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What Is an Ultrasonic Sensor?

An ultrasonic sensor is a device that uses ultrasonic waves to measure the distance to an object.

Ultrasonic is a general term for sounds that have a high frequency and cannot be heard by humans. The human ear can detect frequencies between 20 Hz and 20,000 Hz, but sounds of higher frequencies are not audible to humans and are called ultrasonic.

Ultrasonic sensors generate ultrasonic waves and measure distance by detecting the reflected sound waves. In recent years, ultrasonic sensors have become more compact, lightweight, and inexpensive, and are therefore widely used.

Uses of Ultrasonic Sensors

Ultrasonic sensors are widely used in household and industrial applications. For everyday use, the advantage of non-contact distance measurement is utilized in such ways as in-vehicle rangefinders and jet towels. In-vehicle distance meters are rapidly becoming popular due to the mandatory use of collision damage reduction brakes.

Industrial applications include level gauges for wastewater tanks and chemical storage tanks. They are often used for highly corrosive liquids.

Fish finders also use ultrasonic sensors. This is an application of ultrasonic sensors that have been used for a long time.

Principle of Ultrasonic Sensors

Ultrasonic sensors measure distance by transmitting ultrasonic waves and detecting the reflected waves.

The speed of sound is determined by the atmosphere in which the sound, and is estimated to be 340 m/s in air and 1,500 m/s in water. If the propagating atmosphere is known, the distance can be converted by measuring the time it takes for the reflected wave to reach the receiving element.

The main component of ultrasonic sensors is the piezoelectric element. The piezoelectric element converts electrical energy into kinetic energy, and then back into electrical energy when pressure is applied via the reflected wave.

Therefore, the piezoelectric element performs both transmitting and receiving functions. It converts the input electrical signal into ultrasonic waves, senses the reflected waves, and outputs an electrical signal.

In principle, the advantages and disadvantages of ultrasonic sensors are as follows.

Advantages of Ultrasonic Sensors

• Non-contact detection of object distance
• Can detect transparent objects such as glass
• Possible to pass through even if there is some dirt or dust between the object and the sensor
• Ultrasonic waves are fast, so the sensor can detect moving objects

Disadvantages of Ultrasonic Sensors

• Easily affected by temperature and wind
• Soft and bumpy objects cannot be detected

The most important feature of ultrasonic sensors is that they can measure distances without contact. They are mostly used when non-contact measurement is required.

What Is a Digital Multimeter?

A digital multimeter is generally used to measure basic electrical characteristics such as DC voltage, AC voltage, DC current, and resistance. Higher-end models can measure more exotic power profiles, including those that capture complex AC-based data. For example, AC (Alternating Current) power is frequency-based. High-end digital multimeters are capable of capturing peak currents and average currents, which are stored at different positions on an AC waveform. This kind of data can be used to troubleshoot impedance issues, power factor correction problems, and much more.

On the device, while conventional voltmeters, ammeters, and resistance meters have analog displays in which the meter pointer indicates the measured value, a digital multimeter is called a digital multimeter because it has multiple measurement functions and three- to eight-digit numerical displays. Models with extended measurement functions such as capacitance, AC frequency, and temperature are also available.

Compact and lightweight models suitable for use at construction sites are also called digital testers. The number of digits displayed is about 4 digits, and the measurement accuracy is generally 0.05 to 0.1% for DC voltage and 0.5 to 1% for AC voltage. Although the accuracy is insufficient for precise measurements in the laboratory, they are easy to use for outdoor applications. In anticipation of such use, models with a sturdy construction to withstand drops are also available.

Uses of Digital Multimeters

Digital multimeters are used in a variety of situations, including measurements in laboratories, electrical adjustment of products on factory production lines, and construction and maintenance inspections of electrical facilities.

They are often incorporated into power-receiving equipment and power control panels. In such cases, in addition to basic parameters such as current, voltage, and resistance, some have built-in functions to measure capacitance, frequency, and temperature.

In addition to the specialized applications described above, inexpensive models are also available for use in general household electronic construction.

Principle of Digital Multimeters

The core of a digital multimeter (DMM) consists of a high-precision, high-resolution analog-to-digital converter (A/D converter) and a processor that calculates measurement values based on digital output. The A/D converter converts the analog signal acquired by the test procedure into a digitally recognizable measurement that’s then processed by a microchip. The means of collecting the analog measurement data are described as follows.

1. DC Voltage Measurement

The voltage between two probes is converted to a voltage within the dynamic range through an amplifier or attenuator that affects the voltage by either amplifying it (for low voltage) or attenuating it (for high voltage) to become the input voltage that’s transferred to the A/D converter. The processor calculates the voltage between the probes based on the digital value, amplifier gain, and attenuation factor of the attenuator, and displays the DC voltage value on the display unit.

