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I need help to get rid of the nodules in gold plating


Q. In the developmental laboratory we electroplate gold using a cyanide bath on electronics/semiconductor wafers. After plating we observe gold nodules (balls) stuck to the surface at random places. Some times they cause short circuits and failure of devices.

Can any one explain why and how these gold nodules are caused and what we can do to get rid of them?

Thank you for any suggestions.

Anil R. Dholakia
Private corp. - Allentown, Pennsylvania

A. It almost has to be a conductive burr or trash on the part. An outside possibility is trash in your plating solution. The burr causes a very high current density area, so it plates at a much faster rate than the flat surface does. You might want to check your amps per square foot. You may be high.

James Watts
- Navarre, Florida


A. Hello Anil,
Nodules are normally caused by microscopic particles that are not properly filtered out of the solution. What is the micron rating of the filter are you using? Are you using a high solution agitation system? Sometimes in high agitation plating cells particles remain suspended in solution. You want to make sure the free Cn in the bath is high enough, that can cause problems as well. You didn't mention a microetch process, if you have one you want to make sure you are getting a clean etch with good rinsing. Look foward to hearing from you.

Mark Baker
process engineer - Malone, New York

Q. I have some questions:
Nodule, is it like a ball? If it like a ball or dome, I am faced with same problem.
Check your filter, or pump

MH Daedupark
- Cheong-ju Korea
May 8, 2013

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