How to use ultrasonic cleaning equipment
In the past 10 years, ultrasonic cleaning equipment is developing in two aspects. One is that various types of multi-cylinder or transmission chain or lifting ultrasonic cleaning production lines have been introduced one after another; the second is the development of low-frequency ultrasonic cleaning machines to high-frequency ultrasonic cleaning machines. In the United States, Japan, Europe and the Asia-Pacific market, the total volume of multi-cylinder ultrasonic cleaning equipment has increased significantly, up to 50% of the total, and multi-station semi-automatic, fully automatic transmission chain or lifting ultrasonic cleaning line Body equipment has also risen to more than 40% of the total.
The application of ultrasonic cleaning technology in China has achieved good results. First, the cleaning of mechanical parts before and after electroplating or cleaning before spraying, cleaning of parts for repair requires high cleaning degree, such as cleaning of oil pump nozzles, bearings, brakes, fuel filters and valves. The second is the cleaning of printed circuit boards, silicon wafers, wafers, component housings, seats, signal control relays for railway systems, components, connectors, picture tubes, and electric vacuum devices. The third is the cleaning of optical systems such as glasses, microscopes, telescopes, sights, and sampled glass sheets. The fourth is the cleaning of various bottles used in medical instruments, food, pharmaceutical, biochemical and other tests. The fifth is the cleaning of spinnerets, precision molds, precision rubber parts, jewelry and crafts.
There are nearly 40 types of ultrasonic cleaning equipment manufacturers in China, but their distribution is mainly concentrated in the southeast coastal areas. According to statistics, manufacturers in coastal areas account for 85% of the total number of the country. It can be seen that the application of ultrasonic cleaning technology in economically developed areas is not only prior, but also widespread and popular. At the same time, it proves that ultrasonic cleaning technology is popularized in the central and western regions. The prospects are very broad. As far as the product level is concerned, the technological progress of the contemporary products is also very obvious compared with the products of the 1970s and 1980s.
In recent years, due to the technical transformation of the traditional cleaning process of the automobile brake production line and the refrigerator compressor production line, an ultrasonic cleaning process is proposed. In the foreign automobile chassis frame, the car shell before the ultrasonic cleaning before spraying, with special cleaning liquid, the rust removal, deoxidation film and phosphating once the cleaning process is completed, after drying, the paint can be applied and developed.
AdvancedSonicProctssingSvstems Inc. of the United States has introduced a series of equipment for cleaning coal or precious metal minerals, such as cleaning the soil and colloidal substances on the surface of metal particles, so that the chemical agent can play a better role; the coal washing powder removes ash and sulfur, etc., the treatment rate It is more than ten tons per hour.
The application of Dvpont in the New Jersey pharmaceutical factory reports that ultrasonic cleaning can remove the dirt on the surface of the reaction tank or chemical treatment barrel, save energy by common methods, low cost and reduce environmental pollution. The cleaning process is simple, as long as it is dissolved. Fill the device with water, heat to 65 ° C, and add 2% surfactant, for 2-4 hours, you can clean.
Some European manufacturers have cleaned 9.1m3 tanks, which were previously heated to the boiling point with methanol for 4-8h. A total of 5 cleanings were required to meet the requirements, and ultrasonic cleaning required only one treatment to meet the requirements, saving solvent. Improve efficiency and reduce environmental pollution.
With the increasing use of ultrasonic cleaning equipment, various new ultrasonic cleaning equipments that have been continuously improved and improved are replacing old-fashioned equipment that has already been introduced.
The megahertz ultrasonic cleaning technology refers to cleaning with ultrasonic waves with a frequency of 700 kHz to 2 MHz. The cleaning system generally consists of a piezoelectric transducer display, a cleaning container and a cleaning solution, a high-frequency electric power generator and a control circuit. For some specific cleaning objects, there are sometimes hot air drying and special cleaning racks (baskets). ) and the filtration circulation system of the cleaning solution.
The main features of the megahertz ultrasonic cleaning technology are: avoiding the surface damage of high-gloss objects; secondly, removing submicron-sized particles attached to the surface; and third, immersing in the liquid, the side facing the transducer can be washed. Therefore, it is necessary to carry out double-sided cleaning.
At present, commercial megahertz ultrasonic cleaning equipment has been available in foreign markets. Verteq, Imtec, and ProSys have developed such equipment for use in semiconductor production lines. In the cleaning of 100-300mm silicon wafers, small particles as small as 0.15μm on the surface of the silicon wafer can be removed, and the rinsing process can be accelerated. And effectively prevent particles from reattaching on the surface of the wafer. Megahertz ultrasonic cleaning is an indispensable standard equipment in the production process of many large-scale integrated circuit manufacturers abroad.
