Treatment of Power Supply and Ground Wire
Even if the wiring in the entire PCB board is completed very well, the interference caused by improper consideration of the power supply and ground wire will reduce the performance of the product, and sometimes even affect the success rate of the product. Therefore, the wiring of the power and ground wires must be taken seriously, and the noise interference generated by them should be minimized to ensure the quality of the product. Every engineer engaged in the design of electronic products understands the cause of noise between the ground wire and the power wire, and now only the reduced noise suppression is expressed. It is well-known to add coupling capacitors between the power supply and the ground wire. Widen the width of the power and ground wires as much as possible, preferably making the ground wire wider than the power wire. The relationship should be ground wire > power wire > signal wire. Usually, the signal wire width is 0.2 to 0.3mm, with the smallest width being 0.05 to 0.07mm, and the power cord being 1.2 to 2.5mm. For the PCB of the digital circuit, a wide ground wire can be used to form a loop, that is, to form a ground net to use. Use a large area of copper layer as the ground for wire use, connect the unused places on the printed board to the ground as a ground wire. Alternatively, it can be made into a multi-layer board, with the power supply and ground wire occupying one layer each.
Common Ground Processing of Digital Circuit and Analog Circuit
Nowadays, many PCBs are no longer single-function circuits (digital or analog circuits), but are composed of a mixture of digital and analog circuits. Therefore, it is necessary to consider the mutual interference between them when wiring, especially the noise interference on the ground wire. The frequency of the digital circuit is high, and the sensitivity of the analog circuit is strong. For the signal line, the high-frequency signal line should be kept as far away as possible from the sensitive analog circuit devices. As for the ground line, the whole PCB has only one node to the outside world, so the issue of digital and analog common ground must be dealt with inside the PCB. The digital ground and analog ground inside the board are actually separated, not connected to each other, but are connected at the interface (such as plugs, etc.) where the PCB connects to the outside world. There is only one connection point between the digital ground and the analog ground. Additionally, there are also non-common grounds on the PCB, which are determined by the system design.
The Signal Line is Laid on the Electric (Ground) Layer
In the multi-layer printed board wiring, because there are not many wires left in the signal line layer that have not been laid out, adding more layers will cause waste and increase the production workload, and the cost will increase accordingly. To solve this contradiction, you can consider wiring on the electrical (ground) layer. The power layer should be considered first, and the ground layer second. It is best to preserve the integrity of the formation.
The Place Where the Legs are Connected in the Large Area Conductor
In large-area grounding (electricity), the legs of commonly used components are connected to it, and the treatment of the connecting legs needs to be considered comprehensively. In terms of electrical performance, it is better to connect the pads of the component legs to the copper surface. There are some undesirable hidden dangers in the welding and assembly of components, such as that welding requires high-power heaters and it is easy to cause virtual solder joints. Therefore, both electrical performance and process requirements are made into cross-patterned pads, called heat shields or thermal pads. This can greatly reduce the possibility of virtual solder joints due to excessive cross-section heat during welding. The processing of the electrical connection ground leg of the multilayer board is the same.
The Role of the Network System in Cabling
In many CAD systems, the wiring is determined according to the network system. Although a dense grid and increased paths may improve performance, if the grid is too dense and step is too small, this will require more storage space and have a greater impact on the operation speed of electronic products. Some paths are invalid, occupied by the pads of component legs or mounting holes. A well-spaced and reasonable grid system is necessary to support the wiring. The distance between the legs of standard components is typically 0.1 inches (2.54mm), so the basis of the grid system is generally set to 0.1 inches (2.54 mm) or less than an integral multiple of 0.1 inches, such as 0.05 inches, 0.025 inches, 0.02 inches, etc.
WellCircuits Limited is a manufacturer specializing in the production of high-precision double-sided, multilayer and impedance-controlled, blind buried vias, thick copper circuit boards. Our products cover HDI, thick copper, backplanes, rigid-flex combined, buried capacitance, buried resistance, Golden Finger, and other types of circuit boards, meeting various customer needs.
