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Printed circuit boards (PCBs) require cleaning when they are manufactured for the following reasons:

1. Remove impurities: During the production process, impurities such as oil, flux residues, and dust particles may contaminate the circuit board, thereby affecting its performance and even causing circuit failures.

2. Remove solder slag: When assembling circuit boards, soldering operations are required. Flux residues and solder slag may remain on the board surface, causing circuit short circuits, insulation degradation, and other problems.

The process of cleaning PCB boards is as follows:

1. Pretreatment: First remove large particles of impurities, and then apply a protective film to prevent damage to sensitive parts.

2. Select detergent: Select organic solvents, aqueous detergents, or acidic detergents according to needs.

3. Cleaning: Soak the PCB board in a cleaning solution or use spraying, ultrasonic and other methods to clean it to remove surface impurities and residues.

4. Rinse: After cleaning, rinse thoroughly to completely remove the detergent and residues.

5. Drying: After cleaning, the PCB board needs to be dried to ensure that the board surface is dry to prevent moisture from causing circuit failures.

There are two main reasons for the generation of foam during the cleaning process:

1. Volatilization of cleaning agents: The volatile components in some cleaning agents generate gas when they encounter the board surface, and foam is easily formed between the gas, detergent, and dirt.

2. Foam adhesion: Some impurities form foam on the board surface, which may be caused by the physical and chemical properties of the impurities and the characteristics of the cleaning agent. Such foam can adhere to the circuit board, resulting in impurity residues.

PCB cleaning defoamer can inhibit the generation of foam and keep the cleaning process stable. Defoamers for PCB cleaning are chemical substances added to cleaning agents that can change the surface tension of the liquid, making it difficult for bubbles to form or easy to break. Defoamers help reduce the number and volume of foam, reduce the generation of residues, improve the cleaning process, and improve the cleanliness and quality of PCB boards.