Hi Jan and Stella,

        It's me again, The Gold over bare copper is a real no! no!, since gold
diffuses very rapidly in copper (even at room temperature), this again creates
a gold/copper intermetallic which may be worse than the tin/copper ( I'm not
sure about the degree. Almost everyone plating gold uses a Nickel barrier plate
of about 200 microinches over copper before plating Gold.

 I hope this is also of some help.

        Les Connally

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>  From: [log in to unmask], on 8/14/97 10:49 AM:
>  > I'm no soldering expert, but I Know a little bit. The general problem
>  > with mutiple thermal cycles is this: The tin forms a Tin/Copper >
>  intermetallic with the Copper upon reflow.
>
>  Les,
>  "The board laminate is special nylon material and has gold over the bare
>  copper pads." I'm neither a soldering expert but something got me
>  thinking, Stella had gold over bare copper.
>  Cu and Sn/Pb intermetallics are no good, the intermetallic is bronze (i
>  think) and it's "almost" no-way you can solder on that. But that wasn't
>  the issue here. As i wrote earlier, i'm no expert but anyway, does
>  anyone know what kind of intermetallics you get from multiple thermal
>  cycles with gold on bare copper??!
>
>  Thank you,
>  Jan Merstrand
>
>