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Saturday, April 17, 2021

IGBT Online

IGBT (Insulated Gate Bipolar Transistor), insulated gate bipolar transistor, is a composite fully controlled Voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOS (insulated gate field effect transistor), which also has MOSFET The advantages of high input impedance and low on-Voltage drop of GTR. The saturation voltage of GTR is reduced, the current-carrying density is high, but the driving current is large; the MOSFET driving power is small, the switching speed is fast, but the conduction voltage drop is large, and the current-carrying density is small. IGBT combines the advantages of the above two devices, with low driving power and reduced saturation voltage. It is very suitable to be used in converter systems with a DC voltage of 600V and above, such as AC motors, frequency converters, switching power supplies, lighting circuits, traction drives and other fields.



In layman's terms: IGBT is a high-power power electronic device. It is a non-on-off switch. IGBT has no function of amplifying voltage. It can be regarded as a wire when it is turned on, and it is regarded as an open circuit when it is turned off. The three main characteristics are high voltage, high current, and high speed.

  1. IGBT module

IGBT is the abbreviation of Insulated Gate Bipolar Transistor (Insulated Gate Bipolar Transistor). IGBT is a device composed of MOSFET and bipolar transistor. Its input is MOSFET and output is PNP transistor. It combines these two The advantages of the device are not only the advantages of low driving power and fast switching speed of MOSFET devices, but also the advantages of reduced saturation voltage and large capacity of bipolar devices. Its frequency characteristics are between MOSFET and power transistors, and it can work normally at several times. Within the frequency range of ten kHz, it has been used more and more widely in modern power electronic technology, and it has occupied a leading position in high-frequency and medium-power applications.

The equivalent circuit of IGBT is shown as in Fig. 1. It can be seen from Figure 1 that if a positive driving voltage is applied between the gate and emitter of the IGBT, the MOSFET is turned on, so that the collector and base of the PNP transistor are in a low resistance state and the transistor is turned on; if the IGBT If the voltage between the gate and the emitter is 0V, the MOS is cut off, cutting off the supply of the base current of the PNP transistor, making the transistor cut off. The IGBT is also a voltage-controlled device like the MOSFET. A DC voltage of more than ten V is applied between its gate and emitter, and only the leakage current of the uA level flows, and basically does not consume power.

  1. The choice of IGBT module

The voltage specification of the IGBT module is closely related to the input power supply of the device used, that is, the test power supply voltage. The relationship between them is shown in the table below. When the collector current of the IGBT module increases during use, the resulting rated loss also increases. At the same time, the switching loss increases, which intensifies the heating of the original. Therefore, the rated current should be greater than the load current when selecting the IGBT module. Especially when it is used as a high-frequency switch, due to the increase of switching loss and heat generation, it should be used when selecting it.

  1. Precautions in use

Since the IGBT module is a MOSFET structure, the gate of the IGBT is electrically isolated from the emitter by a layer of oxide film. Because this oxide film is very thin, its breakdown voltage generally reaches 20-30V. Therefore, gate breakdown due to static electricity is one of the common causes of IGBT failure. Therefore, pay attention to the following points in use:

When using the module, try not to touch the driver terminal part with your hands. When you must touch the module terminal, first discharge the static electricity on the human body or clothes with a large resistance ground before touching;

When using conductive materials to connect the drive terminals of the module, please do not connect the module before the wiring is connected;

Try to operate with the bottom plate well grounded.

In applications, although it is guaranteed that the gate drive voltage does not exceed the maximum rated voltage of the gate, the parasitic inductance of the gate connection and the capacitive coupling between the gate and the collector will also produce an oscillating voltage that damages the oxide layer. For this reason, twisted-pair wires are usually used to transmit drive signals to reduce parasitic inductance. Connecting a small resistor in series with the gate connection can also suppress the oscillating voltage.

