月: 2022年9月

What Is Heat Shrinkable Tubing?

Heat shrinkable tubing is tubing that has been processed to shrink when heat is applied.

It is a molded resin tube that has undergone radiation treatment and is widely used mainly to protect and insulate electric wires. To use, simply pass the wires through the heat shrinkable tubing and apply heat with a heat gun or similar device. The process is simple and can be used in any work environment.

Uses of Heat Shrinkable Tubing

Heat shrinkable tubing is a material that shrinks to fit the covered wires, and is mainly used to protect, insulate, waterproof, and prevent corrosion of wires and parts.

Specific applications are as follows:

• Internal wiring used in home appliances
• Internal wiring used in electronic products
• Power feed wiring for industrial equipment
• Wiring harnesses for automobiles
• Surgical equipment for laparoscopic surgery

Principle of Heat Shrinkable Tubing 

Heat shrinkable tubing is made of high molecular polymers such as polyethylene and various elastomers. These materials have the property of shrinking under heat while retaining their flexibility.

The above polymer polymers are irradiated with electron beams to induce a cross-linking reaction during the tubing manufacturing stage. When the tubing after the cross-linking reaction is heated and stretched, it solidifies while remaining elongated, and when heated again, the tubing shrinks and returns to the size it was before being stretched. This is the principle of Heat Shrinkable Tubing.

Types of Heat Shrinkable Tubing

Heat shrinkable tubing can be classified into single-layer Heat Shrinkable Tubing and double-layer Heat Shrinkable Tubing, depending on the difference in structure.

When heat is applied, the tubing shrinks in the diameter direction, and the shrinkage ratio is approximately 2:1 to 3:1. Materials include rubber-based, PE-based, fluoroplastic-based, and silicone resin-based. There are many types of Heat Shrinkable Tubing, so proper selection is essential.

1. Single Layer Heat Shrinkable Tubing

One-layer heat shrinkable tubing is a common type of tubing and is divided into “thin-wall,” “medium-wall,” and “thick-wall” types based on the thickness of the tubing. The purpose of single-layer Heat Shrinkable Tubing is to provide insulation or partial protective guarding. Each color of tubing is sold in different colors and can be used for identification.

2. Two-Layer Heat Shrinkable Tubing

Two-layer heat shrinkable tubing consists of two layers, an inner layer and an outer layer. It is used for electrical insulation and mechanical protection. Due to the thicker layers, it may be used to protect against humidity and corrosive environments. Like single-layer heat shrinkable tubing, it is sold in various colors for identification purposes.

Other Information on Heat Shrinkable Tubing

1. How to Use Heat Shrinkable Tubing

Heat shrinkable tubing is selected so that the inner diameter after shrinking is thinner than the object. The length will also shrink slightly, so select and cut a slightly longer length. Shrinkage rates also vary depending on the material, so check the heating conditions before working with it. When cutting, it is important to align the cut surface neatly, as the cut surface may break.

Heat shrinkable tubing generally shrinks from about 120℃, so a heat gun should be used as the heating device. Low-temperature types shrink from about 80°C, so they can be worked with a hair dryer. A soldering iron can also be used in place of a soldering iron for small diameters and small quantities. In this case, care should be taken to prevent the tip of the iron from touching the surrounding area. 

2. Cautions for Heat Shrinkable Tubing

Heat shrinkable tubing requires the use of a heating apparatus. To use it safely, it is essential to be careful of burns and to use the apparatus properly. In particular, when using an open flame such as a gas burner, the tube will melt due to overheating, so the flame must be turned off at the appropriate time.

In addition, when wrapping items with good heat conductivity, such as metals, it is difficult to shrink them because they easily lose heat during heating, and this can be handled by applying heat for a longer period of time than usual. Never use it for electrolytic capacitors, secondary batteries, etc. This is because they may burst due to heating. Therefore, working near them should also be avoided as much as possible.

What Is an Anemometer?

An anemometer is a device that measures the speed of the wind. Anemometers measure the speed of the wind and display it in units such as m/s or knots. Anemometers can be used to measure various wind speeds, such as those caused by atmospheric conditions, wind caused by rotation, and wind coming out of air conditioning exhaust vents.

Wind speed is a vector quantity. For this reason, many anemometers can measure both wind speed, which is a magnitude, and wind direction, which is a direction. Anemometers are available in a variety of operating principles. For example, anemometers include wind cup anemometers, windmill anemometers, ultrasonic anemometers, and thermal anemometers.

