1. Vacuum Degassing to Enhance Cavitation Efficiency and Uniformity

   · Traditional Problem: Cleaning liquids at normal pressure dissolve a large amount of air. This gas acts as a "cavitation nucleus," generating a large number of irregular, uncontrollable large bubbles under ultrasonic action. Although these large bubbles have significant collapse energy, their distribution is uneven, easily causing cleaning dead spots and erosion damage.

   · Vacuum Solution: Applying vacuum to the cleaning tank before or during cleaning removes a large amount of gas (mainly air) dissolved in the liquid. The gas content in the liquid is drastically reduced.

   · Effect: When ultrasonic waves are applied to the degassed liquid, the resulting cavitation bubbles are smaller, more uniform, more numerous, and their energy is more focused. This allows the cleaning force to act on the entire surface of the workpiece more delicately and uniformly, significantly improving the cleaning effect, especially for microscopic structures and high aspect ratio blind holes, and reducing surface damage (cavitation corrosion) caused by the collapse of large bubbles.

2. Eliminate Bubble Shielding to Achieve Thorough Cleaning of Deep Holes, Blind Holes, and Dense Structures

   · Traditional Problem: When cleaning workpieces with deep holes, micro-holes, and complex inner cavities, the air inside the holes cannot escape, forming "air blockage" or "bubble shielding," preventing the cleaning liquid from entering, leading to cleaning failure.

   · Vacuum Solution: Under vacuum, the air inside the holes is drawn out, and then the cleaning liquid is injected. Through alternating cycles of vacuum and normal pressure (or pressurization), the cleaning liquid is forced to completely penetrate the deepest, finest pores, "squeezing" out internal contaminants.

   · Effect: This is the most irreplaceable advantage of vacuum ultrasonic cleaning, solving the problem of thoroughly wetting and cleaning through-holes/blind holes that traditional methods cannot handle.

3. Vacuum (or Hot Air) Drying to Achieve Spot-Free, Residue-Free Drying

   · Traditional Problem: After water-based cleaning, water stains remain on the workpiece surface, especially within microstructures. Upon water evaporation, scale, spots, or chemical residues are left behind.

   · Vacuum Solution: After cleaning and rinsing, the boiling point of water is significantly lowered in a vacuum environment (e.g., water can boil at about $40^{\circ}\text{C}$ at $-0.09\text{MPa}$). Through vacuum drying, residual liquids (including moisture and solvent) rapidly boil and vaporize at low temperatures, being drawn out by the vacuum pump.

   · Effect: Achieves fast, low-temperature, non-oxidizing, spot-free, perfect drying. Crucial for workpieces that are sensitive to high temperatures, prone to oxidation, and require absolute cleanliness (such as wafers, high-end optical lenses).

4. Inhibits Oxidation, Suitable for Reactive Metal Materials

   · The entire cleaning and drying process can be conducted under the protection of low-oxygen or oxygen-free vacuum or inert gas (such as nitrogen), effectively preventing active metals like copper, aluminum, and magnesium alloys from oxidizing or producing water marks during the cleaning process.

5. Increases Cleaning Agent Efficiency, Reduces Consumption

   · After vacuum degassing, the cleaning agent solution can better contact the workpiece surface, increasing the utilization rate of its active components. This can sometimes allow for lower cleaning agent concentration or reduced cleaning time, making it more environmentally friendly and economical.

Comparison Summary with Standard Ultrasonic Cleaning

| Feature | Standard Ultrasonic Cleaning | Vacuum Ultrasonic Cleaning |

| :--- | :--- | :--- |

| Cavitation Quality | Varied bubble sizes, uneven energy distribution | Bubbles are fine and uniform, energy is concentrated and stable |

| Penetration Ability | Limited by air resistance, difficult to clean deep/blind holes | Can thoroughly penetrate the deepest and finest pores |

| Drying Effect | Normal pressure drying, prone to water spots and scale | Vacuum low-temperature drying, spot-free and residue-free |

| Oxidation Risk | Oxidation risk exists | Effectively inhibits oxidation (with inert gas) |

| Workpiece Damage | Potential for cavitation corrosion | Reduced cavitation corrosion, more gentle and uniform |

| Process Complexity | Simple | Complex, requires control of vacuum, pressure, and timing |

| Equipment Cost | Low | Very expensive |

| Application Field | General precision cleaning | Cutting-edge, ultra-high cleanliness requirement fields |

Main Application Fields (High-End Manufacturing)

Due to its superior performance and high cost, vacuum ultrasonic cleaning is mainly used in fields with extreme cleanliness requirements:

· Semiconductor and MEMS (Micro-Electro-Mechanical Systems): Cleaning wafers, silicon chips, sensors, removing nanoscale particles and organic matter.

· High-End Optics and Optoelectronics: Laser crystals, precision optical lenses, fiber optic connectors, requiring absolutely no spots or residues.

· Medical Devices and Implants: Cardiac stents, surgical tools, high-value implants, requiring bio-level cleanliness and pyrogen-free.

· Aerospace and Automotive Core Components: Fuel nozzles, turbine blades, precision hydraulic valves, ensuring absolute cleanliness of deep holes.

· Precision Instruments and Bearings: Gyroscopes, high-precision bearings, used to remove sub-micron contaminants before assembly.

Conclusion

The essential characteristic of vacuum ultrasonic cleaning is the combination of the powerful physical cleaning force of "ultrasonic cavitation" with the revolutionary changes that a "vacuum environment" brings to liquid properties, penetration ability, and drying method. By enhancing cavitation through degassing, achieving complete penetration via bubble disruption, and realizing perfect drying through vacuum, it solves the three major pain points of traditional cleaning, making it an indispensable, cutting-edge technology for future ultra-high-precision manufacturing, valued primarily for cleaning top-tier precision parts that are "uncleanable, inaccessible, and undryable" by conventional methods.