Brake cleaner is cheap and cleans PCBs really well

[Monkeh]

If you're not buying them by the barrel, plus it's packed in an aerosol can, I fail to see how that's at all atypical retail markup.

Tim

I buy 600ml cans of brake cleaner for £2.50 or so.

[T3sl4co1l]

That's pretty good. I get a liter of acetone around here for like $10.  Haven't looked at brake cleaner in a while...

Tim

[tom66]

You have a strange definition of not expensive for a blend of cyclohexane, isopropanol, and heptane. Electrolube are laughing to the bank with that stuff. Oh, there's a bit of antifreeze in it too.

I bought two cans about two years ago and I'm about half-way through the first.  I think I'll manage with paying the retail markup.

[MathWizard]

On the little PCBs I've been working on this year, I've just been using hot soapy water, and a toothbrush. Then I just dry them over my computers fans. It seems to work pretty well, but some stuff I really don't like getting wet.

I've been using some strong MG flux, and it leaves conductive residue sometimes, I should not use it on SMD anymore.

[T3sl4co1l]

Interesting. I don't know that I've used any flux that would respond much at all to soapy water, even after a looong soak.  Strong bases though, saponify the rosin acids effectively.  But that does nothing for the metal soaps/salts already present (i.e. the cruddy stuff that the rosin did its job at dissolving).  So it'll still leave crud, plus being rather aggressive towards anything else present (may degrade plastics?).

Heh, or you're using so much rosin that the base chemicals (usually some combination of petroleum jelly and glycol ethers?) stick around (the deposit is still gooey?), and the metal oxides are well dissolved and dispersed, not clumpy.  So everything suspends and washes away.  There's never too much flux...

I would suppose a combination of base (maybe a milder one like ammonia will do? -- may complex (dissolve) some of the metal salts too) and alcohols might do the best.  Not sure what all they use in commercial blends.  (Note that acetone is incompatible with base, it'll oligomerize; alcohols are okay, as are most detergents.)

(Heh, and that's pure base by the way; carbonates, phosphates, silicates, etc. will all precipitate metal ions, no chance of them dissolving.  Probably just as good a reason as any, why base isn't as effective as I might first imagine...)

Tim

[helius]

You joke, but isopropyl alcohol is just metabolized to acetone, which then is largely excreted through breathing.  As I understand it, it's a shitty buzz... but surprisingly not very toxic, on par with ethanol.

So, while I wouldn't suggest making a cocktail with acetone or isopropyl; it is true that ethanol is suitable for cleaning, if you happen to have it in a reasonably pure form (Everclear for the drinkable kind, or denatured whatever if not).

Acetone and MEK are often okay for electronics as well, but as with all of these, BE CAREFUL AND CHECK FIRST.  A lot of inks and plastics soften, swell or dissolve in the more aggressive (more aliphatic, or aromatic for that matter) solvents.  Electrolytics may be compromised by exposure.

Acetone is only excreted in the breath to a limited degree. It also passes into, and acidifies, the urine. The test for so-called "ketone bodies" in urine (mostly acetone) is used as a sign that fats are being metabolized.

Isopropyl alcohol is not fatal to ingest (within reasonable limits), but it causes intense colic-like abdominal pains. That is why you do not hear about people drinking it (ethanol itself is a "shitty high" compared to many alternatives).
Ingestion of elemental iodine also causes such pains.

As the subject of brake cleaners comes up with some regularity, it needs to be pointed out that the term is ambiguous. CRC Industries makes two major types of BrāKleen: 05089 is nearly pure perchloroethylene; 05088 is a mixture of methanol, toluene, and hexane. Both are powerful degreasers, but Perc is not generally plastic or rubber safe. The other products in the line are diluted with acetone to comply with local air quality laws, which is an issue because acetone is also not safe on plastic or soldermask. So while they will definitely dissolve flux residue, they are not formulated to be safe on electronics.

[BrokenYugo]

If I was to substitute automotive cleaners for electronics use - and I probably wouldn't - mass airflow sensor cleaner may be a safer choice. They are designed to be sprayed on electronic components and plastic.

CRC MAF cleaner claims to be mostly naptha*, 2-methylpentane, and some other solvents. But like I said earlier, none of these solvent soups are at all standardized, you have to do the homework.