Uses of Anemometers

Anemometers are used in many everyday applications. For example, they are used for repair and maintenance of air conditioners, and to measure the anemometric velocity of gases from exhaust vents. Anemometers are also used to determine atmospheric conditions for meteorological observations.

There are several types of anemometers, including windmill, ultrasonic, thermal, and wind cup types. The most common type of anemometer is the windmill type, which is used by organizations, such as the Japan Meteorological Agency. Anemometers of the windmill or wind cup type are used for the purpose of measuring outdoor wind speed. The characteristic feature of their use is that they are installed outdoors and measure the degree of wind speed outside by rotation.

Anemometers of the windmill and wind cup types have been increasingly digitized in recent years. The digitalization of anemometers makes it possible to check the wind speed at a distance from the location where the Anemometer is installed. Real-time wind speed can be checked on a PC or smartphone indoors. Anemometers mainly used indoors are thermal and ultrasonic types. Thermal and ultrasonic anemometers are often portable.

Thermal and ultrasonic anemometers are used by placing the instrument directly on the area where the wind speed is to be measured, or by hand, and by taking continuous measurements on the spot. Both thermal and ultrasonic anemometers provide instantaneous wind speed data at your fingertips. They are also characterized by their flexibility of use, as the installation position can be easily changed. However, care must be taken to ensure that the wind speed is not affected by the movement of people.

Types of Anemometers

In general, to measure wind speed, one must decide the purpose and under what environmental conditions the results are desired. The type of anemometer to be used depends on whether the measurements are to be made indoors or outdoors.

There are four types of anemometers: wind cup anemometers, windmill anemometers, ultrasonic anemometers, and thermal anemometers.

1. Anemometer

Anemometers use a cone-shaped blade called a wind vane. The wind speed is calculated by measuring the number of rotations of the rotating blades with a generator or rotary encoder. The wind speed is not related to the direction of the wind, but only to the wind speed, making it very sensitive to wind changes.

2. Anemometer With Wind Turbine

Anemometers use propeller-like blades that are rotated by the wind. Wind speed is measured by using the rotational speed of the rotating blades, which is measured by a generator or other device. Anemometers that can simultaneously measure wind direction by attaching a propeller to one end of the anemometer and a weathervane to the other end are common. 

3. Ultrasonic Anemometer

Anemometers measure wind speed by measuring the amount of change in the speed of sound, which varies with wind speed. The ultrasonic wave is transmitted from the transmitter and received by the receiver, and the time taken from transmission to reception is used to measure the wind speed.

4. Thermal Anemometer

Thermal anemometers use the temperature change of the measuring section cooled by the wind. The anemometer measures the wind speed by measuring the electrical signal generated from the temperature sensing element. Some thermal anemometers can measure not only wind speed but also humidity and pressure at the same time.

How to Select an Anemometer

Anemometers have a variety of measurement principles, so care must be taken when selecting one. For example, some anemometers are resistant to rain and snow, making them suitable for outdoor use, while others are suitable for use in clean rooms and other manufacturing sites where precision is required.

Anemometers should therefore be selected appropriately according to the application for which they are to be used. Anemometers are used at workplaces, to measure the effectiveness of smoke control, and so on. Recently, however, there are more and more opportunities to measure wind speeds close at hand. For example, you may check wind speed and flow when playing golf, sailing or other outdoor activities, or when using the air conditioner at home.

When selecting an anemometer, the most common type of anemometer is the compact type. Anemometers of the compact type are available in windmill and thermal types, and can be purchased at reasonable prices by the public. The advantage of the compact type Anemometer is that it is a handheld type. Anemometers are characterized by their light weight, which makes them convenient to carry.

In addition, since the measurement result display screen is integrated with the instrument, the wind speed measurement results can be checked immediately. Anemometers of the handy windmill type are mainly used for outdoor leisure and sports activities. Thermal anemometers, like windmill anemometers, are also available at reasonable prices. Thermal-type anemometers can be used to measure wind speeds mainly outdoors and at home under conditions where an air conditioner or circulator is used.

What Is a Power Relay?

Power relays are relay components capable of carrying a current greater than 3A.

Relays can be roughly classified into two types: contact relays and non-contact relays, and power relays are contact relays. Power relays are of robust construction to withstand large currents, as they are expected to carry larger currents than general control relays.

Because of their characteristics, power relays are sometimes used as relays for safety circuits when an abnormally large current flows in a circuit.

Uses of Power Relays

Power relays are one of the most widely used components in industry.

