Please forgive me, Peg Leg, but nothing in your post makes any sense and I feel compelled to jump in here because the readers shouldn't get false hopes.
Circuit boards don't melt, but they will burn. I assume you mean that you sweated the solder off, which, incidentally, contains zero silver. The only silver solder I have seen on boards are on the ends of the tiny monolithic capacitors and it would take lots and lots of boards to get an ounce of silver. That is, if you knew how to separate the silver from the other metals. And I also doubt that any of this silver got into the metal you sweated. Are you sure you're not mistaking tin for silver - it's in all of the lead-tin solder? Where did you pull the 40% silver figure out of?
And gold? You probably should have removed it before melting everything together. Now you have a mess. If it didn't come off with the solder, it has surely migrated into the copper, considering the heat you applied. Can you explain the process you will use to get the gold? There probably isn't much gold on there, anyway. At today's market, figure about 20 cents for a square inch of gold plating.
I pray that you don't get sick from breathing all of those lead fumes.
If you really want to learn how to do all this stuff, safely and correctly, go here:
http://goldrefiningforum.com/