In addition, when there is an open circuit between the gate and the emitter, if a voltage is applied between the collector and the emitter, as the collector potential changes, due to the leakage current flowing through the collector, the gate potential rises and the collector Then there is current flowing. At this time, if there is a high voltage between the collector and the emitter, it may cause the IGBT to heat up and damage it.

In the case of using IGBT, when the gate loop is abnormal or the gate loop is damaged (the gate is in an open state), if a voltage is applied to the main loop, the IGBT will be damaged. A resistance of about 10KΩ is connected in series between the pole and the emitter.

When installing or replacing the IGBT module, the state of the contact surface between the IGBT module and the heat sink and the degree of tightening should be paid great attention to. In order to reduce the contact thermal resistance, it is best to apply thermal grease between the heat sink and the IGBT module. Generally, a heat dissipation fan is installed at the bottom of the heat sink. When the heat dissipation fan is damaged, the IGBT module will generate heat and malfunction when the heat dissipation of the heat sink is poor. Therefore, the cooling fan should be checked regularly. Generally, a temperature sensor is installed on the heat sink close to the IGBT module. When the temperature is too high, it will alarm or stop the IGBT module.

Three, IGBT drive circuit
The function of the IGBT drive circuit is mainly to amplify the power output by the single chip microcomputer to achieve the purpose of driving the IGBT power device. On the premise of ensuring the reliable, stable and safe operation of IGBT devices, the drive circuit plays a vital role.

The equivalent circuit and conformity of IGBT are shown in Figure 1. IGBT is controlled by the positive and negative voltages of the gate. When a positive grid voltage is applied, the tube is turned on; when a negative grid voltage is applied, the tube is turned off.

IGBT

IGBT has similar volt-ampere characteristics to bipolar power transistors. As the control voltage UGE increases, the characteristic curve shifts upward. The IGBT in the switching power supply makes it work alternately in two states of saturation and cut-off through the change of UGE level.

(1) Provide proper forward and reverse voltage to enable IGBT to be turned on and off reliably. When the positive bias voltage increases, the IGBT on-state voltage drop and turn-on loss will decrease, but if the UGE is too large, the IC will increase with the increase of UGE when the load is short-circuited, which is detrimental to its safety. It is better to use UGEν15V. Negative bias voltage can prevent the IGBT from being turned on by mistake due to excessive surge current during turn-off. Generally, UGE=-5V is appropriate.

(2) The switching time of IGBT should be considered comprehensively. Fast turn-on and turn-off are beneficial to increase the operating frequency and reduce switching losses. However, under large inductive loads, the switching frequency of the IGBT should not be too large, because high-speed switching and switching will produce high peak voltages, and may cause the IGBT itself or other components to breakdown.

(3) After the IGBT is turned on, the drive circuit should provide sufficient voltage and current amplitude so that the IGBT will not exit saturation and be damaged under normal operation and overload conditions.

(4) The resistance RG in the IGBT drive circuit has a greater impact on the working performance. The larger RG is beneficial to suppress the current rise rate and voltage rise rate of the IGBT, but it will increase the switching time and switching loss of the IGBT; RG is small , It will cause the current rise rate to increase, causing the IGBT to be turned on or damaged by mistake. The specific data of RG is related to the structure of the drive circuit and the capacity of the IGBT, generally ranging from a few ohms to several tens of ohms. The RG value of a small-capacity IGBT is larger.

(5) The drive circuit should have strong anti-interference ability and protection function for IG2BT. The control, drive and protection circuits of IGBT should match its high-speed switching characteristics. In addition, G-E cannot be opened without proper anti-static measures.

IGBT

Fourth, the structure of IGBT
IGBT is a three-terminal device, which has a gate G, a collector c and an emitter E. The structure of IGBT, simplified equivalent circuit and electrical graphic symbols are shown in the figure.

