Modern vacuum coating equipment (uniform heating technology, temperature measurement technology, unbalanced magnetron sputtering technology, auxiliary anode technology, intermediate frequency power supply, pulse technology) is mainly composed of vacuum chamber, vacuum pumping section, vacuum measurement section, power supply part, process gas input system, mechanical transmission part, heating and temperature measurement part, ion evaporation or sputtering source, water cooling system and other parts.
1. Vacuum Chamber
Coating equipment mainly divided into continuous coating production line and single chamber coating machine. Due to the high requirements of the molds and tools coating on the heating and mechanical transmission parts, as well as the big different of the shape and size of the mold, the continuous coating production line is usually difficult to meet the requirement and single chamber coater is always used.
2. Vacuum Pumping System
In the vacuum technology, the vacuum pumping system is an important part. Due to the high adhesion requirements of molds and tools coating, the coating process requires a good background vacuum, so a reasonable selection of the vacuum pumping system of equipment is essential to achieve a high vacuum degree. For the time being, there is no pump that can operate from atmospheric pressure until it approaches ultra-high vacuum. Therefore, the good vacuum is not achievable by single vacuum equipment or methods. Several pumps must be used in combination, such as mechanical pumps system, molecular pump systems and so on.
3. Vacuum Measurement System
The vacuum measurement part of the vacuum system is used to measure the pressure in the vacuum chamber. Like vacuum pump, there is no vacuum gauge that can measure the entire vacuum range. So many kinds of vacuum gauges are produced according to different principles and requirements.
4. Power Supply System
The target power supply mainly includes DC power supply (such as MDX) and intermediate frequency power supply (such as PE, PEII, and PINACAL of American AE Company). The workpiece itself usually needs to be supplied with DC power (such as MDX), pulsed power supply (such as PINACAL+ that produced by American AE Company), Or RF power supply (RF).
5. Process Gas Input System
Process gases, such as argon (Ar), helium (Kr), nitrogen (N2), acetylene (C2H2), methane (CH4), hydrogen (H2), and oxygen (O2) are generally supplied by gas cylinders. They are inlet the vacuum chamber through gas pressure reducing valve, gas shut-off valve, pipeline, gas flow meter, solenoid valve, piezoelectric valve. The advantage of this type of gas input system is that the piping is simple and clear, and it is easy to repair or replace the cylinder. Also, each coating machine does not affect each other. Besides, there are also cases where multiple coaters share a group of cylinders, which may be found in some of the larger coating shops, the advantages are that it reduces the consumption of gas cylinders, and makes unified planning and layout. The disadvantage is that the chance of leakage increases due to lots of joints. Moreover, the coating machines will interfere with each other, and the air leakage of a coating machine pipe may affect the product quality of other coating machines. In addition, when replacing the cylinders, it must be ensured that all the mainframes are in a non-use state.
6. Mechanical Transmission System
The tool coating requires that the film must be uniform in thickness. Therefore, there must be three rotations in the coating process to meet the requirements. That is, while a large workpiece table rotation running, a small workpiece carrying table also rotating, and the workpiece itself can rotate at the same time. In the mechanical design, generally there is a large driving gear in the center of the bottom of the large workpiece turntable, surrounded by some small star wheels to mesh with it, and then use the shift fork to toggle the workpiece to rotate. Of course, when making the mold coatings, generally two rotations are sufficient, but the load capacity of the gear must be greatly enhanced.
7. Heating and Temperature Measurement System
When making the mold coating, how to ensure the uniform heating of the workpiece is much more important than that in decorative coating process. The mold coating equipment generally has two heaters front and back, and the thermocouple is used to measure and control the temperature. However, due to the different clamping points of thermocouple, the temperature reading cannot be the true temperature of the workpiece. There are many ways to measure the true temperature of the workpiece. Here is an easy-to-use Surface Thermomeer. The working principle of this thermometer is that when the thermometer is heated, the spring on the bottom will be heated to expand, so that the pointer will push the positioning pointer to rotate till to maximum temperature. When the temperature is reduced, the spring shrinks and the pointer rotates in the reverse direction, but the positioning pointer remains at the highest temperature position. After the door is opened, the temperature indicated by the positioning pointer is read, that is, the highest temperature that the surface thermometer has reached when heated in the vacuum chamber.
8. Ion Evaporation and Sputtering Sources
The evaporation source of multi-arc plating is generally round, commonly known as round target. In recent years, rectangular multi-arc target has also appeared, but no obvious effect has been observed. The round target is mounted on the copper target holder (cathode holder) and the two are screwed together. There is magnet in the target holder, and the magnetic field strength can be changed by moving the magnet back and forth, and also the moving speed and track of arc spot can be adjusted in this way too. In order to reduce the temperature of the target and the target holder, cooling water is continuously supplied to the target holder. And in order to ensure high electrical and thermal conductivity between the target and the target holder, the tin (Sn) gasket can also be added between the target and the target holder. Besides, magnetron sputtering coating generally uses rectangular or cylindrical targets.
9. Water Cooling System
For the mold coating, in order to increase the atomization rate of metal atoms, each cathode target holder adopts large power output as much as possible, which requires adequate cooling. In addition, the heating temperature of many kinds of tools and molds coatings are 400~500℃. Therefore, cooling of the vacuum chamber wall and each sealing surface is also very important, so, cooling water is preferably supplied from a chiller of about 18 to 20℃. In order to prevent the low-temperature vacuum chamber walls and cathode targets dissolving water when contact with hot air after opening the door, the water cooling system should be able to switch to the hot water supply state about 10 minutes before the door is opened. The hot water temperature is about 40~45℃.