Letter 5026

Alternative etches and activators 

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We run a standard plating on plastic line for plating A.B.S plastic. We use the conventional chromic/sulphuric etch and a tin/palladium activator, Because of the related hazards with the etch and the cost of palladium I am interested to know if there are any other commercially viable alternatives to these processes that will give the same results.

Tim Strickland
- New Zealand

Some plastic platers use or used a gaseous etch in place of that gruesome chromic-sulphuric molasses mix; I'm confident that a literature search would reveal sufficient details for you to take it further.

A lot of research has gone into activation, and it happens that I was just reading a few historical papers recently. People have tried gold instead of palladium, and they tried silver nitrate, but palladium chloride seemed to be the instant winner with no real challengers in the literature. But there may be a proprietary that does not use palladium; in fact, I thought one of the name brands had a system that used only tin chloride with no palladium chloride step involved.

 
Ted Mooney, P.E. - Finishing.com Inc. - Brick, NJ

Hi Tim,

Tremendous efforts have been devoted to developing novel plastic etching process prior to plating. Most potential technologies are still in lab-scale. As Ted mentioned, gaseous plasma etching may have been introduced to very limited industrial production a few years ago. It is inconvenient and too costly for majority of job shops to adopt this technology.

The purpose for etching is to roughen surface and convert hydrophobic surface to hydrophilic surface. Only very strong oxidizing agents, such as chromic acid, can offer this function under adequate conditions. Latest work focuses on aqueous nitric acid and peroxides system or aqueous oxygen free radical system. But a commercially viable process is still not available at the present. Hopefully, something will come up in a few years.

Regards, Ling

L. Hao
METALAST International - Minden, NV

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