I finally caved and bought a temperature-controlled iron (a Weller WES51: yay, accurate control; boo, arcane °F temperature scale). I don't think I have the right temperatures dialled in yet. What would folks recommend for 96.3% tin, 0.7% copper and 3% silver (MG Chemicals #4900 — Lead Free Solder)? At the moment, I'm getting little spherical joints rather than the more familiar conical ones.
Unleaded solder generally does require higher temps. From the datasheet you linked:
Lead free/leaded solder comparison Lead Free Solder (Sn/Ag/Cu) Sn63/Pb37 (Leaded Solder)
Melting Point 217-221 º C (422.6 - 429.8 º F) 183 º C (361.4 º F)
If your SAC alloy doesn't 'behave' as expected, there are several things to do:
- make sure your materials are clean in good shape, that is no excessive oxidization is present (dull copper)
- use more flux, maybe even a more aggressive flux
- increase the temperature. once you get 'instant charcoal' it is too high.
You'll have to do some testing. Personally I hate 'lead free' solder, and it hates me as well.
I suggest using eutectic lead/tin solder like God intended.
If that is an option, it's the best way to go. 
I myself tried to go 'green' a while ago and still have a much hated 200g spool of supposedly 'easy to use' and 'quasi eutectic' lead free solder sitting here. Every time I see it, my heart skips a beat or two... :0
Sorry, leaded isn't an option. I guess I'll just have to fiddle with the temperatures, thanks.
As a newbie solderer I found the temp controlled iron was a big help with lead free solder.
I had a big reel of lead solder handed down from my wifes dad. No idea how old it was but its lasted me a long time and gave great results even with a cheap iron.
The difference I found is that the lead solder is more forgiving.
The lead free solder needs extra flux and everything immaculately clean.
I find rubbing the solder pads with the pcb rubbers/cleaners, even if they look clean, essential.
Gordon
I have a big reel of leaded solder that I bought in 1980 for what seemed like a huge amount of money at the time. Its getting pretty thin now. But I do find it just so much easier than the lead-free variety.
Given that my last reel of solder has lasted me 30 years, I don't feel too 'un-green'.
You can still buy leaded solder - CPC in the UK sell it, and would hope most of the big components suppliers will sell it too.
I hate lead-free solder, but I have to use it beacause of work.
I find that for through hole tin/lead i set between 700F to 750F
Tin/lead SMT i set 600F to 650F (a little high)
lead free:
750 SMT
800 TH
now before everyone flips that my temps are high, remember that I solder fast. These are momentary touches to component leads
Si:
Given that my last reel of solder has lasted me 30 years, I don't feel too 'un-green'.
It's not a "green" thing. It's a "not wanting to have a listed neurotoxin in an uncontrolled cycle" thing. Lead's quite spiffy if you can keep it in a closed use-recycle loop, like with car batteries. The way I solder, the word control doesn't come into it ...
Anyway, with some fiddling about, I've found that 275°C/530°F has a decent balance between
- melting the solder quickly
- not burning off the flux before it has a chance to work its magic.
I think I had the iron too hot, hence the blobby, unwetted joints before.
Thanks for all the help.
Lead is not the boogey-man some have made it out to be. Don't ingest it and there are no problems. This amounts to having the brains to wash your hands before eating and not letting kids gnaw on it.
I find it quite ironic that allegedly "green" groups are pushing CFLs, which contain mercury which is a problem, quite mobile once it gets loose in the environment, etc.
Your 530 degree iron sounds a bit too low to me. Ironically, a too-low iron temperature can result in heat damage to components. You can end up with an unacceptably long dwell-time and transfer lots of heat into the part, where a higher temperature will allow you to get the joint soldered and remove the heat source before the component gets so hot.
-j
kg4wsv:
Lead is not the boogey-man some have made it out to be. Don't ingest it and there are no problems. This amounts to having the brains to wash your hands before eating and not letting kids gnaw on it.
Pretty much all elemental metals are fairly nasty to ingest. Lead's a bad one; there was a lot of lawsuits and industrial action in the early part of the 20th century from the garment makers (white lead used as a marker), painters (white lead causing wrist and leg drop) and petroleum workers (tetra-ethyl lead fumes). Lots of unfun reading in books like Markowitz, Gerald and David Rosner. Deceit and Denial. Berkeley: University of California Press, 2002.
I know I would follow the guidelines, but I can't guarantee that the people that get my stuff after me will. Having known someone whose life was blighted by lead poisoning, I don't want to take that risk.
I find it quite ironic that allegedly "green" groups are pushing CFLs, which contain mercury which is a problem, quite mobile once it gets loose in the environment, etc.
I work in the power industry. Even if CFLs are disposed in the worst way possible, the mercury released is far less than the mercury emitted by power plants needed to drive incandescents. Either way, I'm glad that domestic LED lighting is now affordable, and I'm replacing CFLs as they fail with LEDs.