Explain the importance of LED display PCB design

First:

preliminary preparation. This includes preparing component libraries and schematics. “If a worker wants to do his job well, he must first sharpen his tools.” To make a good board, in addition to designing the principles well, you must also draw well. Before designing the PCB, you must first prepare the component library of the schematic SCH and the component library of the PCB. The component library can use peotel’s own library, but it is generally difficult to find a suitable one. It is best to make your own component library based on the standard size data of the selected device. In principle, make the PCB component library first, and then make the SCH component library. PCB component library requirements are relatively high, which directly affects the installation of the board; SCH component library requirements are relatively loose, as long as you pay attention to defining the pin attributes and the corresponding relationship with PCB components. PS: Pay attention to the hidden pins in the standard library. After that comes the design of the schematic diagram. Once completed, you are ready to start PCB design.

Second:

PCB structural design involves creating the layout of the circuit board in the PCB design environment, taking into account the determined size and mechanical positioning. Connectors, buttons/switches, screw holes, assembly holes, and other components are placed according to specific requirements. The design also considers the wiring area and non-wiring area, determining the boundaries around features like screw holes that belong to the non-wiring area. This step is crucial for ensuring the functionality and reliability of  heavy copper PCBmetal core PCB, and aluminum PCB.

Third:

PCB layout. To put it simply, layout means placing devices on the board. At this time, if the preparations mentioned above are done well, you can generate the network list on the schematic diagram (Design->Create Netlist), and then import the network list on the PCB diagram (Design->Load Nets). I saw the devices piled up all over the place, and there were flying wires between each pin to indicate connection. Then the device can be laid out. The general layout is carried out according to the following principles:
According to the reasonable zoning of electrical performance, it is generally divided into: digital circuit area (that is, fear of interference and interference), analog circuit area (fear of interference), and power drive area (source of interference);
Circuits that complete the same function should be placed as close as possible, and each component should be adjusted to ensure the simplest connection; at the same time, the relative position between each functional block should be adjusted to ensure the simplest connection between functional blocks;
For components with large mass, the installation location and installation strength should be considered; heating components should be placed separately from temperature-sensitive components, and heat convection measures should be considered if necessary;
The I/O driver device should be as close to the edge of the printed board and the lead-out connector as possible;
The clock generator (such as crystal oscillator or clock oscillator) should be as close as possible to the device that uses the clock;
A decoupling capacitor needs to be added between the power input pin of each integrated circuit and ground (usually a monolithic capacitor with good high-frequency performance is used); when the circuit board space is dense, a decoupling capacitor can also be added around several integrated circuits. Tantalum capacitor.
A discharge diode (1N4148 is sufficient) should be added to the relay coil;
The layout must be balanced, dense and orderly, and cannot be top-heavy or heavy. Special attention is required. When placing components, the actual size of the components (area and height) and the relative position between the components must be considered. , to ensure the electrical performance of the circuit board and the feasibility and convenience of production and installation. At the same time, on the premise of ensuring that the above principles can be reflected, the placement of the components should be appropriately modified to make them neat and beautiful. For example, the same components should be placed neatly , the direction is consistent and cannot be placed “at random”.
This step is related to the overall image of the board and the ease of wiring in the next step, so you need to put a lot of effort into it. When laying out, you can do preliminary wiring first and give full consideration to areas that you are not sure about.

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Fourth:

Wiring is the most crucial step in the entire PCB design process.
It directly impacts the performance of the PCB board. In PCB design, wiring is typically divided into three key areas: routing, electrical performance, and aesthetics. Routing is the fundamental requirement for PCB design.

If the lines are not properly laid out and there are flying wires everywhere, the board will be considered subpar. The satisfaction of electrical performance is a measure of the quality of a printed circuit board.
After laying out the wiring, it is important to carefully adjust it to achieve optimal electrical performance.
Aesthetics also play a role in wiring. Even if the wiring is clear and does not affect the performance of electrical appliances,
if it appears messy and colorful, it will be perceived as substandard.

