General > General Technical Chat

Brake cleaner is cheap and cleans PCBs really well

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helius:

--- Quote from: T3sl4co1l on July 22, 2021, 04:27:48 am ---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.

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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:

--- Quote from: John B on July 23, 2021, 01:40:03 am ---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.

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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:

--- Quote from: bson on July 25, 2021, 06:37:07 pm ---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...

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Who didn't read the first page?  ;)

tooki:

--- Quote from: M4trix on July 22, 2021, 12:39:31 am ---mmmm.... I'm happy with my IPA.  :phew:

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--- Quote from: floobydust on July 22, 2021, 07:46:00 pm ---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.

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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??

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