Epoxy adhesion to nickel plating

Q. I have a supplier who is using an epoxy as a potting material to prevent leaking. We do a 100% test at the assembly level at 30 psi to check for leaks. We also have to do an exposure to thermal stress as part of the test going from 70 °C to -40 °C.

The epoxy adheres well initially but after thermal stress we start to see separation between the epoxy and the side wall of the nickel plated aluminum. For 1 part a Loctite EA E-90FL [affil links] is used, for another part a 3M DP190 ⇦this on eBay or Amazon [affil links] is used. Both parts have seen leaking issues every now and then. Any suggestions on how to retain adhesion during thermal stress exposure?

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Q. I am investigating a problem regarding a polyimide PCB debonding from a nickel plated Kovar carrier. All other things being equal, what is the preferred nickel plating process if epoxy adhesion is the primary concern? Am I wrong to assume that surface roughness and finish are far more important than concerns about electroless vs electrolytic processing?

A. Dear Kevin,

I suggest you should look for an additive free dull nickel plating process. I don't know if you're planning to outsource this but surface cleanliness will be crucial too. To check you can do plasma cleaning.

I'm absolutely not sure if electroless Nickel (Containing Boron or Phosphor) will behave better or worse. I think it's worth a try, as the bond mechanism of your epoxy is unknown to me and the combination of epoxy and surface really can make the big difference.

Success, I think an investigation in some more detail is inevitable.

Kind regards,

Harry van der Zanden
consultant - Tilburg, Netherlands

Babbitt adhesion to nickel plating

Q. Dear readers.
I've decided to cast a lead base babbitt on a nickel electroplated bronze backing. But I don't know that is it possible to cast babbitt directly onto a nickel barrier or whether tinning process is required?
Thank you for attention.
Best regards