The following are examples of power relay applications:

• Circuits for solar panels and their power feeders
• Driving large powered robots
• For driving elevators and heavy equipment at construction sites
• In charging facilities for electric vehicles, etc.
• Main circuits of hybrid cars

Principle of Power Relays

Power relays are composed of terminals, contacts, and electromagnetic coils. 

1. Terminals

The terminal is the part that connects to the wiring. In many cases, Power Relays are fixed to the wiring by solder wear. In other cases, Power Relays are mounted on a terminal block unit and the wiring is connected to round terminals or other terminals that have been processed. 

2. Contacts

Contacts are driving components that provide a path for electricity. There are larger and more numerous contacts with a higher current application.

To reduce electrical resistance, silver alloys and gold are used for contacts. Silver alloys are widely used because of their low electrical resistance. Gold alloys are more resistant to oxidation than silver alloys, but they have a lower melting point and are more expensive, making them suitable for small loads.

There are two types of contacts in power relays: movable contacts and fixed contacts. Fixed contacts are firmly fixed to the casing or other components. The movable contacts are driven together with the movable iron strip, and when they make contact with the fixed contacts, they conduct electricity. 

3. Electromagnetic Coil

The electromagnetic coil is a component that drives the movable iron strip by electromagnetic force. The movable iron strip has a movable contact point, which is brought into contact with the fixed contact point by the electromagnetic force of the electromagnetic coil. When the electromagnetic coil is de-energized, the contacts are pulled apart or in contact with each other by a spring.

Types of Power Relays

Power relays are broadly classified into DC-driven relays and AC-driven relays.

1. DC Driven Power Relay

DC-driven relays are power relays in which the coil is driven by a DC power source. DC power sources are resistant to inductive voltages and are characterized by stable operation even at low voltages. The relay coil is often connected to a diode to prevent reverse current.

The standards include 5 VDC, 12 VDC, 24 VDC, etc., which are used according to the intended use. A 24V power supply with a higher voltage is used when the transmission distance is long or when a relay circuit is built in a control panel. For intrinsically safe explosion-proof circuits, 12 VDC, 5 VDC, etc. are used.

2. AC-Driven Power Relay

The AC drive is a power relay whose coil is driven by an AC power source. The commercial power supply is AC power and can be used directly, eliminating the need for a power supply required for the DC version.

Coil voltages of 100 VAC or 200 VAC are used; AC400 V control circuits are rarely used due to the difficulty of maintaining isolation distances.

Other Information on Power Relays

Power Relay Failures

Power relays are mechanically actuated by electromagnetic forces and have a limited life span. The life expectancy in terms of number of operations is about several hundred thousand times.

If the life is exceeded or excessive shocks are applied, the following failures can occur:

1. Coil Disconnection
This is a failure in which the electromagnetic coil in the power relay is disconnected. The coil disconnection causes all contacts to cease operation. This failure is relatively easy to detect because there is no sound of the contacts operating. 

2. Welding
This is a failure that occurs when excessive current flows through the power relay, causing the contacts to weld together and not open. Diagnosis is made by switching the relay on and off and checking the continuity of the contacts.

3. Inoperative Contacts
This is a malfunction in which the relay contacts become frayed or dirty, resulting in a loss of electrical continuity. The contacts remain open without shorting. Diagnose by checking continuity and voltage, as in the case of welding. 

4. Short-Circuiting of Coils
This is a failure that occurs when the varnish on the electromagnetic coil peels off, resulting in a short circuit. When the electromagnetic coil is energized, the control power supply itself is tripped, and this is identified.

Since control circuits often have multiple power relays connected in parallel, it may take some time to detect the fault.

What Is a Build-Up Board?

A build-up board is a printed circuit board consisting of multiple layers.

The use of build-up substrates allows the use of high-density substrates in a small area, making it possible to create multifunctional products, even for small devices. Build-up substrates consist of layers of conductors and layers of insulators stacked on top of each other, with laser drilling and wire processing to penetrate the layers, making it possible to obtain complex substrates in a small area.

Emergence of Build-up Substrates

With the increasing density of substrates, it has become increasingly difficult to deal with the current via-hole structure alone. The development of cell phones has led to the demand for lighter, smaller, and more compact substrates, and substrates that can handle these demands have become necessary. Build-up boards began to appear around 2000 and have continued to the present day.

As the name “build-up” implies, it refers to a printed circuit board with many layers stacked on top of each other. Normally, a multilayer board can be built up into a single layer, but since it is built up many times, the number of processes increases, which means that it costs more. However, the use of this method is gaining momentum due to its ability to reduce wasted space and make small holes with a laser.

