micky wrote:
On Tue, 23 Aug 2011 07:07:04 -0700,
wrote:

N_Cook wrote:

(...)

There's me thinking all those decades that cold solder joint meant lack of
sweating, ie lack of wetting (melding) to the metal surface due to lack of
heating

Me. too.

It can.

Yeah, but I thought that's what it always meant. In part, I'm
sure, because from age 9 to 19, all I had was a wood-burning iron,
which I never used to burn wood, and which was just a little too cold
to solder with well. It worked. but in the process I had loads of
cold solder joints that were really cold.

Insufficient heat will do it for sure.

If you still have that tool, I think it would be very
interesting to see if you could get good quality joints
by polishing the parts to be joined and using added flux
before applying heat.

Wood burning tools can generally achieve 500 F and
60/40 solder melts at ~476 F.

I'd never recommend this as a normal practice because there
is not enough thermal headroom to do a consistently good
job with larger joints and 60/40 solder is inferior to
63/37 solder for electronic applications, all else being
equal. Still, it would be interesting, yes?

(...)

http://www.youtube.com/watch?v=I_NU2ruzyc4
This video is difficult to watch for folks that
already know how to do electronic soldering because
it illustrates some really bad technique, initially.

These are the reason I didnt' trust what I'd read about having to
desolder before resoldering. A lot of bad info out there, by people
who mean well.

I understand the reason why they show the poor technique
initially. Hopefully, a user would recognize their way
of doing it and have a chance to correct. This isn't too
fantastic; I've seen some astoundingly bad technique used
by techs in companies that you would instantly recognize
the names of.

I got out of the biz before having to do *any*
'lead free' electronic soldering. I suspect that one
could do acceptable repairs with the proper tools.
I wouldn't expect that the proper techniques would
change much at all.

--Winston