After PCB (printed circuit board) assembly, the choice of cleaning process is crucial, it not only affects the appearance of the PCB quality, but also directly related to the electrical performance and reliability of the circuit board. The following are several common PCB cleaning processes and their selection recommendations:
First, common PCB cleaning process
Solvent cleaning
Principle: Use the dissolution ability of organic solvents (such as acetone, ethanol, isopropyl alcohol, etc.) to remove dirt and grease from the surface of the PCB.
Features: Simple operation, relatively low cost, good cleaning effect. However, organic solvents are flammable and explosive, which may have an impact on the environment and human health, and strict safety protection measures are required when used.
Application scenario: It is suitable for occasions where the cleaning cost is more sensitive and the environmental and safety requirements are not very strict.
Ultrasonic cleaning
Principle: Using the high-frequency vibration generated by ultrasonic waves in the cleaning solution to form tiny bubbles, these bubbles will have a strong impact force and micro-flow when they break, so as to remove the stains and residues on the surface of the PCB.
Features: It can penetrate into the tiny gaps of the PCB, remove the hard-to-reach stains, the cleaning effect is good, and there is no mechanical damage to the circuit board. However, the cost of the equipment is high, which may cause damage to the sensitive components.
Application scenario: Suitable for high cleaning quality requirements, and there are small gaps and hard-to-reach stains on the PCB occasions.
Dry ice snow wash
Principle: Using solid carbon dioxide (dry ice) as the cleaning medium, dry ice particles are sprayed to the PCB surface under high pressure, due to the low temperature characteristics of dry ice, when it contacts with the PCB will rapidly sublimate into a gas, and produce a strong impact force in the process, the surface dirt impact stripping.
Features: Environmental protection, no pollution, good cleaning effect, no residue, no need to clean twice. However, the equipment and technical requirements are higher, and the initial investment and maintenance costs are larger.
Application scenario: It is suitable for occasions with high environmental protection requirements and strict cleaning quality requirements.
Water cleaning
Principle: With water as the cleaning medium, the dirt on the surface of the PCB is removed by spraying and soaking. Surfactants, additives and corrosion inhibitors can be added to the water to improve the cleaning effect.
Features: Good safety, no burning, no explosion, wide cleaning range. However, the consumption of water resources is large, some components can not be cleaned with water, and the drying process has a large energy consumption.
Application scenario: It is suitable for situations that require high cleaning safety and are not very sensitive to water consumption and energy consumption in the drying process.
Semi-water cleaning
Principle: The use of organic solvents and deionized water, plus a certain amount of active agents, additives composed of cleaning agents. Cleaning and rinsing use two different properties of media.
Features: Strong cleaning ability, can remove polar pollutants and non-polar pollutants. However, the treatment of waste liquid and wastewater is more complicated.
Application scenario: It is suitable for situations that require high cleaning capacity and have certain preparation for waste liquid and wastewater treatment.
No-clean technology
Principle: In the PCB welding process using no-clean flux or solder paste, welding directly into the next process, no additional cleaning.
Features: Simplified process, save manufacturing costs, less pollution. However, the choice of flux or solder paste needs to be careful to ensure welding quality and reliability.
Application scenario: It is suitable for the occasions where the cleaning process is strictly limited and the flux or solder paste is strictly required, such as mobile communication products.
Second, the choice of cleaning process suggestions
Select according to cleaning requirements: Select the appropriate cleaning process according to the pollution degree of the PCB, the type of stain and the requirements after cleaning. For example, for PCB with less pollution, you can choose solvent cleaning or water cleaning; For PCB with heavy pollution or small gaps, you can choose ultrasonic cleaning or dry ice snowflake cleaning.
Consider the cost factor: the cost of cleaning process includes equipment cost, cleaning agent cost, energy consumption cost and waste liquid wastewater treatment cost. When choosing the cleaning process, it is necessary to consider these factors comprehensively and choose the most cost-effective scheme.
Attention to environmental requirements: With the increasingly stringent environmental regulations, the environmental protection of the cleaning process has also become an important consideration. When selecting the cleaning process, it is necessary to pay attention to whether it meets the environmental protection requirements and whether it will produce harmful substances emissions.
Consider equipment compatibility: Different cleaning processes may require different cleaning equipment. When choosing a cleaning process, factors such as the compatibility of existing equipment and whether new equipment is needed need to be considered.
Test verification: Before practical application, it is recommended to test and verify different cleaning processes to evaluate their cleaning effect, impact on PCB and cost. Through the test verification, you can choose the most suitable cleaning process for your needs.
In summary, the cleaning process selection after PCB assembly needs to be comprehensively considered according to the specific situation. In the selection process, it is necessary to pay attention to cleaning requirements, cost factors, environmental requirements, equipment compatibility and test verification to ensure that the most suitable cleaning process for your needs is selected.
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