tegwin
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| posted on 16/2/10 at 05:13 PM |
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Plumbing flux on electrical components?
Does anyone know if I can use plumbing flux paste in very very small quantities to help solder electrical components to a circuit board?
Is it any different to electrical flux?
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minitici
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| posted on 16/2/10 at 05:19 PM |
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Plumbing flux is probably a very acive acid based flux.
PCB fluxes tend to be a lot less aggressive and can often be left on the joints without any adverse effects.
The plumbers flux will probably eat away the boards, tracks and components over time !
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bigandy
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| posted on 16/2/10 at 05:21 PM |
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yes you can, but make sure that you clean it all off after tyou have finished! Quite often, pluumbing flux is rather agressive (acid based?) and if
left on after soldering, it can cause corrosion of delicate electronicy bits.
Washing it off thoroughly, should alleivate that problem though.
Normla electronics type solder has a rosin core, which is non corrosive...
Andy
Dammit! Too many decisions....
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Toltec
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| posted on 16/2/10 at 05:26 PM |
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I have never tried it, however the flux cored electrical solder is more for convenience than anything else so it should work.
Plumbing flux formulations vary and they are probably more aggressive than electronics types so make sure you clean off any residue immediately. I
would suggest you try some test joints, if you get a nice smooth shiny joint then I suspect you will be fine.
ETA - Too slow 
[Edited on 16/2/10 by Toltec]
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tegwin
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| posted on 16/2/10 at 05:32 PM |
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What would be best to clean off the plumbing flux?
I have a few of these surface mount LEDs I need to stick down to test..
So was going to use flux to help the solder flow under the component... although I guess I could just tin the pads and the board and use a bit of heat
to remelt the solder...rather than use extra plumbers flux...
and yes.... thats a 5p!
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minitici
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| posted on 16/2/10 at 05:38 PM |
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Probably want to use a solder paste to solder those SMDs.
The paste has the flux combined with the solder.
You can often use a very small heat gun to run the solder.
Failing that a small tipped solering iron (especially if you can get to an edge of the component solder pads).
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tegwin
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| posted on 16/2/10 at 05:42 PM |
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Yup.. solder paste would be ideal... I dont really want to order any in unless I need it though... Trying to build my test setup on a budget.... but
dont want to damage the LEDs though... at nearly £4 each...  special order from the states lol
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r1_pete
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| posted on 16/2/10 at 05:46 PM |
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You really should use fine, 0.6mm resin cored electronics solder, and a fine tipped iron for this.
Using flux paste is likely to result in the solder flowing everywhere and bridging the pcb conductors. It is also very corrosive, ok on copper pipe it
can be flushed away afterwards but not on electronics.
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rf900rush
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| posted on 16/2/10 at 05:58 PM |
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Flux for Surface mount helps,
As with any type of work, practise first.
Most electonics parts use surface mount.
So just remoive parts and re-fitting parts from an old broken unit will get youy some good practise.
You could use the plumbers flux but clean well. use IPA (alcohol).
Note. The new Eurocrap lead free is useless, may work on large production lines but you can't beat the old leaded solder for hand work.
Martin
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BenB
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| posted on 16/2/10 at 06:04 PM |
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I thought plumbers solder flux was just tallow?
"A soldering fat for tin-plate, preferable to ordinary rosin, as it can be more easily removed after soldering, is prepared as follows: One
hundred and fifty parts beef tallow, 250 parts rosin, and 150 parts olive oil are melted together in a crucible and well stirred, 50 parts powdered
sal ammoniac dissolved in as little water as possible being added."
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BenB
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| posted on 16/2/10 at 06:04 PM |
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Though that's from a 1916 book
http://chestofbooks.com/reference/Henley-s-20th-Century-Formulas-Recipes-Processes-Vol3/index.html
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rf900rush
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| posted on 16/2/10 at 06:12 PM |
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I mounted power led's on 6mm wide copper strips mainly for the heatsinking effect.
Good control of heat will be needed if the led has a thermal pad as well.
This was my 1st power led use.
I think Cree XPG (LINK) are worth a look at as well.
I think currently the highest Light output per input power.
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Andybarbet
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| posted on 16/2/10 at 11:02 PM |
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You can use a product called 'FLUX OFF' to remove it, we use it at work a lot & im pretty sure RS sell it.
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02GF74
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| posted on 17/2/10 at 07:31 AM |
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can't recall ever using plumber flux..
you can make your own solder paste by filing a piece of flux, collecting the filings and mixing it with flux - no idea how it compares with the pukka
stuff.
be ware of using any heat gun, the flame is very hot and not very concentrated so it is easily to burn and melt components near the bit you are trying
to solder (no need to ask how I know that).
A fine tip soldering iron would be much better.
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iank
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| posted on 17/2/10 at 08:50 AM |
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When I soldered down some SMT LED's I just built up the pad into a small mound of solder (similar amount to a through hole resistor) balanced
the LED on both ends (holding gently with some tweezers) and applied the fine tip iron onto the solder from the side, it melts and 'sucks
down' the LED onto the pad.
You can buy all the proper stuff from RS or Farnell but for a few components now and again it's not worth it.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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