Before delving into the details of vacuum coating technology, we first need to understand its common classification methods. These classifications not only help us better grasp the diversity of this technology but also provide more options for practical applications. Next, we will explore the world of vacuum coating classifications to see the characteristics and application scenarios of different types of coating technologies.

Classification of Vacuum Coating

Among the numerous vacuum coating technologies, we can classify them according to different criteria. These classification methods help us more clearly understand the unique features of various coating technologies and provide more appropriate solutions for practical applications. Next, we will delve into several common classification methods of vacuum coating.

1.1. Vacuum Coating Technology as an Important Branch of Surface Treatment

Vacuum coating technology, as a key technology in the field of surface treatment, plays an indispensable role in many fields. It changes or enhances the overall performance of materials by covering their surfaces with a thin film with specific functions. This technology is not only widely used in industrial manufacturing, aerospace, and many other fields but also shows unique advantages in electronic products, optical devices, and other aspects. Next, we will explore several key classifications and applications of vacuum coating technology.

1.2. Common Classifications of Vacuum Coating Technology

Vacuum coating technology can be divided into two major categories: wet coating methods and dry coating methods. These two methods have their own characteristics and application fields, together forming the rich diversity of vacuum coating technology. Next, we will introduce these two methods in detail.

1.2.1. Classification of Wet Coating Methods

Wet coating methods mainly include electroplating and electroless plating. These two methods occupy an important position in the field of vacuum coating, each with unique working principles and applicable scenarios. Next, we will delve into the details of these two wet coating methods.

1.2.2. Dry Coating Methods, also known as vacuum coating methods or vapor deposition methods, include two main technologies: Physical Vapor Deposition (PVD) and Chemical Vapor Deposition (CVD). In the field of PVD, we further subdivide into vacuum evaporation coating, vacuum sputtering coating, and vacuum ion coating. It is worth noting that in vacuum evaporation, technologies such as resistance heating evaporation, electron beam heating evaporation, ion beam-assisted evaporation, and magnetron sputtering coating in sputtering have attracted much attention.

2. Historical Background

Vapor deposition technology, as an emerging technology, has been continuously developing in the past 30 years since its birth. Although its application has a long history, its progress was relatively slow in the early stage due to the limitations of vacuum technology and other related fields. However, during World War II, fascist Germany cleverly applied this technology to the war for manufacturing various military optical lenses and reflectors, which greatly promoted the rapid development of vapor deposition technology in the optical industry. Thus, thin-film optics emerged as an important branch of the optical field. It not only represents a breakthrough in vacuum application technology but also integrates new technological achievements in multiple fields such as physics and chemistry.

3. Definitions

Vacuum coating method refers to the process of evaporating or sputtering metals, alloys, or compounds in a vacuum to deposit them on the object to be coated, which is called the substrate. Among them, vacuum evaporation, or evaporation for short, is a process in which the film material is heated by a specific method in a vacuum environment to vaporize and deposit on the surface of the workpiece, thereby forming a solid thin film. Sputtering is a process in which energetic particles bombard the material surface through momentum transfer, so that the surface atoms gain enough energy to escape. Magnetron sputtering technology has become an efficient and low-temperature sputtering method due to its characteristics of high sputtering rate and low substrate heating. Ion coating technology, or ion plating for short, is a process in which gas or evaporated substances are partially ionized through gas discharge under vacuum conditions, and at the same time, the evaporated substances or their reaction products are deposited on the substrate by bombardment with gas ions or evaporated substance ions. Resistance heating evaporation is a commonly used evaporation method, which directly or indirectly heats the film material through resistance to make it evaporate and deposit on the substrate.

3. Definitions

Electron beam heating evaporation is a method in which the film material is placed in a water-cooled copper crucible and heated by a high-energy-density electron beam. During this process, the film material will melt and vaporize, and then condense on the surface of the substrate to form the required thin film. To further improve the adhesion of the film layer and enhance its compactness, ion beams can be used for bombardment during the coating process, a technology known as ion beam-assisted evaporation.

4. Applications

Vacuum coating technology, as an important branch of surface treatment technology, has a wide range of application fields.

Optical films: Vacuum coating technology has important applications in the optical field, such as various filters and high-reflection mirrors used in CCD and CMOS.

Functional films: This technology is also suitable for manufacturing resistors and capacitors, preparing semiconductor films, coating cutting tools, and producing in fields such as car lights, car light covers, lasers, and solar energy.

Decorative films: Vacuum coating technology is indispensable for decorative coating of mobile phones and home appliances, production of automobile signs, coating of cosmetic box covers, and processing of architectural decorative glass, automobile glass, and packaging bags.

Analysis of Current Situation

Although vacuum coating technology started late and was limited by vacuum technology, resulting in relatively slow development in the early stage, it is still an emerging technology. At present, this technology has been widely used in some developed countries abroad. In China, due to a later start and technical limitations, its application range is relatively small, but it has huge potential and is worthy of further development and application