Resistors, often called resistors, are one of the most common and widely used electronic components. Understanding the characteristics of the manufacturing process of the resistor has important help for us to learn and understand the main parameters of the resistor, and to correctly select and use the resistor.
The resistor is made of a material with a relatively high resistivity, which plays a role of stabilizing or adjusting current and voltage in the circuit.
Resistance classification:
(1) According to the resistance can be adjusted divided into fixed resistors, variable resistors two major categories.
Resistors with a fixed resistance are called fixed resistors; resistors with a continuously variable resistance are called variable resistors (including trimmer resistors and potentiometers).
(2) There are carbon film resistors, metal film resistors, wire wound resistors, etc. according to the material of manufacture.
(3) Axial lead resistors and leadless resistors are divided according to the lead wires.
(4) According to the use of different general purpose resistors, precision resistors, high frequency resistors, thermistors, photoresistors, varistors and so on.
The classification of these resistors is introduced below.
1. Carbon film resistor The carbon film resistor separates the carbon of organic compounds in a high-temperature vacuum furnace, and then deposits carbon on the surface of the ceramic substrate to form a certain resistance value. (The resistance value can be changed by changing the thickness of the carbon film. Or a length of carbon film (resistor body), and finally after appropriate joints are thinned and coated on the surface with an epoxy resin seal to produce a resistor, which is also called a pyrolytic carbon film resistor. .
The main feature of carbon film resistors is their high frequency characteristics, wide resistance range, and low price but poor accuracy. Is China's current production of the largest, most widely used universal resistors. It is widely used in recorders, televisions and other electronic products.
2. Metal film resistor Metal film resistor is made by depositing a layer of alloy powder on a porcelain substrate under vacuum conditions. Different resistance values ​​can be obtained by changing the thickness or length of the metal film. Metal film resistors mainly include metal thin film resistors (CN) metal oxide film resistors (RS) and metal glaze film resistors (RK).
Due to its advantages of high power, low noise, small temperature coefficient, high precision, high frequency characteristics, and wide resistance range, the metal film is widely used in high-end audio equipment, computers, test instruments, and automation equipment.
3, precision metal film resistor precision metal film resistor is a nickel-cadmium or similar alloy vacuum plating technology, the resistance material is coated on the surface of the white porcelain rod, after cutting and debugging resistance, in order to achieve the final requirements of the precision resistance. Precision metal film resistors have a precise resistance and a small tolerance range. They are mainly used in applications where the resistance of the resistors is required to be precise.
4. Impact-resistant glass glaze film power resistance Impact-resistant glass glaze film power resistor is a kind of resistor produced by metal glass glaze plating on magnetic rod, which has excellent impact resistance and high temperature stability. It is mainly used in High power devices.
5, wirewound resistor wirewound resistor is the resistance wire (constantus wire or manganese copper wire) around the heat-resistant porcelain body, the surface coated with heat, humidity, non-corrosive non-flammable protective coating. Wirewound resistors have the advantages of good heat resistance, small temperature coefficient, light weight, short-time overload resistance, low noise, stable resistance, and low inductance, but their high frequency characteristics are poor, so they are widely used in low-frequency precision instruments. .
6, cement resistance Cement resistance is also a kind of winding resistance, is the resistance wire wound around the heat-resistant ceramic parts, coupled with heat, moisture and corrosion resistant materials from outside fixed. Cement resistance is usually put resistor body into a square porcelain frame, made of special non-flammable heat-resistant cement filled and sealed, because of its shape like a white rectangular cement block, it is called cement resistance.
Cement resistance has high power, good heat dissipation, high stability, moisture resistance, shock resistance and so on. Mainly used in high-power circuits, such as power circuit over-current detection, protection circuit, audio power amplifier power output circuit.
7. The fuse resistor is also known as the fuse resistor. The fuse resistor has both the resistance and the fuse function. It can be used as a resistor at ordinary times. Once the current is abnormal, it will act as a fuse to protect the equipment.
The fuse resistor plays the dual role of fuse and resistor in the circuit, and is mainly applied in the power output circuit. The resistance of the insurance resistor is generally small (a few ohms to tens of ohms) and the power is also small (1/8---1W).
