Solder Problems (PDP-8/m related) - test-drb@ccmp.vtda.org

3 Dec 1999

On Dec 3, 20:19, Joe wrote:

...
  I have a spool
(1 lb?) sitting behind me of 96 SN silver solder, wasn't
"too" expensive and melts with a slightly hotter tip in my weller. 
   That's the same kind of stuff that they sell here for soldering copper
 water pipes. NO LEAD ALLOWED! The last time I checked it costs about
 $16/pound. That's cheaper than good electrical solder. 
Same here, at least for new installations.  There are regulations about the
flux, too, I beleive.

...
     You have to watch out for any solder and make sure
it's for electrical
 work. There are many other kinds of solder and many (most?) of them have
 acid fluxs. You can use it on electrical stuff but you'll be replacing
 everything in about six months! 
Yes, most fluxes apart from rosin are at least mildly acidic, including
some electrical types -- you just have to ensure you wash them off properly
(and soon).

...
    That's an interesting idea. But I certain that
you'd have to heat the
 joint to the melting pont of the old solder before this stuff would alloy
 with it. If that's the case then you could just take the part off then and
...
  not go through all the rest of the procedure. 
I've mixed various lead
 alloys for casting bullets and you have to heat the mix to the melting
 point of the element with the highest melting point before they will all
 melt and alloy together. This is true even if the alloy has a lower MP than
...
  the individual elements. 
Curiously, that's not always the case, especially if you consider surface
effects.  Solder actually sticks to a metal surface by forming a very thin
layer of an alloy with it.  In effect, the solder dissolves the other metal
very slightly.  That's partly why a copper soldering iron bit gradually
wears away even if you keep it well tinned, and partly why thin plain
copper cable that has tinned ends is weakest just at the point where the
tinning ends (the solder leaches away a tiny amount of copper, leaving the
wire slightly thinner just at the junction).

-- 

Pete						Peter Turnbull
						Dept. of Computer Science
						University of York