:   I have seen the existance of electronics solder with a 2% silver
: content that seems to have good wetting and fatique reatings.
:   Can anyone tell me why it is not used? (silver is not such an expensive
: metal).
: 
: 
: Andy
: 

For the most part, silver-solder is not used for general soldering
tasks due to the mechanism of dendritic growth. Silver-solder, when
exposed to high humidity and placed in an electric field, will actually
grow dendrites which are conductive and will adventually electrically
short across closely spaced nodes which are creating the field. For this 
reason, silver is allowed only in hermetically sealed assemblies.
Fortunatly, tin-lead solder is quite stable and will not grow dendrites
as fast as silver-solder. Therefore, it is used extensively.

 
Jerry Long