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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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Electroless plating plastic parts for EMI shielding
Q. I am a designer spec'ing the shielding requirements for the skins for a small medical device. We are transitioning to volume production which includes changing the present Ni-painted polyurethane parts to el-less plated PC-ABS molded parts.
My present spec is for 30 uins of Ni over 30 u-ins of Cu, & the vendor is telling me this is double the cost of Ni alone. My understanding is that Ni requires an underplating of Cu.
Appreciate some clarification if someone would care to comment,
Regards,
Tom Drechsler
- Marlboro, Massachusetts, USA
September 19, 2011
September 19, 2011
A. Hi, Tom.
I can't comment on the EMI shielding capacity of 30µ EN vs. your double layer spec., but I think the EN by itself will be a more satisfactory finish from a plating standpoint. Copper is not catalytic to nickel, which means the nickel plating has to be jump started with rectifier current, and that could be an issue if less than the entire surface were plated.
My understanding is that the principal reason for copper under nickel in plating-on-plastic is for structural resilience in thermal cycling applications like exterior automotive plating, where the somewhat more flexible copper offers a buffer between the differing coefficient of thermal expansion of ABS vs. nickel. But that's just my understanding, so additional comments are welcome.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. The copper layer is for EMI shielding and the EN nickel is to protect the copper from tarnishing.
Usually EMI shielding is not processed like ABS with chromic acid and colloidal palladium but with a conductive paint.
Between the electroless copper and the electroless nickel there is a dip in ionic palladium (to activate the copper layer) which is much cheaper than the colloidal palladium
Sara Michaeli
Tel-Aviv-Yafo, Israel
September 22, 2011
September 22, 2011
Thanks for the informed answer, Sara. I was guessing, and not too well :-)
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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