カテゴリー: category_usa

What Is a Probe Card?

A probe card is an instrument required for wafer-level inspection in the semiconductor manufacturing process.

They are used by attaching them to wafer inspection equipment. Most of the cost of semiconductors is determined by the manufacturing equipment, but the cost of the package itself and packaging also has a large impact during the manufacturing stage. Therefore, it is possible to reduce costs by determining whether a product is good or bad at the wafer level after the semiconductor manufacturing process is complete, and sending only the good products to subsequent processes.

A wafer consists of several hundred to several thousand chips on a single wafer, and wafer inspection is the process of sorting these chips by determining whether they are good or bad before cutting them into individual pieces and packaging them.

Use of Probe Cards

Wafer inspection consists of an LSI tester that inputs electrical signals called test patterns to a chip and determines the output signal pattern by comparing it with expected values, a wafer prober that performs chip-level positioning control to connect signals accurately to the electrode terminals of each chip, and a probe card that performs positioning control to hit hundreds to tens of thousands of electrode terminals accurately, within a chip. Probe Cards with an equal number of needles (probes) positioned to precisely hit the hundreds of thousands of electrode terminals on the chip are used.

Probe cards must be made specifically for each chip design, which is costly in itself and requires re-creation due to wear from use, but is essential to overall manufacturing costs. Semiconductor chips are used in countless products, not only in computers, but in almost every product in our lives, and probe cards are one of the supports of these products.

Probe Card Principle

A probe card is mounted on the wafer prober and acts as a connector between the electrode terminals of the chip and the LSI tester through the wafer prober.

The LSI test head has spilling contact pins and high-density pins mounted for connection, but the placement pitch of the electrode terminals of a semiconductor chip is narrower than the pin placement density of the test head, at several tens of microns, so it is necessary to connect the two through the probe card.

Probe Card Structure

The upper side of the probe card has the connection pins to the test head, and the lower side has the needles to connect with the electrode pins of the semiconductor chip.

By connecting the test head and the probe card’s connection terminal, and then connecting the semiconductor chip’s electrode terminal and the probe card’s needle, an electrical connection is formed, and each semiconductor chip on the silicon wafer is tested by judging whether it is good or bad based on electrical signals from the LSI tester.

Probe cards are available in advanced and cantilever types. In the advanced type, a block with vertical terminals is attached to the board, and the probes can be freely arranged for easy maintenance. In the cantilever type, probes are directly attached to the board without any blocks, which makes it easy to accommodate narrow-pitch terminals.

Other Information on Probe Cards

Probe cards are often made of ceramic substrates, due to the fine and high level of reliability required in wafer inspection. For example, Kyocera uses thin-film single-layer and thin-film multilayer ceramic substrates with metallization for probe cards for DRAM, flash memory, and logic devices.

Generally, spring connectors or high-density connectors are used for the signal connections of large-scale integrated semiconductor circuits called LSIs or system LSIs. Probe cards also serve as an intermediary between the test head and the wafer to be inspected, and since they are required to have a high level of connection reliability and electrical inspection performance functions, their mechanisms and materials are delicate. Materials, such as ceramics are used.

However, the durability of probe cards is limited, and even the slightest distortion due to physical shock will prevent them from fulfilling their intended use. They are also consumable parts that are difficult to repair and must be replaced on a regular basis.

What Is a Programmable Controller?

A programmable controller is a control device with a built-in microprocessor.

Normally, inputs from sensors and switches in equipment are output to motors, displays, and other devices via mechanical relays, timers, and other control mechanisms. In contrast, a programmable controller controls the operation of a device using an internal program, without the need for mechanical relays or other control mechanisms.

Since there are fewer mechanical contacts, the device can be controlled without contact wear and defects between electronic components, cumbersome input/output devices, and wiring between mechanical relays for control. In addition, electrical wiring can be simplified, facilitating downsizing and mass production of devices.

Figure 1 shows a simple example of a control panel that uses mechanical relays, timers, etc. to control lamps.