2. AC Voltage Measurement

The AC voltage is converted to DC voltage through a rectifier circuit, then input to the A/D converter, and the AC voltage value is displayed on the display unit through the same process as DC voltage.

3. Resistance Measurement

A constant current is applied to the resistance to be measured through two probes from the constant current power supply built into the digital multimeters. The DC voltage appearing at both ends of the probes is input to the A/D converter to measure the voltage at both ends of the resistor to be measured. From this voltage value and the current value of the constant-current power supply, the processor calculates the resistance value to be measured.

4. Current Measurement

To measure DC current, the voltage at both ends of the micro resistor generated by the measured current flowing through in the digital multimeters is input to an A/D converter. The processor calculates the current value from the output value of the A/D converter and displays the current value on the display unit. For AC current, the AC voltage at both ends of the micro resistor is converted to DC voltage by a rectifier circuit and input to the A/D converter.

5. A/D Converter

The A/D converter of digital multimeters requires very high precision (high resolution), e.g., 24 bits or more for a 7-digit display, so a double-integral type is generally used. Therefore, the time required for conversion is relatively long, and several measurements per second is the most that can be done. However, by reducing the number of displayed digits and shortening the conversion time of the A/D converter, it is possible to shorten the measurement time.

How to Use the Digital Multimeters

A description of how to use digital multimeters follows

1. Voltage and Current Measurements

In digital multimeters, the system to be measured is connected between the two input terminals, the Hi and Lo terminals. When measuring DC voltage, connect the Hi terminal to the high voltage side and the Lo terminal to the constant voltage side, and the voltage on the Hi terminal side will be displayed based on the potential on the Lo terminal side. When measuring DC current, if the current to be measured flows in from the Hi terminal and out from the Lo terminal, the current value is displayed as positive, and in the opposite direction, it is displayed as negative. In AC voltage, current, and resistance measurements, polarity need not be taken into consideration.

2. Measurement Range Setting

For general use, the AutoRange function automatically switches to the optimum range for the voltage and current within the maximum input rating, so there is no need to search for the optimum range. However, if you need to reduce measurement time, such as when adjusting a production line, you will need to manually set the range based on the expected measurement value.

3. Effect on the Circuit to be Measured

Connecting digital multimeters may affect the system under measurement and cause fluctuations in measured values. For example, if digital multimeters are connected to a circuit with very high impedance, such as when measuring the output voltage of an optical sensor in a dark environment, its internal impedance may load the measurement system, resulting in a lower value than the original output voltage.

Similarly, when measuring the current of a circuit with a small impedance, the minute resistance for voltage detection present in the digital multimeters may cause a non-negligible error in the circuit under measurement. Therefore, the influence of the digital multimeters on the circuit under measurement should be considered before deciding whether or not to use digital multimeters.

4. Low Resistance Measurement

There are digital multimeters that can perform 4-terminal measurements for resistance measurement. As the term “4-terminal” implies, it consists of a pair of constant-current power supplies and a pair of voltmeters. A constant-current power supply is connected to both ends of the resistor to be measured. The voltmeter is connected to the constant-current terminals of the resistor to be measured.

The voltmeter measures the voltage at both ends of the resistor by placing a probe inside the constant-current terminals, at a point on the resistor side. The resistance is calculated from this measured voltage and the constant current value. Since the contact resistance of the constant-current terminal does not affect the measured voltage and the contact resistance of the probe of the voltmeter is negligible compared to the internal resistance of the voltmeter, which is typically as high as 10-MΩ, low resistance can be accurately measured.

What Is Semiconductor Inspection Equipment?

Semiconductor inspection equipment is equipment that inspects wafers and semiconductor chips for defects in the semiconductor manufacturing process.

The main semiconductor manufacturing processes include the photomask manufacturing process, which is equivalent to a printing plate, the wafer manufacturing process, which is the foundation of semiconductors, the front-end process of forming fine circuit structures on wafers using photomasks, and the back-end process of packaging individual semiconductor chips after circuit formation. If we look at the details, there are hundreds of processes.

In recent years, semiconductor microfabrication technology has reached the nanometer range (about 1/10,000th the thickness of a human hair), and at the same time, wafers have become larger in diameter, so that several thousand semiconductor chips containing billions of transistors can be produced from a single wafer.

Inspection equipment is extremely important in the semiconductor manufacturing process, which boasts such high productivity, leading to early rejection of defective products, cost reduction, and improvement of quality and reliability. The criteria for selecting semiconductor inspection equipment should take into consideration the diameter of the wafer, the process to be used, and the type of defects to be detected.

Uses of Semiconductor Inspection Equipment

Semiconductor inspection equipment is used in various phases of the semiconductor manufacturing process.