The principle of ultrasonic cleaning The principle of ultrasonic cleaning is complicated in theory. There are many factors and effects involved in it. It can reflect the following three main points:
(1) Cavitation When a strong ultrasonic wave is radiated into the liquid, the cleaning liquid is changed centering on the static pressure (a standard pressure). When the pressure is below zero pressure, the oxygen dissolved in the liquid forms a tiny bubble core. In turn, numerous tiny voids (holes) that approximate the vacuum are produced. The tiny cavity at the positive pressure of the ultrasonic wave is crushed in the adiabatic compression state. This strong shock wave occurs at the moment of crushing, and can directly destroy the pollutant and disperse it in the liquid to form a cleaning mechanism. This powerful cleaning action in the test can erode the aluminum foil into numerous small holes in tens of seconds.
The use of cavitation cleaning has a better effect on degreasing. Generally, the mechanical parts are cleaned at a frequency of 28KHZ to 50KHZ. The ultrasonic intensity of the cleaning machine is mostly set at 0.5~1w/cm2.
(2) Acceleration cleaning liquid is irradiated by ultrasonic waves, and liquid molecules vibrate. This vibration acceleration is 103 times of gravity acceleration at 28KHZ and 105 times at 950KHZ. This strong acceleration can peel off the surface of the contaminant. Cleaning. However, the ultrasonic wave of 950KHZ does not generate holes, and is not suitable for the cleaning of oil stains. Only in the semiconductor manufacturing of the electronics industry, the contamination of submicron particles can be cleaned.
(3) The promotion of physicochemical reaction is caused by the action of holes to locally generate high temperature and high pressure (1000 MPa, 5500 ° C), and then stirred by vibration to promote the multiplication of chemical or physical effects, and the liquid is continuously emulsified and dispersed, further The rate at which chemical reactions are promoted.
Determination of the depth of the cleaning solution Ultrasonic waves in the liquid will form a "standing wave" phenomenon due to the mutual interference and convergence of the traveling wave and the echo (see Figure 1). Determining the depth of the liquid that generates the standing wave can give a good ultrasonic radiation effect. The depth of the liquid from which the standing wave is generated can be calculated by the following formula.
Liquid depth (λ/2) = speed of sound / frequency ÷ 2
The positive multiple of the liquid depth is also the depth suitable for Zui. For example, at 20 ° C water temperature, 28K1c, the liquid depth is 27mm, 54mm, 81mm, etc., at 38KHZ, the liquid depth is 21mm, 42mm, 63mm, etc., but different liquids The liquid temperature and ultrasonic oscillator have different standing waves. See Table 1.
Table 1 shows the generation of standing waves compared to the sound velocity of cleaning liquid λ/2
Water 20 ° C 1483mm27mm
Freon 20 ° C 717mm13mm
IPA20°C1168mm21mm
Acid and alkali cleaning agent 20 ° C 1483mm27mm
The ultrasonic generation method and the cleaning condition setting ultrasonic wave generation method are shown in Table 2, and can be selected according to different cleaning purposes. Currently, a continuous oscillation method capable of performing strong cleaning is commonly used. Frequency modulation and multi-frequency methods have more uneven cleaning during cleaning and are not suitable for cleaning contaminated objects.
Table 2 Ultrasonic generation mode Content characteristics Continuous oscillation amplitude and frequency are fixed and can be strongly cleaned. The cleaning is uneven by the standing wave action, and the shaking should be increased to achieve the cleaning uniformity.
Widening modulation amplitude variation has good degassing effect, good cleaning performance for different objects, and high noise.
The frequency modulation (FM oscillation) oscillation frequency is uniformly washed by performing a change of several kilohertz. Poor cleaning efficiency and low average output power.
At the same time, multiple frequencies and multiple frequencies simultaneously form a balanced sound field, and the cleaning is uniform, and it is difficult to obtain strong ultrasonic waves.
Multi-frequency alternates each frequency to generate multiple frequency cleaning equalization, which is not easy to get strong cleaning.
The cone-shaped radiation cleaning uses ultrasonic waves made of stainless steel to perform ultrasonic irradiation. Generally, in the case of insufficient cleaning, the strength of 10 times or 20 times of conventional ultrasonic waves can be obtained, and the performance is high. However, the cleaning surface is small, and the selection of the noise cleaning conditions is mainly as follows.
