IPC-6012, Qualification and Performance Specification for Rigid Printed 
Boards, identifies the following minimums:

                             Class 1       Class 2      Class 3
Nickel to act as a            
barrier for copper-tin        1.0 um        1.3 um       1.3 um
compounds

Gold for edge-board 
connectors and areas not      0.8 um        0.8 um       1.3 um
to be soldered

um = micrometers

It should be noted that this document is in proposal stage. These numbers 
are subject to revision during the development of the document. This 
document is to replace IPC-RB-276.

****************************************
Lisa M. Williams
Technical Staff
IPC
2215 Sanders Road
Northbrook, IL 60062
phone: (847) 509-9700 x 379
fax:   (847) 509-9798
email: [log in to unmask]
****************************************



On Mon, 26 Feb 1996 [log in to unmask] wrote:

> A question,
> 
> Are there any reports or IPC data which details the minimum amounts of 
> electroless nickel needed to provide a sufficient barrier to copper migration 
> and the minimum amounts immersion gold needed to provide sufficient plating 
> finish.  
> 
> Concerns are solderability failures and corrosion of components.
> 
> Annmarie Rainford
> Merix Corporation
> Forest Grove, Oregon  97116
> 503-359-9300 x74426
> 
>