Defects to be detected using semiconductor inspection equipment include distortion, cracks, scratches, and foreign matter on photomasks and wafers, misalignment of circuit patterns formed in the front-end process, dimensional defects, packaging defects in the back-end process, and many other cases.

For this reason, it is necessary to select appropriate semiconductor inspection equipment and software for each process, and automation using AI, etc. is being promoted to speed up inspections and reduce manpower.

Principle of Semiconductor Inspection Equipment

Semiconductor inspection equipment consists of measurement equipment, software to process the measured data, and facilities to perform the appropriate measurement.

High-resolution cameras, electron microscopes, and laser measuring instruments are used as measuring devices. Software for processing the measured data is developed with algorithms that are specific to the process to be inspected. Vibration suppression and lighting equipment are also necessary to ensure proper measurement. The image imaging, image processing, and defect classification technologies that are central to semiconductor inspection equipment are described below.

• Image Imaging Technology
  Image imaging technology measures defects by irradiating a laser beam onto a wafer and then detects the scattered light. By illuminating minute irregularities, foreign matter and damage can be detected.
• Image Processing Technology
  Image processing technology is a technology that detects defects by comparing adjacent patterns, utilizing the fact that the patterns formed on all chips on the wafer are the same. It is capable of high-speed and wide-area processing.
• Defect Classification Technology
  Defect classification technology is a technology that, after detecting a defect, classifies the defect and extracts the cause. This technology is necessary to identify and address the causes of defects.

Types of Semiconductor Visual Inspection

1. Visual Inspection in Wafer Manufacturing Process and Front-End Process

Wafers are made from semiconductor raw materials such as silicon, which are formed as cylindrical monocrystalline materials called ingots, sliced to a thickness of about 1 mm, and polished on the surface, with a diameter of 12 inches (about 30 cm) these days.

Defects in wafers include not only attached foreign matter but also surface flaws, cracks, uneven processing, and crystal defects on the wafer itself, etc. Detecting these defects mainly by laser beam irradiation is the visual inspection in the wafer manufacturing process.

The front-end process proceeds in the wafer state, and there are two main types of defects that occur there, referred to as random and systematic. Random defects are mainly caused by the presence of foreign matter, but because they are random, their locations are unpredictable. Therefore, random defects on wafers are detected by image processing. Systematic defects, on the other hand, are defects caused by particles adhering to the photomask or exposure process conditions, such as on the photomask, and tend to occur at the same location on each semiconductor chip lined up on the wafer.

2. Visual Inspection in the Back-End Process

In the back-end process, wafers are cut into individual chips (dicing), placed in resin or ceramic packages, and sealed by connecting terminals on the chips to those on the package (wire bonding). The second stage of the process consists mainly of electrical inspections, but also includes visual inspections for wire bonding defects, part number printing defects, etc.

Other Information on Semiconductor Visual Inspection

1. Importance of a Semiconductor Visual Inspection

In general, visual inspections in the manufacturing process often aim to check for dirt, scratches, etc., and in some cases have nothing to do with product functionality or performance. However, dirt, scratches, etc. in semiconductor manufacturing are not merely apparent problems; in almost all cases, they are problems that affect functionality and performance.

Semiconductors are electronic devices, and like other electrical and electronic devices, electrical inspections are performed. However, it is extremely difficult to inspect all the billions of transistors and the wiring that connects them, and only visual inspections can confirm things like transistor gates and wiring detail.

2. Accuracy of a Semiconductor Visual Inspection

In semiconductor processes at the nanometer level, the thickness of a single wire and the spacing between adjacent wires are several nanometers.

If there are nano-order defects here, they can cause wiring shorts or wire breaks. Furthermore, even if the wiring width is 90% of the designed value due to a defect of 1/10th the size, the resistance and capacitance of the wiring will change. When an electric current flows through this wiring, a phenomenon called electromigration, in which metal atoms move due to the movement of electrons, occurs, rapidly thinning the wiring and causing disconnections to occur in a short period.

Thus, semiconductor manufacturing requires visual inspections with extremely fine precision, and as microfabrication technology continues to evolve, the required precision will continue to increase.

What Is an AC Power Supply?

AC power stands for alternating current power. It refers to power that changes direction and magnitude with frequency. Distributed network power, the lines that supply industries, commercial ventures, and homes all use AC power.

All electric power supplied by power companies to ordinary households is AC power. Air conditioners, refrigerators, lighting fixtures, and other home appliances that are plugged into electrical outlets all run on AC power. It’s the same with industrial premises: motorized pumps, large-scale refrigeration units, and even the control systems that manage all of these larger electrical machines, all supply AC power. Sometimes that power is supplied as a single-phase line, sometimes as a three- or four-phase line power supply, but it still travels as a frequency-regulated alternating current AC power supply.

