Factors of film formation nonuniformity in pvd coating equipment

Because the pvd coating equipment must be able to maintain the characteristics of self revolution of the workpiece, the transfer technology of the workpiece between different vacuum chambers is the main difficulty in manufacturing multi chamber continuous coating equipment for three-dimensional dispersed parts. At present, the conveyor mechanism is mainly a chain tunnel conveyor developed on the basis of the conventional, widely used in the surface coating of plates and belts, and workpiece free rotation mechanism.

The chain tunnel type continuous transmission mechanism is developed on the basis of the transmission mechanism in the traditional plate and strip surface coating equipment. For the vacuum coating equipment manufacturing enterprises, there is no difficulty in production. The existing three-dimensional dispersion piece continuous coating equipment on the market uses this type of model. Several domestic enterprises have applied for patents for this purpose. It is the structural design drawing of chain tunnel transmission mechanism. The transmission process is that the rotary table A drives the flexible metal steel belt B to rotate, the shaft sleeve D of the rotation shaft is welded on the flexible steel belt, and the mechanical mechanism is fixed on the rotary table. At the same time, the fixed disk F with internal teeth is used to gear the gear E on the rotation shaft C to ensure its rotation. The steel strip B of flexible metal material can be freely disconnected at G, and enters the work-piece frame of the next vacuum coating chamber from the opening H of the internal tooth fixed disc F through a linear motion.

The defects of chain tunnel transmission mechanism are:

1. The connecting valves between vacuum chambers need to be larger, so that the atmosphere between different vacuum chambers is easy to string together, thereby reducing the coating quality and yield.

2. High design accuracy and processing level are required. Due to the flexible structure, it is easy to have inaccurate matching, leading to transmission failures. The transmission process of reciprocating step rack pushrod conveyor for vacuum coating equipment is: gear G, rack H-pushrod mechanism that is fixed on the top or chassis of the coating chamber (on the same side as the rotary table) and can reciprocate, to realize the transmission of self rotating workpiece rod Am from the rotary table Jm of vacuum chamber M to the rotary table Jn of vacuum chamber N. The power used by the gear and rack is realized by the motor whose shaft is sealed outside the vacuum chamber. In order to make the self rotating workpiece rod leave the male rotary table and enter the next male rotary table, an open connection is adopted between the male rotary table and the self rotating shaft, and at the same time, an opening is made at the corresponding position of the internal gear disc fixed in the coating chamber and maintaining rotation, so that the self rotating workpiece rod can be transferred from the coating chamber M to the next coating chamber N.

Compared with the chain type transmission mechanism, this mechanism is rigid transmission, and there is no problem of inaccurate toothing. At the same time, because of the small transition space required, it can save the opening and closing time of valves between vacuum chambers, and further reduce the atmosphere between different vacuum chambers. Therefore, the stability and reliability of the coating process, the yield, and the energy consumption and cost are greatly improved.

Uneven film formation of vacuum coating equipment

With the development of coating technology, all kinds of vacuum coating equipment are gradually emerging. No matter what kind of vacuum coating equipment, the uniformity of the film will be affected by some factors. Now, we will use the magnetic sputtering vacuum coating equipment to analyze the factors of non-uniform film formation.

The uneven air extraction of the coating equipment will affect the coating uniformity. It is important that the substrate is clean. Before vacuum coating, the substrate surface shall be carefully cleaned to remove oil, dirt and water from the workpiece. Substrate surface pollution refers to all kinds of dust, grease, polishing paste, sweat, etc. attached to the parts during processing and transportation. In a humid environment, the substrate surface is easy to oxidize, forming an oxide film to absorb gas. These dirt can be cleaned by degreasing or chemical methods. Clean substrates should not be placed outside directly. They should be stored in closed containers to reduce contamination. The coating room will also accumulate dust, so it is necessary to clean the coating room, bake for degassing, and place the machine in a clean environment. Pay attention to the return oil of diffusion pump. There are many raw materials for coating, such as resins, silicones, silicohydrochloric acid, polymers, etc. The ratio of auxiliary materials and formulas is different, and the film is also different.

The above are the factors of non-uniform film formation of vacuum coating equipment.