The proper way to clean PCBs...before & after soldering
BR
Posts: 92
What is the "best practice" for cleaning PCBs? I've caught snippets of information here and there on the forums, but would like to be sure I've got it right.
I believe the following to be true:
1) I should clean my PCB with isopropyl alcohol both before and after soldering. The before is to be sure the pads are clean of any oils or films. The after is to remove the flux, which is mildly acidic (?) and, over time, will attack the solder joint.
2) I should use the type of isopropyl alcohol that you get in the paint section of Lowes or Home Depot (which is ~95% alcohol), and NOT rubbing alcohol (which is 50% alcohol, 50% water).
3) I should clean the PCB by dipping a q-tip or small brush in alcohol and wiping it across the PCB surface, following that with a wipe from a clean cloth or q-tip to dry it a bit.
Should I clean both top and bottom of the PCB after soldering is complete? If so, how do I ensure that I've thoroughly cleaned the front, as the many nooks and crannys of the components seem like they'd be tough to clean. I assume, but do not know, that it would NOT be a good idea to simply drop the populated PCB into a pan of alcohol, swish it around a bit, and tamp dry with a cloth.
Any advice on tools, techniques, and procedures would be appreciated.
I believe the following to be true:
1) I should clean my PCB with isopropyl alcohol both before and after soldering. The before is to be sure the pads are clean of any oils or films. The after is to remove the flux, which is mildly acidic (?) and, over time, will attack the solder joint.
2) I should use the type of isopropyl alcohol that you get in the paint section of Lowes or Home Depot (which is ~95% alcohol), and NOT rubbing alcohol (which is 50% alcohol, 50% water).
3) I should clean the PCB by dipping a q-tip or small brush in alcohol and wiping it across the PCB surface, following that with a wipe from a clean cloth or q-tip to dry it a bit.
Should I clean both top and bottom of the PCB after soldering is complete? If so, how do I ensure that I've thoroughly cleaned the front, as the many nooks and crannys of the components seem like they'd be tough to clean. I assume, but do not know, that it would NOT be a good idea to simply drop the populated PCB into a pan of alcohol, swish it around a bit, and tamp dry with a cloth.
Any advice on tools, techniques, and procedures would be appreciated.
Comments
You are pretty close to the whole idea.....
I sometimes use an old toothbrush (should be teethbrush) on the boards to get into the nooks and crannys. We also do drop boards into a ultrasonic cleaner with IPA (isopropyl Alcohol). There is a caveat to this. If you have any parts which are not to be washed, this is not a good idea. Usually these parts are buttons or dip switches. The Datasheet will say. Also......there are possibilities you may break a chip with ultrasonic. Most of the time I do not have problems, but when I do it's typically a crystal which dies.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
I remove flux after soldering by brushing with 99% IPA. The diluted stuff is useless.
Leon
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Amateur radio callsign: G1HSM
-Phil
Phil,
We have a fire suppression system in the enclosure that the ultrasonic cleaner sits in (Halon). It also has a lid on at all times in operation. We thought of the possibility of fire when using ultrasonic with IPA.
It does create a serious fire hazard. The ultrasonic cleaner creates a huge amount of alcohol vapor when in operation. That is why we enclosed it and vented it with a sealed fan. We were going to seal the tank it but wasn't ever successful making a lid which would seal during operation.
It should be noted that anyone who places a flammable liquid in an ultrasonic cleaner should be aware of the risks. This is inherently dangerous unless serious safety provisions are used. Even then, a possibility of a fire or explosion is possible. We do not take responsibility of anyone who tries this on their own!
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
@Leon: "PCBs don't need cleaning before soldering if they have been made properly."
An interesting statement...could you elaborate a bit? What constitutes a "proper" PCB? Are you saying that the pads can be laid out in such a way that having a bit of oil or other contaminate does no harm to the joint? Or are you saying that if they've been manufactured to high standards, they should arrive in a clean and ready-to-solder condition? And if the latter, let's say that I've handled the PCB a few times and gotten my grubby fingerprints on it...in which case prudence suggests I ought to go ahead and clean it a bit before soldering. Or maybe it would be fine to just wipe it off and call it good?
@James/Phil: no worries, I assure you that an ultrasonic cleaning machine is well beyond my means and needs at this point, but thanks for the info. Duly noted.
Leon
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Amateur radio callsign: G1HSM
Post Edited (Leon) : 12/29/2009 10:11:45 PM GMT
I clean assembled boards with a toothbrush dipped in isopropyl alcohol. Most of my hand assembled boards need two cleanings - I use a lot of flux.
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·"If you build it, they will come."
-Phil
Addendum: But no Scotchbriting boards with soldermask! You could easily scrape it off.
DJ
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There are many more issues with water soluble paste. First open air time is much shorter. Humidity can be a definite problem (shortens the open air time further).
The ramp to reflow needs to be very close to the needed profile, and doesn't deal well with much variation.
James L
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James L
Partner/Designer
Lil Brother SMT Assembly Services
Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
generally you only have to clean the pcb after you solder the board though if you find solder does not run easy to the pads they have probably oxidized and cleaning or strong flux is needed.
Generally I use IPA and a hog hair brush. I have a special dispensing container for the IPA that dispenses a small amount at a time and any excess not used rapidly evaporates. This way you can not contaminate the IPA.
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24 bit LCD Breakout Board now in. $21.99 has backlight driver and touch sensitive decoder.
I've never needed to clean the board before soldering, but I guess if your board has been sitting out for a few months, you might need to.
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-Phil
The MG spray is actually 90% Ethanol, 5% ethyl acetate, 5% IPA.
Acetone is reactive to some plastics (like DIP sockets), so you shouldn't spray it on the plastics side of the board. It's only effective in dissolving epoxies before they harden, (or so says wikipedia) so it doesn't attack the FR4 or soldermask.
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But I also use 5 core Rosin solder that eats oxidation for lunch and dinner , so I normality don't ever have a issue with pre cleaning ..
As for post cleaning I use IPA for the " light stuff " and I use toothpaste with a hacked (needed new batts) soniccare brush for the hard to remove stuff.
After I use DI to wash the PCB ....
Works Wonders!
Peter KG6LSE
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peterthethinker.com/tesla/Venom/Venom.html
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LOL
And as I found out recently, it also reacts nicely with the plastic lid on my washing machine, and the epoxy coating on my floor boards [noparse]:([/noparse]
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Life may be "too short", but it's the longest thing we ever do.
Well, that'll learn ya to wash your clothes and your car in acetone...
</sarcastic_voice>
I don't think so that there is any need for cleaning PCB before soldering. But if you think that your board might have some dirt or other pollutants then cleaning board before soldering have no issues as well.
If you don't clean your flux off after soldering you have a boards that looks horrible, all covered in brown gunge. At least mine do.
The only times I have had to clean boards before soldering was when using really old stock PCB from a surplus store that where all the copper had a good thick layer of oxide on it. A quick rub sown with a scouring pad made soldering those boards much easier.
https://www.elektormagazine.com/news/saturday-afternoon-give-your-oscilloscope-a-good-wash-down
Here is the recipe from the Tek service engineer mentioned in the article.
Besides looking extremely ugly, some fluxes become slightly conductive after being heated. The flux paste I use contains zinc chloride and absolutely becomes conductive. ISA and a toothbrush does remove it. ( I should get rid of that little can, it's about 40 years old! )