As shown in the figure, it is a cross-sectional schematic diagram of the internal structure of an N-channel IGBT (N-IGBT) combined with an N-channel VDMOSFFT and GTR. IGBT has one more layer of P+ implantation area than VDMOSFET, forming a large-area PN Junction J1. Since the P+ injection region emits minority carriers to the N base region when the IGBT is turned on, the conductivity of the drift region is modulated, and the IGBT has a strong current flow capability. The N+ layer between the P+ injection region and the N- drift region is called a buffer zone. The presence or absence of a buffer determines the different characteristics of the IGBT. IGBTs with N* buffer are called asymmetric IGBTs, also called punch-through IGBTs. It has the advantages of small forward voltage drop, short dog-off time, and small tail current when it is turned off, but its reverse blocking ability is relatively weak. IGBTs without N-buffer are called symmetrical IGBTs, also called non-punch-through IGBTs. It has strong forward and reverse blocking capability, but its other characteristics are not as good as asymmetric IGBTs.

The simplified equivalent circuit shown in Figure 2-42 (b) shows that the IGBT is a Darlington structure composed of GTR and MOSFET. Part of the structure is driven by a MOSFET, and the other part is a thick base PNP transistor.

IGBT

Five, the working principle of IBGT
Simply put, an IGBT is equivalent to a thick base PNP transistor driven by a MOSFET. Its simplified equivalent circuit is shown in Figure 2-42(b), where RN is the modulation resistance in the base area of ​​the PNP transistor. It can be clearly seen from this equivalent circuit that IGBT is a composite device of Darlington structure composed of transistors and MOSFETs. The transistor in the picture is a PNP transistor, and the MOSFET is an N-channel field effect transistor, so the IGBT of this structure is called an N-channel IIGBT, and its symbol is N-IGBT. Similarly, there are P-channel IGBTs, namely P-IGBTs.

The electrical graphic symbol of IGBT is shown in Figure 2-42(c). IGBT is a kind of field control device. Its turn-on and turn-off are determined by the voltage UGE between the gate and the emitter. When the gate-to-emitter voltage UCE is positive and greater than the turn-on voltage UCE(th), a channel is formed in the MOSFET and is PNP The type transistor provides the base current to turn on the IGBT. At this time, the holes (minority carriers) injected from the P+ region to the N- region modulate the conductance of the N- region, reducing the resistance RN of the N- region, making the IGBT highly resistant. The low voltage IGBT also has a small on-state voltage drop. When no signal or reverse voltage is applied between the gate and the emitter, the channel in the MOSFET disappears, the base current of the PNP transistor is cut off, and the IGBT is turned off. It can be seen that the driving principle of IGBT is basically the same as that of MOSFET.

① When UCE is negative: J3 junction is in reverse bias state, and the device is in reverse blocking state.

②When uCE is positive: UCUTH, an N channel is formed under the insulated gate, and conduction occurs in the N-region due to the interaction of carriers Modulate to make the device forward.

1) Conduction

The structure of the IGBT silicon chip is very similar to that of the power MOSFET. The main difference is that JGBT adds a P+ substrate and an N+ buffer layer (NPT-non-punch-through-IGBT technology does not add this part), and one MOSFET drives two bipolar devices. (There are two polarity devices). The application of the substrate creates a J junction between the P and N+ regions of the tube body. When the positive gate bias causes the P base area to be reversed under the gate, an N channel is formed, and an electron flow appears at the same time, and a current is generated exactly in the manner of a power MOSFET. If the voltage generated by this electron flow is in the range of 0.7V, J1 will be forward biased, some holes will be injected into the N- zone, and the resistivity between N- and N+ will be adjusted, which reduces the power conductance. The total loss of the pass and initiates the second charge flow. The final result is the temporary emergence of two different current topologies within the semiconductor hierarchy: an electron flow (MOSFET current); a hole current (bipolar). When UCE is greater than the turn-on voltage UCE(th), a channel is formed in the MOSFET to provide base current for the transistor, and the IGBT is turned on.

2) Conduction pressure drop

The conductance modulation effect reduces the resistance RN, and the on-state voltage drop is small. The so-called on-state voltage drop refers to the tube voltage drop UDS when the IGBT enters the on-state. This voltage decreases as UCS rises.

