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Surface Roughness of Electroless Nickel / Gold plating

I work as Quality Manager for a precision machine shop in Toronto. As part of our product base we supply mechanical components (mainly housings for electrical assemblies) for the telecommunications industry. Virtually all of our products require some form of plating or processing that we farm out to processing / plating job shops.

Recently I encountered a problem which I would like some clarification on...

The material is C14500 copper. After machining, the surface finish on the part is approx. 10 to 20 microinch. The part is plated Electrolytic Gold over Electroless Nickel to the following Specs...Electrolytic Gold per MIL-G-45204, Type 1, Grade C 0.5 µm min, Electroless Nickel per MIL-C-26074 [on DLA], Class 1, 4.0 - 7.0 um.

The problem I'm experiencing is the Surface Finish after plating. The parts actually feel like sandpaper and measure over 40 microinch Ra. I've had many other parts (but none of them copper) plated in a similar fashion and never experienced this. What could cause this rough texture? Could it be the copper? Has the plating been done poorly?

Allan Mcneill
Machined component manufacturer - Brampton, Ontario, Canada
2004

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Possible causes are suspended solids in the plating bath, or a chemically out of balance bath. This is a plating problem, not a machining problem. What does your plater say? If he's clueless, you will have to find a better plater.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

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I would think this would be either a cleaning issue, prior to the plating process or a contaminated bath. Ask your plater if they do regular preventative maintenance on their plating lines..i.e.: change filters, etc. also, ensure they monitor the chemistry closely, especially in an electroless nickel bath, if the nickel percent is above 100% it will cause many problems..the components should be checked at least every 10 hrs.

Jason A. Brown
- Athens, Pennsylvania, USA
2005

All of the above are first choices. An additional possibility is overetching in the process tanks, especially if they are for iron based metals.

James Watts
- Navarre, Florida
2005

Does your plater use a sulfuric-peroxide microetch? If so..they should be checking the etch rate by using a coupon and immersing it for one minute and determining the rate of etching by the weight change of the coupon.

Jason A. Brown
- Athens, PA , USA
2005

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Q. Hi,

I have problem with roughness issue at electroless plating. After the product goes thru pre treatment, the product will plate at nickel tank with 75 mins plating time. The issue is, high reject for roughness if I plate with 75 mins plating time.

However if I plate with 98 mins plating time, the roughness gradually back to normal with same process. The difference is only plating time, the rest all the same.

Could you advice what is the root cause?

Junaidi Sudin
- Johor Bahru, Johor, Malaysia
April 14, 2012

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