Even if the wiring in the entire PCB board is completed very well, the interference caused by improper consideration of the power supply and ground wire will reduce the performance of the product, and sometimes even affect the success rate of the product. Therefore, the wiring of the power and ground wires must be taken seriously, and the noise interference generated by them should be minimized to ensure the quality of the product. Every engineer engaged in the design of electronic products understands the cause of noise between the ground wire and the power wire, and now only the reduced noise suppression is expressed. It is well-known to add coupling capacitors between the power supply and the ground wire. Widen the width of the power and ground wires as much as possible, preferably making the ground wire wider than the power wire. The relationship should be ground wire > power wire > signal wire. Usually, the signal wire width is 0.2 to 0.3mm, with the smallest width being 0.05 to 0.07mm, and the power cord being 1.2 to 2.5mm. For the PCB of the digital circuit, a wide ground wire can be used to form a loop, that is, to form a ground net to use. Use a large area of copper layer as the ground for wire use, connect the unused places on the printed board to the ground as a ground wire. Alternatively, it can be made into a multi-layer board, with the power supply and ground wire occupying one layer each.
Common Ground Processing of Digital Circuit and Analog Circuit
Nowadays, many PCBs are no longer single-function circuits (digital or analog circuits), but are composed of a mixture of digital and analog circuits. Therefore, it is necessary to consider the mutual interference between them when wiring, especially the noise interference on the ground wire. The frequency of the digital circuit is high, and the sensitivity of the analog circuit is strong. For the signal line, the high-frequency signal line should be kept as far away as possible from the sensitive analog circuit devices. As for the ground line, the whole PCB has only one node to the outside world, so the issue of digital and analog common ground must be dealt with inside the PCB. The digital ground and analog ground inside the board are actually separated, not connected to each other, but are connected at the interface (such as plugs, etc.) where the PCB connects to the outside world. There is only one connection point between the digital ground and the analog ground. Additionally, there are also non-common grounds on the PCB, which are determined by the system design.
The Signal Line is Laid on the Electric (Ground) Layer
In the multi-layer printed board wiring, because there are not many wires left in the signal line layer that have not been laid out, adding more layers will cause waste and increase the production workload, and the cost will increase accordingly. To solve this contradiction, you can consider wiring on the electrical (ground) layer. The power layer should be considered first, and the ground layer second. It is best to preserve the integrity of the formation.
The Place Where the Legs are Connected in the Large Area Conductor
In large-area grounding (electricity), the legs of commonly used components are connected to it, and the treatment of the connecting legs needs to be considered comprehensively. In terms of electrical performance, it is better to connect the pads of the component legs to the copper surface. There are some undesirable hidden dangers in the welding and assembly of components, such as that welding requires high-power heaters and it is easy to cause virtual solder joints. Therefore, both electrical performance and process requirements are made into cross-patterned pads, called heat shields or thermal pads. This can greatly reduce the possibility of virtual solder joints due to excessive cross-section heat during welding. The processing of the electrical connection ground leg of the multilayer board is the same.
The Role of the Network System in Cabling
In many CAD systems, the wiring is determined according to the network system. Although a dense grid and increased paths may improve performance, if the grid is too dense and step is too small, this will require more storage space and have a greater impact on the operation speed of electronic products. Some paths are invalid, occupied by the pads of component legs or mounting holes. A well-spaced and reasonable grid system is necessary to support the wiring. The distance between the legs of standard components is typically 0.1 inches (2.54mm), so the basis of the grid system is generally set to 0.1 inches (2.54 mm) or less than an integral multiple of 0.1 inches, such as 0.05 inches, 0.025 inches, 0.02 inches, etc.
WellCircuits Limited is a manufacturer specializing in the production of high-precision double-sided, multilayer and impedance-controlled, blind buried vias, thick copper circuit boards. Our products cover HDI, thick copper, backplanes, rigid-flex combined, buried capacitance, buried resistance, Golden Finger, and other types of circuit boards, meeting various customer needs.
