Listen to the old engineer explain the PCB layout experience
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For electronic products, printed circuit board design is a necessary design process for turning an electrical schematic into a specific product. The rationality of the design is closely related to product production and product quality. For many people who have just engaged in electronic design, they have little experience in this area. Although they have learned the printed circuit board design software, the printed circuit boards they designed often have various problems. There are few articles on this aspect in many electronic journals. The author of this article has been engaged in printed circuit board design for many years. He would like to share his experience in printed circuit board design with you, hoping to serve as a starting point for discussion. Board layout: The usual order of placing components on a printed circuit board is: Place components in fixed positions that fit closely with the structure, such as power sockets, indicator lights, switches, connectors, and the like. After these devices are placed, use the LOCK function of the software to lock them so that they will not be moved by mistake in the future; Place special components and large components on the circuit, such as heating components, transformers, ICs, etc. Place small components. Distance between components and the edge of the board: If possible, all components should be placed within 3mm from the edge of the board or at least larger than the thickness of the board. This is because guide grooves are required for mass production of assembly line plug-ins and wave soldering. At the same time, it is also to prevent the edge from being damaged due to shape processing. If there are too many components on the printed circuit board and it is necessary to exceed the 3mm range, a 3mm auxiliary edge can be added to the edge of the board. The auxiliary edge has a V-shaped groove and can be broken by hand during production. Isolation between high and low voltage: On many printed circuit boards, there are both high voltage circuits and low voltage circuits. The components of the high voltage circuit part should be separated from the low voltage part. The isolation distance is related to the withstand voltage to be borne. Normally, at 2000kV, the distance on the board should be 2mm, and the distance should be increased proportionally above this. For example, if it is to withstand a 3000V withstand voltage test, the distance between the high and low voltage lines should be more than 3.5mm. In many cases, in order to avoid creepage, grooves are also opened between the high and low voltage on the printed circuit board. Printed circuit board routing: The layout of printed conductors should be as short as possible, especially in high-frequency circuits; the bends of printed conductors should be rounded, and right angles or sharp angles will affect the electrical performance in high-frequency circuits and high wiring density; when wiring two panels, the conductors on both sides should be perpendicular, oblique, or curved to avoid parallelism to reduce parasitic coupling; printed conductors used as input and output of the circuit should be avoided as much as possible to avoid adjacent parallel to avoid feedback, and it is best to add ground wires between these conductors. Printed wire Width: [/font ] The conductor width should be suitable for meeting the electrical performance requirements and being easy to produce. Its minimum value is determined by the current it bears, but the minimum should not be less than 0.2mm. In high-density, high-precision printed circuits, , the wire width and spacing can generally be 0.3mm; the wire width must also consider its temperature rise under high current conditions. Single-panel experiments show that when the copper foil thickness is 50μm, the wire width is 1~1.5mm, and the current is 2A, the temperature rise Therefore, generally, the use of 1 to 1.5 mm wide wires may meet the design requirements without causing temperature rise. 62)] [font=Optima-Regular, The common ground line of the printed conductor should be as thick as possible. If possible, use a line larger than 2 to 3 mm. This is especially important in circuits with microprocessors, because when the ground line is too thin, the current The change of current, the change of ground potential, and the instability of the level of the microprocessor timing signal will deteriorate the noise tolerance. When routing between the IC pins of the DIP package, the 10-10 and 12-12 principles can be applied, that is, When two wires pass between the two pins, the pad diameter can be set to 50 mil, the line width and line spacing are both 10 mil. When only one wire passes between the two pins, the pad diameter can be set to 64 mil, the line width and line spacing are both 10 mil. The distance is 12mil. [/ align] [color= rgb(62, 62, 62)]Pitch between printed wires: The distance between adjacent wires must meet the electrical safety requirements, and for ease of operation and production, the distance should be as wide as possible. The minimum distance must at least be suitable for the voltage to be tolerated. This voltage generally includes the working voltage, additional fluctuation voltage and Peak voltage caused by other reasons. If the relevant technical conditions allow a certain degree of metal residue between the wires, the spacing between them will be reduced. Therefore, designers should take this factor into consideration when considering voltage. When the voltage is low, the spacing between signal lines can be appropriately increased. Signal lines with large differences in high and low levels should be as short as possible and the spacing should be increased. [/ align] Shielding and grounding of printed conductors:[ /color] [align= The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be retained as ground wire on the printed circuit board. The shielding effect obtained in this way is better than that of a long ground wire. The transmission line characteristics and shielding effect will be improved, and the distributed capacitance will also be reduced. . [ /align] The common ground line of the printed conductor is preferably formed into a loop or mesh. This is because When there are many integrated circuits on the same board, especially those with high power consumption, the ground potential difference is generated due to the limitation of the pattern, which causes the reduction of noise tolerance. When the circuit is made, the ground potential difference is reduced. Small. [/ In addition, the ground and power patterns