Uses of Programmable Controllers

Programmable controllers are used in a wide range of fields, including factory automation systems, automobiles, home appliances, and industrial equipment. They are mainly used in industrial and commercial equipment.

Examples of commercial applications include their use in large washers and dryers with sequence control because they are cheaper and more robust than using a PC. Another factor is that they usually do not require cooling systems because there is no graphics board and the microprocessor generates little heat.

Programmable controllers can be either all-in-one, in which all the electronic components necessary for operation are built in, or modular, in which you select each functional component yourself.

It is important to select the memory, processor, and output/input terminal specifications according to the electronic device to be used.

Principle of Programmable Controller

A programmable controller consists of an input module, an output module, a processor, and memory. The input module is connected to sensors and switches. The processor processes that input data based on the internal program stored in the memory and outputs it to motors, displays, communication devices, etc.

If you wish to change the operation of an electronic device equipment controlled by the programmable controller, you do not need to make any changes to the wiring or other components. You only need to change the program code, which saves time and labor costs.

Programs used in programmable controllers include the ladder method, SFC method, flowchart method, and stepladder method, with the ladder method being the most common. In the ladder method, programs are written on a PC by connecting symbols such as relays, switches, and timers between two parallel lines like a ladder.

This method is easy to learn because the program code can be created using a graphical user interface.

Other Information on Programmable Controllers

1. The Difference Between a Programmable Controller and a Sequencer

If you work in production, you may have heard the term “sequencer.” As it turns out, there is no difference between a programmable controller and a sequencer.

Sequencer refers to the trade name of Mitsubishi Electric’s programmable controller. It was marketed under the name Sequencer as a mechanical device that enabled sequence control and remains in use today as another name for programmable controllers.

2. Connection Between Programmable Controllers and PCs

Generally, a PC is used to store a program in a programmable controller. Each company that sells controllers sells PC software for editing the programs stored on them.

Serial signals have long been used for connection to PCs. In the past, many PCs had serial ports permanently installed, but these days serial ports are rare.

Also, serial signals required matching COM ports or installing special drivers. In recent years, sequence editing is often performed using USB ports, which do not require COM port matching and are familiar to general users.

It is also now possible to edit multiple controllers from an Ethernet port when available.

What Is a Photointerrupter?

Photointerrupters are devices that detect the presence, absence, or position of an object using a light-emitter and receiver. They are classified into transmissive and reflective types. Transmissive photointerrupters work by blocking light between the emitter and receiver, while reflective photointerrupters detect light reflected off an object back to the detector.

Though both are used in various devices, this discussion focuses on transmissive photointerrupters, where the emitter and receiver are positioned opposite each other within a single package.

Uses of Photointerrupters

Employed across automotive, food, semiconductor, and other industries, photointerrupters serve various functions, including:

• Measuring lens ejection and aperture diameter in digital cameras.
• Detecting the timing of photosensitive drums and paper passage in photocopiers.
• Monitoring print head position and paper flow in printers.
• Tracking human movement in automatic ticket gates.
• Validating banknote passage in vending machines.

Principle of Photointerrupters

Comprising a near-infrared LED emitter and a phototransistor detector, photointerrupters operate by continuously projecting light from the emitter to the detector. The interruption of this light path by an object decreases the phototransistor’s collector current, which is then processed to signal the object’s detection.

Integrated types align the optical axes during manufacturing, eliminating the need for post-installation adjustments. Conversely, separate types require precise alignment of the emitter and detector at setup.

Other Information on Photointerrupters

Precautions for Using Photointerrupters

Considerations include:

• Detecting highly transparent objects may be challenging due to their light transmission properties.
• Small objects might not be detected if they are smaller than the emitter’s slit.
• Ambient light can saturate the phototransistor, hindering object detection, especially near 1,000 nm wavelength light sources.
• The near-infrared LED’s light output may decrease over time, potentially affecting device operation. Designing with sensitivity margin is advisable.

What Is a Slurry Pump?

A slurry pump is a pump used to transport slurry, which is a mixture of liquids and solids.

