Author Topic: what chemical to clean the pcb after leaking capacitors  (Read 23104 times)

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Offline Terry Bites

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #25 on: August 30, 2023, 07:41:08 am »
I think Mr C would say if he was using acetone or ipa instead of laquer thinners.
Have a look at this evil cocktail.
 

Offline David Hess

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #26 on: August 30, 2023, 02:50:04 pm »
Acetone and isopropyl alcohol are at least miscible with water.

Aluminum electrolytic capacitor electrolytes are typically something like boric acid and ethylene glycol so a majority of the cleaner should be simple water.  The components of lacquer thinner are less useful here.
 
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Offline helius

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #27 on: August 30, 2023, 06:45:20 pm »
Lacquer thinner is made for one thing only: spraying nitrocellulose lacquer coatings.
The process was invented in the 1920s and relies on multiple solvents with varying weights. The lacquer-solvent mixture is super thin as it exits the spray nozzle, and enough solvent evaporates in flight to make it significantly thicker by the time it hits the workpiece. This makes it possible to spray vertical surfaces without runs.

As I said on page 1 it has no application to electronics.
 

Offline swanng

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #28 on: January 12, 2025, 11:46:40 pm »
I have been using methylethylketone (MEK) for over 30 years with no problems (aside from the smell). It evaporates very fast, yet cleans PCB's FAR better than any alcohol.
 

Offline helius

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #29 on: January 14, 2025, 07:17:10 pm »
MEK is very similar to acetone in its effects. They both can absorb into plastic chip carriers, which could cause problems, as well as removing any markings, whether they are inked or laser marked. Indeed, acetone (or MEK) is a good method to detect fake black-topped chips because the black coating will get rubbed off. Removing silkscreen print is another possible effect.

The question in choosing a solvent is what type of soil do you need to remove, and how powerful a cleaning is required? Using a solvent that is "FAR better" is not necessarily a good thing because it will remove more material than desired.

The other part of cleaning is technique. Just rubbing some solvent around until it evaporates won't remove any soil! Where did you expect it to go? Cleaning must transfer the soil to a waste receptacle of some kind, either by flushing with large amounts of solvent so it runs off into the bin, or by agitating with a cellulose towel so the soil moves into the towel. This is why fast-evaporating solvents are usually a disadvantage for cleaning circuit boards.
« Last Edit: January 14, 2025, 07:18:59 pm by helius »
 

Offline jpanhalt

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Re: what chemical to clean the pcb after leaking capacitors
« Reply #30 on: January 14, 2025, 07:53:44 pm »
Acetone, MEK, IPA and such are great solvents for some things, but an aluminum electrolytic capacitor (assumed) or any other electrolytic cap. contains an electrolyte.  That is, something ionic, and none of those solvents are great for ionic substances.  There are exceptions for some alcohols.
FromWikipedia:
Quote
Aluminum electrolytic capacitors with non-solid electrolyte
may use a liquid electrolyte based on ethylene glycol and boric acid, so-called "borax" electrolytes, or
based on organic solvents, such as DMF, DMA, GBL, or
based on high water containing solvents, for so-called "low impedance", "low ESR" or "high ripple current" capacitors

Borate with vicinal  alcohols (like ethylene glycol) is one of the exceptions.  IPA is not a vicinal alcohol.  In any event, a water-based cleaner for flux should work great.  You can make you own from may household cleaners.
 


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