Ultrasonic cleaning implies producing ultrasonic vibrations to remove contamination on hard surfaces. The application of ultrasound causes the high speed cleaning process and increases the quality. In many cases, the method provides an opportunity to replace flammable and toxic solvents with safer cleaners, providing the quality of comparable level. The process requires using high quality ultrasonic cleaner equipment, represented on the market in a variety of solid brands, such as Hilsonic. The company concentrates its effort on innovative ultrasound developments, boasting a good number of patents acquired and truly cost-effective pricing program (fact: the company claims its average customer is saving up to 18% on operational expenses within the first 24 months of using the equipment).
How it works?
Ultrasonic cleaning is used in many industries for the repair and production of machinery and jewelery, it is used in restoration business, in medicine, as well as in the production of printed circuit boards for washing the surface with solder paste residues, organic matter, contamination, solder and flux.
Ultrasonic vibrations cause the emergence of liquid standing waves due to the combined action of various nonlinear effects arising in the liquid under the action of high-power ultrasonic vibration is cleaned. These effects: cavitation, acoustic streaming, sound pressure, acoustic-capillary effect of cavitation play a crucial role. Cavitation bubbles collapsing in vicinity of polluted areas destroy the contamination build-ups. This effect is known as cavitation erosion.
An effective ultrasonic cleaning process envisages correct selection of the washing liquid to effectively dissolve or emulsify contaminants not affecting the surface to be cleaned itself. The latter is especially important for washing printed circuit boards, because ultrasound is usually much faster physical and chemical processes in liquids and aggressive detergent can quickly damage the surface. Low cavitation resistance allows the surface to be cleaned by the ultrasonic method quite easily. Thus, for example, the grease films from aluminum parts are likely to be removed quite easily.
From the point of view of ultrasonic cleaning dirt on three different criteria:
- Cavitation resistance, that is, the ability to withstand microshock load.
- Adhesion to the surface to be cleaned, and resistance to delamination.
- The degree of interaction with the cleaning fluid that is capable of if and how this fluid is able to dissolve or emulsify dirt.
Cavitation stubborn dirt responds well to ultrasonic cleaning only if it is weakly bound to the surface or interacts poorly with the cleaning solution. These are the grease that are well laundered in weakly alkaline solutions. Coating of varnish or paint, scale, oxide films are usually well connected with the surface. Ultrasonic cleaning of dirt needs sufficiently aggressive solutions. Cavitation-unstable contamination types (dust, porous organics, corrosion products) are removed relatively easily, even without the use of special solutions.
Ultrasonic cleaning largely implies using water and aqueous solutions of detergents and organic solvents. The choice of contaminants is determined by the type and properties of the surface being cleaned. Perhaps, the best known products for cleaning printed circuit boards with ultrasonic method are provided by Zestron.