Slurry is very viscous and can wear out or clog the internal parts of the pump. Therefore, they differ from ordinary pumps in that they are specially designed to be highly durable.

There are two types of pumping methods: volumetric, which transports slurry by changing its volume, and centrifugal, which uses centrifugal force to transport slurry.

Applications of Slurry Pumps

Slurry pumps are widely used in various industrial fields. The following are just a few examples of applications for slurry pumps.

1. Ore and Oil Mining Industry

In the mining industry, slurry pumps are used to transport mined materials and sludge. Since transporting particulate matter is often necessary in the ore mining industry, slurry pumps are especially useful.

They are also widely used in the oil drilling industry. During oil drilling, rock needs to be scraped out to reach the depths of oil wells. Slurry pumps are used to pump out the rock debris slurry that forms.

2. Hydroelectric Power Plants

Slurry pumps are also frequently used in hydroelectric power plants. Hydroelectric power plants supply water to spin turbines, and river water contains solid particulates. Slurry pumps are used to discharge water mixed with sediment and other particles after filtering through a screener or other equipment.

3. Construction Industry

Slurry pumps are used to transport crushed stone and sand used at construction sites. They are also used to transport large quantities of earth and sand at dam construction sites.

Principle of Slurry Pump

Slurry pumps require a special design due to the high density of slurry and the variety of solid particles it can contain. The pump consists of an intake to receive the slurry, an impeller to accelerate the slurry inside the pump, and a discharge port to discharge the slurry.

The slurry is drawn in at the intake and accelerated by the rotation of the impeller. The slurry accelerated by the impeller is sent to the discharge port.

Slurry pumps have multiple auxiliary vanes inside the pump to accommodate high-density fluids. This allows for higher pressures to be generated.

Types of Slurry Pumps

Slurry pumps are used in a wide variety of applications. The following are examples of slurry pump types.

1. Single-Stage Type

A single-stage slurry pump is a basic pump for transporting slurry. It consists of a single-stage impeller and is characterized by its simple structure and low cost. However, since it has a single-stage impeller, the corresponding head is often low. 

2. Multi-Stage Type

A multi-stage slurry pump has a multi-stage impeller. The multi-stage design allows for a high head and efficient transport of slurry. However, they are typically more expensive than single-stage pumps. Due to the large number of parts, the possibility of failure or blockage is higher than with single-stage pumps.

3. Wear-Resistant Slurry Pump

These slurry pumps have high wear resistance. The materials used in the pump are resistant to abrasion and corrosion. Special alloy steel, rubber, ceramic, and other materials are used for internal parts to improve durability and service life.

How to Select a Slurry Pump

When selecting a slurry pump at the design stage, select the pumping system based on the purpose of transportation, the shape, and hardness of the object, whether it is chemically corrosive or not, and the operating temperature.

It is of utmost importance to understand the nature of the slurry to be transported. The specific gravity and solids concentration of the slurry can provide useful information for selection. Once the nature of the slurry is known, the flow rate should be selected according to the required capacity for pressure.

Ease of maintenance and repair should also be considered. Slurry pumps are often used in harsh environments and may be difficult to maintain and repair. It is ideal to select a pump that can be easily maintained.

Cost is also an important consideration. Slurry pumps are typically more expensive than other pumps due to their characteristics. However, even if the initial cost is high, selecting the right slurry pump may save money in the long run.

What Is a Motion Sensor?

A motion sensor is a detection device that senses the movement of an object as a physical quantity and outputs a signal.

They consist of a combination of an acceleration sensor and an angular rate sensor.

Uses of Motion Sensors

Motion sensors are used in a wide range of applications, from consumer products to industrial equipment.

Examples of use are listed below:

• Automatic doors and ticket gates
• Smartphone and game console controllers
• Automatic faucets and automatic flashing lights
• Automatic temperature monitors
• Drones

Motion sensors can be used in a wide range of applications because they can detect human movement without contact.

