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Impossible Specification?

2000

We are experiencing very small blisters on the machined surfaces particularly the I.D. of a threaded bushing which is drilled with a thru hole and counter bore. The areas that are not machined or threaded on the O.D. usually are O.K.

Process:

• Copper .000025" minimum
• Nickel .000025" minimum
• Silver .0001"-.0002"

Adhesion Test:

• 350 ± 20 Deg C. for 30 minutes.
• No evidence of blisters at 10X mag.

Are we trying to meet a spec that is impossible?

Tom Dudenhoeffer
- Erie, Pennsylvania

The aspect ratio, or the diameter of the hole/depth of the hole is the controlling factor. Trying to plate the inside of a #6 hole that is an inch deep is for all practical purposes impossible. As the ratio gets better, plating becomes more possible.

You are probably going to have to use electroless copper followed by electroless nickel and possibly an immersion coat of silver. Silver with a high metal, high cyanide and low caustic with a very low amps per sq ft may be able to plate it, but I would not bet on it.

When you talk about 0.25 deep with a 0.25 hole it becomes quite possible.

James Watts
- Navarre, Florida
2000

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2000

Tom:

Doing "the impossible" - especially with nickel and nickel alloys - is something that we enjoy! You may want to consider CVD of nickel (Chemical Vapour Deposition). It is very much faster than plating or nickel forming (up to 25 times faster!) and can plate or form complex shapes, because the process is gaseous.

The technology is not very well-known, as the "art" has been perfected only in the past few years. However, I did want to offer it as a possible solution and will be pleased to explain more to you, if needed.

Sincerely

Mick O'Meara
- Toronto, Canada

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