A few questions regarding cleaning a PCB

[clee290]

So I swapped the switches on my keyboard today and there is the flux residue (from today's soldering job and the first time I solder switches on), so I'd like to clean it up and I have a few questions.

What's the best method of doing this? I've read some people say to use a high percentage of Isopropyl Alcohol (over 90%) and a toothbrush to scrub it. Is this still a good method?

Also, I noticed that I can buy it in a plain bottle form and also in a spray bottle. Would it be better to spray the alcohol directly onto the PCB and then scrub it or put some alcohol into a small container, dip the brush into the alcohol and then scrub?

I think that's all the questions I have for now.

[hasu]

yes, they work well. you can use ESD safe brush instead but you won't have problem with toothbrush.
I'm using 99% IPA now, though 75%+ works well for me. Lower than that takes longer time to dry and I can't bear it.
Apply it with small bottle with nozzle. And you will need lint free paper to wipe solved residue, Kimwipes is useful there.

[clee290]

yes, they work well. you can use ESD safe brush instead but you won't have problem with toothbrush.
I'm using 99% IPA now, though 75%+ works well for me. Lower than that takes longer time to dry and I can't bear it.
Apply it with small bottle with nozzle. And you will need lint free paper to wipe solved residue, Kimwipes is useful there.

Thanks for the reply, Hasu! Love your HHKB controller, btw Gonna look to pick up some IPA tomorrow!

[jcoffin1981]

I use a 3/4 inch brush from a craft store (I don't know if it's horse hair, it may be synthetic). I dip it in the alcohol and wipe the pcb.  In a pinch you can use 70% alcohol as the higher percent ones can be hard to find.  In theory the 70% may work a little better because of the water content.  It still evaporates fast enough where the higher moisture content isn't a problem. 

Kimwipes are great because the don't break, rip, or leave any paper crumbs.  I use them for an assortment of things.  There intended use is for cleaning of microscope lenses and stuff, but can be used anywhere.

[tp4tissue]

I wouldn't use the tooth brush,   depending on the quality of the board, you might either break something off,  or lift a pad, or dig under the lacquer causing rust.


The alcohol is fine, but in this case it's Flux that you're cleaning,  flux is only somewhat soluable in alcohol.

they make special flux cleaner that you can buy.

I would stick to paper towels



Flux cleaner is expensive and difficult to use though , but it's 100% safe on the board, that's why they sell the stuff.


Alcohol may work faster,  and is more practical,  but it's aggressive on the lacquer and can sometimes cause rust.

[clee290]

Thanks for the replies. I ended up cleaning it before seeing your posts, but I appreciate the tips! I picked up some 91% earlier today and got to work. The toothbrush didn't end up working that well for me. It seemed too soft and felt like I would've needed to scrub quite a bit. I ended up using the toothbrush to apply the IPA (sort of like a stamp) to the spots of flux and then took an old cotton t-shirt, wrapped a layer of it around my finger and rubbed/scraped at the flux until it was gone. Hopefully that's not a terrible way to do it

[tp4tissue]

always be careful with cloth, because it's much stronger than paper,   if it gets caught on an smd component, you could rip that component off..  whereas the paper itself would've been torn vs the cloth.

[clee290]

Ah, I didn't really think of that. I did wrap the shirt pretty tightly around my finger, so that may have inadvertently helped me avoid getting the shirt caught on SMD components. I will go with paper towels next time though 

[lolkey]

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Try these ^