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Nickel Plating Alternatives?

I have a question for you on an issue that I have been dealing with for about a month now. A backshell made from nickel plated zinc with a copper barrier has a circuit board in it. The circuit board is then covered and sealed with an epoxy. Approximate size of device 1.5in x .5in x .5in. Our problem is that we cannot get any epoxies/potting compounds for our extended temperature ranges (-40 to +85C) to bond to the nickel. My question is if there is an alternate surface finish that will provide the same corrosion and mar resistance as the nickel plating but create a better surface to bond the epoxy to?

It has been suggested that a nickel sulfamate finish would provide a good porosity for the epoxy, but I am concerned about the porosity of the finish absorbing skin oils and other process contaminantes. Is this concern valid? Are there various concentrations of sulfamate nickel that might be appropriate for this application?

Our main concern is appearance and corrosion resistance to the zinc base metal. We are open to any finishing methods. Would a platic coat work?

Thanks for any and all information.

J. Mark Elliott, Reliability Engineer
- Beaverton Oregon
1998

The nickel is probably bright nickel for cosmetic purposes. You would probably have to find another plater to go with a nickel that had less or no brighteners in it.

I will argue with the "porosity" of sulfamate nickel. It can have a very matte finish, but is not porous by most standards. The matte finish will definitely accept bonding better than bright nickel will. Unfortunately, being matte, it is a relatively dull finish and will show fingerprints. It also will not wipe off as well.

You might try a very light abrasive blast on the surface you want to bond to.

James Watts
- Navarre, Florida
1998

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1998

Dear Mr Elliott ,

Why not try just simply yellow chromating the Zinc , I havre assumed it is a diecast piece , the only thing to remember is that after chromating the parts must stand at room temperature for at least 24 hours to allow the chromate layer to come to equilibrium .

If that fails then try a layer of Brush plated nickel ( say 4/10 of a thou thick ) it should be porous enough to give you some bonding sites

Regards

John Tenison - Woods
- Victoria Australia

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1998

Dear Mr. Elliot,

You might want to try a coupling agent. These silane compounds are available through Dow Chemical. I use several types depending on the metal and resin combination being bonded. For your application I would try an "amino silane",(designed for use with epoxies) product code Z-6020. These are water based compounds and can provide enhanced bonding at very low coating levels, 0.25%.

Good Luck.
Bob

Bob Duvall
- Mamaroneck, New York