Acoustic waves can be divided into three main frequency ranges according to frequency differences: infrasound waves, audible sound waves, and ultrasonic waves:
Infrasound waves (< 20Hz): Used for the monitoring of natural phenomena (such as seismic waves), with limited industrial applications.
Audible sound waves (20Hz - 20kHz): Within the human auditory range, used for sonar and communication.
Ultrasonic waves (> 20kHz): The core frequency band for industrial cleaning (20kHz - 1MHz), with two major technical advantages:
Directional energy transmission: With a short wavelength (37.5mm corresponding to 40kHz), the energy is concentrated in a micron-level area, enabling deep cleaning of precision structures.
Liquid penetration ability: It can penetrate a liquid medium of more than 100mm, meeting the cleaning requirements of complex structures such as deep holes and blind holes.
Flow field characteristics: A directional liquid flow of 10-15cm/s is formed, driving the cleaning liquid to penetrate into slits smaller than 0.1mm, accelerating the mixing of the dirty liquid and the new liquid, and increasing the dissolution rate of oil-based contaminants by 35%.
Application scenarios: Cleaning of deep holes (> 150mm) in automotive engine blocks, ensuring a carbon deposit removal rate of > 98% (ISO 16232-10 standard).
Action mechanism: Liquid particles obtain high-speed kinetic energy (> 5m/s), and remove nanoscale contaminants (such as 0.2μm particles on the surface of semiconductor wafers) through non-contact impact.
Technical advantages: The surface roughness is controlled to < 0.1μm, and the coating damage rate is < 0.01%, meeting the wafer-level cleaning requirements of the SEMI standard.
Function enhancement:
Supports the complex frequency output mode (alternating between 28kHz rough cleaning and 40kHz fine cleaning), reducing the sound field blind area by 40%, and decreasing the cleaning dead angle rate of complex curved surfaces from 18% to 3%.
Dynamic power adjustment technology (accuracy ±5%), automatically matching the energy output according to the load, increasing the energy efficiency ratio by 15%, and reducing the risk of cavitation corrosion.
The cleaning tank body is made of 316Ti stainless steel with stronger corrosion resistance. Compared with the traditional 304 stainless steel, its resistance to acid and alkali erosion is increased by about 60%, and it can be adapted to various strong acid and strong alkali cleaning media. The transducer adopts a matrix vibrating rod layout, combined with the design of the curved surface reflective tank wall, to achieve 360° omnidirectional sound emission. Through actual measurement, the sound field uniformity can reach more than 93%, effectively solving the problem of energy attenuation existing in traditional single-side vibrating box equipment. The supporting functional accessories include: a graded aperture mesh basket (0.5mm/1.0mm/2.0mm), which can meet the classification cleaning requirements of workpieces of different sizes; the anti-static fixture is made of a special material with a surface resistance < 10⁶Ω, providing reliable protection for the cleaning process of electronic components.
| Power Density (W/cm²) | Applicable Scenarios | Cleaning Characteristic Index | Safety Threshold Control |
|---|
| 0.3 - 0.8 | Precision optics/semiconductor components | Surface damage rate < 0.01% | Temperature ≤ 40°C (to prevent coating damage) |
| 0.8 - 1.5 | Industrial metal parts/automotive parts | Oil removal efficiency > 98%, particle removal rate 95% | Time ≤ 15 minutes (to prevent over-cleaning) |
| 1.5 - 2.2 | Heavily polluted workpieces/castings | Used in combination with chemical strengthening agents | Vibration frequency ≥ 30kHz (to prevent metal fatigue) |
Advantages: Strong cavitation effect, suitable for removing heavy oil stains and metal burrs.
Applications: Post-processing of 3D printing (removing residual powder in microholes, reducing the porosity to 0.3%), deburring of bearing rollers (surface roughness Ra ≤ 1.6μm).
Advantages: Balanced cleaning power and surface protection, suitable for cleaning before precision assembly.
Applications: Removal of soldering flux on printed circuit boards (ion residue < 5ppb), decomposition of biofilms on medical implants (certified by AAMI ST79 standard).
Advantages: Mainly the acoustic streaming effect, non-destructive cleaning.
Applications: Wafer-level cleaning (0.2μm particle removal rate 99.8%), nanoscale purification of MEMS devices (surface energy maintained > 72mN/m).
Aqueous system: Adding nanoscale surfactants (particle size < 50nm) to improve the microhole penetration efficiency, suitable for hydrophilic materials such as aluminum alloys and glass.
