Frequency and cleaning effect in ultrasound
Cleaning effect in a lower frequency range suitable for "general cleaning use"
Cleaning in a lower frequency range， utilizing cavitation， has the following features:
(1) The impact pressure caused by cavitation is effective in the cleaning of stubborn dirt.
(2) The long wavelength of a standing wave， with parts of strong and weak sound pressure appearing at every 1/2 wavelength， is likely to cause unevenness of cleaning.
(3) Erosion is remarkably accelerated on a vibrational emitting surface.
Accordingly， this method is not suitable for the precise cleaning of an object that is apt to be easily damaged; whereas this method is suitable for "general cleaning use"， such as cleaning a metal product soiled with stubborn dirt， removing cuttings from cut mechanical parts， degreasing and removing flux from printed circuits.
Cleaning effect in a higher frequency range suitable for "precise cleaning use"
Cleaning in a higher frequency range， utilizing vibrational acceleration and rectilinear flow， does not show any damage due to cavitation and is effective to removing particles of sub-micron level， and therefore this method is suitable for "precise cleaning use"， such as cleaning silicon wafers for semiconductors， LCD glass substrates， and the parts for hard disk drives. With the increase in packing density and accumulation for integrated circuits， more advanced requirements are emerging even in theMHz cleaning， such as the removal of much finer particles and the reduction of damage to finer patterns. In response to these requirements， it is necessary to improve the cleaning technology， such as homogenization of sound pressure， lowering output and using waves of further higher frequencies. With the increase of frequency， the directivity of ultrasound becomes sharper so that ultrasound is apt not to reach the parts behind an object. It is necessary to consider this problem for improvement.
Cleaning in medium frequency range， combining strength and precise cleaning
Cleaning in medium frequency range(100 to 500kHz)， between the high frequency and low frequency shows both of the features， strength at low frequency and preciseness at high frequency. Thus this range is used for the purpose to remove particles of larger size， the ones MHz range waves cannot remove， for example， to clean glass masks， LCD glass， magnetic heads， etc.
Constitution of an ultrasonic cleaner
An ultrasonic cleaner is composed mainly of three parts: an ultrasonic generator， an ultrasonic vibrator (piezoelectric vibrator +acoustic emitter) and a cleaning tank. The electrical energy with high frequency power supplied by the transmitter is converted to mechanical energy at the piezoelectric vibrator to emit to a medium， bordering on the vibrator