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Vacuum Coating Technologies

Sputtering, Cathodic Arc, Evaporation and PECVD

In PVD coating deposition, a material (the target) is brought into the vapor phase to reach the surface of the object to be coated (said substrate) on which to condense forming the so-called film. This atom by atom mechanism of deposition, in addition to improving the adhesion of the film, allows the use of a wide range of materials to coat various kinds of substrates, from steel to brass, from iron to zamak, but also plastics, glass and ceramics, differently from other technologies that are limited to few types of metals.

Sputtering, cathodic arc and thermal evaporation (often simply called metallization) are the main methods used at industrial level and differ in how the constituents of the vapor phase (atoms and ions) are extracted from the target and the energy given to them. The choice of one method rather than another is dictated by the properties to be obtained, in terms of compactness, adhesion and color of the film, and by the type of material to be deposited. In particular:

  • Sputtering: the target is hit by a cascade of particles coming from an ionized gas (plasma). These "bullets" erode the material and extract the atoms that will then settle on the substrate in a uniform manner.
  • Cathodic arc: an electric discharge produces a localized evaporation of the target that generates a flow of ionized material in the direction of the object to be coated. Being ions, it is possible to supply energy to the beam, thus obtaining compact and resistant coatings.























• Thermal evaporation (or metallization): the material to be deposited is placed in a crucible and brought to a high temperature causing a rapid evaporation towards the substrate.

Vacuum is necessary to trigger these mechanisms, as well as to facilitate the transfer of the material that, not being slowed by air or other fluid, will reach the surface of the substrate with high energy, adhering more firmly. However, despite creating the vacuum in the process chamber may appear to be a complication, actually it involves two fundamental benefits:

1)  Minimizing contamination and therefore obtaining high quality coatings;

2) Having a defined and repeatable deposition process, considering that vacuum is a well-controlled working condition, as opposed to a electroplating deposition which is very sensitive to ionic concentration and additives, current density, temperature and polarization.

A technology often integrated into PVD systems is PECVD, Plasma Enhanced Chemical Vapor Deposition, which consists in the ionization of gases to favor a chemical reaction that will generate a deposition belonging to another range of coatings. PECVD is usually used independently or complementary to PVD to improve surface resistance to scratches and corrosion.

Therefore an in-vacuum coating equipment consists essentially of three main elements: the process chamber, the pumping system and the electronic control. The first two are closely linked to each other: larger chambers require larger pumping systems, while the electronic control (PLC) manages all the system components, checks and tunes the various parameters so that the process is stable and repeatable. The system is completed by a user-friendly Supervisor (HMI) that works as an interface for the final user.