Lately I have started to do work with PCB SMD components and my biggest headache so far has been cleaning the board afterwards (e.g., to remove excess flux). I use 91% IPA and Q-Tips (as that is all I've had on hand) but that tends to leave fibers which then I have to pick off with tweezers.

Since my project will deal with a lot of SMD components (up to now I have just been practicing soldering/desoldering various sizes and footprints) I want to get proper swabs to clean up with.

I checked online and there seems to be two major types, which are microfiber swabs and foam swabs. As I have never used either type of these products, I really don't know which ones I should go with. Can anyone provide some recommendations on the pros/cons of either of these or if it even matters when it comes to using them for PCBs (as they seem to also be used for lab work and in other fields as well)? TIA.

 

leave fibers which then I have to pick off with tweezers

Have you tried using compressed air or a brush? I use a shoeshine brush to get dust off boards. That should work for lint too.


I use a horsehair acid brush with the bristles cut to 1/4" or less (some less than 1/32") with 70% IPA and finish up with 90%+ IPA. To spot dry, I use Kimwipes rolled up and put in heat shrink. I use several different diameters of heat shrink.

90%+ IPA evaporates too quickly unless you submerge the board in it.

For really stubborn cases, I use a commercial flux remover. Spray it on, scrub with an acid brush if needed, and use more spray to wash any residue off of the board.

 

Or, swish board around in paint thinner and use toothbrush where needed. Only when there are no electrolytics, relays, or other parts that may not like a bath in solvent. I also use MG Chemicals Flux Solvent (mostly hexane (white gasoline)) which is super-fast evaporating and "toothbrush" and swabs of several sizes with foam or felt tips which get ripped up but don't leave fibers behind. Unlike a paint remover bath, it takes several times to get the rosin off because the flux remover evaporates so fast. Yeah Q-Tips work but often leave lots of fiber behind. Then there is the dishwasher method...

 

It depends on what solvent your flux dissolves in. Some water-soluble fluxes are only partially soluble in isopropanol, and if you clean the board with it, the result is a thin sticky film of flux all over the board.
For water-soluble flux, I use a toothbrush, washing-up liquid and hot water. Then leave the board on a warm radiator to dry thoroughly. Otherwise, you will find water trapped under large components such as relays and that's not good if they are switching mains! With a brush, you can keep as much of the water as possible on the soldering side.

 

First, get the datasheet for the flux you are using. It should contain information about cleaning.

@Ian0 is correct that IPA may not be sufficient for water soluble flux. You may need to mix IPA with distilled of deionized water (it wouldn’t take much water) to get good removal.

As far as swabs go, the flat foam swabs (usually sold as “clean room” swabs) and some pointy versions will do a good job. The flat ones are far more absorbent than cotton swabs and will absorb a lot more of the solvent-flux solution. The pointy swabs will let you get residue in the smaller spaces where the flat ones may leave something behind.

Which flux are you using?

 

I second the toothbrush recommendation. That is what I use.

 

I was being dragged around a kitchen shop whilst on holiday in Leiden when I spotted my perfect heavy duty pcb cleaning brush
https://www.dille-kamille.com/small-brush-brass-wire-with-beechwood-handle-00005656.html
It was labelled in Dutch so I don't exactly know its original purpose.
I did learn one lesson the hard way about using it: double check that the power is switched off first.

 

I also have some of the jumbo "toothbrushes" in brass and stainless for the hard jobs as well as the nylon ones.

 

Kim-wipes, you can always tell a guy that's been in a Fab for a while.

I never use Q-tips, only line-free wipes and a toothbrush with a hot-air gun set to 90C to remove liquid from under parts.
https://www.testequity.com/category/Electronic-Production-Supplies/Cleanroom/Wipes

 

It depends on what solvent your flux dissolves in. Some water-soluble fluxes are only partially soluble in isopropanol, and if you clean the board with it, the result is a thin sticky film of flux all over the board.
For water-soluble flux, I use a toothbrush, washing-up liquid and hot water. Then leave the board on a warm radiator to dry thoroughly. Otherwise, you will find water trapped under large components such as relays and that's not good if they are switching mains! With a brush, you can keep as much of the water as possible on the soldering side.

I was thinking the same thing. Switching to water soluble flux is the way I have gone. I can wash the board then let it dry. IF there are areas that can retain water, spending 10 minutes in a warm oven (250˚F) will boil out any water moisture that may be left over.

My wife washed our microwave oven. In doing so she loosened grease that had accumulated near the electronics. In her cleaning that grease it became mobile and dripped down onto the board. The oven would no longer work. So I took the control board out and washed it in IPA. Then I washed it a second time using water to rinse out any alcohol that may have been left over. After that I blew the board dry with a hair dryer. Put it back in the microwave and it worked just as before. That was 2 years ago. It's still working fine. No harm was done by the grease, alcohol or water.

 

Kim-wipes, you can always tell a guy that's been in a Fab for a while.

I never use Q-tips, only line-free wipes and a toothbrush with a hot-air gun set to 90C to remove liquid from under parts.
https://www.testequity.com/category/Electronic-Production-Supplies/Cleanroom/Wipes

I always have a box of Kimwipes on the bench (the 4.5” squarish ones), and they are great though they tend to get shredded by through hole boards. I also have a box with the camera gear—they are good for all sorts of things.

I now also keep these on hand. I thought they looked good so I bought some to try. While they are not cheap they are really good. They are non-woven, no lint, but very soft and strong. I found they are effectively reusable for many applications where contamination isn’t an issue. They don’t feel disposable. Really nice.

 

God how I miss Kim Wipes. Had them all over the plant for cleaning eyeglasses and nothing works better.

 

God how I miss Kim Wipes. Had them all over the plant for cleaning eyeglasses and nothing works better.

This is also a common brand.
https://www.texwipe.com/alphawipe-tx1004