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Brake cleaner is cheap and cleans PCBs really well

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SiliconWizard:

--- Quote from: rdl on July 28, 2021, 09:09:59 pm ---IPA is a pretty poor solvent for most things. If it actually does work for something, then ethanol is almost always better.

--- End quote ---

IPA is fine for cleaning... no-clean fluxes. ;D
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:

--- Quote from: T3sl4co1l on July 22, 2021, 04:27:48 am ---Acetone and MEK are often okay for electronics as well, but as with all of these, BE CAREFUL AND CHECK FIRST. 

--- End quote ---

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:

--- Quote from: T3sl4co1l on July 24, 2021, 10:48:31 pm ---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... ;D

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

--- End quote ---

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:

--- Quote from: SiliconWizard on July 28, 2021, 09:27:06 pm ---
--- Quote from: rdl on July 28, 2021, 09:09:59 pm ---IPA is a pretty poor solvent for most things. If it actually does work for something, then ethanol is almost always better.

--- End quote ---

IPA is fine for cleaning... no-clean fluxes. ;D
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.

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

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