Hi Dave,
If you are using the gold as an etch resist, then your etchant must be
controlled within narrow limits. Ammoniacal etchants with chlorides will
attack any exposed nickel on the side walls, if the pH and concentrations
are not adjusted properly. This will leave areas, particularly sidewalls,
with a nickel deficient layer, resulting in gold peeling. The reason you
are not experiencing peeling after baking, is because the gold and nickel
becomes somewhat annealed with the copper forming a complexed
intermetallic, whose bond strengths are strong enough to stand up to tape
testing, but will ultimately fail after prolonged thermal stressing. ( This
is only my suggestion, and I do not have any scientific data to back it up,
maybe someone with more info can qualify or deny it.
Regards,
Lenny Kurup
On Tue, 4 Aug 1998, Modular Components National, Inc. wrote:
> I have a question?
> Why if you plate a panel with NiAu then you do a
> tape test prior to your etch process and at that
> point the Au passes the test. After you etch the
> panel it then fails the tape test, now one more
> thing if you bake the panel at 300 F for one hour
> then do another tape test now you pass. So my
> question is should you always bake NiAu, or is
> that just a fix on a problem that we have with
> are plating process? Last thing guys when I say
> that it fails the tape test it is the adhesion
> between the NiAu. Any imput would be appreciated.
>
>
> Dave Blevins
>
> Modular Components National, Inc.
> 2302 Industry Court
> Forest Hill, MD 2150
> PH (410) 879-6553
> Fax (410) 838-7629
>
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