Hi Tom,
Your PCB vendor is giving you a mish-mash of correct statements and technical 
nonsense.
>>The gold vaporizes during your reflow process and the adhesion is solder to 
nickel.
A: this is absolute nonsense—the Au disolves very quickly in the Sn of the 
solder.

>>By the same token, there is no embrittlement problem with immersion gold as 
there would be with electro-plated gold.
A: Correct.

>>Secondly the grain structure of immersion gold and electro-plated gold is 
very different. Electro-plated gold having a long grain structure in comparison 
to immersion gold.
A: this is absolute nonsense—certainly, iAu and eAu have different structures 
as plated, but what difference does this make once the disolve to form SnAu 
IMCs.

Werner

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