1. High frequency ultrasonic cleaning
For ultrafine dirt particles as small as a few micrometers on the surface of a silicon wafer, conventional ultrasonic cleaners cannot do anything, even if increasing the power density does not help. Recently, a high frequency ultrasonic cleaning technology with megahertz level has been developed. Due to high frequency, the cavitation effect is no longer effective. Therefore, the key to cleaning is not the air bubble, which is the scrubbing action of the high-frequency pressure wave, and the removal rate of the dirt is close to 100%. High-frequency cleaning has developed rapidly recently and is mainly used for dirt cleaning on ultra-large-scale integrated circuit chips, as well as the cleaning of special dirt such as silicon wafers, ceramics, and photomasks.
2. Focused cleaning
For the cleaning of microporous objects such as spinnerets and filters in the textile industry, the conventional ultrasonic cleaning effect is very unsatisfactory and the sound intensity does not meet the requirements, while the mechanical scanning focused ultrasonic cleaning is used, and the contamination in the micropore of the spinneret is very obvious. Focused cleaning requires high sound intensity, and the frequency currently selected is mainly low frequency. Commonly used 20kHz and 15kHz two kinds of frequency,and the frequency of individual is also 28kHz, its electric power is generally 500-700W in the situation of continuous wave, the working condition of the gap pulse, the power can be higher.
3. Multi-frequency cleaning
In a cleaning tank, two or more transducers with different frequencies are installed, and multiple generators respectively drive transducers of respective frequencies. When the operating frequency of the washer is high, the cavitation strength of the liquid is low and the cavitation density is high, but the opposite occurs when the operating frequency is low. The low-frequency ultrasonic wave has high intensity and is favorable for cleaning the surface of the object. The high-frequency ultrasonic cavitation density is high, and the shock wave can penetrate through fine structures such as grooves, slits, and deep holes. At the same time, the problem of uneven cleaning caused by single frequency cleaning standing wave field is overcome.
4. Sweep frequency and frequency hopping cleaning
Sweeping frequency and frequency hopping cleaning are all aimed at improving the sound field structure in the slot. The former solves the uneven standing wave field in the slot and makes the cleaning uniform, while the frequency hopping and multi-frequency take into account the high and low frequency cleaning. The difference is that frequency hopping uses a transducer and a generator, and the transducer itself has two resonant frequencies.