Reason 1: to reduce wasted space

When using via holes (holes to connect other layers) on a multilayer board, wiring cannot be done outside of the connecting layer because of the vias. Therefore, wiring efficiency will not be improved even if a multilayer board is used.

Reason 2: small holes can be drilled with a laser

Advances in equipment have made it possible to drill smaller holes at higher speeds with lasers than with drills. When drilling with a drill, the hole will penetrate the underlying layer. On the other hand, with lasers, it is possible to drill holes in the resin and stop the process on the copper, depending on the combination of conditions. Therefore, by repeating the process of drilling holes with a laser, plating, and then building up the next layer and processing it with a laser (build-up), the area of the via holes can be effectively used and high-density is possible.

By using build-up substrates, high-density substrates can be used in a small area, making it possible to create multifunctional products, even for small devices. Complex substrates in small areas can be obtained.

Uses of Build-up Substrates

Build-up substrates are widely used in small, lightweight electronic devices. When build-up substrates were first commercialized, they were used in PCs and cell phones. Today, they are used in small measurement devices, and IoT devices such as smart meters, digital camera modules, and PC peripherals.

The accuracy of drilling and other operations in the build-up board manufacturing process has a set standard, and it is necessary to choose exactly what level of accuracy to request when requesting the creation of a build-up board.

Build-up Substrate’s Process

This section describes the manufacturing process of build-up boards. The manufacturing process for build-up substrates includes insulator layer formation, via processing, smear removal, and plating on vias. Each of these processes is described below.

Formation of the Build-Up Layer

An insulator layer is built up on top of the printed circuit board. Prepreg, a rigid material, is used in some cases, while film is used in others. Prepreg is often used for digital cameras, smartphones, and semiconductor packages.

Via Processing

This is the process of drilling holes called vias in the insulator layer between substrates. Currently, holes are generally drilled using lasers.

Various types and wavelengths of lasers are used, including carbon dioxide gas and UV-YAG. Carbon dioxide lasers have a long wavelength (infrared) and are commonly used in digital cameras and smartphones, while UV-YAG lasers have a short wavelength (ultraviolet) and are used in high-density areas such as semiconductor package substrates.

Resin Residue Removal (Desmear)

The residue generated by laser processing is called smear. Resin residue cannot be connected, so it must be removed.

This process is called desmear. If the smear remains on the build-up substrate, it will lead to poor connections, etc., so it must be removed without fail. A strong chemical (potassium permanganate) must be used to remove the smear. However, recent high-speed resins may not be able to remove the smear by themselves, so plasma or other methods may be used in combination with the removal process.

Plating On Vias

Via plating is used to connect circuits between substrates with insulators in between. Since plating is done on small holes, it is necessary to prevent air bubbles from entering.

Names of Vias On Build-Up Boards

The names vary depending on the placement and structure of the holes, so a brief explanation is given below.

Staggered Vias 

This is a method of shifting the position of vias like a staircase.

Stacked Vias

A via is stacked on top of another via. A via that overlaps on all layers is called a full-stack via.

Build-up Substrate Materials

Currently, two types of materials are mainstream: glass cloth, which is the same material used for ordinary substrates, and film, which is mainly used for packages. Looking at the past, various materials have been used, which are briefly explained below.

Originally, build-up substrates started when IBM developed a technology to support large computer flip-chip mounting for its product line. Various studies were conducted in the process.

As a result, we adopted a method of exposure and development using a UV-curing resin known as photovia. This had the advantage that vias could be formed in a batch. Since interlayer thickness was required, we developed and mass-produced the product based on solder materials resist for curtain coaters, which can earn film thickness. As with solder resist, an insulating layer was formed by applying, exposing, and developing, followed by final curing with heat.

After that, chemical copper is deposited and electrolytic copper plating is performed to form layer after layer. In addition, chemical copper formation is difficult to achieve peel strength because of the resin that causes photo-polymerization, and it is very difficult to control the conditions. In addition, the development process required a solvent and was subject to various regulations, so it could not be said to be a technology that would be widely used.

Subsequently, the micro via formation method was changed from optical formation to laser processing, as the processing speed of vias increased dozens of times due to the significant evolution of laser processing equipment. At that time, RCC (Resin Coated Copper Foil: copper foil with resin) was adopted. This is a thermosetting resin that is coated on top of the copper foil and is in the same semi-cured state as prepreg.

Therefore, it has the advantage that the lamination process, which is the same process used for conventional substrates, can be used. In addition, since peel strength is easy to achieve, via formation by light has been replaced by laser formation of RCC.

As electronic devices have become smaller and more handy, the use of build-up substrates has expanded. In this context, further cost reduction and reliability that can handle high density are required.

