I've used the old 60/40, 1/16" diameter, rosin-core solder for years. 
But I wanted something smaller gauge to use for SMDs.  And I figured I 
should transition to lead-free.  So, I've been trying Kester lead-free 
0.02" no-clean solder.

I'm having a hard time with it.  Basically, the iron tip doesn't wet - I 
can't tin it with this stuff.  After the first few joints, I can't even 
melt the solder by pushing the tip against it hard.  Re-tinning with the 
plain old lead stuff resuscitates it for a little while.

Should I not be mixing both types of solder with the same iron tip?

I'm using a Kester Flux-Pen to flux the components and pads, but very 
little of that may be getting on the iron.  Is there some way I should 
be getting flux onto the iron?

Or... am I missing something else?

I'm prepared for lead-free solder to look a little duller, but not being 
able to get it to flow at all seems like a show-stopper.  For now, I've 
gone back to the 1/16" diameter stuff for SMDs; I end up getting too 
much solder on the joints, but at least the darn things stick where 
they're supposed to.

Open to any suggestions.
-- 
Timothy J. Weber
http://timothyweber.org
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