3) Shutdown

When a negative bias is applied to the gate or the gate voltage is lower than the threshold, the channel is prohibited and no holes are injected into the N-region. In any case, if the current of the MOSFET drops rapidly during the switching phase, the collector current will gradually decrease. This is because after the start of commutation, there are still a few carriers (less than) in the N layer. The reduction of this residual current value (wake current) depends entirely on the charge density at turn-off, and the density is related to several factors, such as the amount and topology of dopants, layer thickness and temperature. The attenuation of minority carriers gives the collector current a characteristic wake waveform. Collector current will cause increased power consumption and cross-conduction problems, especially in equipment using freewheeling diodes, the problem is more obvious.

In view of the fact that the wake is related to the recombination of minority carriers, the current value of the wake should be closely related to the chip's Tc, IC: and uCE, and has a close relationship with the hole mobility. Therefore, depending on the temperature reached, it is feasible to reduce this undesirable effect of the current acting on the terminal equipment design. When a back pressure or no signal is applied between the gate and the emitter, the channel in the MOSFET disappears, the base current of the transistor is cut off, and the IGBT is turned off.

4) Reverse blocking

When a reverse voltage is applied to the collector, J will be controlled by the reverse bias, and the depletion layer will expand to the N-region. If you reduce the thickness of this layer too much, you will not be able to obtain an effective blocking ability, so this mechanism is very important. In addition, if you increase the size of this area too much, it will continuously increase the pressure drop.

5) Positive blocking

When the gate and emitter are shorted and a positive voltage is applied to the collector terminal, the J junction is controlled by the reverse voltage. At this time, the depletion layer of the N drift zone still bears the externally applied voltage.

6) Latch

The IGBT has a parasitic PNPN thyristor between the collector and the emitter. Under special conditions, this parasitic device will turn on. This phenomenon will increase the amount of current between the collector and the emitter, reduce the ability to control the equivalent MOSFET, and usually cause device breakdown. The thyristor turn-on phenomenon is called IGBT latch-up. Specifically, the causes of such defects are different, but they are closely related to the state of the device.

Friday, April 16, 2021

Analysis of the advantages and disadvantages of PA6 nylon plastic raw materials

The main advantages of PA6 nylon plastic materials:
1. High mechanical strength, good toughness, high tensile and compressive strength. The specific tensile strength is higher than that of metal, and the specific compressive strength is comparable to that of metal, but its rigidity is not as good as that of metal. The tensile strength is close to the yield strength, more than twice as high as ABS. The ability to absorb shock, stress and vibration is strong, and the impact strength is much higher than that of general plastics, and is better than acetal resin.
2. Outstanding fatigue resistance, the parts can maintain the original mechanical strength after repeated inflections. Common escalator handrails, new bicycle plastic rims and other occasions where periodic fatigue is extremely obvious, PA is often used.
3. High softening point and heat resistance (such as nylon 46, etc., high crystalline nylon has a high heat distortion temperature and can be used for a long time at 150 degrees. After PA66 is reinforced with glass fiber, its heat distortion temperature can reach 250 degrees or more).
4. The surface is smooth, the friction coefficient is small, and it is wear-resistant. It is self-lubricating when it is used as a movable mechanical component and has low noise. It can be used without lubricant when the friction is not too high; if lubricant is really needed to reduce friction or help heat dissipation, water, oil, grease, etc. can be selected. As a result, it has a long service life as a transmission component.
5. Corrosion resistant, very resistant to alkalis and most salt solutions, also resistant to weak acids, engine oils, gasoline, aromatic compounds and general solvents, inert to aromatic compounds, but not resistant to strong acids and oxidants. It can resist the erosion of gasoline, oil, fat, alcohol, weak base, etc. and has good anti-aging ability. It can be used as packaging material for lubricating oil and fuel.
6. It is self-extinguishing, non-toxic, odorless, good weather resistance, inert to biological erosion, and has good antibacterial and antifungal capabilities.
7. It has excellent electrical properties. Good electrical insulation. Nylon has a high volume resistance and high breakdown voltage. It can be used as a power frequency insulating material in a dry environment, and it has good electrical insulation even in a high humidity environment.
8. The parts are light in weight, easy to dye and easy to shape. Because of its low melt viscosity, it can flow quickly. It is easy to fill the mold, the solidification point is high after the mold is filled, and the shape can be set quickly, so the plastic machining has a short molding cycle and high production efficiency.

