· Several ion sources commonly used in coating
Although there are many ion source types, the purpose is no more than on-line cleaning, improving the energy distribution and modulation on the surface of the plating to increase the energy of reactive gas. Ion source can greatly improve the bonding strength of the film and matrix, and the hardness and wear resistance of the film itself can also be improved. If the wear-resistant layer of the plating tool is larger in general and the film thickness uniformity is not required high, ion sources with larger ion current and higher energy level can be used, such as hall ion source or anode ion source.
The anode layer ion source is similar to hall ion source principle. In a narrow circular (rectangular or circular) slit a reinforced magnetic field is applied to ionize the working gas under the action of an anode and in the direction of the workpiece. The anode layer ion source can be made to be very large and long, especially suitable for coating large workpieces such as building glass. The anode layer ionic source ionic current is also large. But the ion flow is more divergent and the energy level distribution is too wide. Generally applicable to large workpieces, glass, wear, decorative workpieces. But the application of advanced optical coating is not too much.
Kaufman ion source is an early application of ion source. It belongs to a grid ion source. First, the cathode generates plasma in the ion source chamber, and then the ions are extracted from the plasma cavity by two or three anode grids. This kind of ion source has strong directivity and concentrated ion energy bandwidth, which can be widely used in vacuum coating. The downside is that the cathode (often tungsten) burns quickly in the reaction gas, and that there are limits to ion flow that may be uncomfortable for users who need large ion flows.
Hall ion source is an anode in a strong axial magnetic field under the cooperation of the process gas ionisation. The strong imbalance of this axial magnetic field separates the gas ions and forms the ion beam. Because the axial magnetic field is too strong, hall ion source ion beam needs to replenish electrons to neutralize the ion stream. The common neutralization source is the tungsten filament (cathode).
Hall ion source features:
1. Simple and durable;
2. The ionic current is almost proportional to the gas flow, and large ionic current can be obtained;
3. The tungsten filament generally straddles the outlet, and the ion beam impact is quickly eroded, especially for reactive gases, which need to be replaced within 10 hours. And there will be some pollution from the tungsten filament. To solve the defects of tungsten wire. There are longer life neutralizers such as a small hollow cathode source.
Hall ion source is the most widely used ion source.
If the wear-resistant decorative film plating, film thickness, and the need for a strong body adhesion, and uniform requirements are not high. Hall ion source is available. The ionic current is large and the ionic energy level is high. If it is coated with optical film, the main requirements of ionic current energy concentration, ionic current uniformity. Therefore, it is best to use Kaufman or RF ion source, and conditional use of ECR (electron cyclotron) or ICP(induction coupling) ion source. Also, consider consumables, such as halogen wires that burn out in the reaction gas in about 10 hours. Advanced ion sources such as ICP can work continuously in reactive gases for hundreds of hours.
Coated lamp aluminum films. Since it is a metal film, of course, DC magnetron sputtering is good. Speed is fast. Intermediate frequency is suitable for coating compound film. If you choose an ion source, a hall ion source is enough. But pay attention to the size of the lamp. Generally hall ion source is circular, the area covered by ion source is limited. You must cover all the workpieces with the ion beam. If the ordinary hall ion source is too small, the anode layer ion source can be considered. One reason ion sources don't glow is that the magnetic field is too weak to excite the plasma. There are many kinds of ion sources, but they basically produce the plasma first, then extract the gas ions from the plasma and accelerate them into ion beams, then the rear vision to inject electrons and the ion stream.