Vacuum Surtec carries out on its premises PVD and PACVD coatings with very different structures and characteristics, in order to meet the different technical-qualitative requirements of various sectors.
What is PVD?
PVD (Physical Vapor Deposition), or the physical deposition of vapour, is a set of techniques and technologies for thin film deposition on substrates. The films are constructed from individual atoms or molecules, brought to the vapour phase from solid sources through physical processes (e.g. titanium, zirconium, chromium, titanium-aluminium, etc.) and joined with a suitable reaction gas to obtain for example TiN (Titanium Nitride) ZrN (Zirconium Nitride) CrN (chromium nitride) TICN (titanium carbonitride) TiAlN (Titanium Aluminium Nitride) TiAlCN (titanium-aluminium carbonitride) TiO2 (Titanium Dioxide), etc. After being transported in a high vacuum or plasma environment, these types reach the substrate where they condense and take part in nucleation and growth processes. The obtainable thicknesses range from a few tens of nanometres up to a few microns.
What is CVD?
CVD (Chemical Vapor Deposition), or chemical deposition from vapour, is a set of technologies which, like PVD, are designed to deposit thin films, in very controllable thicknesses. In CVD a gaseous precursor of the material to be deposited is introduced into a reactor in an environment at different vacuum levels and, thanks to the application of energy, undergoes a series of chemical reactions where the product is a compound that is deposited on the substrate. The energy can be applied in various forms, such as heat or plasma; in the second case we are referring to PACVD (Plasma Assisted - CVD), or plasma-assisted chemical deposition.
Why rely on the PVD / CVD techniques?
This technological sector has been continuously developing over the past 30 years and has considerable advantages that make it a good competitor for other material coating techniques:
- Ability to deposit coatings of an extremely varied chemical nature: metal, ceramic, intermetallic (cermets), organic, crystalline or amorphous form;
- Elevated purity of the deposited material, thanks to the vacuum environment in which the processes take place;
- Possibility of creating decorative, technical finishes, or functional and versatile;
- Possibility of coating a wide range of materials, including plastics, ceramics and metals;
These are green technologies, with no environmental impact and risks to health (unlike many products used in the electroplating industry).
The coatings that can be deposited with these technologies are built with very different architectures, allowing the best solution to every specific problem to be found. The possibilities are:
- "Monobloc" structure coatings, that is a single thick layer;
- Multilayer coatings, built up through an alternation of thin layers, also from very different chemicals and even in large numbers;
- "Graded" coatings, chemistry that changes gradually with increasing thickness, thus allowing a variation to the properties on the film.
Diamond-like Carbon is a form of amorphous carbon (non-crystalline) that can only be obtained as a thin film and that has become increasingly popular in the thin coatings field for its exceptional properties that guarantee a wide range of industrial applications.
Carbon is a natural element present in 3 different forms of hybridisation, which depend on how the atoms bond to each other, these are sp1, sp2, sp3.
DLC is made up from a structure in which the bonds between atoms are mixed, both sp2 and sp3. The prevalence of one fraction over the other determines the microscopic properties and thus the preferential use of the film: a prevalence of sp2 bonds gives the film a graphitic character and is more interesting for electronic applications, while a prevalence of sp3 (most common option), gives a diamond-like character and ensures better mechanical performance.
DLC can be produced with both PVD and CVD techniques, obtaining microstructures with very different characters and chemistry. What can be obtained are:
- pure carbon films, such as a-C (amorphous carbon) and ta-C (tetrahedral amorphous carbon, with a higher content of sp3 bonds), which are extremely hard;
- hydrogenated carbon film, abbreviated a-C:H or ta-C:H, a form with very versatile properties;
- films "doped" with metals (titanium, chromium) and nonmetals (silicon), so-called a-C:Me and a-C:X, for specific functional applications.
The main properties for which the DLC is known and, below, the applicative consequences:
High hardness, in some forms the values are the closest between the materials known as those typical of crystalline diamond.
→ excellent resistance to wear and scratching (machining tools, industrial moulds).
Low friction coefficient, in some forms it is comparable to that of Teflon.
→ plain shaft applications, with reduced use of lubricants (automotive components, razor heads).
High chemical inertia, especially against oxidising acids.
→ a material that is extremely resistant to corrosion, increasingly known for applications in the biomedical field (prostheses, coronary stents, surgical tools).
→ high impermeability to gases (coating plastic bottles).
Changeable electrical properties depending on the structure’s chemistry:
→ high electrical insulation films or conductors for optical (lasers) and electronic applications (hard-disk reading systems).
high aesthetic properties:
→ "valuable" colours, iridescent, glossy and matte (jewellery, furnishings).