The main disadvantages of PA6 nylon plastic raw materials:
1. Easy to absorb water. The water absorption is large, and the saturated water can reach more than 3%. To a certain extent, it affects the dimensional stability and electrical performance, especially the thickening of thin-walled parts has a greater impact; water absorption will also greatly reduce the mechanical strength of the plastic. When selecting materials, consideration should be given to the influence of the use environment and the accuracy of coordination with other components. Fiber reinforcement can reduce the water absorption rate of the resin, so that it can work under high temperature and high humidity. Nylon has a very good affinity with glass fiber. It is commonly used to make machining uhmw combs, toothbrushes, clothes hooks, fan bones, net bag rope, fruit outer packaging bags and so on. Non-toxic, but not long-term contact with acid and alkali. It is worth noting that after adding glass fiber, the tensile strength of nylon can be increased by about 2 times, and the temperature resistance can be improved accordingly.
2. Poor light resistance. In a long-term high temperature environment, it will oxidize with oxygen in the air, and the color will turn brown at the beginning, and then the surface will be broken and cracked.
3. The injection molding technology requirements are strict: the presence of trace moisture will cause great damage to the molding quality; the dimensional stability of the product is difficult to control due to thermal expansion; the existence of sharp corners in the product will cause stress concentration and reduce the strength of CNC mechanical parts; If the wall thickness is not uniform, it will cause distortion and deformation of the parts; the precision requirements of the CNC machining factory equipment are very high during the post-processing of the parts.
4. It will swell by absorbing water and alcohol. It is not resistant to strong acids and oxidants, and cannot be used as acid-resistant materials.

The advice of the CNC master, you must do this for CNC, otherwise you will not be able to get ahead!

    Think about it before 2008, when the post-70s generation wanted to enter a similar factory, they had to ask acquaintances, treats and gave gifts. What now? On the other hand, no young people want to enter the factory as workers anymore, and the bosses can't get up anymore, licking their faces and telling all the good things, even coaxing and cheating, it is difficult to recruit people.
     In the past, 90% of the urban residents in China's coastal cities were the children of workers, but these people are no longer working at all, and young people in the suburbs also despise being workers. Even if they have no way, they have to find a freelancer in the factory. Management position, half-hearted messing around. A large number of small and medium-sized manufacturing industries are in a bad world today. The reason they can barely maintain is because there are a group of migrant workers born in the 60s and 70s who are supporting them. The motivation for working hard is that their children will never go to the factory as workers, which can change the destiny of the family.
If it takes another ten years, when these people retire or can't do anything, there will be no workers in the manufacturing workshops.


