Summary for gold plating nodules Discussion
gold plating nodules are described here as random balls or domes on cyanide gold-plated electronics and semiconductor wafers that can cause shorts and device failure. Anil R. Dholakia asked why they form and how to eliminate them. James Watts said the cause almost has to be a conductive burr or trash on the part, with an outside possibility of contamination in the plating solution; he noted that a burr creates a very high current-density spot, so it plates faster than the surrounding surface, and suggested checking amps per square foot because the current may be too high. Mark Baker added that nodules are normally caused by microscopic particles not properly filtered out of the solution, and asked about filter micron rating and agitation, warning that high agitation can keep particles suspended. He also advised ensuring free cyanide is high enough and that any microetch gives a clean etch with good rinsing. A later commenter asked whether the nodule is like a ball and suggested checking the filter or pump.
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
2006
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
2006
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
2006
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