Principle of Motion Sensor

The motion of an object in three-dimensional space can be described by acceleration and angular velocity in three axes. Motion sensors use this mechanism to detect the motion of an object. Acceleration sensors and angular rate sensors are mainly used, at least one for each of the three axes.

The method and type of sensor employed varies with the design of each sensor. They can have a variety of characteristics, including those that capture overall movement and those that capture detailed movement at close range.

Motion sensors that detect living organisms without contact mainly use radiation temperature sensors and photoelectric sensors, among others. Sometimes referred to as a motion sensor, the most common type of sensor is one that detects temperature changes.

Other Information on Motion Sensors

1. Motion Sensor Market Trends

Against the backdrop of the spread of new coronavirus infections, the motion sensor market is expanding. According to a study by a marketing firm, the market size is expected to grow from $5.7 billion in FY 2019 to approximately $9.3 billion in FY 2025.

Photoelectric sensors make up the majority of the motion sensor market. Among these, demand for CCD and COMS image sensors are likely to grow due to their use in drones and robots, as well as in accident prevention with in-vehicle cameras.

Motion sensors are also being introduced in factories, where the IoT is gaining momentum. They are used to improve manual processes that are not suitable for automation by measuring human movement, and in systems that automatically inspect products and parts in the process of manufacturing.

2. Security of Motion Sensors

In 2017, motion sensor security issues were raised by universities in the United States and the United Kingdom. Michigan State University in the US pointed out that accelerometers can malfunction when given certain sound waves. According to published information, some sound waves can intentionally cause a traffic accident.

The University of Newcastle in the UK also pointed out the possibility of personal information being extracted from a smartphone motion sensor. It appears that passwords and unlock PINs can be identified based on the timing of tapping for text input and the tilt of the smartphone.

If a web browser is given permission to access the motion sensor, information could be stolen simply by visiting malicious sites. Therefore, caution should be exercised when using smartphones.

What Is Molybdenum?

Molybdenum is a type of metal. Its atomic number is 42 and the element symbol is Mo.

In industrial products, it is used as molybdenum sulfide for lubrication purposes and as an anti-seizing agent. It may also be used as an additive in steel materials.

Uses of Molybdenum

Molybdenum sulfide is rarely used in consumer products, and is more often used in industrial applications.

It is used in lubricants for special applications. It is a material that, when blended in oils and greases, improves heat resistance temperatures and load bearing capacity. Thus, it is sometimes used as an anti-seizing agent for bolts. In other cases, it is used as a solid lubricant for oilless bushings.

It may also be used as an additive for steel materials. Chromium molybdenum steel, to which chromium and molybdenum are added to iron, is robust and supple. For this reason, it is sometimes used as an automotive material.

Properties of Molybdenum

Molybdenum is a rare metal. It has a high melting point, a high boiling point, and high strength at high temperatures. It is not used as a conductive material due to its high electrical resistance and high cost. It has a low coefficient of thermal expansion and is not subject to much distortion even at high temperatures.

Principle of Molybdenum

Molybdenum is a silvery metal that is solid at room temperature and pressure. It has a very stable structure and is not highly reactive.

Worldwide reserves of pure molybdenum are said to be around 8.5 million tons, most of which are buried in China.

In air, molybdenum forms an oxide film, so it is a pure metal inside. It does not react with sodium hydroxide, but is soluble in sulfuric acid and hydrochloric acid. At high temperatures, it oxidizes in air to form molybdenum oxide.

Other Information on Molybdenum

1. Molybdenum as a Nutrient

Molybdenum works to detoxify toxic components in the body, and also to remove the detoxified components from the body. It is one of the most important nutrients for humans. It is present in about 10 mg in an adult organism, mostly distributed in the liver and kidneys.

An example of Molybdenum’s role is as a capture factor for oxidoreductases such as xanthine oxidase and aldehyde oxidase. A capture factor is a substance other than a protein, such as an organic substance or ion, that activates an enzyme. Redox enzymes activated by a capture factor work to change one substance into another through an enzymatic reaction.

