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topic 716

Adhesion tests for electroless nickel over brass substrate


(1998)

I am looking for a method to test plating adhesion of electroless/watts nickel over a brass base with a copper underplate.

We currently perform a "bend" test of 90 degrees and look for flaking, but we have lots of plated parts that pass this test, yet we see flaking of the plating within a few days (during other processing operations). The parts are small (.080 to .120 dia. pins.

Please reply with any suggestions you might have

Rick Stockwell
(1997)

Rick,
I do not have a lot of experience with plating on copper, but would like to make a few comments knowing that some people will not agree with them.

1. Bend test is "normally" 180 degrees over a mandrel that is 4 times as thick as your part. This will give a "u" and is a far more severe test than 90 degrees.
2. an option is bake it at 250 C for a few minutes, let it cool and check for blisters under a 10 X or so optic.
3. you need to know where your "peel" problem is. Very carefully take one of your peeling parts and poke at it with an Xacto knife to lift a flake that you can look at under a microscope.
4. My guess is that you are using a free cutting brass which is probably leaded. This is going to require a slightly different preprocess steps to remove the minute surface amounts of lead.
5. Try running a small amount without the copper strike and see if that helps or hurts. I assume that you are using a Watts strike before EN. If so, check the recommended concentrations, particularly pH for plating on copper and or brass.

Hope that this helps or stimulates more knowledgeable people to comment.

James Watts
- Navarre, Florida


(1997)

Mr. Watts,That was a very knowledgeable answer. I did recently hear of a quick way to heat small parts for testing adhesion. Mr. Joe Mazia told me that if you turn up a laboratory hot plate to "high" and drop a few parts on it for a few minutes, it will be a close approximation to baking at 400 F, which corresponds to some bake test in the specs. Maybe this would help in developing a rigorous test for this job.

tom pullizzi monitor
Tom Pullizzi
Falls Township,
   Pennsylvania 



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