A technique for producing thin-film materials. The atoms of the material in the vacuum chamber are separated from the heating source and hit the surface of the object to be plated. This technology is used in the production of aluminum coatings on compact discs (CDs) and metal coatings on printed circuit boards by masks.
Vacuum Plating Films are prepared in vacuum, including simple or compound films such as crystalline metals, semiconductors, and insulators. Although chemical vapor deposition also uses vacuum means such as reduced pressure, low pressure or plasma, vacuum coating generally refers to the use of physical methods to deposit thin films. There are three forms of vacuum coating, namely evaporation coating, sputtering coating and ion plating.
Evaporation Coating
By heating and evaporating a certain substance to deposit it on the solid surface, it is called evaporation coating. This method was first proposed by M. Faraday in 1857, and it has become one of the commonly used coating techniques in modern times.
Evaporated substances such as metals, compounds, etc. are placed in a crucible or hung on a hot wire as the evaporation source, and the workpiece to be plated, such as metal, ceramic, plastic and other substrates, is placed in front of the crucible. After the system is evacuated to a high vacuum, the crucible is heated to evaporate the contents. The atoms or molecules of the evaporated substance are deposited on the surface of the substrate in a condensed manner.
The thickness of the film can range from hundreds of angstroms to several microns. The thickness of the film is determined by the evaporation rate and time of the evaporation source (or the loading amount), and is related to the distance between the source and the substrate. For large-area coatings, a rotating substrate or multiple evaporation sources are often used to ensure the uniformity of the film thickness. The distance from the evaporation source to the substrate should be less than the mean free path of vapor molecules in the residual gas to prevent the collision of vapor molecules with residual gas molecules from causing chemical effects. The average kinetic energy of vapor molecules is about 0.1 to 0.2 electron volts.