should be as parallel to the data flow direction as possible to suppress The secret to enhancing noise resistance; multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can be regarded as shielding layers. Generally, the ground layer and power layer are designed in the middle of the multi-layer printed circuit board. Inner layer, signal line is designed in inner layer and outer layer.The conductor width should be suitable to meet the electrical performance requirements and be easy to produce. Its minimum value is determined by the current it bears, but the minimum should not be less than 0.2mm. In high-density, high-precision printed circuits, the conductor width and spacing can generally be 0.3mm; the conductor width should also consider its temperature rise under high current conditions. Single-panel experiments show that when the copper foil thickness is 50μm, the conductor width is 1~1.5mm, and the current is 2A, the temperature rise is very small. Therefore, generally using a 1~1.5mm wide conductor may meet the design requirements without causing temperature rise. The common ground wire of the printed conductor should be as thick as possible. If possible, use a line larger than 2 to 3 mm. This is especially important in circuits with microprocessors. Because when the ground wire is too thin, the noise tolerance will be degraded due to changes in the current flowing through, changes in the ground potential, and unstable levels of microprocessor timing signals. When routing between the IC pins of the DIP package, the 10-10 and 12-12 principles can be applied, that is, when two wires pass between the two pins, the pad diameter can be set to 50 mil, and the line width and line spacing are both 10 mils. When only one wire passes between the two pins, the pad diameter can be set to 64 mil, and the line width and line spacing are both 12 mils. [ align=left] Pitch of printed conductors: [ align=left] The spacing between adjacent wires must meet the electrical safety requirements, and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing must at least be suitable for the voltage to be tolerated. This voltage generally includes the operating voltage, additional fluctuation voltage, and peak voltage caused by other reasons. If the relevant technical conditions allow a certain degree of metal residue between the wires, the spacing will be reduced. Therefore, designers should take this factor into consideration when considering voltage. When the wiring density is low, the spacing between signal lines can be appropriately increased, and the signal lines with a large difference in high and low levels should be as short as possible and the spacing should be increased. Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as ground wire on the printed circuit board, so that the shielding effect is better than that of a long ground wire, the transmission line characteristics and shielding effect will be improved, and the distributed capacitance will be reduced. The common ground wire of the printed conductor is preferably formed into a loop or mesh. This is because when there are many integrated circuits on the same board, especially components with high power consumption, the ground potential difference is generated due to the limitation of the graphics, which causes the noise tolerance to decrease. When it is made into a loop, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers. The conductor width should be suitable to meet the electrical performance requirements and be easy to produce. Its minimum value is determined by the current it bears, but the minimum should not be less than 0.2mm. In high-density, high-precision printed circuits, the conductor width and spacing can generally be 0.3mm; the conductor width should also consider its temperature rise under high current conditions. Single-panel experiments show that when the copper foil thickness is 50μm, the conductor width is 1~1.5mm, and the current is 2A, the temperature rise is very small. Therefore, generally using a 1~1.5mm wide conductor may meet the design requirements without causing temperature rise. The common ground wire of the printed conductor should be as thick as possible. If possible, use a line larger than 2 to 3 mm. This is especially important in circuits with microprocessors. Because when the ground wire is too thin, the noise tolerance will be degraded due to changes in the current flowing through, changes in the ground potential, and unstable levels of microprocessor timing signals. When routing between the IC pins of the DIP package, the 10-10 and 12-12 principles can be applied, that is, when two wires pass between the two pins, the pad diameter can be set to 50 mil, and the line width and line spacing are both 10 mils. When only one wire passes between the two pins, the pad diameter can be set to 64 mil, and the line width and line spacing are both 12 mils. [ align=left]Pitch of printed conductors: [ align=left] The spacing between adjacent wires must meet the electrical safety requirements, and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing must at least be suitable for the voltage to be tolerated. This voltage generally includes the operating voltage, additional fluctuation voltage, and peak voltage caused by other reasons. If the relevant technical conditions allow a certain degree of metal residue between the wires, the spacing will be reduced. Therefore, designers should take this factor into consideration when considering voltage. When the wiring density is low, the spacing between signal lines can be appropriately increased, and the signal lines with a large difference in high and low levels should be as short as possible and the spacing should be increased. Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as ground wire on the printed circuit board, so that the shielding effect is better than that of a long ground wire, the transmission line characteristics and shielding effect will be improved, and the distributed capacitance will be reduced. The common ground wire of the printed conductor is preferably formed into a loop or mesh. This is because when there are many integrated circuits on the same board, especially components with high power consumption, the ground potential difference is generated due to the limitation of the graphics, which causes the noise tolerance to decrease. When it is made into a loop, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers. PingFangTC-light] The common ground wire of the printed conductor should be as thick as possible. If possible, use a line larger than 2 to 3 mm. This is especially important in circuits with microprocessors. Because when the ground wire is too thin, the noise tolerance will be degraded due to changes in the current flowing through, changes in the ground potential, and unstable levels of microprocessor timing signals. When routing between the IC pins of the DIP package, the 10-10 and 12-12 principles can be applied, that is, when two wires pass between the two pins, the pad diameter can be set to 50 mil, and the line width and line spacing are both 10 mils. When only one wire passes between the two pins, the pad diameter can be set to 64 mil, and the line width and line spacing are both 12 mils. [ align=left]Pitch of printed conductors: [ align=left] The spacing between adjacent wires must meet the electrical safety requirements, and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing must at least be suitable for the voltage to be tolerated. This voltage generally includes the operating voltage, additional fluctuation voltage, and peak voltage caused by other reasons. If the relevant technical conditions allow a certain degree of metal residue between the wires, the spacing will be reduced. Therefore, designers should take this factor into consideration when considering voltage. When the wiring density is low, the spacing between signal lines can be appropriately increased, and the signal lines with a large difference in high and low levels should be as short as possible and the spacing should be increased. Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as ground wire on the printed circuit board, so that the shielding effect is better than that of a long ground wire, the transmission line characteristics and shielding effect will be improved, and the distributed capacitance will be reduced. The common ground wire of the printed conductor is preferably formed into a loop or mesh. This is because when there are many integrated circuits on the same board, especially components with high power consumption, the ground potential difference is generated due to the limitation of the graphics, which causes the noise tolerance to decrease. When it is made into a loop, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers. PingFangTC-light] The common ground wire of the printed conductor should be as thick as possible. If possible, use a line larger than 2 to 3 mm. This is especially important in circuits with microprocessors. Because when the ground wire is too thin, the noise tolerance will be degraded due to changes in the current flowing through, changes in the ground potential, and unstable levels of microprocessor timing signals. When routing between the IC pins of the DIP package, the 10-10 and 12-12 principles can be applied, that is, when two wires pass between the two pins, the pad diameter can be set to 50 mil, and the line width and line spacing are both 10 mils. When only one wire passes between the two pins, the pad diameter can be set to 64 mil, and the line width and line spacing are both 12 mils. Pitch of printed conductors: The spacing between adjacent wires must meet the electrical safety requirements, and for ease of operation and production, the spacing should be as wide as possible. The minimum spacing must at least be suitable for the voltage to be tolerated. This voltage generally includes the operating voltage, additional fluctuation voltage, and peak voltage caused by other reasons. If the relevant technical conditions allow a certain degree of metal residue between the wires, the spacing will be reduced. Therefore, designers should take this factor into consideration when considering voltage. When the wiring density is low, the spacing between signal lines can be appropriately increased, and the signal lines with a large difference in high and low levels should be as short as possible and the spacing should be increased. Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as ground wire on the printed circuit board, so that the shielding effect is better than that of a long ground wire, the transmission line characteristics and shielding effect will be improved, and the distributed capacitance will be reduced. The common ground wire of the printed conductor is preferably formed into a loop or mesh. This is because when there are many integrated circuits on the same board, especially components with high power consumption, the ground potential difference is generated due to the limitation of the graphics, which causes the noise tolerance to decrease. When it is made into a loop, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers. 62)]Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as the ground wire on the printed circuit board. The shielding effect obtained in this way is better than that of a long ground wire. The transmission line characteristics and shielding effect will be improved, and the distributed capacitance will also be reduced. The common ground line of the printed conductor is best formed into a loop or a mesh. This is because when there are many integrated circuits on the same board, especially those with high power consumption, the ground potential difference is generated due to the graphic limitations, which causes the noise tolerance to be reduced. When a loop is made, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers. 62)]Shielding and grounding of printed conductors: The common ground wire of the printed conductor should be arranged at the edge of the printed circuit board as much as possible. As much copper foil as possible should be reserved as the ground wire on the printed circuit board. The shielding effect obtained in this way is better than that of a long ground wire. The transmission line characteristics and shielding effect will be improved, and the distributed capacitance will also be reduced. The common ground line of the printed conductor is best formed into a loop or a mesh. This is because when there are many integrated circuits on the same board, especially those with high power consumption, the ground potential difference is generated due to the graphic limitations, which causes the noise tolerance to be reduced. When a loop is made, the ground potential difference is reduced. In addition, the ground and power patterns should be parallel to the direction of data flow as much as possible. This is the secret to enhancing the ability to suppress noise. Multi-layer printed circuit boards can use several layers as shielding layers. The power layer and ground layer can both be regarded as shielding layers. Generally, the ground layer and power layer are designed in the inner layer of the multi-layer printed circuit board, and the signal line is designed in the inner and outer layers.
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