The PCBA water cleaning technology uses water as the cleaning medium. A small amount (usually 2% to 10%) of surfactants, corrosion inhibitors and other chemical substances can be added to the water. After washing, the PCBA cleaning process is completed after multiple washing and drying of pure water or deionized water. The advantage of water cleaning is that the cleaning medium for water cleaning is generally non-toxic, does not endanger the health of workers, and is non-flammable and non-explosive.
Good safety performance, water cleaning has a good decontamination effect on particles, rosin flux, water-soluble pollutants and polar pollutants: water cleaning makes the compatibility with component packaging materials and PCB materials good, The rubber parts and coatings are not swelled or cracked, so that the marks and symbols on the surface of the components can be kept clear and complete, and they will not be washed off. Therefore, water cleaning is one of the main processes of non-ODS cleaning.
The disadvantage of water washing is that the entire equipment investment is great, and it is also necessary to invest in water production equipment of pure water or deionized water. In addition, it is not suitable for non-hermetic devices, such as adjustable potentiometers, inductors, switches and other water vapor entering the device is not easy to discharge, and may even damage the ring components.
Water washing technology can be divided into two processes: pure water washing and adding surfactant in water. The typical PCBA process is as follows:
Water + surface activity → water → pure water → ultrapure water → hot air → washing → rinsing → drying.
Generally, an ultrasonic device is added in the washing stage, and an air knife (nozzle) device is added in addition to ultrasonic device in the cleaning stage. The water temperature is controlled at 60-70 ° C, the water is in high quality, and the resistivity is 8-18MQ · cm. This alternative technology is suitable for PCBA companies with large production batches and high product reliability requirements in SMT processing aspects. For small batch cleaning, small cleaning equipment can be selected.