中低頻超聲波的清洗作用

The cleaning effect of medium and low frequency ultrasound

超聲波作為一種機(jī)械波，其在液體中的傳播引發(fā)了強(qiáng)烈的機(jī)械振動(dòng)。以中低頻超聲波為例，其頻率為20 kHz，液體質(zhì)點(diǎn)在聲波擾動(dòng)下做微小振動(dòng)，振動(dòng)速度和加速度巨大。這強(qiáng)烈而快速變化的機(jī)械運(yùn)動(dòng)對(duì)于不溶性固體顆粒有強(qiáng)大的剪切作用，可以使固體顆粒從物體表面脫落，實(shí)現(xiàn)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.

高頻超聲波的清洗作用

The cleaning effect of high-frequency ultrasound

隨著超聲波頻率增加到幾百千赫的高頻，波長縮短，聲場(chǎng)中質(zhì)點(diǎn)的密區(qū)與稀疏區(qū)界線變得模糊，液態(tài)聲場(chǎng)中空化現(xiàn)象減少。在硅晶片和光刻清洗中，高頻超聲波表現(xiàn)出更為精細(xì)的擦洗作用，每秒進(jìn)行95萬次的擦洗，迅速擴(kuò)散到基片與粒子之間，使工件表面水化，從而有效地去除亞微米粒子。

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

超聲波清洗可被視為由固-液兩相組成的非均勻介質(zhì)系統(tǒng)。在固-液界面，附著在界面的氣泡或游離的空化氣泡在聲場(chǎng)中受力作用下形成微小振動(dòng)，并聚集到工件表面。這些氣泡最終形成空化真空球形氣泡，崩塌時(shí)產(chǎn)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

微射流的直徑小而速度快，作用時(shí)間短暫，但沖擊力強(qiáng)大。它垂直于固體表面，像錘擊釘子一樣，反復(fù)敲打固體表面，使附著的污物被擊碎脫落，實(shí)現(xiàn)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“空化腐蝕”作用

3. The "cavitation corrosion" effect of micro jets

與傳統(tǒng)認(rèn)為的由真空氣泡潰滅產(chǎn)生的沖擊波引起的“空化腐蝕”不同，現(xiàn)代研究表明微射流是導(dǎo)致超聲波清洗中物體表面損傷的主要原因。微射流的強(qiáng)大沖擊力可能在作用時(shí)間過長時(shí)導(dǎo)致固體表面的局部破壞。

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.