Darrell Daigle posted a request for info on the effect of solder on a 
     gold-plated finger that is to be inserted in a gold socket.  If the 
     solder is not in an area that makes contact with the socket fingers, 
     there is no effect.  Otherwise, either high humidity or finger sliding 
     due to vibration or temperature changes will bring about corrosion.  
     
     The corrosion due to sliding is referred to as "fretting corrosion".  
     Sliding scrapes off the protective oxide layer; this freshly exposed 
     solder surface then oxidizes.  The process, when repeated often 
     enough, leads to an open circuit, or worse, an intermittent open or 
     high-resistance connection.
     
     A colleague of mine tells me of a case where solder on DIP leads 
     inserted into gold-finger sockets led to timing problems in a circuit. 
     The field engineering solution was to push down on all the DIP's on 
     the board.  This fix had to be repeated every few months.
     
     Where the operating environment can lead to corrosion for any of these 
     reasons, the corrective action is to remove the solder and replate the 
     gold.
     
     Gordon Davy

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