In addition, significant improvements in laser processing technology have made it possible to process commonly used materials with glass cloth, which has led to a significant shift to materials with glass cloth. Cell phones, digital cameras, and various types of mobiles are of this type.

On the other hand, in LSI packaging, high-density, multi-stage build-up has been demanded in response to higher-density LSI flip chips. To meet the demand for multiple layers and low thickness, thinner interlayer thickness, smaller vias, and flat surfaces are required. Film-type materials were developed to meet these requirements.

To fill the circuit with resin, a vacuum laminator is required, and a line dedicated to the unique process is needed to deposit chemical copper on the resin surface. This requires a large capital investment. In packaging applications, it is used for MPU large-scale LSI in PC smartphones.

What Is a Diode Module?

A diode module is a semiconductor rectifier device that controls the conduction and interruption of electricity by arranging multiple diodes.

Diode modules have the characteristic of being able to control the flow of current in only one direction in an electric circuit, and are generally incorporated as relay components in circuit design.

Elements with similar behavior include thyristors and triacs. Depending on the process you wish to implement, these modules are used in different ways.

Uses for Diode Modules

Diode modules are widely used components in industrial products.

The following are examples of applications of diode modules:

• Power source for DC motors
• Power supplies for inverters
• Control devices for battery charging and discharging
• Inside power supplies

Diodes are widely used inside DC power supplies because they allow current from an AC power supply to be taken out in only one direction. When used in conjunction with a smoothing capacitor, etc., AC current can be converted to DC current.

Principle of Diode Modules

To understand the principle of the diode module, it is necessary to understand the structure of a diode. The internal structure of a diode consists of alternating layers of n-type and p-type semiconductors, which conduct when voltage is applied from the anode side to the cathode side. On the other hand, when voltage is applied in the opposite direction, charge moves away from the internal n- and p-type semiconductors, resulting in no current flow.

Using this characteristic, the diode can be used as a graded-grain element in which electricity flows in one direction.

Types of Diode Modules

There are various types of diodes depending on their properties.

1. Rectifying Diode

A diode that rectifies alternating current by allowing it to flow in. They are also called silicon diodes. They are used in power supply circuits and protection circuits by taking advantage of the property that electricity flows in only one direction.

A well-known example is a diode bridge that combines four rectifier diodes. 

2. Detector Diode

A diode that extracts audio signals from radio waves by taking advantage of its low forward voltage drop in the low current range (around 0.1 mA). They are used for voice communications, such as radios.

In the past, germanium diodes were often used. However, they are now being replaced by Schottky barrier diodes due to their extremely high cost.

3. Constant Voltage Diode

A diode whose voltage remains constant even when the current changes. Also called a Zener diode. They are used in over-voltage protection circuits by utilizing the Zener phenomenon, in which electricity flows at a constant voltage when voltage is applied in the reverse direction.

4. Photodiode

A photodiode that utilizes the property of light at the PN junction to generate an electric current and voltage. They are used in photoelectric sensors and optical communications.

They are sometimes used in solar cells, in devices that read laser light reflected from uneven surfaces on DVDs, and in the receiving part of TV remote controls.

5. Constant-Current Diode

A diode that conducts a constant current when the voltage is within a predetermined range. Applying a voltage higher than a predetermined level may damage the diode. They are used in battery charging/discharging circuits and ground-fault circuit breakers.

Other Information on Diode Modules

1. Internal Structure of Thyristor

Thyristor is a semiconductor component with a gate electrode added to a Diode Module, which conducts when a positive bias is applied from the anode side to the cathode side in the circuit and a gate current flows.

Once gate current flows, the module maintains conduction until the next time the bias from the anode side to the cathode side becomes negative or the gate current becomes zero.

Also, thyristors will only conduct with a unidirectional bias. If you want to operate against bias in both directions, a triac with thyristors installed in both directions is used. 

2. Difference Between a Diode Module and a Power Module

Like diode modules, power modules are used in power circuits. Power modules also perform switching and rectification, but they are used in products that require high voltage and high power.

A familiar example is an inverter that controls the speed of a motor in a railroad, for example. As a response to energy conservation, the improvement of the efficiency of power devices that handle high voltage and high power is attracting worldwide attention.

What Is an AC Solenoid?

AC solenoid is the name for a solenoid that operates when alternating current is applied. A solenoid is a spirally wound copper (or other conductive) wire that conducts electricity, and is generally referred to as a coil.

While a coil is a general term for all kinds of windings, such as flat or three-dimensional ones, a coil wound in a spiral shape is called a solenoid coil, or solenoid for short.

