True ultrasonic cleaning technology The market will create the direction of evolution..
- Asia’s exploding market for cleaning machines is demanding bold and incisive changes in ultrasonic cleaning technology and ultrasonic application technology.
Intense competition creates new technologies.
Third generation ultrasonic cleaning technology and applications 2004.
(1)Larger ultrasonic vibration plates.
- Larger ultrasonic vibration plates.
Larger ultrasonic transducers The most important feature of this field is the larger size of ultrasonic transducers for glass substrates.As ultrasonic transducers are made up of a large number of piezoelectric elements connected in parallel, the increase in size naturally requires technical innovations in the attachment of the transducers and in inspection in general.It is not simply a matter of bonding a large number of elements to a large plate.Currently, in response to the increasing size of glass substrates, the practical application of this technology is being developed for the 7.5 generation, from 3600 W to 9600 W and combinations thereof.At one extreme of ultrasonic cleaning equipment with cavity enhancement systems using spherical cavities, a number of cleaning equipment with ultrasonic reflective surface designs of only 75 mm are also in practical use.
- Review of ultrasound frequencies.
The effectiveness of ultrasound in this field has long been in doubt.An extreme example is the MHz ultrasonic spray or shower, in which ultrasonic waves are applied to a spray for cleaning.It is true that the author was the first to put this technology to practical use in Japan 15 years ago and obtained a patent for it, but at the time I was unable to solve certain problems and I withdrew from the project myself.That problem still does not appear to have been solved.MHz has a linearity, but because of its high frequency, it has a high defoaming capacity and a large number of microbubbles of less than 1 mm are generated from the surface of the diaphragm, effectively absorbing and blocking the ultrasonic waves.At the same time, bubbles adhere to the diaphragm surface, forming a reflective surface with bubbles, leading to an empty oscillation state and the destruction of the diaphragm.To prevent this, a high-speed water flow (turbulence) is created on the diaphragm surface to remove the air bubbles that cause the empty oscillation.The diaphragm (element) is thus protected, but turbulence and the supply of large amounts of liquid generate more bubbles and effectively eliminate MHz.Currently, in LCD glass substrate cleaning, the ultrasonic waves generated by the MHz diaphragm do not reach the glass substrate at all, and appear to be merely cleaning it with an intense shower of pure water.Moreover, the effective range of MHz spray cleaning is only less than 10 m and the cleaning time per unit area of glass substrate is only a few seconds.The time the substrate is in the cleaning tank is longer, though.(although these problems have been solved by the author).In the first place, MHz entered this field before the Cavitation Enhancement System (third generation ultrasonic cleaning) was put into practical use in many fields, and due to the negative effects of the misuse of low-frequency gas nebula cavities.I now recommend simultaneous wide-area multiplexing up to 535 KHz with a basic frequency of 50 KHz, 80 KHz and 130 KHz for the efficient use of spherical nebula cavities for ultrasonic cleaning of increasingly larger glass substrates and the like.The impact force of the cavities can be controlled, and it is a mistake to try to solve this problem by reducing the power output or raising the frequency to an extreme level (e.g. to MHz) in order to avoid damage.To reduce the power output is to reduce the number of cavities and lose the cleaning effect, and to evacuate to extreme high frequencies is to lose the impact force of individual cavities.The fact that substrates are becoming larger, more delicate and more precise means that the cleaning power expected from the cleaning object must also be increased to a higher level.However, the smaller the foreign substance, the greater the adhesion force per unit area.What is required here is a cavitation control technology to generate cavities more uniformly and in greater numbers and with the necessary positive and negative impact force = cleaning power, without causing damage.Although it is not possible to go into too much detail here due to the number of pages, some ultrasonic cleaning designers are oblivious to the nature of glass in glass cleaning.More than 99% of the glass used for liquid crystals passes through ultrasonic waves.Reflected waves cannot form on their own.If this is the case, what is the correct position of the glass in ultrasonic cleaning, relative to the vibrating plate?(To be precise, this question is incorrect.)Alternatively, which position from the reflective surface can be passed through to make cleaning possible?The very idea that ultrasonic cleaning is possible when a glass substrate is passed over a diaphragm is a first generation ultrasonic cleaning idea.
(2)Ultrasonic cleaning in the semiconductor field
The approach is basically the same as in the field of liquid crystals.We will focus on the application of ultrasonic cavities.We are fully aware of the importance of the hardware, but we believe that what is lacking now, or what has stagnated for the past 20 years, is the software aspect of ultrasonic cleaning technology.