[bson]

Just be very careful with brake cleaners and heat.  At 315 deg C tetrachloroethylene becomes phosgene, which will kill you in relatively small concentrations.  Personally I'd never use a brake cleaner with tetrachloroethylene to clean a PCB, but I do use it to clean mechanical parts - however I personally only use it outdoors.  The reason for not using it to clean PCBs is I expose the PCBs to heat in a closed room, and while it can be argued they're dry, it has all evaporated, etc - it's not worth the risk to me.  I find it prudent to avoid the possibility of mistakes that can't be made...

[Gyro]

Just be very careful with brake cleaners and heat.  At 315 deg C tetrachloroethylene becomes phosgene, which will kill you in relatively small concentrations.  Personally I'd never use a brake cleaner with tetrachloroethylene to clean a PCB, but I do use it to clean mechanical parts - however I personally only use it outdoors.  The reason for not using it to clean PCBs is I expose the PCBs to heat in a closed room, and while it can be argued they're dry, it has all evaporated, etc - it's not worth the risk to me.  I find it prudent to avoid the possibility of mistakes that can't be made...

Who didn't read the first page? 

[tooki]

mmmm.... I'm happy with my IPA. 

IPA works fine, just let it soak in a bowl and it works really well. People don't have patience and resort to harsh chemicals.

The problem with isopropyl is that many modern fluxes, especially the no-clean types, are not fully alcohol-soluble. No amount of IPA will fully dissolve them, leaving behind the infamous white deposits. Ironically, cheap 70-90% rubbing alcohol may work better for these fluxes than 99% IPA, since many of those residues are water-soluble.

But commercial flux removers do a much better job, frankly, and do it in much less time. I a) can't have a bowl of IPA sitting around at work (and you'd still need a separate rinse!), b) not all components can be immersed, and c) I don't have the time to wait for things to soak. Why use navigable amounts of IPA and lots of time to achieve only an OK result, when a commercial product lets me use tiny amounts, does the job quickly, and leaves the boards squeaky clean??

[BrokenYugo]

mmmm.... I'm happy with my IPA. 

IPA works fine, just let it soak in a bowl and it works really well. People don't have patience and resort to harsh chemicals.

The problem with isopropyl is that many modern fluxes, especially the no-clean types, are not fully alcohol-soluble. No amount of IPA will fully dissolve them, leaving behind the infamous white deposits. Ironically, cheap 70-90% rubbing alcohol may work better for these fluxes than 99% IPA, since many of those residues are water-soluble.

But commercial flux removers do a much better job, frankly, and do it in much less time. I a) can't have a bowl of IPA sitting around at work (and you'd still need a separate rinse!), b) not all components can be immersed, and c) I don't have the time to wait for things to soak. Why use navigable amounts of IPA and lots of time to achieve only an OK result, when a commercial product lets me use tiny amounts, does the job quickly, and leaves the boards squeaky clean??

Can confirm, I've tried to clean boards every way imaginable with 91% IPA and get the white crap, I even tried a vapor chamber. The stuff seems fairly insoluble in water too, you have to scrub it off. Haven't gotten far enough to figure out if it's the old 90s Radio Shack 60/40, The MG 835 RA, or both.

[G7PSK]

Its the UV UVc being the main culprit due to its high energy from arc welding that breaks down carbon tet. to phosgene. IPA fumes wont cause you any harm in the quantities that most are likely to encounter. The same goes for brake cleaner and carb cleaner, unless you are sloshing it around by the gallon just ensure adequete ventilation.

[ElektroQuark]

FWIW, with MG Chemicals No Clean Flux Paste Cat. No. 8341 and IPA you get TONs of that white residue. 

[tooki]

FWIW, with MG Chemicals No Clean Flux Paste Cat. No. 8341 and IPA you get TONs of that white residue. 

Can confirm, as that’s the flux paste I have at home. As I said, very common for no-clean fluxes. But to be clear, MG does not claim it to be cleanable in IPA: they recommend “solvent systems” like [several of their flux cleaner products], so the facepalm isn’t warranted.

[rdl]

IPA is a pretty poor solvent for most things. If it actually does work for something, then ethanol is almost always better.

[SiliconWizard]

IPA is a pretty poor solvent for most things. If it actually does work for something, then ethanol is almost always better.