Neat and uniform wiring is essential, avoiding a criss-crossed and disorganized layout. These standards must be met while ensuring the performance of the electrical appliances and meeting other specific requirements. Otherwise, it will result in wasted time.
The use of heavy copper PCB can enhance the performance and durability of the PCB board.

When wiring, mainly follow the following principles:
Generally, the power and ground wires should be routed first to ensure the electrical performance of the circuit board. Within the scope of conditions permitting, try to widen the width of the power and ground wires. It is best to make the ground wire wider than the power wire. Their relationship is: ground wire > power wire > signal wire. Usually the signal wire width is: 0.2 ~ 0.3mm , the thinnest width can reach 0.05~0.07mm, and the power cord is generally 1.2~2.5mm. For digital circuit PCBs, wide ground wires can be used to form a loop, that is, to form a ground network (the ground of analog circuits cannot be used in this way)
Wire lines with strict requirements (such as high-frequency lines) in advance. The edges of the input end and the output end should avoid being adjacent and parallel to avoid reflection interference. If necessary, ground wire isolation should be added. The wiring of two adjacent layers should be perpendicular to each other. Parasitic coupling is easy to occur when parallel.
The oscillator case should be grounded, and the clock line should be as short as possible and not lead everywhere. The ground area below the clock oscillation circuit and the special high-speed logic circuit part should be increased, and other signal lines should not be used to make the surrounding electric field approach zero;
Use 45o polyline wiring as much as possible, and do not use 90o polygonal lines to reduce the radiation of high-frequency signals; (double arcs should also be used for lines with high requirements)
Do not form a loop in any signal line. If it is unavoidable, the loop should be as small as possible; the number of vias in the signal line should be as small as possible;
The key lines should be as short and thick as possible, with protective grounds on both sides.
When transmitting sensitive signals and noise field band signals through flat cables, they must be led out using the “ground wire-signal-ground wire” method.
Test points should be reserved for key signals to facilitate production and maintenance testing.
After the schematic wiring is completed, the wiring should be optimized; at the same time, after the preliminary network inspection and DRC inspection are correct, the unwired area should be filled with ground wires, and a large area of copper layer should be used as ground wire. Wherever it is used, it is connected to the ground and used as a ground wire. Or it can be made into a multi-layer board, with power supply and ground wires occupying one layer each.

Fifth:

Wiring optimization and silk screen printing. “There is no best, only better”! No matter how hard you put your mind into designing, you will still feel that there are many places that can be modified after you take a look at it. A general design rule of thumb is that optimizing wiring takes twice as long as initial wiring. After you feel that there is nothing that needs to be modified, you can lay copper (Place->polygon Plane). When laying copper, ground wires are generally laid (pay attention to the separation of analog ground and digital ground). For multi-layer boards, power supply may also be required. For silk screen printing, be careful not to be blocked by components or removed by vias and pads. At the same time, when designing, face the component surface squarely, and the characters on the bottom layer should be mirrored to avoid confusing the layers.

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Sixth:

Network and DRC inspection and structural inspection. First, on the premise that the circuit schematic design is correct, conduct a network check (NETCHECK) on the physical connection relationship between the generated PCB network file and the schematic network file, and make timely corrections to the design based on the output file results to ensure wiring. The correctness of the connection relationship;
After the network check is passed correctly, DRC check is performed on the PCB design, and the design is corrected in time based on the output file results to ensure the electrical performance of the PCB wiring. Finally, the mechanical installation structure of the PCB needs to be further inspected and confirmed.
Seventh:

plate making. Before this, it is best to have an audit process.
PCB design is a job that requires careful thinking. Whoever is thoughtful and experienced will design a better board. Therefore, you must be extremely careful when designing, fully consider all factors (for example, ease of maintenance and inspection, which many people do not consider), and strive for excellence, and you will be able to design a good board.

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