What Is Physical Vapor Deposition?

Physical Vapour Deposition (PVD) technology means that under vacuum conditions, a physical method is used to vaporize a material sourcesolid or liquid surfaceto gaseous atoms, molecules, or a portion of the ionization to ions, and pass low pressure gas (or plasma) ) Process, the technology of depositing a thin film with a special function on the surface of the substrate. The main methods of physical vapor deposition include vacuum evaporation, sputtering coating, arc plasma coating, ion coating, and molecular beam epitaxy. Developed to the present, physical vapor deposition technology can deposit not only metal films, alloy films, but also compounds, ceramics, semiconductors, and polymer films.

Physical vapor deposition

Physical Vapour Deposition (PVD) technology means that under vacuum conditions, physical methods are used to vaporize a material sourcesolid or liquid surfaceto gaseous atoms, molecules, or a portion of the ionization to ions, and pass low-pressure gas (or

Physical vapor deposition technology has been used as early as the beginning of the 20th century, but it has developed rapidly in the past 30 years and has become a new technology with broad application prospects, and it is developing towards the trend of environmental protection and cleanness. From the beginning of the 1990s to the present, it has become more and more widely used in the watch industry, especially the surface treatment of high-end watches.

The basic principle of vacuum evaporation is to evaporate metals, metal alloys or compounds under vacuum conditions, and then deposit them on the surface of the substrate. The methods of evaporation are commonly resistance heating, high-frequency induction heating, electron beam, laser beam, and ion beam high-energy bombardment. The material is evaporated into a gas phase and then deposited on the surface of the substrate. Historically, vacuum evaporation is the earliest technique used in PVD.

The basic principle of sputter coating is that under argon (Ar) gas-filled vacuum conditions, argon is glow-discharged. At this time, argon (Ar) atoms are ionized into argon ions (Ar +). The argon ions are accelerated by the electric field force. The cathode target made of the plating material is bombarded, and the target will be sputtered out and deposited on the surface of the workpiece. If direct current glow discharge is used, it is called direct current (Qc) sputtering, and radio frequency (RF) glow discharge is called radio frequency sputtering. Magnetron (M) glow discharge is called magnetron sputtering. The basic principle of arc plasma coating is that under vacuum conditions, an arc starting pin is used to initiate an arc discharge between the vacuum gold wall (anode) and the plating material (cathode). The cathode surface is rapidly moved with multiple cathode arc spots, continuously Quickly evaporate or even "different" plating material, ionize it into arc plasma with the plating material as the main component, and quickly deposit the plating material on the substrate. Because there are multiple arc spots, it is also called a multi-arc evaporation ionization process.

The basic principle of ion plating is that under vacuum conditions, some plasma ionization technology is used to ionize part of the plating material into ions, while generating many high-energy neutrals.

Physical vapor deposition vacuum evaporation

(A) the principle of vacuum evaporation

(1) Vacuum evaporation is to heat and evaporate the plating material under vacuum conditions to vaporize a large number of atoms and molecules and leave the liquid plating material or leave the solid plating surface (sublimation).

(2) Atoms and molecules in gaseous state migrate to the matrix in a vacuum with few collisions.

(3) Plating atoms and molecules are deposited on the surface of the substrate to form a thin film.

(Two) evaporation source

The plating material is heated to an evaporation temperature and vaporized. This heating device is called an evaporation source. The most commonly used evaporation sources are resistance evaporation sources and electron beam evaporation sources. Special-purpose evaporation sources include high-frequency induction heating, arc heating, radiant heating, and laser heating evaporation sources.

(3) Examples of vacuum evaporation process Taking plastic metallization as an example, the vacuum evaporation process includes: pre-plating treatment, coating and post-treatment.

The basic process of vacuum evaporation is as follows:

(1) Pre-plating treatment, including cleaning of plated parts and pretreatment. Specific cleaning methods include detergent cleaning, chemical solvent cleaning, ultrasonic cleaning and ion bombardment cleaning. Specific pre-treatments include static elimination and primer coating.

(2) Furnace installation, including vacuum chamber cleaning and cleaning of plated parts, installation, adjustment of evaporation source, and plated card.

(3) Evacuate, generally first rough pump to 6.6Pa or more. Open the pre-maintaining vacuum pump of the diffusion pump earlier, heat the diffusion pump, and after preheating is sufficient, open the high valve and use the diffusion pump to draw 6 × 10- 3Pa half bottom vacuum.

(4) Baking, baking and heating the plated parts to the required temperature.

(5) Ion bombardment, vacuum degree is generally 10Pa 10-1Pa, ion bombardment voltage is 200V 1kV negative high voltage, and ion strike time is 5min 30min,

(6) Pre-melting, adjust the current to pre-melt the plating material, and degas for 1min to 2min.

(7) Evaporation deposition, adjust the evaporation current as required until the required deposition time is over.

(8) Cooling, the plated part is cooled to a certain temperature in a vacuum chamber.

(9) Out of the oven. After taking the parts, close the vacuum chamber and evacuate to l × l0-1Pa. The diffusion pump is cooled to the allowable temperature before the maintenance pump and cooling water can be turned off.

(10) Post-treatment and top coat.