Short-circuit fault occurs in the circuit load. When overcurrent occurs, the temperature of the fuse resistor will rise to 500°C-600°C in a short time. At this time, the resistance layer will be heated and flammable, which will act as a fuse. To improve the safety of the whole machine.
8, network resistor network resistors, also known as exclusion. The network resistance is a kind of composite resistor that is made by assembling a plurality of resistors together. Network resistors have the advantages of easy assembly and high installation density, and are now widely used in electronic circuits.
9. Surface mount resistors Surface mount resistors are also known as leadless resistors, chip resistors, chip resistors, and SMD resistors.
Surface mount resistors are available in both rectangular and cylindrical shapes. The rectangular surface mount resistor is mainly composed of four parts: a ceramic substrate, a resistive film, a protective layer, and a metal terminal electrode. The ceramic substrate is generally made of 96% aluminum trioxide (AL2O3) ceramics; the resistive film is usually printed on the substrate using a resistor paste consisting of RuO2 and then sintered; the protective layer covering the resistive film is generally made of glass paste. After the material is printed, the glaze is fired; the terminal electrode is composed of three layers of materials: the inner layer (that is, the part contacting the resistive film) is an Ag-Pd alloy with low contact resistance and strong adhesion; the middle layer is Ni, and is mainly used to prevent The tip electrode is detached; the outer layer is a solderable layer composed of Sn or Sn-Pb or Sn-Ce alloy.
Cylindrical surface mount resistors are coated with a metal or carbon resistive film on a high-alumina ceramic substrate, and then metal electrode caps are pressed at both ends, and a layer of heat-resistant insulating paint is applied after the thread grooves are cut to determine the resistance. It is made by spraying color code marks on the surface.
10, NTC, PTC thermistor
The NTC thermistor is a thermal element with a negative temperature coefficient change. Its resistance decreases with increasing temperature and can be used to stabilize the operating point of the circuit. The PTC thermistor is a thermal element with a positive temperature coefficient variation. Before reaching a certain temperature, the resistance value decreases slowly with increasing temperature, and when it exceeds this temperature, the resistance value increases sharply. This particular temperature point is called the Curie point. The Curie point of a PTC thermistor can be changed by changing the proportion of each component in its material. It is widely used in home appliances, such as degaussing resistors for color TVs and thermostats for rice cookers.
The resistor is made of a material with a relatively high resistivity, which plays a role of stabilizing or adjusting current and voltage in the circuit.
Resistance classification:
(1) According to the resistance can be adjusted divided into fixed resistors, variable resistors two major categories.
Resistors with a fixed resistance are called fixed resistors; resistors with a continuously variable resistance are called variable resistors (including trimmer resistors and potentiometers).
(2) There are carbon film resistors, metal film resistors, wire wound resistors, etc. according to the material of manufacture.
(3) Axial lead resistors and leadless resistors are divided according to the lead wires.
(4) According to the use of different general purpose resistors, precision resistors, high frequency resistors, thermistors, photoresistors, varistors and so on.
The classification of these resistors is introduced below.
1. Carbon film resistor The carbon film resistor separates the carbon of organic compounds in a high-temperature vacuum furnace, and then deposits carbon on the surface of the ceramic substrate to form a certain resistance value. (The resistance value can be changed by changing the thickness of the carbon film. Or a length of carbon film (resistor body), and finally after appropriate joints are thinned and coated on the surface with an epoxy resin seal to produce a resistor, which is also called a pyrolytic carbon film resistor. .
The main feature of carbon film resistors is their high frequency characteristics, wide resistance range, and low price but poor accuracy. Is China's current production of the largest, most widely used universal resistors. It is widely used in recorders, televisions and other electronic products.
2. Metal film resistor Metal film resistor is made by depositing a layer of alloy powder on a porcelain substrate under vacuum conditions. Different resistance values ​​can be obtained by changing the thickness or length of the metal film. Metal film resistors mainly include metal thin film resistors (CN) metal oxide film resistors (RS) and metal glaze film resistors (RK).
Due to its advantages of high power, low noise, small temperature coefficient, high precision, high frequency characteristics, and wide resistance range, the metal film is widely used in high-end audio equipment, computers, test instruments, and automation equipment.