In industrial applications, devices that convert direct current (DC) to alternating current are also called AC power supply and are widely used. Inverters may be required for these to run correctly.

Uses of AC Power Supplies

AC power supplies are used in a wide range of applications, from general home appliances to industrial equipment.

Many household appliances, such as hair dryers, air conditioners, and microwave ovens run on AC power. Kitchen appliances, multimedia devices, and wall sockets, all operate on AC power. Most industrial equipment, such as commercial refrigeration units, ventilation blowers for exhaust air, and industrial water pumps, are also powered by AC.

In the IT industry when referring to an AC power supply, the term uninterruptible power supply (UPS) is sometimes used. Uninterruptible power supplies are used to protect critical data servers and data storage. AUPS is a product that supplies AC power while charging the battery with commercial power during normal times, and supplies power from the battery when the commercial power goes out. An inverter is added to a UPS to ensure the batteries inside the unit are charged with DC power.

UPS is also used to supply uninterrupted AC power to precision equipment. Data servers are one example of such critical and precise equipment. Even the slightest disturbance of the AC power supplies can cause them to malfunction, making UPS essential. 

Simulators are also available to test whether electrical equipment can be damaged by intentionally creating disturbances in the AC power supply.

Principles of AC Power Supplies

Commercial AC power is mainly supplied by synchronous generators. Synchronous generators use electromagnetic induction to supply power.

Electromagnetic induction is the principle that voltage is generated when a magnet is placed close to or away from a conducting solenoid (such as a wound copper wire). Synchronous generators create electric power by the voltage generated from rotating the windings at high speed while generating a strong magnetic field inside. A mechanically induced source of kinetic energy supplies rotor-generated force. As that force acts on a rotor, the generator stator receives magnetically induced power. The speed of the generator decides the initial frequency of the AC power.

AC (regulated) power supplies in the IT industry can be broadly classified into two types: AC stabilizer type (AVR) and frequency converter type (CV/CF).

1. AC Stabilizer Type

The AC stabilizer type stabilizes the output voltage and waveform, while the frequency converter type also stabilizes the frequency.

AC stabilizer systems are broadly classified into SLIDAC systems and tap-switching systems. The SLIDAC method uses a servomotor (servo motor) or a similar device to continuously switch the taps of a transformer to maintain constant AC voltage.

The tap-switching method compares the voltage of the input AC current with a reference voltage, corrects the error, and outputs the result.

2. Frequency Converter Type

Frequency converter systems are broadly classified into linear amplifier systems and inverter systems. In both methods, the AC current is converted to a DC current.

The output voltage and frequency are then corrected using a linear amplifier (linear amplifier method) and a DC/AC inverter (inverter method) and put out as AC power supplies.

Advantages of AC Power Supplies

There are two major advantages of AC power supplies as follows.

1. Easily Transformable

AC power supplies can be easily transformed according to the winding ratio of the transformer. Long-distance power transmission can be done at high voltage to reduce losses, and power can be easily extracted by placing a transformer at the demand location.

Although it is possible to convert voltage using a DC power supply, the cost of the converter itself and the time required for the conversion are high. The greatest advantage of AC power supplies is that this method of adjusting voltage can reduce the equipment cost of power transmission and distribution. 

2. Easy Circuit Breakdown

AC power is characterized by cyclically alternating a positive and negative voltage. If you want to stop the current temporarily in the event of an accident or disaster, you can use the moment of zero current to interrupt the circuit, thereby minimizing damage to the electrical system and the circuit breaker itself.

Other Information on AC Power Supplies

Invention of AC Power Supplies

AC power supplies were invented by an inventor named Nikola Tesla. Tesla was born in what is now the Republic of Croatia and excelled in mathematics from an early age.

While a student at the Technical University of Graz, he saw a “gram generator” (a device for generating a direct current that functions as both a generator and a motor), which inspired him to think about ways to improve power generation. Five years later, he succeeded in inventing the world’s first AC current generator, the two-phase AC motor.

Tesla then developed his ideas on alternating current and went on to work for Thomas Edison, who was famous for inventing direct current. However, Edison was against Tesla’s invention of the AC current.

Both Edison and Tesla appealed to the usefulness and safety of the current they had invented, and a “DC current Edison vs. AC current Tesla” configuration was later created. After this confrontation, Tesla’s alternating current was recognized by the public, and today alternating current is indispensable.

What Is a Micropump?

Micropumps are small, precision pumps.

They are used in analytical instruments and in the medical, biotechnology, and nanotechnology fields for controlling and manipulating microscopic liquids. Micropumps can be classified into mechanical types, which require a mechanical power mechanism, and non-mechanical types, which are driven by physical external forces.

