[Amps] 3-500ZG brands

[peter.chadwick at Zarlink.Com]

There's a lot of things described as 'silver solder'. Basically, there are 
three types - 'soft', 'medium' and 'hard'. Soft solders with some silver 
in them are relatively low temperature solders,  and the silver content 
generally leads to better flow characteristics, and better joints. these 
are available with a melting point around 220 C, cored, without any lead, 
zinc, cadmium or antimony. $4 for a 5 foot length, for example.

Then there's'hard'' silver solders, such as 'Easyflo' which melt at around 
red heat. There are various proprietary fluxes for these, and in 
emergency, you can use ordinary borax. If you can get the pins to red heat 
while keeping the glass to metal seal below 220C, then classical silver 
solder would be ideal. These are what I call genuine silver solders - 
they're used often instead of classical brazing with spelter. Some of them 
have cadmium in them, so you need to watch the ventilation, as the fumes 
of  the cadmium are nasty.

The medium silver solders are slightly higher in melting point - I can 
find them at around 240C, and I believe you can get them to 300 or 350C, 
although that needs some research. They tend to need a more active flux, 
too, and there are various proprietary fluxes available.

All silver solders tend to 'run' very well, and to fill cracks. Indeed, 
you should leave a gap of about 0.001- 0.002 inches or so for it to 
penetrate for best results. The high temperature solders come with various 
melting points, so you can do part of an assembly at high temp and then go 
down in temperature for other parts. But you do need to make sure you have 
enough heat, and a model locomotive boiler in copper requires an awful lot 
of heat to get it up to temperature for hard silver soldering!

Hope this helps

73

Peter SM/G3RZP