IPA is fine for cleaning... no-clean fluxes.
Yes, no-clean fluxes also leaves residues, and whereas those are supposed to be harmless, I still prefer cleaning the boards.
But yeah, for other kinds of fluxes, IPA mixed in can leave an awful gunk.

[Cerebus]

Acetone and MEK are often okay for electronics as well, but as with all of these, BE CAREFUL AND CHECK FIRST. 

MEK will definitely make rubber swell, it was sold to the offset litho printing trade as "blanket restorer" specifically because it would make the rubber 'blanket' used in offset printing swell back to its originally bounciness after it had a few million impressions slammed into it by the impression cylinder. (I was an inky fingered offset litho printer for a couple of years in the dim and distant past.)

[Cerebus]

Interesting. I don't know that I've used any flux that would respond much at all to soapy water, even after a looong soak.  Strong bases though, saponify the rosin acids effectively.  But that does nothing for the metal soaps/salts already present (i.e. the cruddy stuff that the rosin did its job at dissolving).  So it'll still leave crud, plus being rather aggressive towards anything else present (may degrade plastics?).

Heh, or you're using so much rosin that the base chemicals (usually some combination of petroleum jelly and glycol ethers?) stick around (the deposit is still gooey?), and the metal oxides are well dissolved and dispersed, not clumpy.  So everything suspends and washes away.  There's never too much flux...

I would suppose a combination of base (maybe a milder one like ammonia will do? -- may complex (dissolve) some of the metal salts too) and alcohols might do the best.  Not sure what all they use in commercial blends.  (Note that acetone is incompatible with base, it'll oligomerize; alcohols are okay, as are most detergents.)

(Heh, and that's pure base by the way; carbonates, phosphates, silicates, etc. will all precipitate metal ions, no chance of them dissolving.  Probably just as good a reason as any, why base isn't as effective as I might first imagine...)

Tim

A few weeks ago, out of pure curiosity, I tried cleaning flux reside off some slightly scummy old scrap boards I had around (a bunch of small IR remote control boards that came from I remember not where) with warm dilute sodium carbonate (i.e. washing soda) solution, about the same concentration you'd use in a sink or bucket for normal domestic purposes. It did a surprisingly good job and seemed to clean everything off, including the ring of metal salts that often gets left behind by other cleaning methods. As I say, this was idle curiosity, not a proper scientific experiment but the results were encouraging.

[T3sl4co1l]

Ah, interesting!

Tim

[tooki]

IPA is a pretty poor solvent for most things. If it actually does work for something, then ethanol is almost always better.

IPA is fine for cleaning... no-clean fluxes.
Yes, no-clean fluxes also leaves residues, and whereas those are supposed to be harmless, I still prefer cleaning the boards.
But yeah, for other kinds of fluxes, IPA mixed in can leave an awful gunk.

Incorrect. It’s the no-clean fluxes that IPA is bad at removing. It works fine for most traditional rosin fluxes.

[duckduck]

N.B.: Chlorinated brake cleaner makes (at least some) plastic parts extremely brittle. I've now got a new plastic case on the way for my Garmin GPS because I thought it would be smart to clean it with brake cleaner and it crumbled into tiny little crispy bits. 

[amyk]

Chlorinated solvents tend to attack plastics pretty aggressively - methylene chloride can be used for plastic welding, for example.

[helius]

As can MEK, but I find the latter easier to use as it doesn't evaporate instantly as DCM does.

DCM on the left, MEK on the right.
They both work better if a small amount of ABS is dissolved in the solvent (this is how many modeling glues are made). Using the brush cap and returning it to the bottle will carry in plastic resin slowly as well.

[Halcyon]

What about a dishwasher and a bit of detergent?

[jpanhalt]

Has anyone tried E85 "flex" fuel? 

In the US, it is at least 50% ethanol + light petroleum distillates (https://afdc.energy.gov/fuels/ethanol_e85_specs.html ).  Apparently the ethanol percentage is higher in the Summer.  In the US, it is spec'd to contain 51% to 83% ethanol.  Many of the commercial flux removers have petroleum spirits in them too.  Doesn't smell too bad either.  It is also less than $3/gal in my area.

I bought some the other day (Summer in Ohio), but haven't had a chance to use it.