Well, if it "keeps coming up", let's take a pass at keeping down. For: * Requirement that gold be removed from components, pads, etc. is J-STD-001C, 5.4.1 * Context of that requirement [J-STD-001C, 5.4.1] and 6 or 7 references are in IPC-HDBK-001.
Additionally, search the fine SMTnet Archives for discussion about: * Limits of the amount of gold that may be contained in a solder connection and still retain reasonable reliability. * Intermetallic compounds that gold forms with tin.