Evaporative vacuum coating machine coating process

Evaporative vacuum coating machine is the most common vacuum coating machine for daily application. Many materials with low melting point such as aluminum, magnesium fluoride, and zinc sulfide use evaporation coating machine. Because of its low cost and high efficiency, it is the most preferred by coating manufacturers. choose. Evaporation vacuum coating machine, which is divided into resistance evaporation coating machine, induction evaporation coating machine, resistance evaporation coating machine, basically coat some daily hardware workpieces and flexible materials, induction evaporation coating machine is widely used in winding materials, such as Gold-plated silver wire, etc.

1. Preparation before plating

The process includes cleaning of plating parts, production and cleaning of evaporation source, cleaning of plating fixtures in vacuum chamber, installation of evaporation source, installation of plating parts, etc.

(1) Cleaning and handling of plated parts:

The size of the bonding force between the film layer and the surface of the plated part is an important indicator of product quality. It is determined by many factors, and the surface treatment before coating is one of the most basic factors. If there is grease, adsorbed water, dust, etc. on the surface of the plated part, it will reduce the bonding force of the film and affect the surface roughness.

Chemical degreasing. Various metal and non-metal plated parts should adopt the corresponding degreasing and degreasing process. For specific methods, you can search for degreasing in the technical column of this website to view related articles.

Electrostatic precipitator. The plated parts are easily charged with static electricity during the molding process, which can cause pinholes in the film layer or reduce the bonding force of the film, so the static electricity must be removed before the primer is applied.

Primer. Generally, the thickness of the film layer on the bottom of the evaporation is 0.05~0.1um, while the surface unevenness of ordinary plating parts is 0.5um, and the thickness of the film layer is far from enough to fill the pit. In order to reduce the surface roughness, a special primer of 7~10um is generally applied on the surface of the plated parts to eliminate pits and achieve the effect of leveling the surface.

(2) Production of evaporation source:

According to the use requirements of the product and the material of the plated parts, choosing an appropriate evaporation material is the basic condition for obtaining a high-quality film.

The basic principles of selecting metal film materials are: good thermal stability and chemical stability, high mechanical strength, low internal stress, and certain toughness, good bonding with primer, high reflectivity, and outgassing in vacuum. Small; wide material sources, low prices, and corresponding evaporation sources.

Different evaporation materials need to choose the corresponding evaporation source and evaporation plating method.

(3) Cleaning of vacuum chamber and plating fixture:

If the vacuum chamber with the inner cover is polluted, the cover can be removed for cleaning or renewal. If there is no inner cover, it can be wiped with calcium carbonate, then wiped with water, and finally wiped with anhydrous ethanol.

Commonly used aluminum fixtures can be soaked in 20% NaOH solution until the surface is brown, then rinsed with running water, soaked in HNO3 until the brown disappears, and then washed and dried.

(4) Install the evaporation source:

Be careful to wear degreased gloves and degrease tools beforehand. Pay special attention to the good contact between the evaporation source and the electrode.

(5) Place the plated parts:

It should be placed on the ground of the plated parts and the plated parts stably and firmly to prevent the plated parts from being thrown away from the fixture due to the rotation of the fixture during evaporation. It is necessary to wear degreased gloves, do not speak, and keep the plated parts jig clean.

2. Vacuum step

Open the cooling water valve, adjust to the required water pressure, connect the main power supply, close the atmospheric valve leading to the vacuum chamber, close the pipeline valve, start the mechanical pump power supply, and open the pre-vacuum valve. At this time, the mechanical pump evacuates the vacuum chamber, then conducts ion bombardment, turns on the diffusion pump heating power, and closes the pre-vacuum valve. When the diffusion pump reaches the working requirements, close the vacuum valve, open the pipeline valve, and open the high vacuum valve. , Diffusion pump, mechanical pump to pump the vacuum chamber, when the vacuum reaches a certain value, bake, pre-melt and evaporate.

3. Ion bombardment

During the glow discharge, the ions bombard the electrons to obtain a high speed, and the plated parts are rapidly negatively charged due to the large mobility of the electrons. There is energy exchange on the surface, and a chemical reaction occurs between the adsorption layer of the plating piece and the active gas to achieve the effect of cleaning the surface.

The conditions of ion bombardment are that the residual gas pressure is stable at 0.13~13Pa, the voltage is 1.5~10kV, and the time is 5~60min.

4. Bake

It can accelerate the rapid escape of the gas adsorbed by the plated part or the fixture, which is beneficial to improve the vacuum degree and the bonding force of the film layer. When baking, it should be noted that the baking temperature for non-metallic parts should be 20~30℃ lower than the thermal deformation temperature of the plated part. The metal baking generally does not exceed 200 ℃.

5. Premelting

It can remove the low melting point impurities in the evaporation material and the gas adsorbed in the evaporation source and the evaporation material, which is conducive to the smooth progress of the evaporation. The substance should be pre-melted repeatedly, and the general requirement is that when the evaporation material is heated to the evaporation temperature, the vacuum degree will not drop.

6. Evaporation

The evaporation technology of the evaporation vacuum coating machine has a great influence on the quality of the coating, and has different requirements for general metals, special metals and compounds. For example, some metals need to be quickly evaporated, while others are not suitable. The shape of the source also depends on the evaporating material.