Molybdenum is abundant in legumes, grains, and meats, and according to the Dietary Reference Intakes for 2020, the recommended intake of Molybdenum is about 30 μg/day for adult men and 25 μg/day for adult women. Since we can consume a lot of Molybdenum from our normal diet, it is unlikely that we will have a deficiency of Molybdenum in our bodies. If there is a deficiency, symptoms such as increased heart rate and night blindness may occur.

2. Toxicity of Molybdenum

Ingesting large amounts of Molybdenum can increase uric acid levels in the blood and cause gout-like symptoms. However, such symptoms do not occur with normal dietary intake.

The LD50 (half lethal dose: a measure of acute toxicity) values for oral intake in rats are 188 mg/kg for molybdenum trioxide, 250 mg/kg for sodium molybdate, and 680 kg/mg for diammonium molybdate.

Sodium Molybdenum is a highly hazardous substance. The aerosol irritates the respiratory tract and eyes, and inhalation causes symptoms such as coughing and sore throat. If accidentally ingested orally, symptoms such as nausea and vomiting may occur.

What Is a Membrane Filter?

Membrane filters are used to remove fine particles from solutions. Filtration using a membrane filter, also called microfiltration, can reliably remove particles larger than the pore size of the filter. However, membrane filters are prone to clogging, so rough filtration using a pre-filter is often performed before filtration.

Membrane filters are made of a wide variety of materials, including PTFE, PVDF, PES, cellulose mixed ester, and polypropylene. When using a membrane filter, it is necessary to select an appropriate membrane filter based on the chemical resistance of the filtering material, whether or not the components in the sample are adsorbed by the filter material, and whether or not the pore size of the filter is small enough for the particulates to be removed.

Membrane Filter Applications

Membrane filters are made of membranes. Liquid filtration is routinely used in a variety of industries, including food and beverage, medical, electronics, chemical, and textile industries. Membrane filters are used in a process called microfiltration.

Microfiltration is a process that completely traps substances larger than the pore size (pore diameter) of the membrane, enabling stable removal of impurities from liquids. For this reason, microfiltration using membrane filters is used in the semiconductor industry, where even the smallest amount of foreign matter is unacceptable, and before filling, products are sold as solutions.

Material of Membrane Filters

Membrane filters are made of a wide variety of materials. Examples of materials include PTFE (polytetrafluoroethylene), PVDF (polyvinylidene fluoride), PES (polyethersulfone), nylon, cellulose blend esters, and polypropylene.

All of these polymers vary in their resistance to organic solvents, acids, and bases and have very different chemical structures. Therefore, in addition to considering the durability of the solution to be filtered, the ease of sample adsorption on the membrane filter must also be taken into consideration.

Structure of Membrane Filter 

Membrane filters can be compared to pre-filters. These are the same “filter” but have a different internal structure and particle trapping mechanism. Prefilters also called depth filters, are made of glass or other fibrous materials that are pressed together. Therefore, the size of the flow path inside the filter is not constant. Also, during filtration, large particles are trapped by clogging in the middle of the flow path. However, if an excessive amount of material flows through the filter, the clogged particles may be pushed out and pass through the filter.

Membrane filters, on the other hand, have a specified maximum pore diameter, and no flow path can be larger than the pore diameter in the catalog. Therefore, particles larger than the pore diameter are captured on the filter surface and completely separated from the filtrate. However, since all particles accumulate on the filter surface, membrane filters are prone to clogging. In actual processes, filtration is often performed first with a pre-filter for simple filtration and then with a membrane filter.

What Is a Magnet Drive Pump?

A magnet drive pump is a type of centrifugal pump that differs from other centrifugal pumps in one major characteristic. In an ordinary pump, the impeller and motor are directly connected, so a seal is required to prevent the leakage of liquid. A normal pump has a gland packing and a mechanical seal, but the gland packing needs to produce a certain amount of fluid constantly, and if the mechanical seal breaks, the fluid inside may leak.

On the other hand, the magnet pump rotates the motor and impeller via magnets, so there is no place where fluid can leak. Therefore, they can be safely used in environments with corrosive fluids.

