The cleanliness of printed circuit boards (PCBs) directly affects their conductive properties and service life. The production process needs to be controlled throughout the entire process to build a three-dimensional cleaning system of "environment - process - detection".
A clean environment is the basic guarantee. The production workshop must meet the Class 1000 cleanliness standard, be equipped with a high-efficiency air filter (HEPA), change air more than 30 times per hour, and control the diameter of dust particles to ≤0.5μm. Employees must wear anti-static clean clothes, gloves and masks, and enter the workshop after dust removal in the air shower room to avoid human pollutants.
Precise cleaning of key processes. In the etching process, deionized water (resistance value ≥18MΩ) is used to rinse the substrate, and ultrasonic cleaning (frequency 40kHz) is used to remove etching residual liquid to ensure that surface impurities are ≤5mg/m². Before printing the solder mask layer, the board surface is treated with a plasma cleaner to remove organic pollutants, improve ink adhesion, and reduce pinhole defects.
Cleanliness control of equipment and materials. The rollers of the transmission equipment need to be wiped with isopropyl alcohol every 8 hours to prevent oil from contaminating the substrate. Raw materials are stored in vacuum packaging and must be put into production within 2 hours after opening to avoid moisture absorption. Chemicals such as developer and etching solution must be filtered and purified to control the impurity content to ≤0.1%.
Full process inspection and control. Each batch of products is tested for surface cleanliness by a laser particle counter, and a microscope (magnification 500 times) is used to check the residue between the wires to ensure compliance with the IPC-A-600G standard. Through this cleaning control system, the printed circuit board defect rate can be reduced to less than 0.3%, laying the foundation for the stable operation of electronic equipment.
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