SMD Resistor, also known as Chip Fixed Resistor, is a kind of metal glass glaze resistor. It is made by mixing metal powder and glass glaze powder and printing on the substrate using screen printing method. It is resistant to moisture and high temperature and has a small temperature coefficient. . Because of its small size and light weight, it can save circuit space costs and make the design more sophisticated, so it is widely used.
The chip resistor is a very small resistive device. It is rectangular in shape, usually only a few millimeters long and a few millimeters wide, and its thickness is also very thin. This resistive device is usually mounted directly on the circuit board using surface mount technology (SMT). Its function is to reduce the resistance value of the circuit to achieve the purpose of adjusting power performance
Composition of chip fixed resistor
(1) Base material:
The substrate material is generally 96% alumina ceramic. In addition to excellent insulation, the substrate also needs to have excellent thermal conductivity at high temperatures. Characteristics such as electrical performance and mechanical strength. In addition, the substrate needs to be flat and accurately marked to fully ensure that the resistors and electrode pastes are printed in place.
(2) Resistive film:
It is made by printing resistive paste with a certain resistivity on a ceramic substrate and then sintering it. Resistor paste is generally made of cerium oxide
(3) Protective film:
The protective film covers the resistor film and is mainly used to protect the resistor body. On the one hand, it plays the role of mechanical protection, and on the other hand, it insulates the surface of the resistor to prevent the resistor from contacting adjacent conductors and causing failure. During the process of electricity passing through the middle electrode, it can also prevent the resistance film from being eroded by the conductive liquid, resulting in a decrease in resistance performance. The protective film is generally made of low melting point glass paste, which is printed and sintered.
(4) Electrode:
In order to ensure good solderability and reliability of the resistor, a three-layer electrode structure is generally used with inner, middle and outer electrodes.
The inner electrode is the internal electrode connected to the resistor. The electrode material should be selected to have low contact resistance with the resistor film, strong bonding with the ceramic substrate and good chemical resistance. It is easy to perform electroplating operations. It is generally made of silver ingot aluminum alloy packaging, printing and calcining. . The inner electrode is an electroplated nickel layer, also known as the barrier layer
Its function is to improve the heat resistance of the resistor during welding and buffer the thermal shock during welding. It also prevents silver ions from migrating to the resistive layer and avoiding etching of the internal electrodes (which are etched by the solder). The external electrode is a tin-lead layer, also called a solderable layer. Its function is to make the electrode have good solderability and extend the shelf life of the electrode. It is usually plated with tin-lead alloy.
Advantages of chip resistors
Chip resistors are used in a wide range of applications, such as mobile phones, computers, and precision medical electronic equipment. The reason why they are so widely used is mainly because they have the following outstanding advantages:
(1) Small size and light weight
Chip resistors are relatively small and light in weight. They do not take up space on the circuit board during installation, and there is no need to worry about the weight of the equipment causing it to be overweight. It has become a very important chip electronic component in small devices
(2) Has strong and reliable electrical performance
Chip resistors have extremely strong electrical properties and can be installed in electronic equipment to protect circuits and stabilize voltage. For terminal manufacturers, using such resistors can ensure the safety of electronic equipment.
(3) Long service life
Chip resistors have excellent long-term stability and reliability, ensuring long-term stable circuit performance, reducing production costs and improving productivity
(4) Low noise
Due to their stable construction and high-quality materials, these resistors generate minimal electrical noise when sensitive electronic circuits
(5) Easy to weld, disassemble and assemble
Chip resistors do not require via holes, use less tin, and are easy to disassemble and assemble. Even if the components are disassembled multiple times, the circuit board will not be damaged.
Applications
(1) Resistive terminal loads in digital circuits and analog circuits
Chip resistors are widely used in digital circuits and analog circuits. They act as resistive terminal loads to keep signals in digital circuits in a logical state and limit current in analog circuits to a certain range to achieve circuit functions.
(2) Anti-interference resistance of power line
In industrial control and electronic equipment, chip resistors are often used as anti-interference resistors in power lines. The anti-interference ability of the power line will directly affect the stability and performance of the entire device, and adding chip resistors can effectively reduce the electromagnetic interference and noise impact of the power line on the device.
(3) Electronic load regulation in electronic components
Many electronic components, such as LCD screens, LED lights, tuning circuits, etc., need to be used with load resistors. Since electronic components are usually powered by external power supplies, in order to ensure the normal operation and service life of the circuit, it is necessary to adjust the load resistance through chip resistors to prevent equipment damage and personnel safety issues caused by excessive current.
(4) Voltage divider in temperature sensor
Chip resistors are also commonly used as voltage dividers in temperature sensors. The temperature sensor determines the ambient temperature by measuring voltage, and the voltage divider can expand the measurement range and ensure signal accuracy, and the chip resistor is one of the most important voltage divider components.
Chip resistors have a wide range of applications. With the development of electronic technology, chip resistors will play a more important role in various electronic equipment, instrumentation, industrial intelligent control and other fields.
Manufacturers
(1)YAGEO
YAGEO is currently ranked number one in the world in chip resistors, and the company provides one-stop shopping for a complete product portfolio of resistors, capacitors, inductors, transformers, relays, antennas, wireless components and current protection components
The company was founded in 1977. Its main products include traditional resistors, thin film chip resistors, thick film chip resistors, chip resistors, etc...
(2)Samsung Electro-Mechanics
Founded in 1973, Samsung Electro-Mechanics has grown into a world-class company that develops and produces major electronic components. The company's resistor products include: General Resistor, Array Resistor, Current Sensing Resistor (Thick Film Type), Current Sensing Resistor (Metal Plate Type), Anti Sulfur Resistor, High power Resistor, Total Pb free Resistor
(3)Vishay
Vishay is a trusted manufacturer of electronic components and resistors serving the industrial, computing, automotive, consumer, telecommunications and medical markets. Resistor technology options include thin film, thick film, wirewound and Power Metal Strip®
(4) Walsin Technology Corporation
Walsin is a leading global manufacturer of passive components with a one-stop product portfolio and global delivery platform. Walsin provides a complete portfolio of chip resistors to meet diversified applications such as automotive electronics, smartphones, and network equipment.
