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Removing solder paste...A bit hard!

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LAN_403

Killa-X

Sat Feb 06 2010, 06:07PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

I need more suggestions. I have done what most anyone says on google. "Isopropy" and it did NOTHING. Water rinse, nothing. What do you guys recommend? I have had this solder for ages, and it never been a problem. Now that i look into it, I find this.

wrote ...

Cleans and fluxes at the same time. Blended to clean surface oxidation. 100% lead free. Effective on all metals except aluminum, magnesium, and stainless steel. No pre-cleaning necessary for clean sweat copper fittings, for other applications clean excessive dirt and corrosion. Do not use on electrical parts. Use with solid wire solder. This Solder Paste Flux is one of many top quality items in our Solder Paste / Flux department.

And yes, about that bold, I had times where i saw it physically arcing through the fix at close contacts, and a lot of pins on DIP sockets are showing 1Mohm to 30mohm resistance..and anytime i mess with the pins, such as cleaning with a wire, the resistance is changing.

What do you guys recommend to remove this stuff! Please help :( I tryed many things, Next step maybe a soak in rubbing alc.

klugesmith

Sat Feb 06 2010, 06:37PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

First: the name is wrong (but that's what it says on the can).
It should say "paste flux for soldering", and what you want to remove is flux residue.
In electronics, "solder paste" is a material that's mostly powdered solder.

Second: we see that your flux paste is made of Petrolatum, Zinc Chloride, and Ammonium Chloride. That's good for mechanical soldering, but leaves hygroscopic ionic residues that are electrically leaky (as you know), not to mention corrosive.

Try isopropyl alcohol and water, with vigorous application of a short stiff brush -- the gunk isn't going to just rinse off. Look up "Acid Brush". It may be hard to clean under the DIP socket bodies.
In electronic mfg, there are cases where we use No-Clean solder fluxes, whose residue is generally benign.

Good luck.

Sulaiman

Sat Feb 06 2010, 08:32PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

This is what I use at work.

It's for normal (electronic) soldering flux so I don't know how well it will work in your case, but it's worth keeping a can around as it's a REALLY good general-purpose cleaner.

Mattski

Sat Feb 06 2010, 08:36PM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

I'd try a stronger solvent like acetone, that has helped me get many stubborn bits of flux off of boards, it's a lot more effective than isopropyl.

Arcstarter

Sat Feb 06 2010, 09:35PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Like i told you already, carb cleaner is awesome. Really strong stuff, it will eat away at some plastics, and you really don't want it on your hands for too long. That never stopped me. It melts it away, then i use a dremel on low speed with a nylon wheel brush.

After brushing it, i sometimes use more carb cleaner, and i use compressed air to blow most of it off to make sure it does not eat through an IC socket or something crazy. The rest air drys in maybe a minute. That is why isopropyl alcohol is supposed to be good, it drys quick.

I use the same shitty flux. It works, and my connections are fine, but it is messy and very conductive (as in i can have a short caused by this crap pull a few amps at 12v). It is all i can find, i need to go to some electronics store. This stuff is made for soldering pipes and stuff, that is why it is in hardware stores.

Marko

Sun Feb 07 2010, 12:00AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I never found isopropanol to work too well for this purpose neither.
For nearly all hard cleaning purposes I use nitro-lacquer thinner which is basically a mixture of toluene and methanol. The stuff is useful for everything from cleaning solder flux and printer toner to running cars, and is very cheap - just don't inhale too much of the fumes.Thinner you can get may be a different mixture but I think it should work well enough.

Killa-X

Sun Feb 07 2010, 05:47AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Marko wrote ...

I never found isopropanol to work too well for this purpose neither.
For nearly all hard cleaning purposes I use nitro-lacquer thinner which is basically a mixture of toluene and methanol. The stuff is useful for everything from cleaning solder flux and printer toner to running cars, and is very cheap - just don't inhale too much of the fumes.Thinner you can get may be a different mixture but I think it should work well enough.

You can give the whole PCB several rinses in the stuff to clean it completely from the flux. Only take care not to dip any soft plastics like ABS into the stuff because it will readily turn them into sticky goo.

Yup. I remember that. Acetone + Styro = Fun. Melts and you can roll a ball that becomes very dense and hard. I think I'll see if our shop has itor not...Seems good I guess :)

Arcstarter, I know. This stuff suck with close connections, it just shorts out even at a few MA. I'm nearly sure all my issues,is the flux. Some pins that arnt connected read 2Mohms...Clearly a flux issue. Thanks for the helps guy, Sometime monday afternoon I'll give this a try (place close on sunday)

Killa-X

Tue Feb 09 2010, 03:06AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

To sum up this thread, I'll like to say i used Gumout.

As suggested by arcstarter, Carb. cleaner, with dremel nylon brush. I still have to work in the tight areas, but in majority, like the bottom, it FULLY removed the flux. Enough that it now works, minus a few areas that are still messy. I'll be cleaning those areas later with a more precise brush. At first, my output of this board was bad. It was solid high line, made loud buzzing noises, sucked.

Now, after the cleaning, i hear no noise. and, it works, to what i can see. Feeding the feedback with a 100khz 50% 555 timer, and feeding the fiber optical sensor with 400hz. The results:

- 400hz

- 100khz
(the lines on the high and low isnt the driver. The 555 100hz board (breadboard) is outputing that crappy signal.)

Thanks all for helping!

MinorityCarrier

Tue Feb 09 2010, 07:32PM

Registered Member #2123 Joined: Sat May 16 2009, 03:10AM
Location: Bend, Oregon
Posts: 312

Per what Klugesmith pointed out, use distilled water to remove the corrosive ionic salts (zinc and ammonium chloride), follow with an isopropyl rinse to remove the water.

Acetone is a good, if highly flammable, organic flux remover, just keep it away from solvent-sensitive plastics.

Dr. Drone

Tue Feb 09 2010, 08:54PM

Registered Member #290 Joined: Mon Mar 06 2006, 08:24PM
Location:
Posts: 1673

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