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Removing immersion gold from body of glass seal packages

Q. Dear Sir:

I am currently working on a zone plated kovar (iron, nickel, cobalt) part.

The pins on the part are to be Au plated with type III Au and the body is to be plated with nickel only. While plating the pins with Au, I get a Au immersion on the body. This is prior to plating the body with Ni. I have tried numerous processes to remove the Au immersion from the body without affecting the pins but I am having trouble. Either the Au immersion comes off and the Au on the pin is affected (dark or missing) or the Au immersion does not come off. If you have any suggestions for this problem please let me know.

Sincerely,

Wade

Wade Graham
1999

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A. Here is what works for me. The shell of the body is made anodic in a cyanide solution to remove the non adherent immersion gold. It takes almost a split second of current to dissolve the immersion gold. The gold on the pins is not affected. NO gold is dissolved off the pins, and the body will come out clean. Good water rinse - Acid salts - then good DI water rinse. This works absolutely great for me because it is nickel. You will want to find the least amount of cyanide solution that works for you. Let me know how it did for you.

todd Huehn
- coon rapids, Minnesota
1999

A. We successfully plate kovar glass seal packages with nickel all over then plate gold on the leads only. We backstrip the immersion gold left on the body with a diluted gold strip. The nickel on the body reduces the amount of gold immersion allowing us to backstrips without affecting the gold on the leads. This is not possible with unprotected kovar.

Ed Keating
- Attleboro, Massachusetts
1999