[Elecraft] Solder Question...

[Ron D'Eau Claire]

I wasn't aware of that, Don. Have they managed to develop a compound =
that
avoids the plastic state altogether?=20

Eutectic (also?) means that the melting temperature of the alloy is =
lower
than the melting temperature of any of its components. In this case, the
melting temperature of solder is lower than the melting temperature of
either lead or tin alone.=20

Having a low melting temperature reduces the heat soldered parts are
subjected to, of course, and  the solder moves quickly from molten to =
solid,
but I thought that it still passed through the fragile 'plastic' state =
that
other materials pass through as they cool and solidify.=20

Of course, with modern printed circuit boards people today don't have =
the
problems with joints moving while they cool that we did in years past =
doing
point-to-point wiring on terminal strips.=20

Today the majority of "cold solder" joints I run across are the result =
of
someone trying to solder with an iron that is not hot enough. The effect =
is
much the same but it's caused by the solder never getting hot enough to =
flow
and "wet" the surfaces it needed to bond to. Sometimes it is accompanied =
by
burned up parts too, because the person held the iron on for a long time
trying to heat the joint enough to solder it and so heated the =
components as
well. I always use the rule of thumb that when working on a PCB, I never
apply the iron for more than 2 or 3 seconds. If the solder didn't melt =
and
flow completely in that time, my iron is too cool.=20

I don't know a lot about many of the newer alloys, but manufacturers of
high-power solid state amps that I worked on in years past required that =
we
use "silver solder" when making repairs to the high-power RF circuits. =
The
reason given was that the silver made the solder a significantly better
conductor to use in situations where very large RF currents were =
flowing. It
also requires more heat to melt it, which is NOT good for small =
components
in other types of circuits.=20

Ron AC7AC
K2 # 1289

-----Original Message-----
The 63/37 solder is 'eutectic' (sp=3D?) - which means that it has no =
plastic
state, it goes from molten directly to solid.  That means no cold solder
joints caused by movement while the solder is cooling.

73,
Don W3FPR