Uses of AC Solenoid

The most common application of an AC solenoid is a solenoid valve. Solenoid valves are called solenoid valves because solenoid coils are always used in their construction.

Solenoids are mainly used in valves to stop or flow fluids such as water or oil, or to switch the direction of fluid flow,where they are also called 2-way or 3-way valves. In the home, they are used in refrigerators, air conditioners, heat pump water heaters, and other devices that utilize the fluid cooling/heating cycle.

Principle of AC Solenoids

The principle of an AC solenoid is based on the force generated by the electric current and magnetic field. This relationship between current, magnetic field, and force is also exemplified by electromagnets and the electromotive force generated by electromagnetic induction phenomena.

The principle behind Fleming’s left-hand rule states that when the middle finger, index finger, and thumb of the left hand are pointed at right angles to each other in a spiral coil, an electric current (coil) flows in the direction of the middle finger and a magnetic flux (iron core or magnet) is created in the direction of the index finger, generating a force in the direction of the thumb.

This physical phenomenon of the iron core moving by switching the current direction and turning the power on and off is used in actuators such as various solenoid valves. Fleming’s left-hand rule is actually a principle common to all electric actuators, including motors, as well as solenoids.

Types of Solenoids

As explained above, a solenoid is a coil wound in a spiral shape, and the applied electric power is converted into the driving force of a mechanical actuator in the iron core by the law of electromagnetic induction.

1. AC Solenoid

• Inrush current caused by AC tends to occur, and the noise generated is relatively large.
• Stability issues created by the strong pull force on the movable core (plunger) during inrush current.
• The solenoid itself has excellent characteristics, such as operating speed and pull force.

2. DC Solenoid

• Constant current value and stable operation.
• Unlike with AC solenoids, there is no inrush current, and the noise level is relatively low.
• The AC solenoid itself has inferior characteristics to AC solenoids due to its slow operation speed, small current and plunger pull force.

Therefore, an AC solenoid is the best choice for the characteristics. However, since there is a risk of burning out the solenoid itself under excessive load, safety operation measures such as thermal fuse and overcurrent protection circuit are required.

Solenoids are also divided into a push type (push the iron core out of the coil) and a pull type (pull the iron core into the coil) depending on the operation of the movable iron core (plunger). There is also a push-pull type that handles both types of operation.

A characteristic type of solenoid is the self-retaining type, which can fix the position of the plunger using a permanent magnet. This type of solenoid requires current flow only at the moment of plunger operation and does not require current flow during holding, making it suitable for applications where power consumption should be minimized (e.g., equipment using storage batteries).

Solenoids are available in a wide variety of specifications, and it is important to check the specifications carefully for your application before selecting a solenoid.

What Is a Monolithic Ceramic Capacitor?

A monolithic ceramic capacitor, also called MLCC (Multi-Layer Ceramic Capacitor), is a chip component type capacitor with multiple layers of internal electrodes and dielectric layers. Further evolution is expected in the capacitor industry, where miniaturization and capacitance increase.

Barium titanate and titanium oxide are mainly used as dielectric, and the inner electrode and dielectric are formed in multiple layers. Increasing the number of layers makes it possible to increase the capacitance, leading to miniaturization of MLCCs.

Recently, the mainstream sizes of MLCCs are 0603 (0.6×0.3mm) and 0402 (0.4×0.2mm). The next generation 0201 size has already been realized in some capacitance values, but it has not yet become widespread in the market due to handling difficulties.

Monolithic ceramic capacitors are available in chip and radial types. Compared to other capacitors, multilayer ceramic capacitors have low high-frequency impedance and ESR (equivalent series resistance) and good high-frequency characteristics.

Types of Monolithic Ceramic Capacitors

Monolithic ceramic capacitors are available in a wide range of characteristics, and the size, withstand voltage, temperature characteristics, and other factors must be taken into consideration when determining the type of capacitor to be used for a particular application. Monolithic ceramic capacitors can be broadly classified into Class 1 and Class 2 in terms of their characteristics.

1. Class 1

Class 1 capacitors are also called temperature compensated capacitors, and can be compensated relatively easily because they have extremely low ESR, little temperature variation in capacitance, and the variation is linear.

However, the capacitance is usually small, ranging from 1pF to 1μF. ESRs are mainly used in applications where changes in capacitance are undesirable, such as oscillator circuits and time constant circuits.

2. Class 2

Class 2 is also called ferroelectric type, and its main material is barium titanate, which provides large capacitance of about 100 μF even in a small size. However, there are many points to keep in mind when using it, such as a large ESR, large temperature fluctuation of capacitance, and a decrease in actual capacitance when a DC bias is applied.