     Now the post-80s and post-90s, the main purpose of working in the factory is to find someone to fall in love with. By the way, they can learn a little bit and are not interested in learning professional and technical skills at all. This group of people has no chance, they have lost their ideals, they are desperate, and they will give up before they get rich. Plan your own path well and don't follow your feelings.
     Young cnc machining parts engineers should make arrangements according to their personal ideals. Most people do not expect to become academicians or professors, but hope to live more moisturized and refreshed lives. Then, you need to carefully arrange your own trajectory. In which industry you should start with, which products to make, gradually get a deeper understanding of the industry. Don't change jobs frequently, especially don't change positions for a little salary. In the long run, this little money is nothing at all. When you have so much knowledge about an industry After several years of experience, money will not be a problem at all in the future. Frequent turbulence is not the best policy. In the end, you have no idea about any industry, and you will always be a novice! You can do technology, don't indulge in technology, don't devote yourself to technology!
     Don't be a master of machining uhmw technology, just be a master of comprehensive quality!
In a company, we often look down on someone, saying that he "knows nothing, why do you get so much money, why do you get promoted! This is a common and typical engineer's pedantic words. Is Zhou Gong Zhao Gong very good? People who can go up must have his abilities, and they are abilities you don't have.
    Think about it, the boss has been in business for so many years, is it not as knowledgeable as you, a recruit? People may be good at management, good at understanding the boss's intentions, good at department coordination, and so on. Therefore, you must cultivate your own abilities in many aspects, including management, affinity, ability to observe words and expressions, and research skills. To become a master of comprehensive quality, you have a bright future, otherwise you can only hide in the corner and become a "Green Key Man"! Skills other than technology are more important! !
    Make friends of all kinds and don't think that you have a common language and only communicate with CNC engineers. In fact, the more important thing is to interact with other types of people. If you want to be a boss or senior management one day, then these are the people you face all day long. Understanding their experience, thinking habits, hobbies, learning their problem-solving patterns, and understanding the phenomena and problems in all corners of the society are huge capital for future development. Without these, they will be clumsy, stumble, and encounter many difficulties.. ....
     Knowledge is not necessarily specialized, but it must be broad, read more books in other areas! Finance, accounting, import and export, taxation, law, etc., do some accumulation for the future, and the future will be more useful!
      Seize the opportunity to transform to plastic machining technical management or marketing. If you want to have a future, you can't continue to develop. If you want to change to management or sales at an appropriate time, the future will be even greater. The technology was not used in vain before, and it will be used in the future. Got it. Engage in management can cultivate one's own leadership ability, engage in sales can cultivate one's own market concepts and thinking, and at the same time accumulate a huge network of contacts for one's future development!

What is FPGA

FPGA design is not a simple chip research, but mainly uses the FPGA model to design products in other industries. Unlike ASICs, FPGAs are widely used in the communications industry. Through the analysis of the global FPGA product market and related suppliers, combined with the current actual situation in my country and domestic leading FPGA products, we can discover the future development direction of related technologies, which will play a very important role in promoting the overall improvement of my country's technological level.

FPGA
FPGA

Compared with traditional chip design, FPGA chips are not simply limited to research and design chips, but can be optimized for products in many fields with the help of specific chip models. From the perspective of chip devices, FPGA itself constitutes a typical integrated circuit in a semi-custom circuit, which contains a digital management module, an embedded unit, an output unit, and an input unit. On this basis, it is necessary for FPGA chips to focus on comprehensive chip optimization design, and to add new chip functions by improving the current chip design, thereby achieving the simplification and performance improvement of the overall chip structure.

Basic structure
FPGA device is a kind of semi-custom circuit in the application-specific integrated circuit, which is a programmable logic array, which can effectively solve the problem of fewer gate circuits in the original device. The basic structure of FPGA includes programmable input and output units, configurable logic blocks, digital clock management modules, embedded block RAM, wiring resources, embedded dedicated hard cores, and underlying embedded functional units. Because FPGA has the characteristics of abundant wiring resources, repeatable programming, high integration, and low investment, it has been widely used in the field of digital circuit design. The FPGA design process includes algorithm design, code simulation and design, board debugging, designers and actual needs to establish the algorithm architecture, use EDA to establish a design plan or HD to write design code, through code simulation to ensure that the design plan meets actual requirements, and finally board Level debugging, use the configuration circuit to download the relevant files to the FPGA chip to verify the actual operation effect.

