to dry board. Slower evaporation of IPA is very helpful here - you have time to grab duster before it is too late.

Take those images in product webpage with grain of salt - you don't have to spill cleaning fluid all over the PCB or table. Just wetting brush is enough. At the end of the job - spray into brush again and clean it with paper towel/tissue, that's it. After trying such cleaner - you will never use cotton swabs on PCB again

http://www.kontaktchemie.com/koc/KOCproductdetail.csp?division=&product=KONTAKT%20PCC&ilang=all&plang=all