超聲波清洗設(shè)備主要機理是超聲波清洗機產(chǎn)生的超聲波空化作用，超聲波空化強弱與聲學(xué)參數(shù)、清洗液物理化學(xué)性質(zhì)及環(huán)境條件有關(guān)，要獲得良好清洗效果必須選擇適當(dāng)?shù)穆晫W(xué)參數(shù)和清洗液。

The main mechanism of ultrasonic cleaning equipment is ultrasonic cavitation produced by ultrasonic cleaning machine. The strength of ultrasonic cavitation is related to acoustic parameters, physical and chemical properties of cleaning fluid and environmental conditions. In order to obtain good cleaning effect, appropriate acoustic parameters and cleaning fluid must be selected.

1.超聲波聲強或聲壓的選擇

1. Selection of ultrasonic intensity or pressure

在清洗液中只有交變聲壓幅值超過液體的靜壓力時才會出現(xiàn)負(fù)壓，在超聲清洗槽中的聲強要高于空化閾值才能產(chǎn)生超聲空化。對于一般液體，空化閾值約為每平方厘米1／3瓦(聲壓的千方正比于聲強)。聲強增加時，空化泡的大半徑與起始半徑比值增大，空化強度增大，即聲強愈高，空化愈強烈，有利于清洗作用。但不是聲功率越大越好，聲強過高。會產(chǎn)生大量無用氣泡，增加散射衰減，形成聲屏障，同時聲強增大也會增加非線性衰減，這樣都會削弱遠(yuǎn)離聲源地方清洗效果。對于一些難清洗干凈的污物，例如金屬表面氧化物，化纖噴絲板孔中污物的清洗，則需要采用較高聲強。此時被清洗面應(yīng)貼近聲源，這時大多不采用槽式清洗器。而用棒狀聚焦式換能器直接插入清洗液靠近清洗件的表面進(jìn)行清洗。

In the cleaning fluid, only when the amplitude of alternating sound pressure exceeds the static pressure of the liquid, the negative pressure will appear. For general liquids, the cavitation threshold is about 1 / 3 watts per square centimeter. When the sound intensity increases, the ratio of the maximum radius to the initial radius of the cavitation bubble increases, and the cavitation intensity increases. But it's not that the higher the sound power, the better the sound intensity. A large number of useless bubbles will be generated, which will increase the scattering attenuation and form a sound barrier. At the same time, the increase of sound intensity will also increase the nonlinear attenuation, which will weaken the cleaning effect far away from the sound source. For some of the dirt in the fiberboard, for example, it is difficult to clean the dirt on the surface with strong noise. At this time, the surface to be cleaned should be close to the sound source, and most of them do not use slot type cleaner. The rod-shaped focused transducer is directly inserted into the cleaning solution near the surface of the cleaning part for cleaning.

2.頻率選擇

2. Frequency selection

超聲空化閾值和超聲波的頻率有密切關(guān)系。頻率越高，空化閾越高，換句話說，頻率越高，在液體中要產(chǎn)生空化所需要的聲強或聲功率也越大；頻率低，空化容易產(chǎn)生，同時在低頻情況下，液體受到壓縮和稀疏作用有更長時間間隔。使氣泡在崩潰前能生長到較大的尺寸，增高空化強度，有利于清洗作用。目前超聲波清洗機的工作頻率根據(jù)清洗對象，大致分為三個頻段；低頻超聲清洗(20一50KHz)，高頻超聲清洗(50—200KHz)和兆赫超聲清洗(700KHz一1MHz以上)。低頻超聲清洗適用于大部件表面或者污物和清洗件表面結(jié)合強度高場合。

There is a close relationship between the ultrasonic cavitation threshold and the ultrasonic frequency. 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 produce cavitation in the liquid; low frequency, cavitation is easy to produce, and at the same time, in the case of low frequency, there is a longer time interval for the liquid to be compressed and sparse. The bubble can grow to a larger size before collapse and increase the cavitation strength, which is conducive to the cleaning effect. At present, the working frequency of ultrasonic cleaning machine can be roughly divided into three frequency bands according to the cleaning objects: low frequency ultrasonic cleaning (20-50 kHz), high-frequency ultrasonic cleaning (50 & mdash; 200 kHz) and megahertz ultrasonic cleaning (700 khz-1 MHz or above). Low frequency ultrasonic cleaning is suitable for large parts or dirt and cleaning parts with high bonding strength.

頻率低端，空化強度高，易腐蝕清洗件表面，不適宜清洗表面光潔度高的部件，而且空化噪聲大。40KHz左右的頻率，在相同聲強下，產(chǎn)生的空化泡數(shù)量比頻率為20KHz時多，穿透力較強，宜清洗表面形狀復(fù)雜或有盲孔的工件，空化噪聲較小。但空化強度較低，適合清洗污物與被清洗件表面結(jié)合力較弱場合，高頻超聲清洗適用于計算機、微電子元件的精細(xì)清洗，如磁盤、驅(qū)動器，讀寫頭，液晶玻璃及平面顯示器，微組件和拋光金屬件等的清洗。這些清洗對象要求在清洗過程中不能受到空化腐蝕。要能洗掉微米級的污物。

Low frequency, high cavitation strength, easy to corrode the surface of cleaning parts, not suitable for cleaning parts with high surface finish, and cavitation noise is high. When the frequency is about 40KHz, under the same sound intensity, the number of cavitation bubbles is more than that of 20kHz, and the penetration is strong. It is suitable to clean the workpiece with complex surface shape or blind hole, and the cavitation noise is small. However, the cavitation strength is low, which is suitable for cleaning dirt and weak adhesion between the surface of the cleaned parts. High frequency ultrasonic cleaning is suitable for the fine cleaning of computers and microelectronic components, such as disk, driver, read-write head, LCD glass and flat panel display, micro components and polished metal parts. These cleaning objects are required to be free from cavitation corrosion in the cleaning process. To be able to wash out micron scale dirt.

兆赫超聲清洗適用于集成電路芯片、硅片及簿膜等的清洗。能去除微米、亞微米級的污物而對清洗件沒有任何損傷，因為此時不產(chǎn)生空化作用，超聲波清洗機理主要是聲壓梯度、粒子速度和聲流的作用，特點是清洗方向性強，被清洗件一般置于與聲束平行的方向。

Megahertz ultrasonic cleaning is suitable for the cleaning of integrated circuit chips, silicon chips and thin films. It can remove micron and submicron dirt without any damage to the cleaning parts, because there is no cavitation effect at this time. The mechanism of ultrasonic cleaning is mainly the effect of sound pressure gradient, particle velocity and sound flow. It is characterized by strong cleaning directivity, and the cleaned parts are generally placed in the direction parallel to the sound beam.

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