Working Principle
FPGA adopts the concept of logic cell array LCA (Logic Cell Array), which includes three parts: Configurable Logic Block (CLB), Input Output Block (IOB) and Interconnect. Field programmable gate array (FPGA) is a programmable device. Compared with traditional logic circuits and gate arrays (such as PAL, GAL and CPLD devices), FPGA has a different structure. FPGA uses a small look-up table (16×1RAM) to realize combinational logic. Each look-up table is connected to the input of a D flip-flop, and the flip-flop drives other logic circuits or I/O to form a combination that can be realized. The logic function can also realize the basic logic unit module of the sequential logic function. These modules are connected to each other or I/O modules by metal wires. FPGA logic is realized by loading programming data into the internal static storage unit. The value stored in the memory unit determines the logic function of the logic unit and the connection between modules or between modules and I/O, and finally determines The function that FPGA can realize, FPGA allows unlimited programming.

Liquid-crystal display (LCD) Over View

LCD Display History:

Liquid-crystal display (LCD) was invented in 1964 at RCA Laboratories in Princeton, NJ. In 1970, twisted-nematic (TN) mode of operation was discovered, which gave LCD the first commercial success. The LCD manufacturers supplied small-size displays to portable products such as digital watches and pocket calculators. In 1988, Sharp Corporation demonstrated a 14-in. active-matrix full-color full-motion display using a TFT (thin-film-transistor) array. Observing this, Japan launched a true LCD industry. Large-size displays were first supplied to personal computers and then to television receivers. In the second half of 1990s, the industry has moved to Korea and Taiwan.

LCD display

LCD display

Industrial Display Systems:

Industrial Display Systems provide a wide range of reliable displays from 5.7″ to 55″ including LCD displays, touch screen panels, outdoor displays and digital signage displays, and a series of industrial monitors including open frame monitors and panel mount monitors, which work perfectly with embedded boards and systems to fulfill various application needs.

LCD Display Size:

On 2D displays, such as computer monitors and TVs, the display size (or viewable image size or VIS) is the physical size of the area where pictures and videos are displayed. The size of a screen is usually described by the length of its diagonal, which is the distance between opposite corners, usually in inches. It is also sometimes called the physical image size to distinguish it from the "logical image size," which describes a screen's display resolution and is measured in pixels. 

LCD size

LCD size

LCD Monitors:

Liquid crystal displays are flat panel monitors which modify a white backlight by creating a barrier of millions of liquid crystals which can adjust which color is ultimately displayed to the end user.

Application of LCD (liquid crystal display):

  1. The LCDs are commonly used in all the digital wrist watches for displaying time.
  2. The LCD (liquid crystal display) is used in aircraft cockpit displays.
  3. It is used for displaying images used in digital cameras.
  4. It is used in instruments panel where all the lab instruments uses LCD screens for display.
  5. It is used as a display screen in calculators.
  6. The television is main applications of LCD.
  7. Mostly the computer monitor is made up of LCDs.
  8. The LCDs are used in mobile screens.
  9. It is also used in video players.

List of LCD panel manufacturers

China Karson Ho -SHENZHEN GUOJIA
Taiwan AU Optronics
China BOE (bought Hydis)
Japan Casio (former)
Taiwan ChiMei former, merged with Innolux)
Taiwan Chungwha Picture Tubes
China East Rising
Japan Epson
Taiwan Giantplus technology
Taiwan HannStar Display Corporation
Japan Hitachi (former, merged with Japan Display alongside Sony and Toshiba)
China HKC
Taiwan InnoLux Corporation
Japan Japan Display
Japan Kyocera
South Korea LG Display
United States LXD Incorporated
Japan Mitsubishi Electric
Japan NEC Display Solutions (former, now Tianma)
China New Vision Display
China/United States Orient Display
Japan Panasonic Corporation (former)
Japan Pioneer
United States Planar Systems (former)
Taiwan Powertip Technology Corporation
South Korea Samsung Display (former)
Japan/Taiwan Sakai display products(joint venture between Foxconn and Sharp Corporation)
Japan Sharp Corporation
South Korea/Japan S-LCD (former joint venture between Sony and Samsung, now Samsung)
Japan Sony (former, merged into Japan Display)
China TCL (as CSOT)
China Tianma
Japan Toshiba(Former, merged into Japan Display)
Japan Toshiba Matsushita Display Technology(Dissolved in 2009, bought by Toshiba)
China TOPWAY Display
Hong Kong Truly Semiconductors
India Videocon
Taiwan Winstar display
Taiwan PalmTech
China Maclight Display
China HEM
Taiwan/China Microtips Technology