Therefore, when adopting Class 2 monolithic ceramic capacitors, it is essential to design circuits with their characteristics in mind. The main applications of Class 2 multilayer ceramic capacitors are in circuits where slight changes in capacitance have little effect, such as power source smoothing and decoupling capacitors.

Applications of Monolithic Ceramic Capacitors

Monolithic ceramic capacitors have a wide range of applications because their performance can be selected according to the number of layers and their lineup is broad. Monolithic ceramic capacitors are used in cellular phones, televisions, and industrial equipment for decoupling, coupling, and smoothing circuits, in DC/DC converters, in computer power supplies, and for noise reduction.

For automotive applications, long-life and failure-resistant products are selected. For industrial equipment, high capacitance and small capacitors are widely used, and in recent years they have been replacing other capacitors.

Currently, the mainstream monolithic ceramic cCapacitors are quite small, with sizes of 1005 (1.0 x 0.5 x 0.5 mm) and 0603 (0.6 x 0.3 x 0.3 mm), but in the future, ultra-small capacitors such as 0402 (already in use in the market) and 0201 (the next generation) are expected to become mainstream. However, it is expected that ultra-small capacitors such as the 0402 size, which is already in use in the market, and the next-generation 0201 size will become mainstream.

Principle of Monolithic Ceramic Capacitor

The capacitance C of a capacitor is proportional to the dielectric constant ε and the electrode area S, and inversely proportional to the distance d between electrodes. When capacitors are connected in parallel, the overall capacitance is equal to the sum of the capacitances of each capacitor.

Therefore, the key to increasing the capacitance of a capacitor is to use a dielectric with a high dielectric constant, increase the electrode area, and make the distance between electrode plates as small as possible. A monolithic ceramic capacitor has a structure of many layers of very thin electrode plates, which can be considered as many capacitors with close distance between electrode plates connected in parallel.

In other words, the number of layers N is proportional to the capacitance C of the capacitor. Therefore, by increasing the capacitance with the number of layers N, monolithic ceramic capacitors can be made both smaller and larger.

Although barium titanate, which has a very high dielectric constant, is used as a dielectric in most cases, its performance is expected to eventually reach a plateau. Therefore, the development of materials with a superior dielectric constant and less susceptible to wear and tear is expected.

Structure of Monolithic Ceramic Capacitors

Nickel is used for the electrodes and barium titanate is mainly used for the dielectric. Nickel paste, which serves as the internal electrode, is applied to the dielectric in the form of a sheet, and the sheet is then layered and formed under pressure.

It is then cut into small pieces and sintered at about 1000°C. When the external electrodes are attached, the capacitor becomes a monolithic ceramic capacitor. By ensuring that the internal electrodes are connected to the external electrodes alternately on the left and right, the layers are in the same state as if they were joined in parallel.

Since they are produced in sheet form, they have become more efficient, smaller, and thinner. The number of layers can be as many as 1,000. The dielectric materials are classified into two types: low dielectric constant type, which mainly uses titanium oxide, and high dielectric constant type, which uses barium titanate.

Class 1 is used for temperature compensation and low capacitance in signal circuits, etc. Class 2 has a high dielectric constant and a large temperature coefficient, and is used for power supply decoupling and smoothing circuits.

Other Information on Monolithic Ceramic Capacitors

1. Characteristics of Monolithic Ceramic Capacitors

Monolithic ceramic capacitors have a capacitance that varies with temperature. Therefore, when selecting a monolithic ceramic capacitor, you should not only select one based on its capacitance and voltage rating, but also consider the temperature in the operating environment.

Monolithic ceramic capacitors are characterized by low equivalent series resistance (ESR) due to the use of metals such as nickel and copper in the electrodes. Monolithic ceramic capacitors also feature low parasitic inductance (ESL) due to their structure, which makes them suitable for use at high frequencies.

By taking advantage of these features of low ESR and ESL, it is possible to form resonant circuits with high Q-values and low-loss matching circuits, making MLCCs an indispensable component in the field of high-frequency circuit products, as well as in power supply decoupling and noise suppression applications.

By changing the number of layers of electrode plates, it is possible to control the capacitance from small to large. Therefore, a monolithic ceramic capacitor as a product is also characterized by a very wide range of capacitance in the prepared lineup.

2. Basic Technology for Large Capacitance

The capacitance of a capacitor increases in proportion to the area of the internal electrode plates. To achieve high capacitance without changing the size of the monolithic ceramic capacitor, it is important to stack as many electrode layers as possible.

