The secret of gradient color on the back panel of phone

Smartphones are becoming more and more difficult to innovate or break through functionally. So manufacturers began to see how to make the appearance different. In the first half of 2018, Huawei unveiled the Huawei P20 Pro, which features a gradient design. This feeling of bridal brim is very pleasing to the eye, and the design has attracted broad attention online. Now there are many mobile phones with similar aurora colored or gradient colored shell on the market. So how to make this eye-catching design into reality?
The answer is PVD( Physical Vapor Deposition)

Physical vapor deposition technology refers to achieving material transfer in physical processes, in which atoms or molecules transferred from the target to the surface of the substrate, so as to increase the hardness, wear resistance, optical properties, and chemical stability of the substrate surface. The nano-vacuum sputtering technology is adopted in the gradient color process, which is to change the film thickness of the upper, middle and lower areas of the glass substrate (incremental or decremental changes) during film formation by sputtering to form a rainbow color light band.


Gradient coating there is a unique process, in which a dam-board is added between the target material and the workpiece. In the furnace, after bombarding a specific target material with ultra-high speed electrons, and using this specific dam-board, part of the ion cloud is blocked, only for the other part of the ion cloud to attach to the substrate surface, forming a very thin nano-plating layer. By controlling the thickness of the coating, forming a nano-scale thickness difference, and then sprayed on the background color, then the aurora color is achieved.

1. Technical difficulty

The first one is Design. Same as the gradient color, beauty and texture are very different. Before the release of Huawei’s P20, designers sought inspiration from nature, from masterpieces such as “Water lilies” and “Sunrise” by the French impressionist painter Monet, and finally found it, the pure natural aurora color.
Another one  is Magnetic sputtering process . The gradient interval of spectral color is very difficult to control, need to constantly adjust the sputtering machine inside the correction plate to adjust the optical thickness of different areas of the glass. One of the reasons why the yield of original gradient backplane was only about 20% was the requirement of vacuum environment.

The main processes of magnetic sputtering include: pre-treatment, load, vacuuming, sputter coating, cooling treatment and post-treatment. The entire process needs to be done in a vacuum chamber.Vacuum generation equipment is inevitable for the expected vacuum environment. The most typical design is the vacuum system of the fore-line pump plus the molecular pump.

The latest series of magnetically levitated pump, F-400/3500B  and RV series mechanical pump are the perfect match,

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Magnetically levitated molecular pump using suspension technology, external lubrication free, to ensure the clean and oil-free process. F-400/3500B type molecular pump using a new process, light rotors, high pumping speed, good stability, strong anti-shock capability, is the best choice in industrial field. The RV series of mechanical pump bodies are made of new materials available for higher vacuums and stable pumping rates. KYKY offers a complete range of vacuum coating technology innovation solutions, ranging from consulting, production, accessories, application training to after-sales service. To help with vacuum coating, we are serious.

KYKY offers a complete range of vacuum coating solutions, ranging from consulting, production, accessories, application training to A/S service. KYKY is devoted to the development of vacuum coating industry.

By Zhang Zixiao

Pictures from internet

Post time: Sep-02-2021