Ceramic MOBILEPHONE cover plate coating process introduction
With the rapid development of 5G technology, ceramics will become the most concerned material in 5G era by virtue of its no signal shielding and good mechanical properties, and the market prospect of future ceramics will be very broad. The surface treatment of ceramic products requires PVD coating process. At present, the coating process of ceramic products is mainly evaporation and sputtering. Logo or color film and AF treatment are plated on ceramic products. Let's have a look at these two coating processes.
Photo of PVD Logo on the ceramic back cover of mobile phone was taken in the third ring booth
vacuum evaporation coating
Vacuum evaporation film is a kind of film formed on the surface of substrate under vacuum condition.Heat vaporizes the evaporating material and deposition it on the substrate surface to form a solid film.
Figure vacuum evaporation coating schematic diagram
Basic process of vacuum evaporation coating:
Preparation before plating → vacuum → ion bombardment → baking → pre-melting → evaporation → taking parts → membrane surface treatment → finished products
Figure vacuum evaporation coating process flow chart
Characteristics of vacuum evaporation coating:
Advantages: the equipment is simple and easy to operate, the film made of high purity, good quality, thickness can be more accurate control, film forming rate is fast, high efficiency, the film growth mechanism is relatively simple.
Disadvantages: the film formed on the substrate adhesion is small, the process repeatability is not good enough, it is not easy to obtain the crystalline structure of the film.
Magnetron sputtering coating
Magnetron sputtering coating principle:
In the process of accelerating to the substrate under the action of electric field, electrons collide with argon atoms, ionize a large number of argon ions and electrons, and then fly to the substrate. Under the action of electric field, argon ions accelerate to bombard the target, sputtering out a large number of target atoms, and the neutral target atoms (or molecules) are deposited on the substrate to form a film.
FIG. Magnetron sputtering principle
Magnetron sputtering main process:
(l) the substrate is cleaned mainly by steam of isopropyl alcohol, and then soaked in ethanol and acetone, followed by rapid drying to remove oil stains on the surface;
(2) vacuum, the vacuum must be controlled above 2×104Pa to ensure the purity of the film;
(3) heating. In order to remove moisture on the surface of the substrate and improve the adhesion between the film and the substrate, the substrate needs to be heated. The temperature is generally selected between 150℃ and 200℃.
(4) argon partial pressure is generally selected within the range of 0.01~1Pa to meet the pressure condition of glow discharge;
(5) pre-sputtering. Pre-sputtering is to remove the oxide film on the surface of the target material by ion bombardment, so as not to affect the quality of the film;
(6) sputtering: under the action of orthogonal magnetic field and electric field, the positive ions formed after the ionization of argon hit the target at high speed, so that the target particles generated by the sputtering reach the substrate surface and deposit into a film;
(7) during annealing, the thermal expansion coefficients of film and substrate are different, and the binding force is small. When annealing, the mutual diffusion of atoms between film and substrate can effectively improve the adhesion.
Magnetron sputtering process flow chart
According to different sputtering sources, magnetron sputtering can be divided into dc and rf. The main difference between the two lies in the different ways of gas discharge. Rf magnetron sputtering USES rf discharge, while ceramic products use rf magnetron sputtering.
Magnetron sputtering coating features:
Advantages: high purity, dense, uniform thickness can be controlled, the process repeatability is better, strong adhesion.
Disadvantages: complex equipment, low target utilization rate.
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