Analysis of the 6 common gas effects of plasma surface treatment machine:
Commonly used processing gases for plasma surface treatment machines are: air, oxygen, argon, argon-hydrogen mixed gas, CF4, etc.
Analyze the cleaned objects and dirt before using the plasma surface treatment machine to clean the objects, and then select the gas. Generally speaking, the gas in the plasma surface treatment machine has two purposes. According to the principle of plasma action, the optional gas can be divided into two categories. One is the reactive gas such as hydrogen and oxygen. The hydrogen is mainly used to clean the metal surface. Of the oxide, a reduction reaction occurs. Plasma surface treatment machine with oxygen is mainly used to clean the organic matter on the surface of the object, and the oxidation reaction occurs. Cleaning and etching: For example, when cleaning, the working gas often uses oxygen. After it is bombarded by accelerated electrons into oxygen ions and free radicals, it is extremely oxidative. Contaminants on the surface of the workpiece, such as grease, flux, photosensitive film, release agent, punching oil, etc., will soon be oxidized into carbon dioxide and water, which are pumped away by the vacuum pump to clean the surface and improve the wettability and adhesion. The purpose of the result. Low-temperature plasma treatment only involves the surface of the material and will not affect the properties of the main body of the material. Since the plasma cleaning is carried out under high vacuum, the free path of various active ions in the plasma is very long, and their penetration and penetration are very strong, and it can be processed with complex structures, including thin tubes and blind holes. .
The other type is the plasma surface treatment machine with non-reactive gases such as argon, helium, and nitrogen. Nitrogen plasma treatment can improve the hardness and wear resistance of the material. The properties of argon and helium are stable, and the discharge voltage is low (the ionization energy E of argon atoms is 15.57 eV) and it is easy to form metastable atoms. On the one hand, the plasma surface treatment machine uses the physical action of its high-energy particles to clean and easily be oxidized or reduced. Ar+ bombards the dirt to form volatile dirt and is pumped away by the vacuum pump, avoiding the surface material reaction; on the other hand, the use of argon gas is easy to form metastable atoms, and then the charge conversion occurs when it collides with oxygen and hydrogen molecules. Then combine to form oxygen and hydrogen active atoms acting on the surface of the object.

Introducing functional groups: Plasma treatment of polymer materials with N2, NH3, 02, SO2 and other gases can change the chemical composition of the surface and introduce corresponding new functional groups: -NH2, -OH, -COOH, -SO3H, etc. . These functional groups can make polyethylene, polypropylene, polystyrene, polytetrafluoroethylene and other completely inert substrates into functional group materials, which can improve surface polarity, wettability, bondability, reactivity, and greatly improve It has its use value. Contrary to oxygen plasma, low-temperature plasma treatment with fluorine-containing gas can introduce fluorine atoms on the surface of the substrate to make the substrate hydrophobic.
Although the plasma surface treatment machine uses pure hydrogen to clean the surface oxides with high efficiency, the stability and safety of the discharge are mainly considered here. When the plasma surface treatment machine is used, it is more suitable to use argon and hydrogen mixture. In addition, the material is easy to oxidize or easy to reduce. The material plasma surface treatment machine can also reverse the cleaning sequence of oxygen and argon hydrogen gas to achieve the purpose of thorough cleaning.
Argon: Physical bombardment is the mechanism of argon cleaning. Argon is an effective physical plasma cleaning gas because of its large atomic size. The surface of the sample can be bombarded with great force. The positive argon ions will be attracted to the negative electrode plate. The impact force is sufficient to remove any dirt on the surface. Then these gaseous dirt is discharged through the vacuum pump.

Oxygen: In the chemical process, the plasma reacts with compounds on the surface of the sample. For example, organic pollutants can be effectively removed by oxygen plasma where oxygen plasma reacts with pollutants to produce carbon dioxide, carbon monoxide and water. Generally speaking, chemical reactions are more effective in removing organic pollutants. Oxygen is a commonly used active gas for plasma cleaning, which is a physical + chemical treatment method. The ionized body produced after ionization can physically bombard the surface to form a rough surface. At the same time, the highly active oxygen ions can chemically react with the molecular chain after the bond is broken to form a hydrophilic surface of the active group to achieve the purpose of surface activation; the elements of the organic pollutants after the bond is broken will interact with the highly active oxygen ion A chemical reaction occurs to form molecular structures such as CO, CO2, and H2O, which are separated from the surface to achieve the purpose of surface cleaning. Oxygen is mainly used for surface activation of polymer materials and removal of organic pollutants, but not suitable for easily oxidized metal surfaces. The oxygen plasma in the vacuum plasma state is light blue, and it is similar to white under the partial discharge condition. The discharge environment light is relatively bright, and it may appear that there is no discharge in the vacuum chamber when observed with the naked eye.
Hydrogen: Hydrogen can be used to remove oxides on metal surfaces. It is often used in combination with argon to increase the removal rate. People generally worry about the flammability of hydrogen, and the amount of hydrogen used is very small. The greater concern is the storage of hydrogen. We can use a hydrogen generator to generate hydrogen from water. Thereby removing the potential harm. Similar to oxygen, hydrogen is a highly active gas that can activate and clean the surface. The difference between hydrogen and oxygen is mainly that the reactive groups formed after the reaction are different. At the same time, hydrogen has reducing properties and can be used to remove the microscopic oxide layer on the metal surface and is not easy to cause damage to the surface sensitive organic layer. Therefore, it is widely used in microelectronics, semiconductor and circuit board manufacturing industries. Because hydrogen is a dangerous gas, it will spontaneously explode when it merges with oxygen when it is not ionized. Therefore, it is generally forbidden to mix the two gases in the plasma surface treatment machine.
In the vacuum plasma state, hydrogen plasma is red, similar to argon plasma, and slightly darker than argon plasma under the same discharge environment. CF4/SF6: Fluorinated gases are widely used in the semiconductor industry and PWB (Printed Wiring Board) industry. There is only one application in IC packaging. These gases are used in the PADS process. Through this treatment, the oxide is converted to oxyfluoride, allowing flowless welding.
Nitrogen: The plasma formed by the ionization of nitrogen can react with part of the molecular structure, so it is also an active gas, but compared to oxygen and hydrogen, its particles are heavier. Normally, it will be used in plasma surface treatment machine applications. This gas is defined as a gas between the active gas oxygen, hydrogen and the inert gas argon. It can achieve certain effects of bombardment and etching while cleaning and activating, and at the same time, it can prevent oxidation of part of the metal surface. The plasma formed by the combination of nitrogen and other gases is usually applied to the treatment of some special materials. Nitrogen plasma is also red in the vacuum plasma state. Under the same discharge environment, nitrogen plasma will be brighter than argon plasma and hydrogen plasma.