In general, in order to achieve miniaturization and high capacitance, it is necessary to stack electrodes with sub-millimeter order thickness, so thinning electrode layers is an essential technology. For thinning the electrode layer, adjustment of barium oxide, the raw material of dielectric, and printing technology for forming the internal electrode in paste form into a sheet are important.

The dielectric is made of fine particles called grain, which are formed by adding additives to barium oxide, printing it in sheet form, and then sintering it. How the microstructure of the grains is designed is critical to ensure that the thin-layer dielectric functions adequately.

Screen printing technology, such as that used for silk screens, is used to print thin internal electrodes on the paste. By extruding the paste through the micropores, it is possible to form a uniform thin layer of internal electrode. 

3. Share of Monolithic Ceramic Capacitors

Monolithic ceramic capacitors are so widely used in the world of electronics that they are now considered the rice of industry. For example, about 200 to 300 monolithic ceramic capacitors are used per TV receiver, and about 1,000 monolithic ceramic capacitors are used per smartphone.

Electric vehicles use more than 15,000 capacitors per vehicle. Japanese companies account for a large share of the production of these multilayer ceramic capacitors. Although the data is a bit old, the top four companies in terms of market share by value in 2017 are as follows, with three Japanese companies accounting for the majority of the global market share.

• Murata: 33.9% (will exceed 40% in 2020)
• Samsung Electro-Mechanics: 18.1
• Taiyo Yuden: 10.3
• TDK: 8.4

High-performance monolithic ceramic capacitors are especially demanded in automobiles, and Murata and TDK dominate the global market. Monolithic ceramic capacitors are expected to be in short supply for the time being, as their use is expected to further increase after 2021, when 5G generation smartphones will be in widespread use.

What Is a Heat Sink?

A heat sink is a component attached to a device for the purpose of cooling. It is mainly used in electronic equipment to prevent excessive temperature rise. 

It is very simple in principle, structure, and does not require physical operation. Therefore, it has the advantage that it is not prone to breakdowns.

Uses of Heat Sinks

Heat sinks are used in combination with electronic components that generate heat. A typical example is CPU cooling in personal computers.

Electronic components, such as CPUs, will use semiconductors and conductors inside their housings. These parts constantly generate heat during operation, and if left unchecked, the temperature inside electronic products rises, melting the surrounding varnish or burning out semiconductor parts. Heat sinks dissipate the heat from these heat-generating parts and help prevent failures due to overheating.

In a normal CPU, a heat sink is installed and then cooled using a fan. These are called CPU coolers, as a set.

Principle of Heat Sink

A heat sink is made up of metal parts arranged in the shape of a comb. The comb is called a fin, and the comb shape increases the surface area for enhanced heat dissipation performance. The principle of heat sink is the second law of thermodynamics. This is an extremely simple principle that heat always flows from high-temperature materials to low-temperature materials.

Therefore, if a heat sink is operated alone, it cannot lower the temperature below the atmospheric temperature. Hence, it is used for small electronic components and equipment with a high-heat resistance requirement. Cooling efficiency can be improved by using a fan or pump in conjunction with the heat sink to provide forced circulation.

If the heat generation is high, using a device with even higher cooling efficiency, such as a Peltier element or heat pump is advised.

Other Information on Heat Sinks

1. Performance of Heat Sink

Heat sink performance is mainly measured by “thermal resistance.” Thermal resistance is a value that indicates the resistance to heat transfer, meaning “how many degrees the temperature rises when one watt of heat is applied to an object. The unit of thermal resistance is “K/W” or “°C/W”.

Thermal resistance depends on the surface area of the Heat Sink and the material used. The lower the value, the better the performance will be. Heat sinks are designed in a comb or bellows shape because a larger surface area reduces thermal resistance most efficiently.

Another value that indicates the performance of a heat sink is the pressure drop. Pressure drop is a measure of the resistance of air or cooling water passing through a heat sink; the lower the value, The better the performance will be.

2. Heat Sink Material

Heat sinks are made of metals with high thermal conductivity. Aluminum alloys, copper materials such as brass and bronze, and metals such as silver and iron are used. Copper is the best thermal conductor, but it is heavy and expensive. Therefore, it is rarely used as a material for heat sinks.

Aluminum, on the other hand, is lightweight and Low-cost. Aluminum also has high self-dissipation properties, making it more suitable than copper in some environments where airflow is low.

Aluminum is the primary material used for heat sinks. However, other materials are considered when aluminum does not meet the required specifications.