Applications of Micropumps

Micropumps are used in precision instruments, medical devices, biotechnology, and nanotechnology. They also play an important role in devices that are becoming increasingly miniaturized.

For example, in medical devices, micropumps are used for insulin infusion in artificial kidneys and built into artificial hearts. They are also used in rare chemical experimentation and have many other uses across various fields.

Mechanical micropumps are most commonly sold, but non-mechanical micropumps may be more appropriate for some applications.

Principle of Micropumps

Micropumps consist mainly of a pump head and a driver. The pump head transports the fluid and is usually made of silicon. The driver moves the pump head and is generally controlled using electrical signals. They also comprise other electronic components, such as control circuits and power supplies.

There are also pressure-driven, non-mechanical, and light-driven pumps, micropumps operated by nanomotors, and even micropumps that use capillary action.

1. Pressure-Driven Pumps

Pressure-driven pumps use the pressure differences inside and outside of a pump to move liquid. By increasing the pressure inside the pump to push the liquid out, the external low pressure creates the force to suck the liquid out.

Pressure-driven micropumps are highly accurate and reliable, and there are many types available for a variety of applications. For example, there are some designed to handle high pressures and others suitable for moving minute amounts of liquid. The relatively simple structure makes them low-cost to manufacture and suitable for a wide range of applications.

2. Light-Driven Micropump

Light-driven micropumps use light energy to move liquids. Shining light onto the surface of the liquid generates the pressure needed to move the liquid. They are mainly used in the biotechnology field and can pump liquid through minute channels.

However, since light-driven pumps require a light source, they are susceptible to external influences, and their performance may vary depending on the light intensity and direction of the light source.

3. Nanomotor Micropump

Nanomotor micropumps use nanomotors, which can convert intracellular energy into mechanical movement, to transport liquids. Driven by an energy source such as a magnetic or electric field, they can operate even in very small spaces. 

4. Capillary Micropump

Capillary action micropumps use capillary action to transfer liquid in a minute flow path.

A thin tube is placed inside the microchannel and filled with liquid. Then, the surface tension created by bending the narrow tube propels the liquid upward. This makes it possible to transfer liquid through very small channels.

Features of Micropumps

The most important feature of micropumps is their small size. Since they can move fluids through such small channels, they can be used in many microscale applications, such as microfluidics research and the development of tiny biochips.

Micropumps can also be manufactured at a low cost due to the small number of components required for a pump and the relative ease of manufacture. This facilitates mass production and is widely used in fields such as medicine and biology.

What Is a Network Analyzer?

A network analyzer is a test instrument that evaluates the network characteristics of a device under test (DUT). This is done by measuring certain key S-parameters on multi-port networks.

Specifically, it can measure the attenuation and impedance of the input signal to the DUT. In particular, it can evaluate the high-frequency characteristics of electronic components, etc., and has a wide range of applications, including the ability to perform measurements on transmission devices. Such measurements can be conducted on microwave systems, common WIFI networks, corporate networks, basic computer-to-computer connections, and even on large-scale cell phone networks. 

The output of a network analyzer is represented by the S-parameter (scattering parameter), which defines the physical quantities known as forward reflection (S11), forward transmission (S21), reverse transmission (S12), and reverse reflection (S22). This is typically the case with a 2-port network, but the devices or connections being tested may have more than 2 ports. Whatever the network situation, the correct Network Analyzer must be chosen to match the number of ports present. This is a basic premise but an important one if the reflection and loss parameters are to be accurately calculated.

Uses of Network Analyzers

Network analyzers are broadly classified into scalar network analyzers and vector network analyzers (VNA), of which vector network analyzers (VNA), which provide not only amplitude information but also phase information, have a wider range of uses.

The advantages of network analyzers for high-frequency applications are used in the development of matching circuits for high-frequency amplifiers. Here, the design is based on accurate S-parameters for each amplifier, antenna, and/or filter.

In many cases, a network analyzer is also used to evaluate impedance matching. This is because impedance mismatch in the transmission lines of each device or cable in a high-frequency handling circuit network can cause power loss or signal distortion.

Principles of Network Analyzers

A network analyzer is equipped with a signal source, a signal separator, a directional coupler, and at least three receivers.

• Signal Source                                           
  The signal source provides the signal to the system and is supplied by a synthesizer module.
• Signal Separator                                        
  The signal separator uses a resistor splitter to split the input signal into circuit signals and receivers (reference signal R).
• Directional Coupler                                    
  The directional coupler separates the input wave from the reflected wave, which is measured at the receiver (reference signal A).

The output of the DUT is measured at a third receiver (transmission signal B). Evaluation is performed by comparing the signals (e.g., S11 is defined by A/R and S21 by B/R).

