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December 21, 2009

Black Pad Investigation

What could be causing a black pad problem we're observing, the boards have ENIG finish?

What would be a good method to detect and rework the black pads?

J. N.

Experts Comments

The black pads are due to nickel corrosion & oxidation during the gold (Au) deposition step.

This is a common problem for ENIG-type board manufacturers, but it is very correctable once you determine which vendor is supplying the bad boards.

Incoming board inspection should be done in order to determine which vendor is shipping you the bad boards. You can then direct the vendor to take corrective action.

For boards that come in with black pads, you can reduce or potentially remove this surface corrosion by using an appropriate plasma treatment. Such plasma treatments typically utilize argon and/or hydrogen gas to sputter off the contamination (in the case of argon) and/or convert the metal oxide back into pure metal (in the case of hydrogen).

Most plasma system companies like Nordson MARCH will run some samples for you in order to demonstrate how this is done. Being able to fix the black pad problem in your own facility with a plasma treatment will help you reduce scrap, and make you less dependant on the quality of the board vendors.

Scott D. Szymanski
Global Marketing Manager
Nordson MARCH
Mr. Szymanski works to expand strategic alliances, strengthen partnerships with equipment suppliers, and develop future product offerings tailored to the semiconductor market.
NOTE: Mr. Szymanski is no longer working at Nordson MARCH

Black Pad is typically caused by excessive Nickel corrosion when fabricating the PCB. It is something that should be resolved by your PCB fabricator during their ENIG fabrication.

Todd O'Neil
National Sales and Marketing Manager, North America
Optical Control
Mr. O'Neil has been in the electronics manufacturing industry for over 20 years.
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