Composite solvent: Hydrocarbon solvent + chelating agent (metal ion capture rate > 99%), combined with a temperature control of 50-65°C, to accelerate the emulsification of stubborn grease (for example, reducing the engine carbon deposit cleaning time to 8 minutes).
Polymer protection: Plastic/rubber parts are cleaned at a low temperature of 35-45°C (to prevent deformation threshold), and a neutral cleaning agent (pH = 7-8) is used.
Automotive powertrain: Using 40kHz complex frequency ultrasonic + alkaline cleaning agent, the cylinder block is cleaned in 8 minutes, the cleanliness reaches ISO 16232-10 level, and the assembly defect rate is reduced by 60%.
Aerospace components: The vacuum ultrasonic combined technology (-0.09MPa pressure) is used to clean the lenses of satellite sensors, with a surface particle residue < 1 piece/mm², meeting the weather resistance requirements of the space environment.
Wafer-level cleaning: 100kHz megahertz ultrasonic + deionized water, achieving a 0.1μm particle removal rate of 99.5%, meeting the SEMI F20 standard, and ensuring the yield of the lithography process > 99%.
Power chip packaging: The dynamic power adjustment technology (0.5W/cm²) is used to clean the lead frame, with an ion residue < 10ppb, reducing the risk of electromigration failure by 90%.
Lithium battery electrodes: The integrated process of ultrasonic vibration + vacuum drying controls the metal impurities < 8ppm, and the battery cycle life is increased by 20%.
Optical medical devices: The 3D curved vibrating rod system is used to clean the endoscope lens, with a biofilm removal rate of 100% and a light transmittance maintained above 99.7%, meeting the ultra-clean requirements before sterilization.
The propagation uniformity of ultrasonic waves in the cleaning tank directly affects the cleaning consistency. The core control technologies include:
Wavelength matching design: According to the principle of "the distance between adjacent walls = an integer multiple of the half-wavelength of the acoustic wave" (for example, the wavelength of 40kHz ultrasonic waves in water is 37.5mm, and the recommended spacing is 75mm/112.5mm), the sound pressure distribution is pre-researched through the ANSYS sound field simulation software to ensure that the sound intensity difference in the tank < 10%.
Dynamic frequency scanning: Using the ±2kHz frequency conversion technology (such as dynamic switching between 28-30kHz), the energy blind area formed by standing waves is broken in real-time, and the cleaning dead angle rate of complex curved workpieces is reduced from 15% in the single-frequency mode to below 5%.
Vacuum ultrasonic coupling process: In a -0.08MPa vacuum environment, the gas content in the liquid is reduced by 40%, the cavitation threshold is decreased by 25%, and the cleaning efficiency is increased by 35% under the same power, which is especially suitable for the high cleanliness cleaning of aerospace-grade titanium alloy components (surface particle residue ≤ 2 pieces/mm²).
Optimization of the transducer layout: Using a 360° omnidirectional vibrating rod to replace the traditional single-side vibrating box, combined with the design of a 45° inclined tank wall, the sound field uniformity is increased from 75% to 93%, solving the problem of bottom cleaning of deep-hole parts (such as a 150mm long hydraulic valve body).
| Frequency Range | Typical Application Scenarios | Cavitation Bubble Size | Core Technical Advantages | Representative Workpiece Cases | Cleanliness Standard |
|---|
| 20 - 35kHz | Sand removal and deburring of castings | 80 - 150μm | Strong impact force to break the metal adhesion layer | Automotive cylinder block/bearing ring | ISO 16232-9 level |
| 35 - 60kHz | Removal of welding slag from electronic components and rough optical cleaning | 50 - 100μm | Balanced penetration force and structural protection | PCB board/microscope objective lens | IPC-A-610E Class 3 |
| 60 - 100kHz | Cleaning before precision component assembly | 20 - 50μm | Micro-gap cleaning and surface coating protection | Semiconductor lead frame/medical catheter | SEMI F20 particle size standard |
| 100kHz+ | Nanoscale ultra-clean cleaning | 5 - 20μm | Non-destructive cleaning and removal of molecular-level contaminants | Wafer/MEMS sensor | ISO 14644-1 Class 1 |
Low frequency band (20 - 40kHz): The recommended power density is 1.2-2.0W/cm², with an alkaline water-based cleaning agent (pH = 10-13), suitable for removing stubborn contaminants such as engine carbon deposits and die-casting mold release agents. The cleaning time is controlled within 10-15 minutes.
Medium and high frequency band (40 - 100kHz): The power density is 0.6-1.0W/cm², using a hydrocarbon solvent (KB value > 60) + vacuum degassing treatment, suitable for cleaning before optical lens coating, ensuring that the surface residual oil < 0.1μg/cm².