Accurate measurement of the network analyzer is ensured by precise calibration. For calibration, a standard device with known characteristics is used. A commonly used calibration method is the SOLT method, in which a short-circuit, open-circuit, and load-capable standard are coupled to a reference plane in a direct connection (thru).

Since this is a very precise measurement, care must be taken to avoid measurement errors in various aspects such as connector tightening torque, ambient temperature, input signal, cable stability, etc.

Other Information on Network Analyzers

1.  Basic Knowledge of Network Analyzers  

There are two types of network analyzers: vector network analyzers (VNA) and scalar network analyzers. Vector network analyzers are widely used these days.

Network analyzers have a method of measuring amplitude changes in transmission and reflection measurements called S-parameters. S-parameters are also called S-matrices, and there is a numbering system for their definition. The numbering scheme is “Sij i=output port, j=input port,” where S11 represents the coefficient of a signal incident at port 1 that has been transmitted to port 1, S12 represents the coefficient of a signal incident at port 2 that is transmitted to port 1.

The S parameter can be measured by using a VNA measuring instrument. However, the VNA must be calibrated using several calibration methods before measurement.

The basic method of VNA calibration is to use three standard instruments. Widely known calibration methods include the SOLT calibration method, the UnKnown Thru calibration method, and the TRL calibration method described above.

2. About Impedance Measurement

Impedance is an important parameter used to characterize electronic circuits, electronic components, and electronic materials. It is the amount of opposition to an alternating current (AC) that interrupts a circuit or other device at a certain frequency. There are various types of impedance measurement methods, each with its advantages and disadvantages.

The measurement method must be selected in consideration of the frequency range required for the measurement and the resistance and reactance conditions of the impedance measurement range. Measurement methods include the bridge method, resonance method, I-V method, network analysis method, time domain network analysis method, and automatic balanced bridge method.

The bridge method is explained as an example. The advantages of the bridge method are its high accuracy (around 0.1%), its ability to cover a wide frequency range with multiple measuring instruments, and its low cost. On the other hand, one demerit of the bridge method is that it requires a balance operation, and a single unit can cover only a narrow range of frequencies. The bridge method’s measurement frequency range is approximately 300-MHz DC.

3. Trends in Frequency Extension

The maximum frequency extension of network analyzers now extends into the sub-THz band (220 GHz). This is because it is predicted that the next generation communication standard, 6G, will most likely use the 140 GHz band, known as the D-band.

However, because of its high frequency, the sub-THz band is susceptible to electrical length errors, parasitic elements, and other measurement discontinuities, making total calibration accuracy, including that of the RF probe tips and cables, extremely important.

In reality, the frequency range that can be calibrated at one time is often limited, and manufacturers are competing to develop easy-to-use measuring instruments, including the handling of data between calibrations and the addition of frequency extenders dedicated to the millimeter wave band.

4. Addition of Modulated Power Evaluation Function, Etc.

Generally speaking, Network analyzers are used to evaluate the impedance of DUTs and S-parameters, which are small signals. Therefore, models that enable network analyzers to perform modulation analysis, which is mainly handled by conventional spectrum analyzers, are gradually being released. With wireless technologies on the increase, the ability to examine complex RF (Radio Frequency) bands is an essential feature, one worth integrating into a Network Analyzer.

In the future, network analyzers will be used not only for impedance and S-parameter evaluation but also for evaluating switches, filters, high-frequency (RF) amplifiers, low-noise amplifiers (LNA), and other RF front ends, including large-signal analysis and modulation analysis.

What Is a High Voltage Power Supply Unit?

A high-voltage power supply unit is a power supply unit that handles particularly high voltages.

High voltage generally refers to voltages ranging from several thousand volts (V = volts: a unit of voltage) to several tens of thousands of V or higher. The voltage transmitted by power companies is 6.6 kV or higher, but high voltage is generally defined as 600 V AC (750 V DC) or higher.

The electrical appliances we use in our daily lives have low voltages of 100 VAC or 200 VAC. This is due to the fact that the standard power supply voltage transmitted from the power company’s generation facilities to each household is either 100 VAC or 200 VAC.

Although typical power supply units are 100 VAC or 200 VAC, some equipment may want to generate higher voltages depending on the conditions of use. Specifically, these are devices that require higher voltages than the power supply voltage or devices to be tested for tolerance to high voltages. In order to clear this requirement, a transducer that generates higher voltage than the power supply voltage used by general users is needed. High-voltage power supply units are used in such cases.

Uses of Applications of High Voltage Power Supply Units

High-voltage power supply units are mainly used for operating products that require high voltages and to withstand voltage testing.

Examples of equipment that require high voltage include equipment used for painting automobile bodies and construction materials, equipment used for surface treatment of metals and plastics, X-ray radiation equipment used for radiation therapy and x-rays, and electron microscopes.

