Re: Desoldering: Thin layer of solder left on pads

longjohnstuartmill@xxxxxxxxxxx wrote:

I've tried 60/40 tin/lead solder and noticed a huge difference between
the solder with lead and the stuff without, especially when I was using
a 15-watt iron from Radio Shack.  That iron could barely melt the
lead-free stuff.  Most of my solder joints looked like crumpled up tin
foil.

The main reason I was using lead-free solder was to make it safer for
people/pets, because I'm working at home.  I'm not sure if that's a
good reason or not.   I just wasn't crazy about having lots of little
pieces of lead laying around for unsuspecting critters to walk in and
track around the house, or the best way to clean the mess up, so I
avoided the problem entirely. :)

With that said, I may switch back now, as long as I can keep my work
area squeaky clean.  What sort of steps to you take to keep everything
tidy?  Just a decent broom?  Or do you even worry about it?

I do a lot of soldering on the kitchen table and I try to remember to wipe it clean before making a sandwich there, but I don't worry too much about it. The lead in 63 37 solder is pretty well locked up in the alloy as far as absorbing it in the body, compared to lead oxides used in old paint, etc. I think there is very little risk from ingesting an occasional tiny solder ball.

Make sure you have a good quality, activated rosin core solder designed for electrical work. For hand soldering, I have less success with the no clean solder. The flux just doesn't do as good a job at helping the solder wet the board and component leads. Never use plumbing solder paste flux on a circuit board. It leaves a residue that conducts electricity and corrodes metals it contacts.

If the flux and temperature are right, the joints should have a bright shine, especially when eutectic alloys are used. These do not go through a pasty stage (crystals of the excess metal growing in the eutectic liquid before the freezing temperature is reached) but solidify very suddenly.

Here is an interesting document on some flux choices:
http://rocky.digikey.com/WebLib/Kester/Web%20Data/285%20RMA%20Solder.pdf


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