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topic 745

Plating iridium electrodes with silver


(1998)

I am trying to deposit silver on iridium electrodes (10 um x 700 um) from a silver cyanide bath. My deposits are not adhering, I have tried using a strike solution. Do you have any references for this process. I am doing this on a laboratory scale.

Millicent Weldon
University of Michigan - Ann Arbor, Michigan


(1998)

Silver does not adhere well to many base metals, underplates or strikes. Try a gold strike.

bill vins
Bill Vins
microwave & cable assemblies
Mesa (what a place-a), Arizona 


(1997)

I think Bill is right, a gold strike might be more effective. Also, how are you activating the Iridium? A 5-7 oz./gal. cyanide with 35% Hydrogen Peroxide [linked by editor to product info at Amazon] (0.5 ml/ 100 ml of solution) should remove oxides that prevent adhesion. Finally be sure to introduce the work "hot", that is with current on as the parts enter the plating bath to avoid immersion deposits.

Keith Wicklund, CEF-SE



(1997)

The big problem with Iridium is that it is the most corrosion resistant element appearing on the Periodic Table of the Elements. This makes the surface microstructure unalterable by wet chemistries, therefore pre-plate etches or brite dips won't touch it, including Aqua Regia. So how to microetch the surface to provide sufficient toe-holds for the Silver deposit? Iridium can form a stable Cyanide [Ir(CN)6---] complex. A pre-plate anodic treatment in strong, hot, alkaline Cyanide followed by the silver strike may be successful. Otherwise molten salts are required such as KOH + KNO3 heated to red glow. If this is too much process, mechanical abrasion methods will also work. Ir is very hard and abrasion resistant. The Gold strike previously mentioned may also help out if Gold is allowed in the device that you are making.

Good Luck,

Dave Kinghorn
Dave Kinghorn
Chemical Engineer
SUNNYvale, California



(2002)

I am trying to find RuO2 thin film etchant. I have tried with aqua regia, HF and so on. But it didn't work. Do you have any reference for this? Please let me know.

Cho Youngnam
- Old Town, Maine


(2002)

Like Youngnam, I would like to know of any wet etches for RuO2. I have seen dry (plasma) etches for RuO2 reported in the ferroelectrics literature, but I am still curious whether anyone knows of wet etches for RuO2.

Jonathan Foster
University of California, Berkeley - Berkeley, California



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