Metal finishing Q&As since 1989

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Electroplated Au as PCB surface finish?

I am new to this field. Does any manufacturer use electroplated Au as the surface finish? If so, is there any potential issue? I heard about immersion Au a lot, but not much on electroplating for that purpose. What is the main difference between these two Au platings?

Thanks for any information.

Sherry Wang
product designer - Detroit, Michigan
November 6, 2009

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November 10, 2009

Sherry,
Gold has been used on printed circuit boards for over 50 years. Electroplated gold is plated with a specific current density applied (rectification), whereas immersion and electroless gold don't require current. Immersion and electroless golds are being used more and more every day in PCB mfg. When there is a requirement for thicker gold deposits and certain hardness (alloyed gold), electroplated gold is used. Electrolytic gold has a wider window of control and has been the most popular over the years. Almost all PCB mfgs have the capacity to apply gold coatings to boards, whether it be immersion, electroless or electrolytic.

Mark Baker
Fellow Plater - Syracuse, NY, USA

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Thanks Mark.

So how is the electroless Au thickness controlled?

Sherry Wang
- Michigan
November 18, 2009

Gold thickness is controlled by gold concentration and make up salts, dwell time, and temperature of the bath. Frequent additions have to be made to keep the gold concentration in spec. A few years ago I had to estimate the price tag for the set up of an electroless gold line. The payback on the proposed investment (based on the amount of calls we got for electroless gold) was about 3 years. Needless to say, we did not install the line! There are vendors however that specialize in this process and have been doing it for many years.

Mark Baker
Fellow Plater - Syracuse, NY, USA
November 25, 2009