Metal finishing Q&As since 1989

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Hard gold plating queries

I am a production engineer of flex/rigid-flex PCB. I am in charge of the wet area ( PTH, Copper Plate, microclean, etching,gold plating, tin lead plating and ENIG). Among all gold plating and ENIG are relatively new to me.

I have a few question regarding Hard Gold Plating and I need views from you guys out there.

1) What are the reactions that take place at the anode and cathode(pls provide the equation of the reactions)? We are using Platinised platinum for the anodes.

2) Is S.G of the bath plays an important role?

3) I understand that co-deposition of cobalt harden the surface of gold. What happen if it is too high or too low?

4) What actually causing gold peeling?

Qairyul Elfee Md. Latip
circuit boards - malaysia
2000

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2000

Perhaps I can help with 3 and 4. The amount of cobalt in the bath will affect brightness of the deposit. The more cobalt in the bath the lighter the deposit.

If the gold plate is peeling, the substrate needs to be activated better. A dip in an acid activator then a quick rinse will prevent peeling.

Terry Collins
Gold Touch Inc.

Cleveland, Ohio

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In a proprietary bath, the specific gravity is controlled by salts designed to keep the bath in balance, and, yes, the specific gravity can become important. Additionally, once out of spec, it is my experience that it is difficult to get the bath back in spec.

James Totter, CEF
- Tallahassee, Florida
2000