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Advice on SMD Soldering

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Flux should not contain acid. In theory any flux for electronic use should (at worst) look a bit unsightly if you don't clean it off. I have a few bottles of board cleaning liquid that's designed to remove flux residue etc. In most case a spray wit isopropyl alcohol and a scrub with a toothbrush will remove almost everything. I think that main benefit of the exotic cleaning liquid I have is that it's not flammable.
 

shumifan50

Jan 16, 2014
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You can buy aerosol flux remover that I found quite good.

I found that for multi leg ICs, tinning the pads lightly (not too much solder), then tacking 2 corners, a good way to start. Then just use a clean tip (no solder) and push down on the top pad bit of the leg briefly to make the connection for each leg. After the tinning I normally apply flux, with a flux pen, to the tinned pads.
Simple components(which includes 3 leg BJT or mosfets) I tin one pad, hold the component in place and reheat the solder, I then solder the other side(s), adding solder to get a fillet between pad and component end. I then re-solder the first side. This allows the component to be flat against the PCB.
In all cases it is best to use as little solder as you can get away with.
After completing the population of the board, I clean it with aerosol flux remover.

I, like Steve, use a flat tip about 3mm wide for all my SMT work, but be sure to have some de-soldering braid available.

For most hobby purposes, I found 1206 to be perfectly acceptable and it doesn't strain my old eyes as much.
The most difficult items are ICs like 80pin TQFN packages - mostly it is difficult lining them up properly and it is important as tolerances are small on these packages.
 

Supercap2F

Mar 22, 2014
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(*steve*) said:
What sort of soldering iron do you have?

I have this one. They don't have a very good selection of tips, unfortunately. :( Thanks for explaining about the resistor/capacitor size numbers!:)

Regards

Dan
 

Rleo6965

Jan 22, 2012
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Flux should not contain acid. In theory any flux for electronic use should (at worst) look a bit unsightly if you don't clean it off. I have a few bottles of board cleaning liquid that's designed to remove flux residue etc. In most case a spray wit isopropyl alcohol and a scrub with a toothbrush will remove almost everything. I think that main benefit of the exotic cleaning liquid I have is that it's not flammable.
It's very hard for us to buy 100% Isoprophyl alcohol here in Manila. Can I use Denatured alcohol?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Google "Cleaning PCBs" and you'll find lots of information. This is as good as any. And this. (they agree on most points, the difference is in local alternatives)
 
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