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  • Ten Daily Electronic Common Sense-Section 109

    What is the traditional cover type packaging method?

    The traditional cover plate packaging method mainly uses glass as the substrate, glass or metal as the cover plate, and covers the organic functional layer in it. In an inert gas (usually Na) or vacuum environment, the substrate and cover are bonded with epoxy resin uV curing agent. The entire packaging process is completed in a glove box, which isolates the influence of harmful gases from the outside world.
    Although metal-encapsulated devices can block the penetration of harmful components such as water vapor and oxygen into the device. It can effectively protect the OLED functional layer and make the device more robust. However, the opaque properties of metal limit the use of metal cover plates. In order to remove water and oxygen remaining in the device space, a desiccant is often added.

    What is the thermoelectric phenomenon?

    Two conductors of different materials form a closed loop.
    If the temperature of the two junctions is different, a certain current (potential) will be generated in the loop. Its size is related to material properties and junction temperature, and this physical phenomenon is called thermoelectric phenomenon.

    What should be paid attention to in the development of power management?

    1. Pay more attention to safety
    2. Pay more attention to environmental protection
    3. Pay more attention to system integration
    4. Pay more attention to EMI
    5. Analog and digital power

    What methods are available for data type conversion?

    • Type notation method
    • Type function method

    In the RFID system, there are mainly two types of signal interference, what are they?

    One is conflict interference between readers, which is caused by multiple readers sending signals at the same time;
    The other is the conflicting interference between tags, which is caused by multiple tags responding to the reader at the same time.

    What processing techniques are used in the micro-sensor?

    Micro-sensors are fabricated by micromachining technology.
    Including photolithography, etching and other micromachining processes, the volume of sensitive components can be as small as micron level.

    What are the design units allowed by the constant definition statement?

    The design units allowed by the constant definition statement are entities, structures, packages, blocks, procedures, and subroutines.

    What are the two parts of the PMBus specification?

    The PMBus specification has two parts:
    Part I includes general requirements, this part also specifies hardware signal transmission and electrical interface and timing requirements;
    Part II specifies the command language used in PMBus.

    What constitutes a phototransistor?

    The structure and principle of the phototransistor The phototransistor is very similar to the ordinary transistor.
    It consists of two PN junctions, there are NPN type and PNP type.

    Circuit online maintenance instrument maintenance principle for circuit boards:

    To repair a relatively unfamiliar circuit board without any schematic diagram, the so-called “experience” in the past is difficult to do. Although people with deep knowledge of hardware are full of confidence in repairs, if the method is not right, the work will still be less effective. So, how can we improve the maintenance efficiency? According to the statistics of our company’s imported equipment maintenance center, the following principles should be followed in an orderly and orderly manner. 
    Principle 1: Look first and then measure Use tools: multimeter, magnifying glass When holding a circuit board to be repaired, it is a good habit to first check it visually. When necessary, you need to use a magnifying glass to see what? Mainly see: 1. Whether there is a disconnection; 2. There is a disconnection phenomenon when the component components such as resistors, electrolytic capacitors, inductors, diodes, triodes, etc.; 3. The circuit board Is there any breakage, adhesion, etc. in the connecting lines of the printed board; 4. Has anyone repaired it? Which components have been moved? Are there any operational mistakes such as virtual soldering, missing soldering, and reverse insertion. After confirming that the above conditions are not repaired, first measure the resistance between the power supply and the ground of the circuit board with a multimeter. Usually the resistance of the circuit board is above 70-80 degrees Celsius. If the resistance is too small, it is only a few or a dozen ohms. It means that there are components on the circuit board that are broken down or partially broken down, and measures must be taken to find the broken down components. The specific method is to supply power to the repaired board, touch the temperature of each device on the circuit board with your hands, and the hot lecturer focuses on suspecting the object. If the resistance value is normal, use a multimeter to measure the resistance, diode, triode, field effect transistor, dial switch and other force components on the board. The purpose is to first ensure that the measured components are normal. Our reasoning is that if a problem can be solved with a multimeter, don’t complicate it. 
    Principle 2. Use tools: HY circuit online maintenance instrument If the situation allows, it is best to find a good board that is the same as the board to be repaired as a reference. Then use the dual-rod VI curve scan function together to perform a good and bad comparison test of the two boards, and the starting point of comparison can start from the port. Then from the outside to the inside, especially the comparison test of the capacitance, it can make up for the shortcoming that the multimeter is difficult to detect whether there is leakage online. 
    Principle three, first easy then difficult Use tools: HY circuit online repair instrument, electric soldering iron, marker pen to improve the test effect. Before the online functional test of the circuit board, some technical processing should be done on the repaired board to minimize the negative impact of various disturbances on the test process. The specific measures are: 1. Preparation before the test Short-circuit the crystal oscillator, and weld a foot to open the large electrolytic capacitor. Because the charging and discharging of the capacitor can also cause interference. 2. Use the exclusion method to test the device. During the online test or comparison of the device, for any device that passes the test (or is relatively normal), please directly confirm the test result for record. If the test fails (or is out of tolerance), it can be tested again. If it still fails, you can also confirm the test results first, and keep testing like this until the devices on the board are tested (or compared). Then come back to those devices that fail the test (or are out of tolerance). For devices that fail the functional online test, the instrument also provides a less formal but more practical processing method. Since the power supply of the instrument to the circuit board can be applied to the corresponding power supply and ground pins of the device through the test clip. If a knife is applied to the power pins of a device, the device will be disconnected from the board power supply system. At this time, perform an online functional test on the device, because other devices on the circuit board will no longer interfere. The actual test effect is equivalent to “quasi-offline”, and the accuracy rate will be greatly improved. 3. Use the ASA-VI curve scan test to compare and test the devices not covered by the test library. Because the ASA-VI intelligent curve scanning technology can be applied to the comparison test of any device, as long as the test clip can clamp the device, there is another reference board. Through the comparative test, it also has a strong fault detection capability for the device. This function makes up for the deficiency that the online functional test of the device is subject to the test library, and expands the detection range of the instrument for circuit board faults. In reality, it is often impossible to find a good board for reference, and the circuit structure of the board to be repaired does not have any symmetry. In this case, the ASA-VI curve scan comparison test function does not work, and the online functional test is due to the incompleteness of the device test library. It is impossible to test every device on the circuit board, and the circuit board still cannot be repaired. Here is the limitation of the circuit online repair instrument. Just like there is no cure for everything. 
    Principle 4. Static first and then dynamic: Because the circuit online maintenance instrument can only perform functional online testing and static characteristic analysis on the devices on the circuit board at present. Whether it is completely repaired must be tested by the whole machine. Therefore, it is best to first check whether the power supply of the device is correctly supplied to the circuit board as required.


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