Leo,
In the "good ole' days", 1960 to 1996, we at Hewlett-Packard made our own
multilayers by the tens of millions using a pattern-plating electrolytic
Cu/Ni/Au process-more than anyone else in the world put together.  We had
13 pcb facilities around the world. The thickness of Au did not have an
effect on etching, eventually we reduce it to 0.1 microns Au.  BUT, nickel
had a profound effect, especially on undercut.  I advise against using any
acid enchant like CuCL2, as it will go after the nickel and any porosity
in the gold.  You should be using a good alkaline enchant, buffered to a
near neutral pH and having its specific gravity controlled on the high
side.  We always used a Watts nickel, rather than a sulfamate-nickel, as
it had less stress and would not be attacked along the grain boundaries.
You can find the process documented in Coombs PCB Handbook, 4th Edition,
as Clyde Coombs  was the Marketing Mgr for the Printed Circuit Div of H-P
in those days.  I was the Engineering Mgr of the biggest PCB shop in those
days, before the OEMs started closing them down and getting out of the
manufacturing business.
Happy Holden
Asian Pacific Materials




Lin Leo <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
05/27/2006 03:25 AM
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[TN] Electrolytic Ni/Au in DES






Hi,

  Does anyone have experience on electrolytic Ni/Au(Au thickness: ca.
12~20 micro-incheses; Hard gold Au-Co alloy) acting as etching resist in
DES(developing-CuCl2/HCl-stripping) process?  Does Au thickness have
impact on etching solution attack?

  Thanks

  Leo


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