· Cleaning position: The cleaning object is placed at a position where the standing wave pressure is large, and a good cleaning effect can be obtained. However, when the object with a large standing wave is cleaned, it is easy to cause uneven cleaning. At this time, the object should be shaken within tens of millimeters, which is a common method for reducing the poor cleaning.
· Attenuation caused by the mesh: When cleaning small parts, the net basket method is often used. If the size of the net mesh is improper, the ultrasonic attenuation will be caused and the cleaning power will be reduced. For example, in the case of 28KHZ, the mesh diameter of the net basket It needs to be more than 5mm before it can be cleaned normally. If the screw is cleaned, the mesh hole is small to 1mm. If the attenuation is large, the 0.1-0.5mm thin plate mesh blue can be used to obtain the normal cleaning effect.
·Frequency: For the cleaning effect related to the frequency factor, it can be considered that the frequency is low for dirt that is difficult to clean, and the frequency is high, which is suitable for precision cleaning.
Liquid temperature: As the liquid temperature rises, the bubbles that survive in the liquid will block the sound waves and weaken the ultrasonic waves, but in the conventional way, the liquid temperature is increased to increase the cleaning ability. The suitable liquid temperature should be determined for different cleaning liquids and cleaning materials. In general, the liquid temperature is appropriate at 5060 °C.
The cleaning process and the cleaning process of the cleaning device are determined according to the type of contamination, the degree of contamination, and the processing volume. For example, the cleaning of the ophthalmic lens generally requires 10 processes. When using a water-based cleaning agent, the basic process of Zui is formulated as follows:
Ultrasonic cleaning (water cleaning agent) → ultrasonic cleaning (pure water, tap water) → dehydration (drying)
Drying treatment is very important for the cleaning performance of cleaning materials. Common drying methods include hot air drying, air drying, vacuum drying, centrifugal dehydration drying, IPA lifting and drying, etc., according to production batch, cost, product precision, shape of the laundry. Wait for it to choose.
Industrial ultrasonic cleaning machines are mostly single- or double-tank, and automatic cleaning machines are also available in multiple tanks. In recent years, most of the cleaning methods used in the semiconductor industry use a single-piece "US spray" high-frequency cleaning with a 950KHZ ultrasonic bath, which can achieve high-performance cleaning results. The "US spray" method will carry 950KHZ ultrasonics. The formed water curtain is used for ultra-precision cleaning of liquid crystal glass and circuit chips, and dust particles can be close to "zero".
In the future, wet cleaning of different products, if 100% of the performance of the cleaning agent is required, higher requirements will be placed on the ultrasonic cleaning device.
The application of ultrasonic cleaning technology in China has achieved good results. First, the cleaning of mechanical parts before and after electroplating or cleaning before spraying, cleaning of parts for repair requires high cleaning degree, such as cleaning of oil pump nozzles, bearings, brakes, fuel filters and valves. The second is the cleaning of printed circuit boards, silicon wafers, wafers, component housings, seats, signal control relays for railway systems, components, connectors, picture tubes, and electric vacuum devices. The third is the cleaning of optical systems such as glasses, microscopes, telescopes, sights, and sampled glass sheets. The fourth is the cleaning of various bottles used in medical instruments, food, pharmaceutical, biochemical and other tests. The fifth is the cleaning of spinnerets, precision molds, precision rubber parts, jewelry and crafts.
There are nearly 40 types of ultrasonic cleaning equipment manufacturers in China, but their distribution is mainly concentrated in the southeast coastal areas. According to statistics, manufacturers in coastal areas account for 85% of the total number of the country. It can be seen that the application of ultrasonic cleaning technology in economically developed areas is not only prior, but also widespread and popular. At the same time, it proves that ultrasonic cleaning technology is popularized in the central and western regions. The prospects are very broad. As far as the product level is concerned, the technological progress of the contemporary products is also very obvious compared with the products of the 1970s and 1980s.
In recent years, due to the technical transformation of the traditional cleaning process of the automobile brake production line and the refrigerator compressor production line, an ultrasonic cleaning process is proposed. In the foreign automobile chassis frame, the car shell before the ultrasonic cleaning before spraying, with special cleaning liquid, the rust removal, deoxidation film and phosphating once the cleaning process is completed, after drying, the paint can be applied and developed.
AdvancedSonicProctssingSvstems Inc. of the United States has introduced a series of equipment for cleaning coal or precious metal minerals, such as cleaning the soil and colloidal substances on the surface of metal particles, so that the chemical agent can play a better role; the coal washing powder removes ash and sulfur, etc., the treatment rate It is more than ten tons per hour.
