How to wash off flux residue?

For the people who have not used liquid flux pens. They come in regular, no-clean, and water-soluable formulations. Could be more.

At first take it does seem wrong to make flux that needs to be removed. Maybe you can make a more aggressive flux if you expect the user to remove it. Could be less expensive to manufacture.

My sample is not large but, the must-be-removed flux pen was about half the price of the no-clean pen. The must-be-removed flux is more effective but the no-clean works well enough if the board is not too oxidized.

Nigel Goodwin said:

Why is there flux that needs removing in the first place?, I can see the reason for flow soldered boards, but for competent hand soldering there shouldn't be any excess flux to remove?.

Click to expand...

Many of my boards can have excessive flux residue on them. Not all boards are created equal, nor are all parts. The majority of boards that I work on have multiple layers containing solid planes of copper. These boards typically do not utilize thermal reliefs. The components themselves range from 0402 resistors/caps to through hole capacitors to large QFN packaged parts that have a nice thermal pad on the underside. Removing or adding components by hand can require copious amounts of flux.

Cleaning is easy - just soak in an alcohol bath for a few minutes then run under a faucet to rinse, blow off the water with compressed air and stick into an oven to dry.

Sorry, I wasn't aware we were talking about SM boards - where I agree, lots of liquid flux is essential!