Applications and Key Advantages

1. What Is a Vacuum?

A vacuum refers to a state in which a space is filled with gas at a pressure lower than normal atmospheric pressure. Vacuum environments play an important role in many fields, including science, engineering, and medicine.

In the field of science, vacuums are used for the study of atoms and molecules.
From an engineering perspective, vacuum environments are used in the manufacturing of semiconductors, solar cells, and electronic components.
In medicine, vacuums are used for biological research, sample preservation, and the sterilization of surgical instruments.

Types of Vacuum

Absolute Vacuum

Vacuum is also an important concept in physics. In classical theory, an absolute vacuum refers to a state in which no molecules exist in space. Although outer space is often described as a vacuum, trace amounts of molecules are actually present. Therefore, an absolute vacuum is a theoretical concept and does not exist in reality.

Negative Pressure (Vacuum Levels)

Negative pressure refers to a condition in which the pressure is lower than standard atmospheric pressure on Earth (approximately 1 atm at sea level).According to JIS (Japanese Industrial Standards), vacuum levels are classified into four categories: low vacuum, medium vacuum, high vacuum, and ultra-high vacuum.

• Low vacuum: Used for vacuum packaging and the manufacture of vacuum tubes and electronic components 
• Medium vacuum: Used in the manufacture of semiconductor and solar cell materials
• High vacuum: Used in the production of devices such as lasers and electron microscopes 
• Ultra-high vacuum: Used for research on atoms and molecules

2. Applications Requiring Vacuum Environments

So far, we have explained what a vacuum is. Equipment that makes use of vacuum environments, as well as equipment used in outer space, often incorporates motors.

Example 1: Vacuum Thin-Film Deposition Equipment

Vacuum thin-film deposition equipment is used to form thin films of materials such as metals, ceramics, semiconductors, and organic materials.
These thin films are widely used in various applications, including semiconductor devices, solar cells, displays, and optical devices.

A vacuum environment is required in thin-film deposition equipment to remove air molecules that would otherwise interfere with the movement of atoms and molecules necessary for film growth.
In a vacuum environment, the low pressure reduces the likelihood of collisions between atoms and molecules. As a result, they can more easily reach and adhere to the target surface, enabling the formation of uniform, high-quality thin films.

Applications of Vacuum Thin-Film Deposition Equipment

• Semiconductor devices such as transistors, diodes, and capacitors (to improve performance and enable miniaturization)
• Solar cells (to convert sunlight into electricity)
• Displays such as liquid crystal displays (LCDs) and organic EL displays (OLEDs) (to improve image quality and achieve thinner designs)
• Optical devices such as lasers and optical fibers (to improve performance and enable miniaturization)
• Energy devices such as solar cells, fuel cells, and light-emitting diodes (LEDs) (to improve performance and efficiency)
• Protective coatings for materials such as metals, ceramics, and plastics (to protect against wear, corrosion, and ultraviolet radiation)
• Decorative coatings for materials such as glass, plastics, and metals (to enhance appearance, durability, and functionality)

Example 2: Vacuum Metallurgical Equipment

Vacuum metallurgical equipment is used to melt and solidify metals in a vacuum environment.

A vacuum environment is required for metallurgical equipment
because removing atmospheric impurities suppresses metal oxidation and contamination.
In addition, metals solidify more rapidly in a vacuum, resulting in finer and more uniform grain structures.
Furthermore, gas bubbles generated during solidification are reduced, improving metal strength and overall product quality.
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Applications of Particle Accelerators

• Production of high-quality steel
• Production of high-temperature alloys
• Manufacturing of semiconductor materials
• Production of magnetic materials
• Production of superconducting materials

Example 3: Particle Accelerators

A particle accelerator is a device that accelerates particles such as electrons and protons to high speeds by imparting energy to them.
Particle accelerators must operate in a vacuum environment. This is because particles would lose energy if they collided with air molecules inside the accelerator.

In a vacuum environment, such collisions can be avoided, allowing particles to be accelerated to very high speeds.
Particle accelerators are used for research in a wide range of fields, including physics, chemistry, biology, and medicine. 

They are also used in medical diagnostics and radiation therapy, such as particle beam therapy, making them valuable in applications close to our daily lives.

Applications of Particle Accelerators

• Research on the structure of matter
• Development of new materials
• Medical diagnostics
• Radiation therapy
• Nuclear fusion research

Example 4: Motor Applications in Space

In space environments, motors are used to operate many types of equipment on satellites and spacecraft.

Examples of Applications in Space

• Robotic Arms:
  Robotic arms are controlled by motors and enable remote operations such as grasping and releasing objects outside a spacecraft.
• Antennas:
  Antennas are used for communication between satellites, spacecraft, and Earth. Motors are used to adjust their orientation to ensure accurate and stable communication.
• Solar Array Panels:
  Solar array panels supply electrical power to satellites and spacecraft. Motors are used to control their orientation so that they can face the Sun and capture as much solar energy as possible.
• Thrusters:
  Thrusters are propulsion devices used to control the orbit of satellites and spacecraft. They consist of nozzles driven by motors.
  When the motor actuates the nozzle, high-pressure gas is expelled, generating thrust and accelerating the satellite or spacecraft.
• Reaction Wheels:
  Reaction wheels play an important role in attitude and orbit control and consist of a set of wheels rotated by motors. Satellites and spacecraft require precise attitude control.
  For example, when a spacecraft needs to orient itself in a specific direction, the rotational motion of the spacecraft can be controlled by rotating one or more reaction wheels. Reaction wheels are also used for fine adjustments while in orbit and for positioning at specific locations.