3, precision metal film resistor precision metal film resistor is a nickel-cadmium or similar alloy vacuum plating technology, the resistance material is coated on the surface of the white porcelain rod, after cutting and debugging resistance, in order to achieve the final requirements of the precision resistance. Precision metal film resistors have a precise resistance and a small tolerance range. They are mainly used in applications where the resistance of the resistors is required to be precise.
4. Impact-resistant glass glaze film power resistance Impact-resistant glass glaze film power resistor is a kind of resistor produced by metal glass glaze plating on magnetic rod, which has excellent impact resistance and high temperature stability. It is mainly used in High power devices.
5, wirewound resistor wirewound resistor is the resistance wire (constantus wire or manganese copper wire) around the heat-resistant porcelain body, the surface coated with heat, humidity, non-corrosive non-flammable protective coating. Wirewound resistors have the advantages of good heat resistance, small temperature coefficient, light weight, short-time overload resistance, low noise, stable resistance, and low inductance, but their high frequency characteristics are poor, so they are widely used in low-frequency precision instruments. .
6, cement resistance Cement resistance is also a kind of winding resistance, is the resistance wire wound around the heat-resistant ceramic parts, coupled with heat, moisture and corrosion resistant materials from outside fixed. Cement resistance is usually put resistor body into a square porcelain frame, made of special non-flammable heat-resistant cement filled and sealed, because of its shape like a white rectangular cement block, it is called cement resistance.
Cement resistance has high power, good heat dissipation, high stability, moisture resistance, shock resistance and so on. Mainly used in high-power circuits, such as power circuit over-current detection, protection circuit, audio power amplifier power output circuit.
7. The fuse resistor is also known as the fuse resistor. The fuse resistor has both the resistance and the fuse function. It can be used as a resistor at ordinary times. Once the current is abnormal, it will act as a fuse to protect the equipment.
The fuse resistor plays the dual role of fuse and resistor in the circuit, and is mainly applied in the power output circuit. The resistance of the insurance resistor is generally small (a few ohms to tens of ohms) and the power is also small (1/8---1W).
Short-circuit fault occurs in the circuit load. When overcurrent occurs, the temperature of the fuse resistor will rise to 500°C-600°C in a short time. At this time, the resistance layer will be heated and flammable, which will act as a fuse. To improve the safety of the whole machine.
8, network resistor network resistors, also known as exclusion. The network resistance is a kind of composite resistor that is made by assembling a plurality of resistors together. Network resistors have the advantages of easy assembly and high installation density, and are now widely used in electronic circuits.
9. Surface mount resistors Surface mount resistors are also known as leadless resistors, chip resistors, chip resistors, and SMD resistors.
Surface mount resistors are available in both rectangular and cylindrical shapes. The rectangular surface mount resistor is mainly composed of four parts: a ceramic substrate, a resistive film, a protective layer, and a metal terminal electrode. The ceramic substrate is generally made of 96% aluminum trioxide (AL2O3) ceramics; the resistive film is usually printed on the substrate using a resistor paste consisting of RuO2 and then sintered; the protective layer covering the resistive film is generally made of glass paste. After the material is printed, the glaze is fired; the terminal electrode is composed of three layers of materials: the inner layer (that is, the part contacting the resistive film) is an Ag-Pd alloy with low contact resistance and strong adhesion; the middle layer is Ni, and is mainly used to prevent The tip electrode is detached; the outer layer is a solderable layer composed of Sn or Sn-Pb or Sn-Ce alloy.
Cylindrical surface mount resistors are coated with a metal or carbon resistive film on a high-alumina ceramic substrate, and then metal electrode caps are pressed at both ends, and a layer of heat-resistant insulating paint is applied after the thread grooves are cut to determine the resistance. It is made by spraying color code marks on the surface.
10, NTC, PTC thermistor
The NTC thermistor is a thermal element with a negative temperature coefficient change. Its resistance decreases with increasing temperature and can be used to stabilize the operating point of the circuit. The PTC thermistor is a thermal element with a positive temperature coefficient variation. Before reaching a certain temperature, the resistance value decreases slowly with increasing temperature, and when it exceeds this temperature, the resistance value increases sharply. This particular temperature point is called the Curie point. The Curie point of a PTC thermistor can be changed by changing the proportion of each component in its material. It is widely used in home appliances, such as degaussing resistors for color TVs and thermostats for rice cookers.