Joe,
Most of the complaints are really about the reliability issues related
to SJ brittleness when soldering to nickel. The fact that some gold
diffuses throughout the solder joint and then re-concentrates along the
boundary just adds a small amount more of brittleness. But as the Cotts
paper points out, it does lead to a decrease in the overall IMF
reliability over time. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US
SSA)
Sent: Thursday, November 10, 2005 3:30 PM
To: [log in to unmask]
Subject: Re: [TN] Gold plated components, what a pain!!

Werner:
 
The TI paper on Page 5 talks about the factor of 50.  Their volumetric
calculations indicate that you would need 7570 angstroms thickness (30
microinches) to reach 3% in the solder connection, and the max gold
thickness for this process is specified at 150A.
 
About ENIG, you're right, there are plenty of people who are unhappy
with it, but how many of the complaints are about gold embrittlement?
 
-Joe
 
 -----Original Message-----
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, November 10, 2005 2:57 PM
To: Kane, Joseph E (US SSA); [log in to unmask]
Subject: Re: [TN] Gold plated components, what a pain!!



        Hi Joe, It was the argument you advance: "Now the gold flash on
nickel/palladium/gold is only 30 to 150 angstroms thick, which is way
below the level where you'd have to worry about gold embrittlement in
the bulk solder (like by a factor of 50)" that led to the exemption of
ENIG. 
        On the other hand , where to you get the factor of 50 from? It
also presumes that yopu are happy with ENIG--not everybody is.
	
	
	
        Werner
	


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