These are just a few examples, but motors are essential devices for the operation of satellites and spacecraft. They maintain reliable and precise performance even in harsh environments and play a vital role in the success of space missions.

3. What Are the Advantages of Using Vacuum Motors?

​In the past, rotary feedthroughs were commonly used to transmit motion from motors outside the vacuum chamber to the inside.
However, these feedthroughs required significant space, resulting in larger equipment.

By contrast, vacuum motors can be installed and operated directly inside the vacuum environment. This eliminates the need for rotary feedthroughs, enabling more compact equipment designs.

4. Points to Consider When Using Motors in Vacuum Environments

Next, we explain key points to consider when using motors under vacuum conditions.

Risk of Temperature Rise

When electric current flows through motor windings, heat is generated and the winding temperature rises.  In atmospheric conditions, heat is dissipated through air convection. However, in a vacuum environment where air is absent, heat dissipation is limited, leading to a greater risk of temperature rise.Therefore, thermal management is a critical consideration.

SANYO DENKI Vacuum Stepping Motors

• SANYO DENKI’s vacuum stepping motors use heat-resistant materials that enable continuous operation at temperatures of up to 200 °C.

Risk of Outgassing

In vacuum environments, lubricating oils and cooling oils tend to evaporate. When these vapors spread in a vacuum, they can adhere to the surfaces of vacuum pumps and vacuum chambers, leading to performance degradation.
In addition, as lubricants evaporate, it becomes difficult to maintain proper lubrication on the surfaces of components such as bearings and gears.

Furthermore, in standard motors, components such as flanges and end brackets are often manufactured using die casting, a process in which molten non-ferrous metal alloys are injected into molds under high pressure. This manufacturing method can trap microscopic air within the material, which may later be released as outgassing in vacuum environments.

SANYO DENKI Vacuum Stepping Motors

• No rust-preventive oil used in standard motors is applied.
• No painting processes using coatings or solvents that may cause outgassing are used.
• Before assembly, components undergo a baking process to remove outgassing as much as possible, and are then cleaned prior to assembly.  
    (Baking is a process in which gas molecules containing moisture are released by heating the surface.)
• Flanges and end brackets are not manufactured by die casting, but are machined from solid aluminum blocks.
• Vacuum grease that is difficult to evaporate is used for ball bearings.

Furthermore, when the motors are used in ultra-high vacuum environments, customization is available, such as the use of bearings with solid lubrication, in which only the inner race, outer race, and balls are coated.

Motor Reliability

Motor failures in vacuum environments can lead to serious problems. In particular, applications in which repair or replacement is difficult require extremely high reliability.

SANYO DENKI Vacuum Stepping Motors

• The coefficients of thermal expansion of individual components are carefully considered. For example, materials with similar coefficients of thermal expansion are used for the stator and flange, allowing assembly accuracy to be maintained even at high temperatures.

Motor Efficiency

In vacuum environments, heat is difficult to dissipate. Therefore, it is important for motors to deliver high torque with as little electrical power as possible. For this reason, motors with high efficiency must be selected.

SANYO DENKI Vacuum Stepping Motors

• The motor is designed to minimize losses caused by current flowing through the windings. 
• The design minimizes losses generated in the motor core.

5. Introduction to SANYO DENKI Vacuum Stepping Motors (2-Phase and 5-Phase)

Features

• These stepping motors can be installed and operated directly in vacuum environments without the need for rotary feedthroughs.
• They are actuators suitable for vacuum environments that enable high-precision positioning control with ease.
• Customization is available to suit a wide range of environmental pressures, from low vacuum to ultra-high vacuum.
• The allowable operating temperature is up to 200 °C.

Typical Operating Pressure Range

Applications

Semiconductor manufacturing equipment, electron microscopes, particle accelerators, synchrotron radiation analysis equipment, spacecraft robotic arms, and related applications.

Motor Sizes

□42 mm to □86 mm
Full customization is available to provide motors tailored to customer requirements. For more details, please feel free to contact us.

Customization

The usage conditions in vacuum environments vary depending on each customer. 
At SANYO DENKI, various customizations can be provided according to customer requirements. Please feel free to consult with us.

Examples of SANYO DENKI Customization

• Semiconductor wafer inspection equipment / Customization of cable materials
• Space station robotic arms / Full customization
• Vacuum deposition equipment / Customization to geared stepping motors
• Electron microscopes / Customization to geared stepping motors
• Nuclear-related equipment / Radiation-resistant customization for stepping motors
• LCD sputtering equipment / Customization to geared stepping motors, among others

Cooperation: SANYO DENKI CO., LTD. Servo Systems Division, Design Department 1 Sales Headquarters, Servo Systems Business Group

Release date: 2024-05-30 00:00