Applications of Magnet Pumps

Magnet pumps are used in places where liquids must not leak. For example, in chemical lines such as hydrochloric acid and caustic soda. If a leak were to occur, it could cause serious damage. Therefore, gland packing is prohibited, and mechanical seals are not recommended because of the possibility of leakage in case of failure.

In such a situation, a magnet pump with zero external leakage is the most suitable pump. In addition, magnet pumps are sometimes used in ordinary water lines to reduce maintenance costs.

Principle of Magnet Pumps

Unlike ordinary pumps, magnet pumps do not have a direct connection between the motor and the impeller. Instead, the impeller is rotated via a magnet attached to the pump shaft and a magnet attached to the impeller.

As a result, there is no penetration of the shaft into the sealed container in which the impeller is housed, so there is no external leakage. As a result, the pump can be used as a normal pump despite zero external leakage.

If the impeller and sealed container are made of materials such as polypropylene or PTFE, it is possible to make a pump with high corrosion resistance that can be safely used for chemicals.

However, this structure does not allow water or oil supply to the bearings from the outside, so the bearings are lubricated and cooled by the process fluid. Therefore, a dry operation is strictly prohibited, or the bearings will seize, and the pump will be damaged. Because of these precautions, an ammeter or similar device must be installed to monitor dry running when using a magnetic drive pump.

Note that the motor size may be about one size larger than a pump with a directly connected shaft. Although there is not much difference nowadays when pumps are operated 24 hours a day, one size difference can make a big difference in power, so care should be taken.

Difference Between a Magnet Pump and a Diaphragm Pump

While a magnet pump is a volute pump that rotates an impeller, a diaphragm pump is a positive displacement pump that repeatedly suctions and discharges by reciprocating a membrane called a diaphragm. Also, while a magnet pump pumps liquid using a rotary motion, a diaphragm pump pumps liquid using a reciprocating piston motion.

Both are often used in chemical lines, but magnet pumps tend to be more hazardous for liquids. This is because the liquid is infinitely leak-proof. Diaphragm pumps, due to their structure, may leak liquid from flange surfaces, etc. Magnet pumps are superior in terms of preventing leakage. However, diaphragm pumps are easier to maintain and cost less because of their lower unit price.

Causes of Magnet Pump Failure

Although magnet pumps can pump liquid without leaking it outside, they can break down relatively easily if used improperly. Typical causes of failure are described here.

1. Running Dry

Although not limited to magnet pumps, dry running often leads to bearing damage and failure. It is important to have several people, including the operator and maintenance staff, check the pump before an operation, since it is easy to forget to let fluid flow through the pump during operation, whether after long-term pump stoppage or after temporary maintenance during trouble.

2. Clogging

There are various types of clogs. If the inlet side strainer is blocked, the pump will run dry, and the bearings will seize. Also, the pressure pumped will be less. If the outlet-side strainer is blocked, the pump is in closed operation, which also puts a load on the pump and leads to failure. If the impeller or case is clogged, the pump will not operate because it will not rotate in the first place.

Since both of these problems can easily lead to failure, extreme care must be taken when using fluids that tend to stick or are viscous.

What Is Polycarbonate Resin?

Figure 1. Five major general-purpose engineering plastics and their physical properties (Reference: Chemistry Handbook, 5th Edition)

Polycarbonate Resin is a type of engineering plastic and one of the five major general-purpose engineering plastics. Among general-purpose engineering plastics, polycarbonate resin is the only one that is colorless and transparent, and its transparency is so high that it can be compared to that of glass.

It also has the highest impact resistance of all general-purpose engineering plastics, and because it contains two benzene rings in its main chain, it is self-extinguishing, meaning that it will not spread even if set on fire.

Polycarbonate Resin is highly processable, as it is compatible with most of the basic molding techniques used for plastics. However, although cracking and breakage rarely occur, it should be noted that it is susceptible to fatigue and scratching, and that it is weak against alkalis and organic solvents.

