Why it is sometimes necessary to re-seat a board or chip

I was perusing some topics on Wikipedia and came across this enlightening tidbit of information in the article on "Gold plating": "With direct gold-on-copper plating, the copper atoms tend to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide and/or sulfide layer. "A layer of a suitable barrier metal, usually nickel, is usually deposited on the copper substrate before the gold plating. The layer of nickel provides mechanical backing for the gold layer, improving its wear resistance. It also reduces the impact of pores present in the gold layer." http://en.wikipedia.org/wiki/Gold_plating So this is why a re-seating of certain cards, connectors and ICs oftentimes cures a fidgety system. Just thought I'd share this. It was novel to me at least. P.S. I'm assuming this information is accurate :) -- Sellam Ismail Vintage Computer Festival ------------------------------------------------------------------------------ International Man of Intrigue and Danger http://www.vintage.org [ Old computing resources for business || Buy/Sell/Trade Vintage Computers ] [ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]