To avoid melting small parts like wires (especially the end is not
attached to anything), don’t heat the parts directly with burner as
far as possible.
If the parts are fixed firmly, you can protect it by covering with
another metal such as titanium. First make some different size of
titanium cover coil by winding titanium wire, and then cover the
precious metal wire with a suitable size coil. I don’t know the reason
but titanium doesn’t be soldered.
If the parts are not fixed firmly, the above method is not available.
I recommend to use some cooling substances. There are some cooling
substances to avoid conduction of heat, or to cover the surface like
putty. But I don’t know the English names of such substances. The
former is like borax, and the latter is powder of grind stone that is
used by being dissolved with water. When using these you have to take
care not to mingle with borax.
But the most important point is to heat the place a little away from
the easy-to-meling place and put the solder when borax becomes like
melted sugar (but the color is clear).
Takashi Tomoeda @Takashi_Tomoeda