Uses of Polycarbonate Resin

Polycarbonate Resin is used in a great many applications because of its excellent resistance to a wide variety of conditions and its ease of processing.

The following are examples of applications for Polycarbonate Resin along with its characteristics:

1. Transparency

Due to its high transparency, polycarbonate resin is used in optical applications such as eyeglass lenses, camera lenses, and CD and DVD substrates.

2. Impact Resistance

Because of its strong impact resistance, it is used for bulletproof materials, etc., and there is almost no risk of cracking when used in general environments. 

3. Weather Resistance

Because it is resistant to ultraviolet rays and does not deteriorate easily, it maintains its high strength for a long period of time when used outdoors. It is used for roofing materials, solar panel surfaces, and other outdoor applications, as well as for automobile headlamp lenses, roof rails, and door handles.

In recent years, it has also been adapted to molding methods using 3D printers, and its use is expanding more and more. 

4. Dimensional Stability

With its high dimensional stability, polycarbonate resin is used for smartphone cases and other applications.

Polycarbonate Resin Manufacturing Process

There are two industrial production methods for polycarbonate resin: interfacial polymerization and ester exchange. The density varies depending on the manufacturing method, and the addition of modifiers to polycarbonate resin can make it an even better resin material.

1. Interfacial Polymerization Method

Figure 2. Reaction equation of the interfacial polymerization method

In this method, polycarbonate is produced by adding carbonyl chloride to a suspension solution of bisphenol A in aqueous sodium hydroxide solution and methylene chloride or chlorobenzene, which undergoes a condensation polymerization reaction at the interface between the aqueous and oil phases.

Compared to the ester exchange method, the reaction conditions are milder, and polycarbonates of a wide range of molecular weights, from low to high, can be produced.

After polymerization, polycarbonate resin is dissolved in the oil phase, and granular polycarbonate is obtained through the separation, neutralization and purification process, polymer recovery process, and drying process.

2. Ester Exchange Method

Figure 3. Reaction equation for the ester exchange method

In this method, bisphenol A and diphenylcarbonate are melt-mixed in the presence of a catalyst to produce polycarbonate through polycondensation while recovering phenol under high temperature and reduced pressure without the use of solvents. The recovered phenol is reused as a raw material for diphenylcarbonate.

The resulting polycarbonate is obtained in a molten state and can be pelletized into products, making this method of synthesis simpler than the interfacial polymerization method in terms of post-processing.

Other Information on Polycarbonate Resins

1. Polycarbonate Resin Global Market Share

Polycarbonate Resin is used in an extremely wide range of applications, and production facilities are located in various regions. By capital, American manufacturers account for 36%, European manufacturers, mainly from Germany and Belgium, 25%, and Japanese manufacturers, 38%.

2. Processing of Polycarbonate Resin

Polycarbonate resin is a thermoplastic resin that softens when heated. It can be cut like acrylic resin, bent with heat, and welded with solvents.

It can also be used in a manner similar to metalworking to create workpieces that take advantage of its properties. For this reason, there are a number of businesses that make their living processing polycarbonate resin.

What Is a Polyethylene Pipe?

Polyethylene pipes are made of polyethylene (Figure 1). They are used for gas piping, chemical piping in chemical plants, and water supply and distribution pipes.

Polyethylene has excellent weather ability and chemical resistance, so there is no need to worry about red water caused by rust as is observed with steel piping. In addition, because polyethylene is a resin material, it is flexible, which has the advantage of making buried piping networks more resistant to earthquakes and other disasters. One of the major manufacturers of polyethylene pipes is Sekisui Chemical, which specializes in manufacturing and processing resin materials.

Uses of Polyethylene Pipes

Polyethylene pipes have been attracting attention in recent years mainly as infrastructure piping for delivering water and gas. Polyethylene pipes can be used in all applications except high-temperature fluids, such as water distribution pipes because they are rust-resistant and have excellent water hygiene properties, sewage pipes because they are chemically stable and do not cause blockages in pipes due to red rust, and air conditioning pipes because they are lightweight and can be quickly installed.

