Ditto to Werner's assessment of localized gold concentrations in solution.
This is especially prevalent in hand solder applications.  Since the heat is
localized, connector periphery can contain elevated gold content resulting
in embrittled/fractured connections.  Customer product rejects and failure
has resulted from this situation.

Regards Mel Parrish

On 2 Dec 1996, Werner [log in to unmask] wrote:
>Dave Hillman's reply is right on the money regarding the technical aspects
>underlying your questions. I would like to amplify on his answer, since the
>original questions imply the need for some more fundamental explanation. 
>Q: "Could anyone tell me is there any way to reduce the gold leaching from a
>gold plated board. "
>A: Gold in contact with liquid tin/lead solder will rapidly go into solution
>with tin; therefore, there is no practical solution to prevent this
>'leaching'. Dave Hillman writes: "make sure that you have enough solder
>volume to allow the gold to dissolve evenly into the joint AND that your
>process is such that the time and temperature profile allows this dissolution
>to take place"--If there is not enough solder volume for the gold volume
>present, the gold concentration, even at uniform dispersal, can be high
>enough to cause gold embrittlement AND even if there is enough solder volume,
>inadequate time and temperature profiles do not allow for uniform dispersal
>of the gold throughout the solder volume and therefore might lead to locally
>high enough Au concentrations to cause gold embrittlement.  
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