Favorite PCB cleaners

gregz wrote in news: snipped-for-privacy@news.eternal-september.or g:

I hope your compressed air is oil-free. Plus,compressed air can build up a static charge that may harm your semiconductors.

"rubbing alcohol" is IIRC,30% water to begin with,but you can but 91% isopropyl alcohol at CVS.

also,while at TEK,I used to put 2235/36 DMM boards into my dishwasher to clean them,using Calgonite,they had a very hi-Z input section and that wash would often cure leakage problems. After the wash,the boards went into a drying oven,I did NOT use the dishwasher's drying heat,that can damage the board.

also,some city water supplies have a high mineral content. a final rinse in deionized or distilled water may improve your leakage results.

--
Jim Yanik
jyanik
at
localnet
dot com

Rubbing alcohol sold at retail in the US is required to have extra 'stuff' added to it to help discourage idiots from guzzling it.

That added junk leaves a white residue if you try to use it for cleaning.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

If you have a Fry's handy, look for Pure Tronics Technical Grade isopropyl alcohol. In California, there is a warning label on the side to instruct you to dilute it with water to meet VOC standards. Uh, right, sure thing, wink wink. It is about $6 or so for 32Oz and is 99.9$ pure. Maybe they only have it in the gallon size now, according to the website.

You do need to insure everyone in the lab handles chemicals in a manner where they don't contaminate the bottle. Common sense stuff.

Nice link. While some of the denaturing chems are solvents, there is more gunk than I realized.

--------------------------------------- "the remainder consisting of water and the denaturants,with or without color additives,and perfume oils"

--------------------------------------

Depends. We have an oil-less compressor, but it drives everyone outside screaming whenever I turn it on. So, at that facility, I just shake them vigorously and let air dry.

At another facility, I have an oil-lubed compressor with a couple filters in the line, and have no problem with oily stuff coming out the other end.

I don't think the air in a can can really produce enough blast to blow all the remaining alcohol off the board.

Jon

Usually right after soldering it is not a problem. Over two weeks or so, the flux picks up moisture, and conductivity goes up. Some fluxes, like the "no clean" variety are supposed to be less of a problem in this regard, but I have still had some problems with them. Other fluxes can become REALLY conductive over time, sometimes it takes months to get really bad. But, in a few bad cases I have had flux become conductive enough to affect lines that have internal pull-ups or pull-downs on digital chips, so the flux between adjacent chip pins was down below 10K Ohms!

Jon

OK, I'll try that and see what happens.

--

John Larkin, President       Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

A vapor phase degreaser can be made rather inexpensively. Start with an empty 1-gallon can that held paint thinner, or anything like that; it is the size and shape one is looking for. Get some copper tubing,load with sand and bend to fit just inside and near the top of the can; one turn is sufficient. Run tap water thru the tubing for the cold trap and use a 100 watt heating pad at the bottom. Use your favorite degreasing agent: MEK, Gumout Carb+Choke cleaner, Napthalene, Vodka, HOH, etc.

• BUT that compressed air better the hell be oil free (no compressor oil)..

I don't understand vapor degreasing. If you stick a dirty object into hot solvent vapor, the vapor condenses onto the thing, and the crud dissolves and runs off. That's the theory. But if the object is complex and flat (high surface to mass ratio) and has low specific heat - like a PC board - it will heat up rapidly, the condensation will stop quickly, and crud tucked away under surface-mount parts won't get swept away. A PC board immersed in vapor will just drip a little for a few seconds and then stop.

Our cleaning machine has a boiling tank, a refrigerated condenser, and a clean solvent tank. It continually distills solvent from the boiling tank into the clean tank. We clean boards by dunking them into the boiling tank (which includes a defluxing agent) and then lifting them out and spraying them with a wand that sprays clean solvent under high pressure. There's no requirement for condensation onto the board, and the board's specific heat doesn't matter. The board gets blasted with hundreds of times more solvent than condensation would provide.

--

John Larkin, President       Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

Don't use solvents - use Safewash (from Farnell/Newark etc) in an ultrasonic cleaner. Rinse with tap water. Rinse 2 or 3 times with de-ionised water (if you have big chips with small gaps between board and chip a LOT of rinsing is needed, ultrasonic rinse at rinse 2 is good.

Then if it might be damp you need to coat the board.

It's all very well measuring 10E13 ohms on the bench but if you want lowish leakage after a year in service you need to coat.

I once got caught with a circuit with a 10M bias resistor but about *

100 gain from input to output, very low frequencies, but of course the leakage path only needed to be 10M * 100 * 10 = 10G to affect the gain to an unacceptable degree.

You need to be sure the board is REALLY clean before you coat.

Michael Kellett

More bullshit. IF you buy IPA at the store, THAT is what you get. IF you buy some lame crap with something added to it, it will NOT say "IPA" on the bottle. It will declare that it is NOT a singular compound.

IPA is IPA. Your wintergreen CRAP is CRAP, NOT IPA.

So, AGAIN, IF you buy IPA, it doesn't matter where you get it from, if it is properly declared as to what it is.

Only complete and utter retards ever bought something from the store that was NOT pure alcohol, then comes in here pissing and moaning about the store you made the STUPID purchase from, instead of pointing your retarded finger at the purchaser himself.

YOU are an idiot. Pretty much plain and simple.

It doesn't "build up" ANY charge. The problem with ESD that compressed air causes is created at the time the air is passing through the insulative tubing containing the stream. That is where and when the triboelectric effect that "charges" it up occurs (and simply air rubbing on air).

You can buy an inline deionizer from 3M. It goes right at the dispensation head. You should keep your air pressure below 80 PSI too for blowing on parts and assemblies.

You are a goddamned idiot. IPA is poisonous all by itself, and doesn't need an additive to keep some lame skid row idiot from drinking it.

You are a goddamned retard if you do not know how to get 91% or better pure IPA AT your druggist.

You spouted this CRAP before.

You were wrong then too.

They do NOT heat up as fast as you claim and DO allow ALL the "crud" to be freed and rinsed free.

Only idiots like you, who then DIP the assembly in the filthy bath, f*ck up a perfectly good vapor phase cleaning process step.

ZERO mention of a baking step?

You are an idiot!

If you ever coated a board that you cleaned with water and did not bake it or even vacuum bake it first, you didn't know what the f*ck you were doing.

Get proper industrial material like this:

99.8% pure IPA Does not contain denaturant (bitterant) Non-ozone depleting Ideal for electronics cleaning

.. not cheap adulterated consumer products. And make sure H&S rules to respect the flammability are in place.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Hey, Puretronics is 99.9%. Of course, 0.1% borders on audiofoolery. The point is to stay away from the drugstore.

Do you live in East Bumfuck? Just go to an electronics store and get the right stuff.

Call me an idiot. See if I care, given the source.

Hey, I'll call you a Jim Thompson. OK, now we're even.