Thursday, April 15, 2021

Plastic materials and their characteristics

      Plastic materials refer to materials that use polymer synthetic resin as the main component, have plasticity and fluidity at a certain temperature and pressure, can be molded into a certain shape, and keep the shape unchanged under certain conditions. Commonly used plastic materials are divided into thermosetting plastic materials and thermoplastic plastic materials. Thermosetting plastic materials are characterized by being able to solidify into insoluble materials under heat or other conditions. Thermoplastic materials are characterized by repeated heating to soften or cooling to solidify within a specific temperature range. In terms of performance, plastic machining service have the advantages of light weight, good strength, corrosion resistance, good insulation, easy coloring, products can be processed into any shape, high production efficiency, and low price.

      The versatility of the application of plastic materials is inseparable from its own characteristics. The composition characteristics of plastic materials are introduced below.

(1) Molecular structure of plastic materials

The main component of plastic machining  is resin. There are two types of resin, natural resin and synthetic resin.



(2) Composition of plastic materials

Resin: The main function is to bond other components of the plastic material and determine the main properties of the plastic material, such as mechanical, physical, electrical, and chemical properties. The proportion of resin in plastic materials is generally 40% to 65%.

Filler: also known as filler. Correct choice of filler can improve the performance of the plastic material and expand its scope of use.

Plasticizer: Some resins have very little plasticity and poor flexibility. In order to reduce the melt viscosity and melting temperature of the resin, improve its molding processing performance, improve the flexibility, elasticity and other necessary properties of plastic materials, usually Add a non-volatile high-boiling organic compound that is compatible with the resin. Such substances are called plasticizers.

Coloring agent: also known as coloring material, mainly for aesthetics and decoration, including paint part.

Stabilizer: Any substance that can delay the deterioration of plastic materials is called stabilizer, light stabilizer, heat stabilizer and antioxidant.

Lubricant: improve the fluidity of plastic material melt, reduce or avoid friction and adhesion to equipment or molds, and improve the surface finish of Plastic Machining Parts.

 

The most complete classification of polymer materials in history

Macromolecular materials, also called polymer materials, are materials composed of macromolecular compounds as the matrix and with other additives (auxiliary agents).
Polymer material classification
1. Classification by source
Polymer materials are classified into natural polymer materials and synthetic polymer materials according to their sources.
Natural macromolecules are macromolecule substances that exist in animals, plants and organisms, and can be divided into natural fibers, natural resins, natural rubber, animal glues, and so on. Synthetic polymer materials mainly refer to the three major synthetic materials of plastics, synthetic rubber and synthetic fibers, in addition to adhesives, coatings and various functional polymer materials.
Synthetic machining uhmw have properties that are not available or superior to natural polymer materials-smaller density, higher mechanics, wear resistance, corrosion resistance, electrical insulation, etc.

2. Classified by application
Polymer materials are classified into rubber, fiber, plastic, polymer adhesives, polymer coatings and polymer-based composite materials according to their characteristics.

3. Classified by application function
According to the classification of material application functions, polymer materials are divided into three categories: general polymer materials, special polymer materials and functional polymer materials. General polymer materials refer to polymer materials that can be produced on a large scale and have been widely used in major areas of the national economy such as construction, transportation, agriculture, electrical and electronic industries and people's daily lives.
These are divided into different types such as plastics, rubber, fibers, adhesives, and coatings. Special polymer materials are mainly uhmw machining with excellent mechanical strength and heat resistance, such as polycarbonate, polyimide and other materials, which have been widely used in engineering materials. Functional polymer materials refer to polymer compounds that have specific functions and can be used as functional materials, including functional separation membranes, conductive materials, medical polymer materials, liquid crystal polymer materials, etc.