The application of Dvpont in the New Jersey pharmaceutical factory reports that ultrasonic cleaning can remove the dirt on the surface of the reaction tank or chemical treatment barrel, save energy by common methods, low cost and reduce environmental pollution. The cleaning process is simple, as long as it is dissolved. Fill the device with water, heat to 65 ° C, and add 2% surfactant, for 2-4 hours, you can clean.
Some European manufacturers have cleaned 9.1m3 tanks, which were previously heated to the boiling point with methanol for 4-8h. A total of 5 cleanings were required to meet the requirements, and ultrasonic cleaning required only one treatment to meet the requirements, saving solvent. Improve efficiency and reduce environmental pollution.
With the increasing use of ultrasonic cleaning equipment, various new ultrasonic cleaning equipments that have been continuously improved and improved are replacing old-fashioned equipment that has already been introduced.
The megahertz ultrasonic cleaning technology refers to cleaning with ultrasonic waves with a frequency of 700 kHz to 2 MHz. The cleaning system generally consists of a piezoelectric transducer display, a cleaning container and a cleaning solution, a high-frequency electric power generator and a control circuit. For some specific cleaning objects, there are sometimes hot air drying and special cleaning racks (baskets). ) and the filtration circulation system of the cleaning solution.
The main features of the megahertz ultrasonic cleaning technology are: avoiding the surface damage of high-gloss objects; secondly, removing submicron-sized particles attached to the surface; and third, immersing in the liquid, the side facing the transducer can be washed. Therefore, it is necessary to carry out double-sided cleaning.
At present, commercial megahertz ultrasonic cleaning equipment has been available in foreign markets. Verteq, Imtec, and ProSys have developed such equipment for use in semiconductor production lines. In the cleaning of 100-300mm silicon wafers, small particles as small as 0.15μm on the surface of the silicon wafer can be removed, and the rinsing process can be accelerated. And effectively prevent particles from reattaching on the surface of the wafer. Megahertz ultrasonic cleaning is an indispensable standard equipment in the production process of many large-scale integrated circuit manufacturers abroad.
The principle of ultrasonic cleaning The principle of ultrasonic cleaning is complicated in theory. There are many factors and effects involved in it. It can reflect the following three main points:
(1) Cavitation When a strong ultrasonic wave is radiated into the liquid, the cleaning liquid is changed centering on the static pressure (a standard pressure). When the pressure is below zero pressure, the oxygen dissolved in the liquid forms a tiny bubble core. In turn, numerous tiny voids (holes) that approximate the vacuum are produced. The tiny cavity at the positive pressure of the ultrasonic wave is crushed in the adiabatic compression state. This strong shock wave occurs at the moment of crushing, and can directly destroy the pollutant and disperse it in the liquid to form a cleaning mechanism. This powerful cleaning action in the test can erode the aluminum foil into numerous small holes in tens of seconds.
The use of cavitation cleaning has a better effect on degreasing. Generally, the mechanical parts are cleaned at a frequency of 28KHZ to 50KHZ. The ultrasonic intensity of the cleaning machine is mostly set at 0.5~1w/cm2.
(2) Acceleration cleaning liquid is irradiated by ultrasonic waves, and liquid molecules vibrate. This vibration acceleration is 103 times of gravity acceleration at 28KHZ and 105 times at 950KHZ. This strong acceleration can peel off the surface of the contaminant. Cleaning. However, the ultrasonic wave of 950KHZ does not generate holes, and is not suitable for the cleaning of oil stains. Only in the semiconductor manufacturing of the electronics industry, the contamination of submicron particles can be cleaned.
(3) The promotion of physicochemical reaction is caused by the action of holes to locally generate high temperature and high pressure (1000 MPa, 5500 ° C), and then stirred by vibration to promote the multiplication of chemical or physical effects, and the liquid is continuously emulsified and dispersed, further The rate at which chemical reactions are promoted.
Determination of the depth of the cleaning solution Ultrasonic waves in the liquid will form a "standing wave" phenomenon due to the mutual interference and convergence of the traveling wave and the echo (see Figure 1). Determining the depth of the liquid that generates the standing wave can give a good ultrasonic radiation effect. The depth of the liquid from which the standing wave is generated can be calculated by the following formula.
Liquid depth (λ/2) = speed of sound / frequency ÷ 2
The positive multiple of the liquid depth is also the depth suitable for Zui. For example, at 20 ° C water temperature, 28K1c, the liquid depth is 27mm, 54mm, 81mm, etc., at 38KHZ, the liquid depth is 21mm, 42mm, 63mm, etc., but different liquids The liquid temperature and ultrasonic oscillator have different standing waves. See Table 1.
