In the process of receiving customers, we often encounter customers who inquire about the film monitoring of pvd coating machines. They are very concerned about the relevant knowledge in this area and want to know more. We know some relevant knowledge, and we also want to try our best. Share more with customers, so that when they purchase equipment, they will be more clear about which equipment is more suitable for them, and it will also reduce a lot of unnecessary trouble in the later stage. So today, the editor of Huicheng Vacuum will take this opportunity to introduce the film forming control system of the pvd coating machine in detail.

At present, there are many application methods for film monitoring of pvd coating machine, mainly including: visual monitoring method, fixed (extreme) value monitoring, crystal oscillation monitoring, time monitoring and so on. I mainly introduce three kinds of visual monitoring, fixed (extreme) monitoring and crystal oscillation monitoring. Visual monitoring is also called direct monitoring, which is to use eye monitoring. Because the film will change in color due to interference during the growth process, we control the film thickness according to the color change. This method has certain errors, so it is not Very accurate, it needs to rely on experience.

Fixed value (extreme value) monitoring: mainly adopts reflective (transmissive) optical monitoring. Extreme value monitoring method: When the film thickness increases, its reflectivity and transmittance will change accordingly. When the reflectivity or transmittance reaches the extreme point, it can be known that the optical thickness ND of the coating is the monitoring wavelength ( into an integer multiple of one-quarter. However, the error of the extreme value method is relatively large, because when the reflectivity or transmittance changes very slowly near the extreme value, that is, the film thickness ND increases a lot, and the R/T changes. The position where the reflection is more sensitive is at one-eighth wavelength. Fixed value monitoring method: This method utilizes that the coating stop point is not at the quarter-wave position of the monitoring wavelength, and then the computer calculates the reflectance (or transmittance) of the total film thickness at a wavelength of one, which is the stop coating point. Crystal oscillation monitoring: The working principle of crystal oscillation is based on the principle that the vibration frequency of the quartz crystal is inversely proportional to its quality. However, one disadvantage of quartz monitoring is that when the film thickness increases to a certain thickness, the vibration frequency is not entirely due to the characteristics of the quartz itself.
To make a linear relationship between thickness and frequency, a new quartz oscillator must be used.
Several monitoring methods have their own advantages and disadvantages, but usually multi-layer coating, optical monitoring will be the main method, and quartz crystal oscillation will be the auxiliary method. In addition, there are flow control gauges or pressure control gauges that need to be filled with gas during the coating process, which need to be controlled by precise valves and photoelectric sensing systems. In the coating process of the pvd coating machine, a rotation control system is also required, that is, the main shaft of the umbrella is placed in the bearing, and then the motor is used to drive the bearing to make the umbrella rotate. Then PLC controls its rotation speed. The rotation of the crucible is driven by a motor, and the method of photoelectric induction counting is adopted, and the shielding plate is rotated by a pneumatic switch. In order to speed up the pumping rate and achieve a certain degree of vacuum, it is also necessary to refrigerate the vacuum chamber, that is, to freeze the air in the vacuum chamber to minus 130 degrees Celsius, and freeze the water vapor in the vacuum chamber and pump it away. The electrical control part mainly adopts PLC automatic control, that is, the pre-designed program is first input in the PLC, and the main circuit of the processor is connected with each empty driving system on the operation panel. When the switch on the operation panel is pressed, the information is transmitted to the The central processing unit is then analyzed by the central control system and sends out instructions to execute and complete the action by the branch.
pvd coating machine is a multi-disciplinary equipment, which integrates the most advanced electromechanical technology in today's industry, control technology, electrical automation, IT technology, refrigeration technology, microcircuit integration system, high-voltage control system, mechanical technology, processing technology, optoelectronics Technology, optical technology, pneumatic control technology, photoelectric sensing technology, communication technology, vacuum technology, thin film optics and coating technology, etc. It can be said that the vacuum coating machine is a representative of the emerging industry. Today, vacuum coating machines have been widely used, especially for coating thin films. Various thin films produced by them are applied to various optoelectronic systems and optical instruments, such as digital cameras, digital video cameras, telescopes, projectors, energy control, light Communication, display technology, interferometer, satellite missile, semiconductor laser, micro-electromechanical system, information industry, laser production, various filters, lighting industry, sensor, architectural glass, automobile industry, decorations, coins, spectacle lenses Wait, the coating machine has been closely related to human life.