PVD vacuum evaporation coating
Vacuum evaporation coating (evaporation) is a technology in which evaporation material is heated by evaporator to vaporize under vacuum condition, evaporation particle stream directly shoots to the substrate, and solid film is deposited on the substrate. Evaporation is the earliest and widely used coating technology in physical weather deposition (PVD). Although sputter plating and ion plating developed later are superior to evaporation in many aspects, vacuum evaporation coating technology still has many advantages. For example, compared with the equipment and process, it is relatively simple and can deposit a very pure film. Therefore, vacuum evaporation coating technology has many advantages Vacuum evaporation coating is still a very important coating technology. In recent years, due to the wide application of electron bombardment evaporation, high frequency induction evaporation and laser evaporation in evaporation coating technology, this technology is more perfect.
Ⅱ。Principle of vacuum evaporation coating
1. The film is placed in the evaporation source in the vacuum chamber. Under the condition of high vacuum, it is heated by the evaporation source to evaporate. After the atoms and molecules of the film vapor escape from the surface of the evaporation source, and when the average free path of the vapor molecules is larger than the linear size of the vacuum chamber, they are rarely collided and hindered by other molecules or atoms, and can directly reach the substrate surface The temperature is low, so the evaporated vapor particles condense on it to form a film.
2.In the process of evaporation coating, the particles evaporated from the surface of the film move along a straight line in space at a certain speed until they collide with other particles. In a vacuum chamber, when the concentration of the particles in the atmosphere and the pressure of the residual gas are low enough, the particles can fly in a straight line from the evaporation source to the substrate, otherwise they will collide and change the direction of motion. Therefore, it is necessary to increase the average free path of the residual gas in order to reduce the collision probability between the residual gas and the evaporated particles. When the average free path of the evaporated particles in the vacuum vessel is greater than the distance between the evaporation source and the substrate, sufficient vacuum conditions will be obtained.