Table 1 shows the generation of standing waves compared to the sound velocity of cleaning liquid λ/2
Water 20 ° C 1483mm27mm
Freon 20 ° C 717mm13mm
IPA20°C1168mm21mm
Acid and alkali cleaning agent 20 ° C 1483mm27mm
The ultrasonic generation method and the cleaning condition setting ultrasonic wave generation method are shown in Table 2, and can be selected according to different cleaning purposes. Currently, a continuous oscillation method capable of performing strong cleaning is commonly used. Frequency modulation and multi-frequency methods have more uneven cleaning during cleaning and are not suitable for cleaning contaminated objects.
Table 2 Ultrasonic generation mode Content characteristics Continuous oscillation amplitude and frequency are fixed and can be strongly cleaned. The cleaning is uneven by the standing wave action, and the shaking should be increased to achieve the cleaning uniformity.
Widening modulation amplitude variation has good degassing effect, good cleaning performance for different objects, and high noise.
The frequency modulation (FM oscillation) oscillation frequency is uniformly washed by performing a change of several kilohertz. Poor cleaning efficiency and low average output power.
At the same time, multiple frequencies and multiple frequencies simultaneously form a balanced sound field, and the cleaning is uniform, and it is difficult to obtain strong ultrasonic waves.
Multi-frequency alternates each frequency to generate multiple frequency cleaning equalization, which is not easy to get strong cleaning.
The cone-shaped radiation cleaning uses ultrasonic waves made of stainless steel to perform ultrasonic irradiation. Generally, in the case of insufficient cleaning, the strength of 10 times or 20 times of conventional ultrasonic waves can be obtained, and the performance is high. However, the cleaning surface is small, and the selection of the noise cleaning conditions is mainly as follows.
· Cleaning position: The cleaning object is placed at a position where the standing wave pressure is large, and a good cleaning effect can be obtained. However, when the object with a large standing wave is cleaned, it is easy to cause uneven cleaning. At this time, the object should be shaken within tens of millimeters, which is a common method for reducing the poor cleaning.
· Attenuation caused by the mesh: When cleaning small parts, the net basket method is often used. If the size of the net mesh is improper, the ultrasonic attenuation will be caused and the cleaning power will be reduced. For example, in the case of 28KHZ, the mesh diameter of the net basket It needs to be more than 5mm before it can be cleaned normally. If the screw is cleaned, the mesh hole is small to 1mm. If the attenuation is large, the 0.1-0.5mm thin plate mesh blue can be used to obtain the normal cleaning effect.
·Frequency: For the cleaning effect related to the frequency factor, it can be considered that the frequency is low for dirt that is difficult to clean, and the frequency is high, which is suitable for precision cleaning.
Liquid temperature: As the liquid temperature rises, the bubbles that survive in the liquid will block the sound waves and weaken the ultrasonic waves, but in the conventional way, the liquid temperature is increased to increase the cleaning ability. The suitable liquid temperature should be determined for different cleaning liquids and cleaning materials. In general, the liquid temperature is appropriate at 5060 °C.
The cleaning process and the cleaning process of the cleaning device are determined according to the type of contamination, the degree of contamination, and the processing volume. For example, the cleaning of the ophthalmic lens generally requires 10 processes. When using a water-based cleaning agent, the basic process of Zui is formulated as follows:
Ultrasonic cleaning (water cleaning agent) → ultrasonic cleaning (pure water, tap water) → dehydration (drying)
Drying treatment is very important for the cleaning performance of cleaning materials. Common drying methods include hot air drying, air drying, vacuum drying, centrifugal dehydration drying, IPA lifting and drying, etc., according to production batch, cost, product precision, shape of the laundry. Wait for it to choose.
Industrial ultrasonic cleaning machines are mostly single- or double-tank, and automatic cleaning machines are also available in multiple tanks. In recent years, most of the cleaning methods used in the semiconductor industry use a single-piece "US spray" high-frequency cleaning with a 950KHZ ultrasonic bath, which can achieve high-performance cleaning results. The "US spray" method will carry 950KHZ ultrasonics. The formed water curtain is used for ultra-precision cleaning of liquid crystal glass and circuit chips, and dust particles can be close to "zero".
In the future, wet cleaning of different products, if 100% of the performance of the cleaning agent is required, higher requirements will be placed on the ultrasonic cleaning device.
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