PVD gold color matching

A. Gold film transmits green more than other colours. When the film is too thin there is little absorption and it allows mostly green light on to the TiN coated surface. The light reflected by TiN is again filtered by the gold film. Thus we see transmitted green rather than reflected yellow. If the film is thick enough light is almost completely absorbed and we see only reflected light which is yellow.

A. Your supplier is not correct. It is possible to vary deposition parameters to obtain a very wide range of gold shades.

A. I have never seen anyone exactly match 24K gold. The luster L* of the nitrides is not right so they don't have the "softness" of 24K gold. Typical values are for TiN, color is golden yellow (L* = 77-80, a* = 2-5 and b* = 33-37) for 24k gold color is gold (L* = 88-91, a*=(-3.7)-1, and b* = 27-34).

Hope this helps.

A. If the colour is brown, you may try different Vacuum or Bias volts. Sometime I found Ti target from different sources could make different TiN coulour. I have never try on plastic substrates, but have done a lot on metal substrates. There are too many different parameters you could try, like Vacuum, Bias, time etc.

A. Firstly, PVD is more expensive than conventional electroplating because you need a high capital expenditure on a vacuum system and chamber. Assuming you have access to a PVD system you need to deposit a thin layer of TiN (titanium nitride) - this will give you your gold colour. However, it may not be the right colour for you, so you can then plate the TiN with a thin layer of gold. If your TiN is too thick, you will have problems depositing the gold, because TiN is rather non conducting. The trick to it is to use the substrate's conductivity to deposit a thin layer of gold over the TiN, using discontinuities in the TiN layer to allow the current to pass through the TiN. You will get increased wear resistance this way, because the gold will be deposited over a rough TiN surface and it will fill in the "valleys" in the TiN. The gold on the "peaks" will wear away to expose the much harder TiN and this will then protect the gold still left in the valleys.

A. Actually, TiN is a very good electrical conductor. As noted, you may have to add a gold layer on top to get the exact color that you want. Another way is to deposit an alloy nitride, mixing the titanium with zirconium. ZrN is more of a champagne gold. Addition of a little carbon to either will darker the hue. You have to be careful with the carbon, though -- too much and you get magenta.

A. A layer of gold on TiN is generally deposited on watch straps, cases etc in the same chamber by PVD. However depositing gold by PVD requires huge investment in gold and recovery of unused gold is difficult. It would be ideal if gold can be electroplated on TiN. But it appears to be difficult.

A. Andre,
As you might have already figured out, there are companies that specialize in functional PVD coatings and those that specialize in decorative PVD coatings. Decorative PVD coatings are very commonly deposited on faucets and door hardware. As gold PVD is pretty common in the faucet business, replacing gold plating, look for a company in Brazil that makes high end faucets. They either do the PVD coating themselves, or can lead you to their PVD coating supplier.

 Hi Brint. You're certainly welcome to ask. But some people who have achieved success say it depends on a lot of details of the particular type of chamber, and they also may want to restrict some of their know-how to further their own business interests. So I don't know whether any answer will be forthcoming -- you may have to go with just the general guidance they are offering and do some experimentation :-(

Regards,

A. Hi guys

I work for a Mexican factory and we make Gold PVD using TiZr targets with Nitrogen gas, the key to get a good color is proportion of gas and adjust bias control to get very stable coating.

A. As for the color change with time, TiN has a greater coefficient of thermal expansion than glass. As the component cools after coating, the TiN will try to shrink, adding tensile stress to the coating, opening up the structure and darkening the coating. I would look at going to a pulsed bias power supply on your substrate to increase ion bombardment during deposition, improving coating adhesion, providing better coating consistency, and, hopefully, adding enough compressive stress in the coating to overcome the tensile stress associated with the mismatch in thermal expansion.

A. Kushal,
220 °C will give you pretty high compressive stress in TiN. Suggest you look into ZrN coating instead. A lot less stress at low temperatures. To get the deep gold color add a bit of acetylene to the gas mix. If you stay with TiN, reduce the coating thickness. Might also try coating with a pulsed bias.

A. I think you are on the right track, keep trials with small variations in parameters; am sure you get the desired 24 karat colour ... theres no perfect recipe for it.

A. Try going to ZrN instead of TiN. With a little methane or acetylene in the gas mix, you can get a good 24 kt gold look. Very common in the faucet/door hardware decorative coating business.

A. Hi cousin Araz.

As you see, we've added your inquiry to a previous thread on the same subject.

You've posted questions under 3 different names which is making it difficult for readers to know which postings are related and thereby get a full feeling for your situation and how to help you. You're probably having difficulty expressing a non-english name in English ... so is it okay for me change the name on all of your postings to first name Araz and last name shown in your e-mail address? :-)

Regards,

Crow is black, koel is black, what is the difference ?
Come spring, crow is crow, koel is koel.

So goes a short verse ("subhashita") in Samskrit. It is same with gold and TiN.

A. Hello friend.
Try linking oxygen gas to your process in the end. Keep vacuum at around 7.0x-1. Keep bias at 500V, 50%. Do it for 4 mins and surely you will get dark gold on rough surface.
Another way is by using used ARC target. Used targets provide us dark colors. for example...use target which are 50% used compared to original. Hope this helps you.