Main Methods And Steps For Cleaning Before PVD

Cleaning is the chemical and physical removal of oil, rust, dust, etc. from the workpiece to ensure a good coating bond and a smooth production process. Cleaning is an essential process prior to PVD coating and is also a process in PVD coating production. If something goes wrong with cleaning, coating production has to be delayed, the coating process may be interrupted, or there may be problems with the coating bond resulting in customer complaints and compensation, especially if the technical capability of the coating equipment is not high and something goes wrong with cleaning, the above risks are more likely to occur.

There are four factors affecting the quality of cleaning, respectively: cleaning time, chemicals, mechanical action and cleaning fluid temperature, the four factors also affect each other, a weakening of factors, can be enhanced through the role of the other three factors to compensate, and vice versa. In these four factors, the cleaning time of the smaller is also the pursuit of the goal, so as to improve the efficiency of cleaning. Shorten the production time and delivery cycle.

The main methods and steps of cleaning should include: chemical spraying, chemical immersion with ultrasonic cleaning, rinsing and drying.

1) Chemical spraying

Spraying is very effective for cleaning, it can clean off most of the oil and contaminants on the workpiece. It is particularly effective for workpieces with holes, where the chemicals sprayed onto the workpiece flow into the holes or are sprayed directly into the holes to rinse the inner walls of the holes. Therefore, it is important that all workpieces can be sprayed when cleaning the mounting card. In addition, if the chemicals sprayed onto the workpiece do not flow away immediately in time, it will prevent fresh chemicals from continuing to clean the workpiece and will not dry easily in the later drying steps, so when loading the card, ensure that the chemicals flowing onto the workpiece flow away naturally.

2) Chemical immersion and ultrasonic cleaning

Ultrasound is a frequency beyond the human hearing range of 20 kHz or more of sound waves. For the more dirty workpiece, pure immersion cleaning method is difficult to clean the workpiece thoroughly. The use of ultrasound "micro brush" role can destroy the surface layer of dissolved saturated layer, the new chemical to reach the deeper layer of contamination continue to dissolve, ultrasound then continue to destroy the newly formed dissolved saturated layer, and so on, cleaning continues until the workpiece is cleaned.

3) Rinsing

Rinsing is to clean the residue of cleaning solution or other dirt on the workpiece thoroughly, so that the workpiece is cleaner before drying. Residues on the workpiece will be difficult to clean up after drying. In the industrial sector. It is common to use deionised water for rinsing, using deionised water instead of tap water for rinsing. Impurities and contaminants in the tap water can be avoided on the workpiece. However, the aggressive nature of deionised water can cause corrosion to the workpiece. Therefore, a certain amount of rust inhibitor must be added to the deionised water before it can be used to rinse the workpiece. In order to prevent the workpiece from being rusted during the rinsing and drying process.

4) Drying

After cleaning the workpiece is generally put into the oven to dry, the oven includes the box, drainage, heating system, exhaust system and temperature control system. The boiling and vaporisation temperature of water is 100℃, so the baking temperature must be greater than 100℃, and it is recommended to be between 110℃ and 130℃, so that the water can be evaporated quickly to dry the workpiece. And not after drying, the workpiece temperature is too high and needs a long time to cool.