The 5% HCl is rather week for the purpose. I would expose "old" Ni at least
1 min to 15% HCl (50/50, H2O/conc HCl) and then proceed with longer time on
a trial and error basis if needed. However, you should have at least several
hundred nanometers of Ni under the Ni oxide/old Ni, to maintain Ni
continuity.  Remember, after removing oxide you need to transfer for plating
immdiately. Typically, significant Ni oxide grows back within few minutes.
Igor Kadija
www.fibrotools.com

----- Original Message -----
From: "James Zhu" 
To: "General MEMS discussion" 
Sent: Wednesday, May 23, 2007 11:31 AM
Subject: RE: [mems-talk] Activation of 'old' nickel surface

> Hello, all. I want to give gold finish (electroless gold) on top of a
> passivated nickel surface. I tried pre-dip in a 5% HCl solution before
> gold plating, but the gold still can be peel off easily. Can anyone help
> me to improve the gold adhesion to nickel. Thanks J. Zhu from Epigem,UK.