I, as a beginner, would like a few more answers.

1) How should be handled when a board design requires both Au wire bondings
and a solder reflow.  Those two areas are about 50-100 mils away from each
other.
I do need a Au finish on wire bonding area obviouly.  How about solder reflow
areas??  Can't I have the Same Au finish thoughout the board???

> Beside gold thickness, the amount of solder applied should also be
> considered.  Per IPC-D- 279, "Design Guidelines for Reliable Surface Mount
> Technology Printed Board Assembly",  Section 5.4.4.  where gold or palladium
> plating is used, the gold or palladium content in the solder joint should be
> approx 3 %wt. or less.  Here are our thinkess rules for Gold.
>
> Electrolytic AKA hard gold: Mostly for Wire bond
> Elecrtroles AKA Soft gold: Common 15 to 25 u" as long as it follows the 3%wt
> rule
> Immersion: Common 5 to 10 u" (Preferred in SMT assemblies, except edge
> finger connector)
>
> To calculate the weigth factors, these number might help
>      Density of Gold =        19,300 kg per m3
>      Density  of Solder  =    8,500 kg per m3
>
> Please ensure to have at least 100 u" of Ni beneath the gold.
>
>
> Hope that helps
> Michael Yuen
>
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   _________________________________________________________________
   Masatoshi (Bro) Suzuki      |
   Maxtek Components Corp.     |  Email: [log in to unmask]
   P.O. Box 1480, M/S 13-035   |  Voice: (503) 627-4025
   Beaverton, OR  97075-1480   |  Fax:   (503) 627-4651
   _________________________________________________________________

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