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topic 51694

How to lessen gold plating roughness?

A discussion started in 2009 & continuing through 2017 . . .

March 27, 2009

Q. Hello guys!
I am from Shanghai China. One of our products has to be gold plated, but after the gold plating process had been finished, we found that the plated gold surface is very rough. For the moment, I am not really sure how to solve the problem, but we would like to get a very smooth surface, the smoother the better (and cost is not the major concern).
The gold thickness is about 3~4 µm.
Someone said we should use a microwave during plating Au to stir the Au ions, and that may assure Au ion uniformity as the ions are deposited on the substrate surface -- but I did not very much understand what they are talking about.
Please help me .
If you have any pictures, formulas or data can you please share with me?
I thank you very much in advance.

Kurban Awut
- Shanghai, China

March 27, 2009

A. Hi,Kurban. I do not completely discount the idea that microwave energy could prove useful for gold plating-- a local plater did a good bit of experimentation with it many years ago, with some apparently promising results.

But it is not key nor necessary for a smooth gold deposit. You should be receiving some hands-on assistance from the supplier of your gold plating process chemistry.


Ted Mooney, amadeya42.com Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 4, 2009

A. I'm not sure it help or not, but we faced it once, rough gold surface:

1. less conductivity - how to check? by SG (Be'). After adding conductivity salt, gold became OK.

2. pH - due to slight acidic gold solution, low pH promotes slight hydrogen evolution. Therefore layer become rough.


Razak Ismail
- Johore, Malaysia

April 7, 2009

A. It would help if we knew what you were doing to get your rough surface. Please give your process details, including all information on bath make-up, pH, electrode types, temperature, filtration rate etc.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

April 10, 2009

A. Assuming you are plating onto a smooth substrate because gold at 3-4 µ will only be as good as the surface it is plated on.
Temperature, pH, etc can cause many problems but I have never seen them cause roughness. Excess current can cause a 'burned' deposit, but this is usually obvious.
The first thing to do with any solution that gives a rough deposit is to plate a test panel on a known good surface like a hull cell panel.
If this is rough, take a glass beaker full of plating solution and shine a beam of light through it (a small torch works well) and view it from the side. Any particles in the solution show up as bright specks - the Tyndall effect.
The usual cause of an otherwise good solution suddenly plating rough is a failed filter (or no filter at all!)

I cannot imagine any advantage in using microwave radiation. I would expect it to cause a great deal of expense and many new variables which you would have to understand and learn to control.

geoff smith
Geoff Smith

April 12, 2009

A. For a good gold plating solution, it should contain conducting salts, e.g., potassium phosphates, etc.; complexing salts, e.g., potassium citrate etc.; brightener may be inorganic in trace amount or organic and the main potassium gold cyanide. Then you should be able to plate a good gold deposit. Otherwise, a slightly higher current density will produce rough deposit. Assuming clean gold solution (using DI water), proper pH etc., are observed.

Lee Leong Tee
- Malacca, Malaysia

May 8, 2017 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. I am using [Transene] TSG-250 solution. Deposited area is 7.5 cm2, pulse mode %10 duty cycle, 20mA, temperature 50 °C and stirring 200 RPM.

This recipe gives me roughs surface. How can I improve this recipe (I want to obtain smooth gold electroplated surface)?

Onur Tüfekci
- Ankara, Turkey

May 10, 2017

A. Hello, I never encountered rough deposits in gold plating. I can give you some preventative measures however. You want to be positive the roughness is in the gold deposit and not nickel. Examine parts after Ni plate. Clean rinse tanks between the underlying plate and the gold. Take a 1 liter sample and run it through filter paper in your lab to ensure a clean gold plating solution. Run a full analysis on the bath. Your supplier should be able to do this for you. Run a few carbon packs in the gold bath. Ask your supplier if a wetting agent is part of the bath make up. They may have you make an addition. Wetting agents are normally added per ampere hours. Ho these suggestions work for you.

Mark Baker
Process Engineering - Phoenix, Arizona USA

August 25, 2017

? Hello Onur,
Do you have any photos of the rough deposit?

Chance R. Dunstan
Electroplating/forming manager - Placerville, California, USA

Huge and hair-like crystals when plating at high current

October 6, 2017

Q. I'm running a process where my seed is evaporated copper. The potassium cyanide based bath is 60 °CC, plating using a 3:7 ms duty cycle, 20 mA, 14 um patterned using photoresist. When I bump up to 80 mA, the plate becomes chunky and brittle. Under SEM there are huge crystals covered in tiny hairlike crystals. Is this standard for plating at too high of a current or am I seeing this because of some contamination? At 20 mA the plate is dimpled, but reasonably smooth. At 80 mA the plate is spiky.

Quinn Haynie
- Seattle, Washington, USA

December 26, 2017

A. Hi Quinn,
Nodules can be caused by high current density or contamination. Yes, it's a common problem. It seems a reduction in current density is called for in this case. 2 ASI is a good starting point. For fine traces, fixtures, robbers and shields may be needed for the best results.

blake kneedler
Blake Kneedler
Feather Hollow Eng.
Stockton, California

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