Pressure resistance testing is performed on industrial electrical equipment such as electric wires. Products are often tested to withstand voltages of 1500 V for 1 minute or 1800 V for 1 second before shipment, and that insulation withstand voltages be tested. Therefore, the introduction of high-voltage power supply units is mandatory. They are also used for practical training to acquire qualifications as high voltage and special high voltage electricity handlers.

Principle of High Voltage Power Supply Units

High-voltage power supply units are converters that input general AC power transmitted to the end of the line and output it as high-voltage. A converter is a device (unit) that converts the AC power supply voltage transmitted from the power company into DC voltage using a circuit with diodes called a rectifier and smoothes the voltage with an electrolytic capacitor.

However, simply using a converter unit will only output a DC voltage that is smoothed at a low voltage because it is 100V or 200V, and will not provide the high voltage of 10 times or 100 times or more the voltage originally desired. It is possible to boost the voltage simply by the turn ratio of the step-up transformer, but the turn ratio has a practical limit.

To obtain a high voltage, a Cockcroft-Walton circuit combining a diode and a capacitor is used. This method uses the storage capacity of the capacitor and the rectifying action of the diode. After the capacitor stores electricity in response to an AC input in one direction, the voltage is boosted when a current flows in the opposite direction.

This circuit method is commonly used to raise the voltage by layering the rectifier-based circuit described earlier and is also referred to as a doubling voltage circuit or a high-voltage generator circuit among technical personnel. Since the voltage increase is an even multiplication, it is not possible to boost the voltage by an odd number of times. High voltages of 1 kV or higher can be obtained by combining an appropriate high voltage diode and ceramic capacitor.

Other Information on High Voltage Power Supply Units

1. High Voltage Power Supply Module

High-voltage power supply modules are high-voltage compatible power supply units capable of supplying high voltages that generally generate 1 kV or more.

Among these, power supply unit manufacturers with an established reputation for their technological expertise in downsizing through higher efficiency while ensuring low noise and reliability have achieved low prices by improving the quantity and ease of use of their products, and have modularized their high-voltage output power supply modules as general-purpose products.

Major manufacturers and products of high-voltage power supply modules include the OHV series by Bellnix, the TCR series by American High Voltage; the HGP series by Matsusada Precision, HitekPower by General Products; the TMK series by Takasago Machinery Works, the C14051 series by Hamamatsu Photonics, etc. The more the output current increases in addition to the original high voltage, the larger the size of the module becomes. Therefore, it is necessary to select a module with attention to its margin, temperature rise, and dielectric strength depending on the actual use of the load. 

2. High-Voltage Power Supply Board

The substrate of a high-voltage power supply is a high-voltage circuit, so there are some precautions that must be taken for the substrate used in the high-voltage circuit. This is because the higher the voltage, the more the standard requires that the insulation distance of the board be sufficiently secured. The higher the voltage is, the greater the possibility of serious electric shock during work. To ensure safety, safety measures against withstand voltage and electric shock must be taken, including the creepage distance and insulation distance of the circuit board and the installation of safety grounding.

In practice, the IEC standard absolutely requires a board pattern design that ensures insulation distances between conductive copper foil patterns on the board based on each country’s standards. Failure to comply with this requirement may result in fines or other penalties as a violation of the law, and not only penalties, but also a loss of social credibility. Therefore, both the manufacturer and the user must be very careful to ensure that the insulation distance of the board pattern meets the standard.

塗布装置とは

塗布装置とは、製品や材料に薬品などを塗布するための装置です。

一般的な塗布装置は、塗布する対象物の形状や塗布する薬品と塗布の目的によって塗布方法が異なるため、さまざまな用途に応じてロールコータやスピンコータ、ディップコーター、スプレー塗布やディスペンス塗布など、さまざまな塗布方法が用いられています。

近年では、半導体製造分野やFPD (フラットパネルディスプレイ) 製造分野、太陽電池や二次電池製造分野などの工業分野においては、精密な塗布精度が求められるため、塗布技術の向上と共に塗布装置が飛躍的に進化しています。

塗布装置の使用用途

塗布装置は、半導体分野や二次電池など様々な製造工程で対象物に塗液を塗布する用途で使用されています。パソコン、液晶テレビ、スマートフォン、タブレットなど、特に薄型で高機能・高密度化が求められる半導体製造分野やFPD (フラットパネルディスプレイ) 製造分野におけるフォトリソグラフィ工程で、フォトレジストを塗布するスピン塗布装置を利用する場合が多いです。

二次電池や太陽電池、自動車部品から住宅建材・繊維・医療などで使用される機能性フィルムやシート状製品に対しては、シール材や接着剤、電極材をなどの薬品を塗布するロール塗布装置やスプレー塗布装置、ディスペンス塗布装置などが利用されています。

