Why should PVD be performed in a vacuum environment?

PVD (Physical Vapor Deposition) refers to the use of low-voltage, high-current arc discharge technology under vacuum conditions, using gas discharge to evaporate the target material and ionize the evaporated material and gas, and utilizes the acceleration of the electric field The evaporated substance and its reaction products are deposited on the workpiece.

PVD
PVD

1.  Prevent gas “pollution”, such as: it can prevent oxidation when plating metal films,
Various gases in the atmosphere are impurity gases for PVD. If the vacuum is not evacuated, they will react with the PVD material during the PVD process, affecting the purity of the PVD material, and thus affecting various physical and chemical properties of the PVD material.

2.  During the plating process, there will be no collision with air molecules, and a larger momentum will reach the surface of the parts to be plated.
If there is no vacuum, the free path of molecules will be too short. For evaporation plating, it will affect the energy of the PVD film material reaching the substrate, resulting in low adhesion; for sputtering plating, it will affect the sputtering energy of ions and thus Affects the energy of the PVD film material reaching the substrate, and if there is too little gas, the gas molecules cannot become ions, and there are not many that can bombard the target, so it will not work (for evaporation plating, vacuum degree: P ≤ 10-3 Pa, ensuring evaporation, The particles have molecular flow characteristics and move in a straight line; for sputtering plating, the vacuum degree after filling with argon is: 10-2<P<10Pa, which is conducive to glow discharge).

3.  Under vacuum conditions, the melting point of PVD coating materials is lower than that under normal pressure.
The evaporation of metal or non-metallic materials is much easier than under atmospheric pressure conditions. In a vacuum (negative pressure) state, the melting point of PVD coating materials is lower than that under normal pressure, and it is easy to melt and evaporate (for evaporation type coatings), greatly shortening the time evaporation time and improve evaporation efficiency.

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