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Ralph Mowery

In article ,
says...

The reason that gold is used is that it is more resistant than any other of the noble metals to 'dissolving' into anything, forming an oxide or otherwise degrading. If it is attacked by something, that something will be quite toxic or dangerous in its own right. Those compounds would include chlorine, mercury, cyanide and reactants of same. Gold often does not solder well, true, but that depends much on how how
it is alloyed and its purity. 24 karat (pure) gold tends to solder quite easily, if gotten hot enough, but is also very expensive, very soft and for those reasons seldom used. 10 karat gold - the lowest that can still be called 'gold' solders badly unless very high silver-content solder is used, and typically requires a flame. Silver Brazing would be a better description.

Gold is seldom used in soldered components as there is no reason to do so. The only real reason for gold (as it is a poor conductor relative to silver or copper) is its resistance to corrosion on contact-type connectors - jacks, plugs and switches. Soldering *to* a gold-flashed lug or pad is asking for trouble for all sorts of reasons, some obvious, some not so much.

I know gold is used in contacts because it is resistant to oxidation.
They really found that out when computers and memory chips were put
together with the tin contacts instead of gold. I have a ham radio
repeater made by GE that has some cards in it with the tin edge
connectors. About once or twice a year I have to pull them out and give
them a good cleaning. The low level audio stages seem to be the worse
and I have rewired the circuits to byapss those weak points. What I
never did understand is why most of the RF power transistors seem to
have gold leads. Most are soldered in and that solder joint often goes
bad for the reason you stated. Then you have to scrape off the gold and
remove the old solder and put fresh solder on.