[TowerTalk] Silver Solder

[Jim Lux]

On 8/7/15 11:25 AM, David Gilbert wrote:
>
> I
>
> For lightning protection (or any high current application), solder seems
> to me to be a very poor choice.  Solder, including silver solder, almost
> invariably will be the highest resistance element (and the weakest
> thermally) in the system and will act like an explosive fuse if it takes
> a hit.  As Jim says, clamps or welds are the way to go for this.
>

I've used silver brazing in high current pulsed power (well over 10kA, 
10s of kJoule) applications which had significant mechanical loads (from 
the magnetic fields).  I don't think lightning impulses would melt it. 
The "action" is too small.  If a AWG10 wire doesn't melt from the 
lightning, a thin layer of silver/copper/tin alloy isn't going to melt 
either.

Done right (or even half right) brazing is quite mechanically strong: 
it's not like welding steel, but it's used in all sorts of strength 
dependent applications (e.g. bicycle frames).

I don't know about the mechanical properties of "lead free" soft solder 
as used for plumbing with 5% silver content. I'd worry about brittleness 
after temperature cycling.


But you don't need it for lightning protection.  Bolted connections 
(done right) are fine (and of course, exothermic welding, which is 
basically using copper as the filler in a copper:copper joint)

Save the silver solder for where you need low resistance at low voltages 
(that RF ground screen for your top band vertical), where the surface 
corrosion film could lead to all sorts of issues.