Knowledge | 2022-10-25
Process parameters related to the ultrasonic cleaning effect
The selection of ultrasonic cleaning technology mainly refers to the selection and preparation of cleaning fluid, the way of ultrasonic cleaning, the temperature of cleaning fluid, the frequency of ultrasonic, the power density of ultrasonic, and the choice of cleaning time.
The proper cleaning solution has a great influence on the effect of ultrasonic cleaning. Because the mechanism of ultrasonic cleaning is mainly cavitation, so the choice of cleaning fluid must be based on the system's material, grease, or mechanical impurities, but also must consider the viscosity of the selected cleaning fluid to be small, the surface tension to be small, to facilitate the cleaning fluid cavitation. In the case of strict requirements for cleaning quality, several different cleaning fluids are often used to separate tanks or carry out ultrasonic cleaning in sequence, and the effect of each cleaning fluid is different, for optical parts, various cleaning solutions such as trichloroethene, sodium hydroxide water solution, synthetic detergent, water, and alcohol have been used for cleaning. For semiconductor device parts, acetone and 1 * mixed cleaning solutions have been used, 2 * mix cleaning fluid and deionized water, etc.
The most common form of ultrasonic cleaning is in-tank washing, in which a part is immersed in an ultrasonic cleaning tank containing a cleaning fluid. The ultrasonic vibration generated by the Ultrasonic transducer is radiated from the bottom of the cleaning tank to the cleaning fluid for cleaning. This is particularly suitable for small and medium-sized parts. For parts with large size and weight, the local cleaning method can be adopted, that is, parts are partially immersed in the cleaning solution for cleaning, and after cleaning, the unwashed parts are immersed in the cleaning solution for cleaning, until completely washed. Another method is to design the Ultrasonic transducer into a special shape according to the shape of the large part and the local cleaning part requirements to achieve local cleaning. For parts with strict cleaning requirements, several different cleaning fluids are used, and the separate grooves are cleaned by an ultrasonic wave in turn. In addition, it can be used in conjunction with other cleaning methods, such as electronic component washing, which is a combination of heating, soaking, and ultrasonic cleaning. The oil is very thick, thick parts, but also often first with a heating immersion or high-temperature spray, and then use ultrasonic cleaning of the multi-step cleaning method. Multi-frequency cleaning, i. e. cleaning under the action of several different ultrasonic frequencies, can be used for parts with excessively complex shapes, such as holes of different sizes and concave angles.
To improve the efficiency of ultrasonic cleaning, a higher power density is often used. But too high power density because of the cavitation effect is too strong and causes the erosion of the surface of the parts (that is cavitation corrosion), making the parts damaged, which has a variety of coating or aluminum and aluminum alloy parts is particularly prominent. An excessive increase in power density also has no effect due to saturation. For the parts with serious oil pollution, complicated shape, and deep hole blind hole, the cleaning trough should be deep, the viscosity of cleaning fluid should be large, and the power density of high-frequency ultrasonic cleaning should be large too, the power density can be reduced when rinsing with water or alcohol.
Because the cavitation of the cleaning solution is related to its temperature, the increase in temperature is beneficial to cavitation, but the vapor pressure also increases accordingly. Therefore, it is necessary to maintain a certain temperature range, such as water-based solvent cleaning solution at around 45 â ° C, trichloroethene cleaning solution at around 75 â ° C, and water at around 60 â ° C, for easy evaporation flammable cleaning fluid should not be too high temperature.
The effect and quality of ultrasonic cleaning are related to the time of ultrasonic cleaning, and the time is too short to meet the quality requirements of cleaning. But too long time not only low efficiency but also because of cavitation corrosion of the surface of parts and affect the quality. Oil pollution is serious, and the shape of complex parts' cleaning time should be longer. With a variety of coated parts, aluminum and aluminum alloy parts cleaning time can not be too long. Higher Surface finish parts are generally less oily and should not be cleaned for too long. The specific cleaning time should be determined by testing.
To improve the cleaning effect and ensure the normal use of the ultrasonic cleaning device, the position of the cleaned parts in the cleaning tank is noteworthy. First of all, the product should be avoided directly pressed on the radiation surface of ultrasonic vibration, so that the radiation surface can not occur the expected vibration so that the cleaning device can not reach the normal working state. This is particularly important for heavy parts. The parts shall be hung in the cleaning tank with special tools and be as close to the radiation surface as possible. Second, the focus of the cleaning site should be focused on the ultrasound source. Third, should be considered to be washed down so the dirt can be successfully discharged parts. Fourth, to facilitate the flow of cleaning fluid in the cleaning tank. In the use of the cleaning fluid cycle and continuous use of the method, the speed should not be too fast, or because the added cleaning fluid contains more gas, will weaken the cavitation.
For the blind hole cleaning, the blind hole should be filled with cleaning fluid first, and then the blind hole pointing down the ultrasonic source, in the cleaning process, must always keep the hole filled with cleaning fluid, to achieve significant results.