塗布装置の原理

図2. 塗布装置の特徴

塗布装置は、さまざまな生産品材料への対応や薬液などの材料を塗布する装置です。主にロール状塗布、スピン塗布、スプレー塗布、ディスペンス塗布に大別できます。

1. ロール状塗布装置

ロール状塗布装置は、一般的にフィルムやシートなど比較的薄く平面材料に対する塗布に用いられます。

塗布する薬液の液溜まりに接するローラーの回転とフィルムやシートなどの材料の巻取り回転を利用して塗布するグラビアコーター、リバースコーターなどを塗布する薬液の性質や粘度、塗布する膜厚に応じてさまざまな塗布方法が用いられます。

ロールtoロールでの塗布が可能で、最も高速塗布にむいた方法です。これらの方法の特徴は、塗布液と被塗布対象物の間で、ビードを形成し被塗布対象物、または被塗布対象物とロールの両方が移動したり回転したりすることで塗液にせん断力をかけ薄く塗布することです。

このビードを安定化させることが、高品質な塗布に欠かせません。

2. スピン塗布装置

スピン塗布装置は、半導体製造分野やFPD (フラットパネルディスプレイ) 製造分野におけるフォトリソグラフィ工程で使用するフォトレジストを回転するテーブル上の生産品に吐出後、テーブルが回転する遠心力により薬液の広がる作用を利用して薄膜を形成する塗布方式を採用する装置です。

最も薄く塗布できる手法ですが、複数枚の塗布や連続生産ができないため大量生産には不向きです。

3.  スプレー塗布装置

スプレー塗布装置は、自動車や外壁建材などの塗装に対して薬液をスプレーで微細粒子に変換して塗布し、塗布対象物が大型の場合、ロボットの広域可動範囲を利用することで高精度且つ広範囲の塗布方式を採用する装置です。

空気、電気、超音波の3種類の粒状噴霧を生成する方式が存在します。

4. ディップ塗布装置

ディップ塗布装置は、対象物の形状は問わず、ディップコート液に浸けて引き上げる方式です。均一な薄膜を形成することが可能で、光学レンズ、医療系や電子デバイスなどに用いられています。

対象物の形状は問わず、塗布液のロスが少なく均一な薄膜を形成することができる点がディップ塗布装置の特徴です。

5. ディスペンス塗布装置

ディスペンス塗布装置は、比較的精密な線状塗布が求められる状況で使用されます。塗布量のコントロールが可能なディスペンスー機構を備え、更に精密な塗布が要求される場合には、ロボットを用いることで塗布量の精度と正確性を兼ね備えた塗布方式を採用する装置です。 もちろん塗布速度などは劣りますが、細かいところへのスポット塗布や複雑な形状の塗膜が形成可能です。

塗布装置のその他情報

塗布欠陥と塗布装置

図3. 塗布欠落と塗布装置

どんなに高性能な塗布装置にて塗布を行ったとしても、粘度のあわない塗液や塗布速度などの塗布条件によっては綺麗な塗布面が得られないことがあります。コーティングの欠陥の種類とその対処法は、下記の通りです。

1. 塗布によって発生する欠陥

欠陥	原因	対処法
空気同伴	被塗布物に塗液を塗布する際に、空気が逃げ切れないことで発生。	塗布速度を低下させることで解決。
リブスジ	塗布部に塗布方向に対して逆圧力勾配ができることで発生。	塗液の粘度や塗布速度を低下させることで解決。
気泡混入によるスジやホール	塗液中に泡があることで発生。	泡抜き対策を施す。
横ダン状のムラ	主にリバースグラビア方式などで発生。	被塗布物の振動抑制やグラビアの回転速度を変えることで解決。
ムラ	塗液が塗膜内で流動をおこすことで発生。	塗液を改善することで対応する。
異物	塗液が凝集したり、ゲル状になることで発生。	フィルターを導入するなどで対応する。
はじき	塗液の表面張力が高いことで発生。	界面活性剤などを添加することで対応する。

 

2. 乾燥によって発生する欠陥

欠陥	原因	対処法
ゆず肌 (塗面がゆず皮のように凹凸になる)	乾燥速度が早すぎることで発生。	乾燥速度を弱くしたり界面活性剤を添加することで対応。
風紋	熱風乾燥で発生。	吹き付ける熱風の速度を弱めることで対応する。
割れ	塗膜の収縮によって発生。	厚塗りをやめることなどによって対応する。

 

コーティングは塗布装置と乾燥と塗液をそれぞれ適切に選択することで、成立する技術です。使いたい塗液の条件や乾燥炉のスペックなども考慮して、適切な塗布装置を選択することが大切です。

参考文献

https://www.keyence.co.jp/ss/products/measure/sealing/coater-type/