超声波清洗机主要机理是超声波清洗机产生的超声波空化作用，超声波空化强弱与声学参数、清洗液物理化学性质及环境条件有关，要获得良好清洗效果必须选择适当的声学参数和清洗液。

The main mechanism of ultrasonic cleaning machine is the cavitation effect generated by ultrasonic cleaning machine. The strength of ultrasonic cavitation is related to acoustic parameters, physical and chemical properties of cleaning solution, and environmental conditions. To achieve good cleaning effect, appropriate acoustic parameters and cleaning solution must be selected.

频率选择

Frequency selection

超声空化阈值和超声波的频率有密切关系。频率越高，空化阈越高，换句话说，频率越高，在液体中要产生空化所需要的声强或声功率也越大；频率低，空化容易产生，同时在低频情况下，液体受到压缩和稀疏作用有更长时间间隔。使气泡在崩溃前能生长到较大的尺寸，增高空化强度，有利于清洗作用。目前超声波清洗机的工作频率根据清洗对象，大致分为三个频段；低频超声清洗(20一50KHz)，高频超声清洗(50—200KHz)和兆赫超声清洗(700KHz一1MHz以上)。低频超声清洗适用于大部件表面或者污物和清洗件表面结合强度高场合。

The threshold of ultrasonic cavitation is closely related to the frequency of ultrasound. The higher the frequency, the higher the cavitation threshold. In other words, the higher the frequency, the greater the sound intensity or power required to generate cavitation in the liquid; At low frequencies, cavitation is prone to occur, and at low frequencies, the liquid undergoes compression and sparsity with longer time intervals. Enabling bubbles to grow to a larger size before collapse, increasing cavitation intensity, is beneficial for cleaning. At present, the working frequency of ultrasonic cleaning machines is roughly divided into three frequency bands based on the cleaning object; Low frequency ultrasonic cleaning (20-50KHz), high-frequency ultrasonic cleaning (50-200KHz), and megahertz ultrasonic cleaning (700KHz to 1MHz or above). Low frequency ultrasonic cleaning is suitable for occasions with high bonding strength between the surface of large components or dirt and the surface of cleaning parts.

频率低端，空化强度高，易腐蚀清洗件表面，不适宜清洗表面光洁度高的部件，而且空化噪声大。40KHz左右的频率，在相同声强下，产生的空化泡数量比频率为20KHz时多，穿透力较强，宜清洗表面形状复杂或有盲孔的工件，空化噪声较小。但空化强度较低，适合清洗污物与被清洗件表面结合力较弱场合，高频超声清洗适用于计算机、微电子元件的精细清洗，如磁盘、驱动器，读写头，液晶玻璃及平面显示器，微组件和抛光金属件等的清洗。

Low frequency, high cavitation intensity, easy to corrode the surface of cleaned parts, not suitable for cleaning components with high surface smoothness, and high cavitation noise. At a frequency of around 40KHz, under the same sound intensity, more cavitation bubbles are generated than at a frequency of 20KHz, indicating strong penetration. It is recommended to clean workpieces with complex surface shapes or blind holes, as cavitation noise is relatively small. However, the cavitation intensity is relatively low, suitable for cleaning situations where the adhesion between dirt and the surface of the cleaned part is weak. High frequency ultrasonic cleaning is suitable for fine cleaning of computer and microelectronic components, such as disks, drives, read and write heads, LCD glass and flat displays, micro components, and polished metal parts.

这些清洗对象要求在清洗过程中不能受到空化腐蚀。要能洗掉微米级的污物。兆赫超声清洗适用于集成电路芯片、硅片及簿膜等的清洗。能去除微米、亚微米级的污物而对清洗件没有任何损伤，因为此时不产生空化作用，超声波清洗机理主要是声压梯度、粒子速度和声流的作用，特点是清洗方向性强，被清洗件一般置于与声束平行的方向。

These cleaning objects are required to be free from cavitation corrosion during the cleaning process. To be able to wash away micrometer sized dirt. Megahertz ultrasonic cleaning is suitable for cleaning integrated circuit chips, silicon wafers, and thin films. It can remove micrometer and submicron scale dirt without any damage to the cleaned parts, as cavitation does not occur at this time. The ultrasonic cleaning mechanism mainly involves the effects of sound pressure gradient, particle velocity, and sound flow, characterized by strong cleaning directionality. The cleaned parts are generally placed in the direction parallel to the sound beam.

超声波声强或声压的选择

Selection of ultrasonic intensity or pressure

在清洗液中只有交变声压幅值超过液体的静压力时才会出现负压，在超声清洗槽中的声强要高于空化阈值才能产生超声空化。对于一般液体，空化阈值约为每平方厘米1／3瓦(声压的千方正比于声强)。声强增加时，空化泡的大半径与起始半径比值增大，空化强度增大，即声强愈高，空化愈强烈，有利于清洗作用。但不是声功率越大越好，声强过高。会产生大量无用气泡，增加散射衰减，形成声屏障，同时声强增大也会增加非线性衰减，这样都会削弱远离声源地方清洗效果。对于一些难清洗干净的污物，例如金属表面氧化物，化纤喷丝板孔中污物的清洗，则需要采用较高声强。此时被清洗面应贴近声源，这时大多不采用槽式清洗器。而用棒状聚焦式换能器直接插入清洗液靠近清洗件的表面进行清洗。

Negative pressure only occurs when the amplitude of the alternating sound pressure in the cleaning solution exceeds the static pressure of the liquid. In ultrasonic cleaning tanks, the sound intensity must be higher than the cavitation threshold to generate ultrasonic cavitation. For general liquids, the cavitation threshold is approximately 1/3 watt per square centimeter (the square root of sound pressure is directly proportional to sound intensity). When the sound intensity increases, the ratio of the large radius to the initial radius of the cavitation bubble increases, and the cavitation intensity increases. That is, the higher the sound intensity, the stronger the cavitation, which is conducive to the cleaning effect. But it's not that the higher the sound power, the better. The sound intensity is too high. A large number of useless bubbles will be generated, increasing scattering attenuation and forming a sound barrier. At the same time, an increase in sound intensity will also increase nonlinear attenuation, which will weaken the cleaning effect in areas far away from the sound source. For some difficult to clean dirt, such as metal surface oxides and dirt in the holes of chemical fiber spinnerets, high sound intensity is required for cleaning. At this time, the cleaned surface should be close to the sound source, and slot type washers are mostly not used. And use a rod shaped focusing transducer to directly insert the cleaning solution near the surface of the cleaning part for cleaning.