Megahertz band (100kHz+): The power density ≤ 0.5W/cm², combined with deionized water + 0.1% nanoscale surfactant, achieving a 0.2μm particle removal rate of 99.8% for semiconductor wafers, meeting the requirements of extreme ultraviolet lithography (EUV) process.
Automated process system: The precise setting of cleaning parameters (frequency, power, time) is realized through a PLC programmable controller, supporting the linkage control of multiple tank bodies, adapting to the rhythm of the intelligent production line. In typical cases, the batch cleaning efficiency is increased by 40%.
Integration application of robotic arms: Equipped with a six-axis robotic arm to achieve automatic loading and unloading of workpieces, combined with customized fixtures (such as Teflon-coated anti-scratch fixtures), to meet the contactless cleaning of precision devices (such as optical lens groups), with a positioning accuracy of up to ±0.05mm.
Closed-loop cleaning system: Using an integrated device of "ultrasonic cleaning - vacuum distillation - condensation recovery", the recovery rate of hydrocarbon solvents reaches more than 95%, reducing hazardous waste emissions by 60% per year, in line with the EU REACH regulations and the construction requirements of domestic "waste-free factories".
Water-based environmental protection process: Developing biodegradable surfactants (degradation rate > 90%), combined with 80kHz high-frequency ultrasonic, achieving an oil stain removal rate of 98% in the cleaning of aluminum alloy wheels, while avoiding the risk of heavy metal pollution of traditional solvents, meeting the environmental protection manufacturing standards of IATF 16949.
Application of megahertz ultrasonic: The cleaning technology in the high frequency band above 100kHz is mature. Using the acoustic streaming effect to achieve nanoscale cleaning (such as a 0.1μm particle removal rate of 99.5% on the surface of MEMS sensors), combined with a vacuum negative pressure environment, it can meet the ultra-clean requirements of extreme ultraviolet lithography (EUV) lenses (surface residue < 1 piece/mm²).
Integration of composite processes: Combining vacuum ultrasonic and supercritical CO₂ cleaning to achieve perfect cleaning without watermarks and chemical residues in semiconductor wafer manufacturing. After testing, the metal ion residue < 1ppb, significantly improving the chip yield.
Analysis of pollutant composition: Detect the pollutant composition through a Fourier transform infrared spectrometer (FTIR) or a scanning electron microscope (SEM), and select the cleaning medium according to the situation — for example, for resin-based pollutants, a hydrocarbon solvent with a KB value > 70 is preferred, and for metal oxides, an alkaline water-based liquid (pH = 11-13) is recommended.
Material compatibility test: Conduct ultrasonic tolerance tests on new materials (such as silicon carbide and zirconia ceramics), record the safe threshold of power density (for example, for ceramic parts, it is recommended to ≤ 0.8W/cm²) to avoid cavitation corrosion.
Optimal selection of core components: Give priority to selecting cleaning equipment with complex frequency functions (28kHz + 40kHz) and vacuum degassing (-0.08MPa) to balance rough cleaning efficiency and fine cleaning accuracy. For example, after the automotive parts cleaning line adopts this configuration, the bearing cleanliness compliance rate is increased from 85% to 98%.
Standardized parameter library: Establish a corresponding table of "material - pollution type - process parameters" (for example, for titanium alloy parts: 30kHz frequency + 0.6W/cm² power + neutral water-based liquid), and optimize the cleaning time through the orthogonal test method (the recommended error is ±2 minutes) to reduce the trial-and-error cost.
Monitoring of the transducer status: Regularly detect the impedance value of the transducer (recommended once a month). When the impedance deviation exceeds 15%, replace it in time to avoid a decrease in the cleaning effect caused by energy attenuation.
Calibration of the sound field uniformity: Use a hydrophone (accuracy ±0.5dB) to detect the sound pressure distribution in the tank to ensure that the sound intensity difference in each area < 10%. It is recommended to calibrate typical industrial-grade equipment once a quarter.
Automotive industry: Follow the ISO 16232-10 cleanliness level. After cleaning, workpieces need to be detected by a particle counter (> 50μm particles ≤ 3 pieces/100cm²).
Semiconductor industry: Implement the SEMI F20 standard, control the particle residue above 0.2μm < 5 pieces/cm², and it is recommended to be equipped with a cleaning environment at the class 100 cleanroom level.
In the technological evolution of high-end manufacturing and precision machining, ultrasonic cleaning technology is changing from an auxiliary process to a core cleanliness treatment technology.
