mvs sarma

Hi Chemelec,
But most solder wires sold contaon rosin inside and it is equally bad? -- I do agree cleaning with distilled water is done by many. Any other solution to get rid of left over rosin or such material as it is really posing problems in HF circuitry and oscillators.

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Regards,
Sarma.

3v0

I agree. As the spacing between traces and parts decrease the ill effect of flux conductivity increases. It may be a waste of time if you never run a trace between pad or build on a protoboard. The nature of the flux makes a big difference.

Oznog

hmmm... does it have capacitance?

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I thought what I'd do was I'd pretend I was one of those deaf-mutes.

Dean Huster

If the circuit you're building is that terribly sensitive to flux residue, maybe you shouldn't be building it on G-10 glass epoxy board in the first place!

ALL flux is corrosive -- your usual rosin flux (vs an acid flux) is very corrosive at soldering temperatures and pretty inactive at room temperature. If it weren't corrosive, it wouldn't be very helpful with getting the surfaces to be soldered clean.

Yes, "cold" flux in high humidity and on high impedance PCBs (in excess of 10M ohms) could easily be a problem. I don't see any problems with it on digital, processor, audio and HF boards. Does it affect between-trace capacitance? Sure it would, but most the effect won't be that great as the dielectric constant of flux I'm sure is a lot lower that that of glass-epoxy.

Dean

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Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

Nigel Goodwin

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?.

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3v0

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.

OutToLunch

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.

Nigel Goodwin

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

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk