Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Chinese Hard Gold
We have a supplier for PCBs in China, shipping us PCB in US and they use an ENIG process for Nickel/Gold plating. The Gold plating thickness they provide us is much greater than acheivable through immersion. They use "Chinese hard gold" as the term to describe it and confirm that is not electroplating. According to them it is also termed as double immersion process.
Has anyone heard about this term or know how it is possible to get a thicker layer of Gold using immersion.
Thickness of Gold provided is 7-8 micro-inches. I know the limit for immersion gold is 2-4 micro-inches.
Thanks for your help in advance.
Farooq M Chaudary,
Quality Engineer
Quality - Golden, IL,USA
2007
If it's neither immersion gold nor electrolytic gold, Farooq, it sounds like it must be electroless gold (autocatalytic gold). You might inquire of Technic for more info on this.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007
Ted is right, Technic could shed some light on the subject. If I may comment however, this thickness requirement is quite low for PCBs. Even with a double immersion process, it is still really a flash coating. I also was not aware that hard gold could be plated from immersion or electroless process. For years it has been limited to soft gold. How would you control the hardness of the deposit?
Well lets face it, you get what you pay for, as well as the quality of information!
Process Engineer - Syracuse, NY USA
2007
2007
Hi,
What are the specs for your nickel and gold plating layers that you state to your supplier in China?
Are you able to confirm at your side the plating thicknesses or do you depend on the thickness data provided by your China supplier?
Generally I plate up to 0.05 microns. From my experience, I am able to achieve plating thickness up to 0.2 microns (XRF method)through an immersion gold process. Chemistry by Enthone. Draw back is that, to achieve such thicknesses, gold content is kept at 4g/l. Also since the process is a corrosion process, the Nickel contamination should be not be above 1000ppm, also Cu should not be more that 5ppm and Fe not more than 50ppm. (Results from using an AAS)The higher the contamination level, there appears to be a faster rate of deposit for gold and I am able to achieve thickness of 0.5 microns before the solution is spent.Also another drawback is that there is a red film appearing on the surface when thickness are high which can be removed by using an eraser.
- Singapore
July 8, 2010
What is the red film exactly?
Do you know the chemical composition?
What is the cause?
We make many thousands of PCBs with ENIG and sometimes we see such a contamination. On contact pads that's bad, and there's always finger pointing as to it's cause/origin.
- San Jose, California, USA
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