- Silicon wafer manufacturing sector
Although MHz seems to be at the height of its popularity, there are persistent complaints about its cleaning power: as mentioned above, MHz usually generates minute gas nebula-shaped cavities and countless air bubbles in pure water, making it difficult to clean larger and larger wafers.Less than 10% of the ultrasonic energy reaches the liquid surface.Therefore, the amount of dissolved oxygen corresponding to the size of the wafer should be controlled to promote the generation of spherical cavities only and to enhance cleaning power.Care should be taken in this case, as the cavities move perpendicularly to the vibrating plate.However, the author recommends simultaneous multiple waves of 80 KHz and 130 KHz to 535 Hz on the assumption that damage is controlled. a new, powerful, dense, high sound pressure ultrasound that solves the problems of MHz has been created.
- Device manufacturing sector, etc.
Ultrasonic etching is considered a new cavity application technology, and 10 MHz ultrasonic waves have also been used successfully to flux clean 50-00 µ gaps (close contact areas) in high-density flip-flop chips.Ultrasonic deburring and simultaneous precision cleaning of large numbers of packages is another new cavity-applied technology in this field.
(3)Computer-related fields and the field of mobile telecommunications equipment.
25-40 KHz is difficult to use because ultrasonic cavities often cause microscopic damage and contamination in the opposite direction.The author has therefore developed and utilises high acoustic pressure wide-area simultaneous multiple waves up to 535 KHz with 50 KHz and 80 KHz as the basic frequencies. 1200 W to 7200 W with ultrasonic output densities of 1 W/cm2 and 2 W/cm2 class are used in this field as well as for cleaning, as micro burrs are also a cause of defects.Naturally, they are also used for deburring.
(4)Automotive industry-related sectors.
This is an area in which there is a relatively high demand for strong cleaning.However, there are two directions of development in this field as well.The first is in the direction of larger and more powerful machines, and the second in the direction of smaller, faster and more precise machines.Compared to other fields, there are more enquiries for ultrasonic deburring, and ultrasonic cleaning and deburring of metals, plastics, ceramics and composite materials in general has grown to become one of the company’s mainstays.Here, we will discuss continuous vacuum [reduced pressure] ultrasonic cleaning deburring as a representative example, which has seen remarkable growth.This is a new form of ultrasonic cleaning for the future.(Patent pending).
Continuous vacuum [reduced pressure] ultrasonic deburring cleaning.
The author has developed an ultrasonic cleaning system that washes large quantities of clothes in a short time (about two minutes) without moving them, while they are still packed in a basket or on hangers.The author has also developed a short-time ultrasonic cleaning system for high-temperature, high-pressure filters with several thousand layers of metal mesh of several microns, which was said to be impossible with ultrasonic waves.The principle is basically the same.
Ten years ago, the author presented a method of continuous cleaning by first placing the cleaned material in a vacuum to remove air from the interior and surface of the cleaned material, and then introducing a liquid from which dissolved gases have been removed.The disadvantage of this method was that the cleaned material was again released into the air when it was transferred to the next tank, making continuous non-air contact ultrasonic cleaning impossible.Last year, in collaboration with a major Japanese valve body manufacturer, a continuous vacuum [reduced pressure] ultrasonic deburring and cleaning system for valve bodies was developed and successfully put into practical use.
Several valve bodies are placed vertically in a cassette 700 mm long and flow onto a conveyor.The tact time is 70 seconds.The first tank is a vacuum (decompression) treatment tank.The second tank is the ultrasonic deburring tank, with two 25 KHz to 535 KHz, 3600 W ultrasonic transducers on opposite sides of the cleaning tank.Two units of 3600 W are synchronised and resonantly oscillated.The sound pressure of the ultrasonic waves is constantly monitored by the U-sonic ultrasonic cleaning power meter developed by the company, which gives an alarm if the sound pressure is too strong or too weak.The controlled sound pressure is 20-25 V.The third tank is the rinse tank.Between the tanks, there are shutters in each of them, so that the cleaned material does not come into contact with air, including during movement.We refer to this as a submersible ultrasonic cleaner [SUB-MERGING].The same method is basically used for cleaning not only valve bodies but also various engine blocks (including F1).Before the experiment, the cleaned objects are moved up and down in the liquid, and all objects with even the slightest residual air bubbles or complex shapes, which could potentially be left behind, are vacuum treated and then ultrasonically (third generation) cleaned.
New era, development of ultrasonic cleaning technology.
The author is convinced that we are now in the vortex of new developments in ultrasonic cavitation application technology.Ultrasonic cleaning is differentiating between larger and smaller systems, with higher performance based on more precise measurement and control.One area of development, deburring, creates a large market.In addition, ultrasonic etching, ultrasonic abrasive polishing, ultrasonic high-speed pulverisation, ultrasonic organic synthesis, ultrasonic garment cleaning, ultrasonic applications for foodstuffs, etc., will see new applications and developments in the next decade, and we can say with certainty that we are in the vortex of this development.We are convinced that the key lies in the third generation of ultrasonic cleaning technology with cavity enhancement systems.