I've looked at aqua regia and KI+I2 etchants, as well as many other
etchants.
I did not find any that etched gold without etching platinum.

Have you considered plating gold onto the platinum?
Electroplating would require making an electrical connection, however.

        --Kirt Williams, Ph.D.      consultant

----- Original Message -----
From: Alik Widge 
To: 
Sent: Wednesday, March 19, 2003 12:42 PM
Subject: [mems-talk] Removal of Pt black?


> Folks,
>
> I'm currently working on a bioelectronics application wherein we're
> planning to use microelectrode arrays supplied by an outside vendor. The
> vendor's stock electrodes are Au pads with an electrodeposited coating of
> fine-grained platinum (Pt black). Our process involves alkanethiol-based
> self-assembled monolayers, which as far as I know can be formed on the
gold
> surface but not on the Pt.
>
> The manufacturer is willing to provide probes without the Pt, but doing so
> will double our costs because they bill this as a custom order. We've
> considered buying the stock probes and etching off the Pt, but the only
> solution I know that etches Pt is aqua regia, which will also attack Au.
> Does anyone know of an etchant for Pt that either does not attack Au or is
> fairly selective for Pt over Au?
>
> Alik Widge
> MEMS Laboratory
> Carnegie Mellon University
>
>
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