Hello !!
     
Q: Is there any standards for maximum acceptable intermetalic thickness for 
63Sn/37 Pb solder? How much is too much?
A: ???
     
Q: Wihout performing any destructive test, is there any way  to detect 
excessive Sn/Pn migration? ( X-Ray dispresion????? )

A:  I have used SEM/EDS (Line Profiling) successfully to perform reliability 
studies on intermetallic formation and growth on flip chip 10/90 solder.  

I have also used SEM/EDS (X-Ray Mapping) to study tin phase growth and migration
for this flip chip system.

You will have to perform accelerated heat treatments on different samples for 
different times then you can determine the intermetallic growth rate and the 
rate of migration. You will also need high quality cross-sections of these 
samples.

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Nick Biunno
Zycon Corporation
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Thanksfor you response.
     
Mike Yuen