中低频超声波的清洗作用

The cleaning effect of medium and low frequency ultrasound

超声波作为一种机械波，其在液体中的传播引发了强烈的机械振动。以中低频超声波为例，其频率为20 kHz，液体质点在声波扰动下做微小振动，振动速度和加速度巨大。这强烈而快速变化的机械运动对于不溶性固体颗粒有强大的剪切作用，可以使固体颗粒从物体表面脱落，实现了清洗的效果。

Ultrasonic waves, as a type of mechanical wave, cause strong mechanical vibrations through their propagation in liquids. Taking mid to low frequency ultrasound as an example, its frequency is 20 kHz, and liquid particles undergo small vibrations under the disturbance of sound waves, with huge vibration speeds and accelerations. This strong and rapidly changing mechanical motion has a strong shear effect on insoluble solid particles, which can cause solid particles to detach from the surface of the object, achieving a cleaning effect.

高频超声波的清洗作用

The cleaning effect of high-frequency ultrasound

随着超声波频率增加到几百千赫的高频，波长缩短，声场中质点的密区与稀疏区界线变得模糊，液态声场中空化现象减少。在硅晶片和光刻清洗中，高频超声波表现出更为精细的擦洗作用，每秒进行95万次的擦洗，迅速扩散到基片与粒子之间，使工件表面水化，从而有效地去除亚微米粒子。

As the ultrasonic frequency increases to a high frequency of several hundred kilohertz, the wavelength shortens, and the boundary between the dense and sparse regions of particles in the sound field becomes blurred, leading to a reduction in cavitation in the liquid sound field. In silicon wafer and photolithography cleaning, high-frequency ultrasound exhibits a more precise cleaning effect, performing 950000 washes per second and rapidly diffusing between the substrate and particles, causing the surface of the workpiece to hydrate and effectively removing submicron particles.

空化微射流及清洗作用

Cavitation micro jet and its cleaning effect

1. 微射流的成因

1. The causes of micro jets

超声波清洗可被视为由固-液两相组成的非均匀介质系统。在固-液界面，附着在界面的气泡或游离的空化气泡在声场中受力作用下形成微小振动，并聚集到工件表面。这些气泡最终形成空化真空球形气泡，崩塌时产生微射流。

Ultrasonic cleaning can be regarded as a non-uniform medium system composed of solid-liquid phases. At the solid-liquid interface, bubbles attached to the interface or free cavitation bubbles form small vibrations under the force of the sound field and gather on the surface of the workpiece. These bubbles eventually form cavitation vacuum spherical bubbles, which produce micro jets when they collapse.

2. 微射流的清洗作用

2. The cleaning effect of micro jet

微射流的直径小而速度快，作用时间短暂，但冲击力强大。它垂直于固体表面，像锤击钉子一样，反复敲打固体表面，使附着的污物被击碎脱落，实现了高效的清洗作用。

The diameter of a micro jet is small and the speed is fast, the action time is short, but the impact force is strong. It is perpendicular to the solid surface, hitting the solid surface repeatedly like a hammer, causing the attached dirt to be shattered and peeled off, achieving an efficient cleaning effect.

3. 微射流的“空化腐蚀”作用

3. The "cavitation corrosion" effect of micro jets

与传统认为的由真空气泡溃灭产生的冲击波引起的“空化腐蚀”不同，现代研究表明微射流是导致超声波清洗中物体表面损伤的主要原因。微射流的强大冲击力可能在作用时间过长时导致固体表面的局部破坏。

Unlike the traditional belief that cavitation corrosion is caused by shock waves generated by the collapse of vacuum bubbles, modern research has shown that micro jets are the main cause of surface damage to objects in ultrasonic cleaning. The strong impact force of micro jets may cause local damage to the solid surface when applied for too long.