The emergence of ultrasonic cleaning instruments instead of conventional cleaning methods, the use of high and low frequency different ultrasonic frequencies divided into a variety of uses of ultrasonic cleaning machine to improve cleaning efficiency and cleaning results, then the high and low frequency of different ultrasonic frequency between the cleaning effect and what is the difference?
Medium and low frequency ultrasonic cleaning effect
Ultrasound is a mechanical wave, is the propagation of mechanical vibration in the medium. When the ultrasonic waves propagate in the liquid, the liquid mass is disturbed by the sound waves will do a tiny vibration near its equilibrium position, the liquid mass does not have macroscopic movement and migration, but its vibration speed and acceleration is very large. For example, the sound intensity of 1. 0W/cm2, the frequency of 20 kHz ultrasonic waves propagating in water (without considering its nonlinear effects), if the displacement amplitude of the liquid mass is 5 μm, the mass to be subjected to pressure between plus or minus 1. 68atm to do periodic changes in the frequency of 20,000 times per second, the mass vibration speed of about 0, 63m / s, while the acceleration of vibration reached 7.9 X10*m/s’, which is about 8000 times the acceleration of gravity. Such intense and rapid changes in the mechanical movement, in the attachment of dust and other insoluble solid particles on the surface of the solid, strong shear effect is enough to make solid particles from the surface of the object to be cleaned off, so as to achieve the purpose of cleaning.
High-frequency ultrasonic cleaning effect
When the frequency of ultrasonic waves increased to several hundred kHz high frequency, the wavelength is short, λ = 0.7 ~ 1.5mm, the sound field in the dense and sparse area of the mass point boundary blurred, the liquid sound field cavitation phenomenon almost disappeared, ultrasonic energy performance as a medium mass acceleration energy. For example, in silicon wafer and lithography cleaning, the use of 950 kHz ultrasound, the time between the two peaks is only 1. 05μs, not enough to form a cavitation bubble, but the energy will reach 10 times the acceleration of gravity, megasonic cleaning is reflected in the liquid plasmas on the surface of the workpiece 950,000 times per second on the fine scrubbing. This is enough to make the cleaning fluid quickly diffuse to the substrate (workpiece) and particles (dirt) between the surface of the workpiece hydration, become wet. The liquid film acts as a sharp split, so that the particles from the substrate off, while the liquid film also further prevents the secondary adsorption of particles to the substrate, which is very effective in removing submicron particles.