In addition, cross-linked polyethylene pipes can be used at temperatures of 95°C or lower for hot water supply without deterioration over a long period.

Features of Polyethylene Pipes

Compared to steel pipes conventionally used for buried pipes, polyethylene pipes are superior in that they do not rust, do not corrode even in corrosive soil or salt-affected areas, have excellent electrical insulation properties, do not cause electrical corrosion, and are less likely to become blocked due to scale adhesion.

The resin material also has the advantages of being lightweight for efficient transportation and installation, easy bending, and earthquake resistance due to its flexibility.

Pipe joints for polyethylene pipes include fusion joints, mechanical joints, and electro-fusion joints. Infusion joint joining, the insertion point on the polyethylene pipe side, and the receiving end on the joint side are heated in a heating machine to melt them and then joined.

Since this method requires control of the heating temperature, it is desirable to use a dedicated heating machine, and there are some problems in terms of workability. Electrofusion (EF), a type of electrofusion joining, is a method that overcomes this difficulty.

This method is very superior in terms of simplicity of operation, and heating is performed by energizing a joint with a built-in electric heating wire, which simultaneously melts and fuses the pipe and the joint, thereby completing a completely integrated joint.

Because of these advantages, polyethylene pipes are often introduced as an alternative to conventional steel piping and are expected to help build disaster-resistant cities, which have recently become more important in society, and ultimately help realize a sustainable society.

Polyethylene Dual Layer Pipes

A polyethylene dual-layer pipe is a polyethylene pipe consisting of two layers: an outer layer (polyethylene with carbon black) with high weather resistance and an inner layer (natural polyethylene) with high chlorinated water resistance, and is widely used mainly for water supply pipes, drainage pipes, temporary piping, and other water supply applications.

Its excellent flexibility allows it to flexibly follow ground subsidence, earthquakes, etc. It also has excellent chemical stability. It also has excellent chemical stability, so there is no risk of corrosion to the soil in which it is buried.

Furthermore, it is hygienic because no harmful additives are used. In this regard, the pipes are ideal for drinking water piping in terms of water quality retention and hygiene, as there is no rusting and very little scale adhesion.

The inner surface of this piping is extremely smooth and has low frictional resistance, resulting in very little scale adhesion. This pipe has an excellent characteristic of extremely low flow reduction over time.

Differences Between Polyethylene and PVC Pipes

Because both types of piping are made of plastic materials, these two materials are often confusedly understood, but it is important to note that their characteristics and applications are different.

As explained at the beginning of this article, polyethylene pipes are made of polyethylene and have excellent flexibility, making them very earthquake resistant when buried underground.

On the other hand, PVC pipes are pipes made of polyvinyl chloride, and although they have a certain degree of flexibility, the degree of flexibility is not as high as that of polyethylene pipes. Structural differences between polyethylene and polyvinyl chloride

Service Life of Polyethylene Pipes

Polyethylene pipes are known for their long service life. In Japan, there is a demand for water pipelines with a service life of 100 years or longer, and polyethylene pipelines for water distribution are also required to have high durability.

An example of a study in this regard is a 2013 report by the Polyethylene Pipe System Association for Water Distribution (POLITEC). This study examined verification against internal and external pressure, earthquakes (seismic resistance), and residual chlorine (chlorinated water resistance). As a result, the results of all verifications exceeded 100 years under the specified assumed conditions, indicating that polyethylene pipelines for water distribution have a service life well in excess of 100 years.

High-Density Polyethylene Pipes

Polyethylene pipes made from high-density polyethylene (polyethylene with a density of 0.942-0.970) have excellent impact resistance and flexibility (bending and flexing characteristics).

Therefore, the pipes are resistant to damage even in the event of a disaster. Because of these excellent physical properties, the material is used in the fields of civil engineering, agriculture, and mining, including drainage pipes for longitudinal road crossings, canal rehabilitation, small-scale canal culvert conversion, various rainwater drainage works, and industrial waste disposal sites.