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Electroless nickel surface features

What causes the formation of platelet-like features on the surface of electroless nickel plating? The features are typically circular, but not always, and are 5-30 microns in size. Platelets can be dislodged via probing or tape test. Plating is high-phos nickel over Kovar.

Bo Abney
- Casselberry, Florida
2001

Two guesses. Improper preparation steps. Your EN has gone well out of its allowable internal stress parameters.

James Watts
- Navarre, Florida
2001

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What would cause the "allowable internal stress parameters" to go out of control? I've found some literature that appears to show an increase in similar features with a decrease in stabilizer level........?

In regards to pretreatment, I believe our platers are adequately cleaning organics from the surfaces and properly activating the Kovar. We have no adhesion issues other than these 4-20 micron sized platelets coming off the surface. However, could inadequate cleaning of tiny metal particles from the substrate cause such features if dragged into the EN bath?

Bo Abney
- Casselberry, Florida
2001

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Hi, Bo:

I really don't think that loose tiny metal particles would cause the problem. They are very unlikely to remain adhered with all the gassing that evolves from a part when immersed in the EN bath. It makes more sense to me to look for adherent species (copper, lead, etc.). But, above all, the main causes still have to be looked for in the internal stress and (even though you feel confident) in the activation process. This sounds like a problem that should be carried out by you and your E-N supplier (not very likely through this forum). If you are not receiving full support from your supplier it might be time to change.

Guillermo Marrufo
Monterrey, NL, Mexico
2001