Ultrasonic Cleaning Supporting World’s Manufacturing Growth

The continuous increase in the variety of sophisticated electronic components, as well as the growing demand for their reliability and durability gives birth to a need in effective and reliable removal method of impurities in the form of particles, films and other contaminants. Even microscopic contamination can cause significant financial losses due to malfunctions and damage electronic systems. Regardless of the type of items to be cleaned, whether it is silicon wafer, printed circuit boards, electronic contact or light alloy board, there are different solutions, for example, wet chemical cleaning, or carbon dioxide plasma, which can achieve the desired degree of purity in an economically efficient manner.

The universal power of ultrasound

Wet chemical ultrasonic cleaning with solvents, alcohols or modified aqueous solutions is widely used in manufacturing industries. Such companies, like Hilsonic, producing a wide array of ultrasonic cleaner equipment, confirmed the impressive potential of the approach (the line-up of cleaners remove particles, flux residue contamination, oil films and etc.). Apart from the type of detergent another decisive factor is the frequency of the cleaning efficiency of electrical pulses generated and transmitted by the ultrasonic generator in the form of sound waves in the oscillatory system with a liquid container. For this method, the following is true: the lower the frequency of the electrical pulses, the higher the energy of the sound waves is.

A good example of this method is quality cleaning after soldering printed circuit boards for good adhesion of the protective varnish that is applied subsequently. The most important thing is to remove flux residues and fingerprints that may remain on the surface. The standard process consists of two stages: the first one is ultrasonic cleaning of products stored in a container, during which the holder parts also makes additional oscillatory motion. After these steps the products must be washed with double deionised water and dried.

High frequency ultrasound systems operate in the range of 250 and 500 kHz, and the sound system with the frequency of several MHz are used for the cleaning of delicate components and fine structures in semiconductor and electronic industries.

Depending on the desired result it may be needed to clean the tanks with different frequencies of ultrasound, for example, to clean glass plates. In this case, cleaning at various processing stages can be performed at ultrasonic frequencies from 40 kHz to 1 MHz. The last characteristic of the multi-stage wet cleaning is polishing substrates prior to the deposition of conductive layers. Plates are placed in a specially designed racks and treatment is immersed successively in three ultrasonic cleaning tanks containing detergents, from neutral to strongly alkaline. Between the washing steps purification using sonication stage takes place. The subsequent three-stage washing step and a final infrared drying, excludes the presence of any contaminants at the wafer surface. To achieve this, these washing steps are using high purity water. An ideal combination of detergent and ultrasonic frequency can be determined from the results of tests of systems with appropriate detergents.

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