Physical vapor deposition sputter coating

Sputtering coating refers to the process of bombarding the surface of the target material with the particles with functions under vacuum conditions, so that the atoms on the surface of the target can get enough energy to escape, which is called sputtering. The sputtered target is deposited on the surface of the substrate, which is called sputter coating. The incident ions in the sputtered coating are generally obtained by glow discharge, in the range of 10-2Pa to 10Pa, so when the sputtered particles fly to the substrate, they easily collide with the gas molecules in the vacuum chamber to make the direction of movement Random, deposited films tend to be uniform. The developed large-scale magnetron sputtering coating has a high deposition rate, good process repeatability, and ease of automation. It is suitable for large-scale architectural decoration coating and functional coating of industrial materials, and TGN-JR multi-arc or Magnetron sputtering is used to plate nickel, nickel, and silver Ag on the surface of foamed plastics and fiber fabrics.

Physical vapor deposition plasma coating

This refers to the cold cathode arc evaporation commonly used in the PVD field, where solid plating is used as the cathode, and water cooling is used to form many bright spots on the surface of the cold cathode, that is, cathode arc spots. The arc spot is the root of the arc near the cathode. The current density in extremely small spaces is extremely high, and the size of the arc spot is extremely small, estimated to be about 1 m to 100 m, and the current density is as high as 105 A / cm2 to 107 A / cm2. Each arc spot exists for a very short time, and the plating material at the correction point of the ionized cathode is explosively evaporated. The ionized metal ions will also generate new arc spots on the surface of the cathode. Many arc spots are constantly generated and disappeared. So it is also called multi-arc evaporation. The earliest designed plasma accelerator type multi-arc evaporation ionization source is to arrange a magnetic field behind the cathode, so that the evaporated ions can get a Hall acceleration effect, which is conducive to increasing the energy to bombard the volume. Ionization source coating has higher ionization rate, so it is also called arc plasma coating. Since the evaporation and ionization of the plating material depends on the arc, it belongs to the evaporation means different from the second and third sections.

Physical vapor deposition ion plating

Ion plating technology was first developed by D. M. Mattox proposed that in 1972, Bunshah & Juntz launched Active Reaction Evaporation Ion Plating (AREIP), which deposited superhard films such as TiN, TiC, etc. Moley & Smith developed and perfected hollow hot cathode ion plating in 1972, and developed RFIP in 1973. . In the 1980s, magnetron sputtering ion plating (MSIP) and multi-arc ion plating (MAIP) were developed.

(1) Ion plating

The basic feature of ion plating is to adopt a certain method (such as electron beam evaporation magnetron sputtering, or multi-arc evaporation ionization, etc.) to ionize neutral particles into ions and electrons. A negative bias must be applied to the substrate to make the ions The substrate is bombarded, and after the negative bias voltage is appropriately reduced, the ions are further deposited on the substrate to form a film. The advantages of ion plating are as follows: The binding force between the film layer and the substrate is strong. The film layer is uniform and dense. Good winding performance under negative bias. No pollution. A variety of base materials are suitable for ion plating.

(Two) reactive ion plating

If an electron beam evaporation source is used for evaporation, a positive bias voltage of 20V to 100V is applied above the crucible. Reactive gases are conducted in a vacuum chamber. For example, N2, O2, C2H2, CH4, etc. instead of Ar, or mixed with Ar, the high-energy electrons (thousands to tens of thousands of electron volts) in the electron beam, not only melt and evaporate the plating material, but also stimulate Secondary electrons. These secondary electrons are accelerated under the positive bias above, and collide with the evaporated particles of the plating material to ionize into ions. The ionization reaction occurs on the surface of the workpiece to obtain oxides (such as TeO2: SiO2, Al2O3, ZnO, SnO2, Cr2O3, ZrO2, InO2, etc.). Its characteristics are high deposition rate and low process temperature.

(Three) multi-arc ion plating

Multi-arc ion plating is also called arc ion plating. Because there are multiple arc spots on the cathode, it is called "multi-arc". The main features of multi-arc ion plating are as follows: (1) The cathode arc evaporation ionization source can directly generate plasma from a solid cathode without generating a molten pool, so it can be arranged in any orientation, and multiple evaporation ionization sources can also be used. (2) The ionization rate of the plating material is high, generally reaching 60% to 90%, which significantly improves the binding force with the substrate and improves the performance of the film layer. (3) The deposition rate is high, and the efficiency of the coating is improved. (4) The structure of the equipment is simple. The arc power source works under low voltage and high current conditions, and it is safer to work.

The English term "phisical vapor deposition" is abbreviated as PVD. It is a commonly used term in the coating industry.

PVD (physical vapor deposition) coating technology is mainly divided into three categories, vacuum evaporation coating, vacuum sputtering coating and vacuum ion coating. Corresponding to the three categories of PVD technology, the corresponding vacuum coating equipment also has three types: vacuum evaporation coating machine, vacuum sputtering coating machine and vacuum ion coating machine.

In the past ten years, the development of vacuum ion coating technology is the fastest, and it has become one of the most advanced surface treatment methods today. What we usually call PVD coating refers to vacuum ion coating; what is commonly called PVD coating machine refers to vacuum ion coating machine.

Physical Vapor Deposition (PVD)

Physical vapor deposition is the process of evaporation, ionization, or sputtering to generate metal particles and react with reactive gases to form compounds that are deposited on the surface of the workpiece. Physical and meteorological deposition methods include vacuum plating, vacuum sputtering, and ion plating. Ion plating is widely used.

Ion plating uses the inert gas glow discharge to vaporize the plating material (such as metal titanium). The ions are accelerated by the electric field and bombard the surface of the workpiece with higher energy. At this time, if CO2, N2 and other reactive gases are passed in, TiC, TiN coatings can be obtained on the surface of the workpiece, with a hardness of up to 2000 HV. The important features of ion plating are that the deposition temperature is only about 500 ° C, and the coating has strong adhesion, which is suitable for high-speed steel tools and hot forging dies.