Author Topic: I got a dirty mac  (Read 16217 times)

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Offline crerus75

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Re: I got a dirty mac
« Reply #25 on: August 16, 2015, 02:32:34 pm »
Replying to a couple of different posts at once:

Yes, there's a danger that acetone and toluene/xylene will dissolve some plastics, but as Ketturi says, the plastic packages on most board components seem to be resilient.  Individual results, as they say, will vary.

Windshield washer fluid is often a mix of water and methanol, so it will have some cleaning ability.  In my opinion, it's not ghetto if it works-- just clever.  I would still prefer to buy straight methanol or methanol/ethanol at the hardware store, but that's because I have one close by and the chemicals are readily available.

Some of the traditional contact cleaners have been reformulated, banned, or increased in price due to regulations on the ingredients that make them up.  Luckily, methanol/ethanol/IPA are still inexpensive and readily available (at least here), and they're usually sufficient for washing down circuit boards.

If you want to use something more aggressive, I would try a commercial aerosol brake cleaner first.  If there's an MSDS for it (there will be if it's sold in the US, not sure about international regulations), read it first to see (approximately) what's in it.  Non-chlorinated ones tend to be a flammable mixture of hydrocarbons of some type.  Chlorinated ones (non-flammable, usually) are something else entirely.  A quick scan of an MSDS states that tetrachloroethylene and/or perchloroethylene are the ingredients in the chlorinated ones.  I have no idea about their composition or compatibility with plastics or their suitability as a contact/circuit board cleaner.  I tend to use the non-chlorinated variety out of personal preference.  The only reason I mix my own is because I tend to do a lot of mechanical work and when I do I go through a lot of brake cleaner.  It makes sense for me to buy in bulk, but maybe not for you.

Having said all that, whatever type of alcohol (methanol, ethanol, or IPA) you have available to you should remove most of the contamination with little to no residue.  Only use something more aggressive if you really need to. 
 

Offline Stonent

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Re: I got a dirty mac
« Reply #26 on: August 17, 2015, 03:08:59 pm »
In the US I've frequently seen denatured alcohol containing benzene as the denaturant. Bittrex is also frequently added to further deter from trying to drink it.
The larger the government, the smaller the citizen.
 

Offline ShockTopic starter

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Re: I got a dirty mac
« Reply #27 on: November 24, 2015, 09:14:52 am »
Just an update...

I ended up cleaning it in two rounds the second I went across it again completely and gently worked the problem areas. I flooded the board as I went with IPA washing off contamination to the side. Couldn't see any visible corrosion after letting it sit around a few months, even under magnification.

The dirty mac is now back in it's owners hands. Seems to work well, beeps, tells you the time etc.

Fixed! :-/O
Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 189, 87V, 117, 112   >>> WANTED STUFF <<<
Oszilloskopen: Lecroy 9314, Phillips PM3065, Tektronix 2215a, 314
 

Offline Stonent

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Re: I got a dirty mac
« Reply #28 on: November 26, 2015, 01:36:34 am »
Just an update...

I ended up cleaning it in two rounds the second I went across it again completely and gently worked the problem areas. I flooded the board as I went with IPA washing off contamination to the side. Couldn't see any visible corrosion after letting it sit around a few months, even under magnification.

The dirty mac is now back in it's owners hands. Seems to work well, beeps, tells you the time etc.

Fixed! :-/O

Something I'd like to add to this was something I saw in a recent Applied Science video.  Pure alcohol is not always as good of a solvent as a dilute mixture.  He showed cleaning a dirty slide with pure IPA vs 70% and the pure IPA got rid of some of the residue but not all.  The 70% cleaned all of it off because I think it was dirt does not dissolve in IPA but does in water.  So the mixture could clean everything.
The larger the government, the smaller the citizen.
 

Offline helius

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Re: I got a dirty mac
« Reply #29 on: November 26, 2015, 01:34:34 pm »
70% IPA leaves a lot of residues, primarily because some water is left behind after evaporating the alcohol. 91% dries quicker and more evenly and makes a better solvent. Very little flux residue is salt: only fraction of a percent of halides to increase activity. If boards have been extensively handled there may be more salt from sweat on them.
 

Offline briselec

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Re: I got a dirty mac
« Reply #30 on: November 26, 2015, 08:51:40 pm »
I've not looked into break cleaner for this purpose, would it depend on brand as well? What is it made up from? Does it have any downsides in using it?

downsides? That would be a BIG yes. Under certain conditions it can result in a painful death. Another side effect is nerve damage. Google the dangers of brake cleaner. Personally I wouldn't even consider using it.   
 

Offline ShockTopic starter

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Re: I got a dirty mac
« Reply #31 on: November 26, 2015, 11:29:11 pm »
I used 100% pure IPA in a spray bottle, it looked like it needed scrubbing so most of the work was with the soft bristled brush (very gently) when it was saturated with IPA, more as a rinsing action and to prevent static build up rather than dissolve. In this case it worked very well by itself.

The contamination ended up a soft sludge in the bottom of the container I was holding the PCB over.

 

Soldering/Rework: Pace ADS200, Pace MBT350
Multimeters: Fluke 189, 87V, 117, 112   >>> WANTED STUFF <<<
Oszilloskopen: Lecroy 9314, Phillips PM3065, Tektronix 2215a, 314
 


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