I don't know the answer to your questions Nora, but while you are preparing to 
change finishes, you might want to take a look at Palladium/Nickle finish too. 
We were looking for a flatter finish on fp smt and had started to look at Pd/Ni 
as a possibility when the project was sidelined.

A buyout and other changes have moved this to a far back burner for now. Good 
luck!

Charlie Barker
Manufacturing Engineer
Input/Output, Inc.
Stafford, Texas

To: TechNet @ ipc.org @ Internet
cc:  (bcc: Charles Barker/IO-US)
From: qun.n.xiao @ bangate1.tek.com @ Internet
Date: 01/16/96 01:58:49 PM
Subject: Solderability issue on Ni/Au


We are switching from HASL to Ni/Au process and realize that on Ni/Au 
boards, solder paste is not spread out as well as HASL process.  
Wettability of the pad edge becomes a major concern.  I have some 
questions regarding Ni/Au process and would like to discuss with anyone 
who have been involved with this alternative surface finish.

Is this problem associated with the inherent nature of Ni/Au material 
surface characteristics, or is it associated with the oxidation and/or
contamination of the metal surface (Although Au is very stable, Ni tends 
to oxidize even at moderate temperature ) ?  It has been recommended to 
use sulfuric acid or plasma to clean Ni/Au surface, is it a feasible 
approach?  If yes, who shall perform this cleaning step:  PCB fabricator 
or PCB assembler?

By the way, what is the shelf life of Electroless Ni/Immersion Au board
under normal storage condition?  Our vendor claims that HASL and OSP both 
have the avg. shelf life as 12 months, but is unable to provide the 
corresponding avg shelf life for Ni/Au.

Thanks in advance for any response.


Nora Xiao
Process Engineer
Tektronix, Inc.
Beaverton, OR