Suggestions for VT103?

[Chuck Guzis]

On 29 Dec 2008 at 8:57, Sridhar Ayengar wrote:

> It's not the lower melting point.  It's that the mixture is eutectic.

There's a lot of misconception about what solder alloys are really 
about.

The characteristics of various tin/lead ratios are very useful.  I 
work a lot soldering sheet brass.  Normally, I work with 50/50 alloy 
because of its large plastic range and its ability to fill gaps and 
be tooled while cooling.  But if I'm working with something that 
requires a joint to solidify almost immediately from the liquid state 
(eutectic), it'll be a 63/37 alloy.  Melting point isn't a major 
issue as I'm working with an acetylene torch.  60/40 gives you a bit 
of plastic time before solidifying, but not much.

If I were soldering PCBs, I'd want the eutectic alloy--liquid or 
solid, with virtually no plastic phase in between. 

Plumbers and radiator repair shops use the 50/50 alloy because it can 
be tooled while cooling.  (In theory, the term should be "plumbers 
used to use" since lead-bearing solder for plumbing now violates code 
in the USA.  But I've yet to see a plumber who doesn't keep a couple 
of rolls of 50/50 squirreled away for the tough jobs).  The tradeoff 
is that the workpiece must be solidly clamped or otherwise fixed so 
that it doesn't move while the solder is solidifying.

This control of state-change characteristics is one thing for me that 
sets lead-bearing solders apart from the RoHS pack.

Cheers,
Chuck