May.2020 12
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How PCB design becomes more excellent
Six good habits benefit PCB design, details determine success or failure, learn to set rules, tthink more about others, draw a schematic diagram, carry out the circuit layout well and try to do simulation.
PCB layout engineers face thousands of wires on the board every day, various packages, and repeat the work of pulling the cable. Perhaps many people will find it boring and boring. It looks like a software operation porter. In fact, designers have to choose between various design rules in the process, taking into account performance, cost, process and other aspects, and pay attention to the reasonable and neat layout of the board. Simple, requires more wisdom. Good work habits will benefit you a lot, make your design more reasonable, easier to produce and better performance. Here are the following six good habits that will benefit you a lot.

(1) Details determine success or failure
PCB design is a meticulous job, and all you need is carefulness and patience. The mistakes that newcomers who are new to design often make are details. The device pins are wrong, the device package is used incorrectly, the pin order is reversed, and so on. Some can be solved by flying wires, and some may make a board directly into waste. Check again when drawing the package. Compare the printed package with the actual device before throwing the board. Take a look and check again to avoid low-level errors. Otherwise, no matter how good the design of the board is, with flying lines on it, it is far from excellent.

(2) Learn to set rules
In fact, not only advanced PCB design software needs to set wiring rules, some simple and easy-to-use PCB tools can also set rules. After all, the human brain is not a machine, so it is inevitable that there will be negligence and mistakes. So set some problems that are easy to ignore into the rules, let the computer help us check, and try to avoid making some low-level mistakes. In addition, perfect rule setting can better regulate the work behind. The so-called sharpener does not cut the woodworker by mistake, the more complex the scale of the board, the more important the rule setting is. Many EDA tools now have auto-wiring capabilities. If the rule settings are detailed enough, the tool will help you design. Is n’t it a more pleasant thing to have a cup of coffee on the side?

(3) The more you think about others, the less you work
When designing a PCB, consider as much as possible the needs of some end users. For example, if you are designing a development board, you should consider placing more silkscreen information when designing the PCB, so that it will be more convenient when using it. It is not used to find the schematic diagram or find the designer. If you are designing a mass-produced product, you should consider more the problems encountered on the production line. The devices of the same type should have the same direction as possible, whether the device spacing is appropriate, and the width of the board's process edge. The sooner these issues are considered, the less it will affect the later design, and it can also reduce the workload of support and the number of board changes. It seems that the time taken to start the design has increased, in fact, it has reduced the amount of subsequent work. When the board space signal allows, place as many test points as possible to improve the testability of the board, so that it can also save more time in the subsequent debugging stage and provide more ideas for finding problems.

(4) Draw a schematic diagram
Many engineers feel that layout work is more important. The schematic diagram is to generate a netlist to facilitate PCB inspection. In fact, the role of the schematic will be greater in the subsequent circuit debugging process. Whether it is to find problems or communicate with colleagues, or the schematic diagram is more intuitive and convenient. In addition, develop the habit of labeling in the schematic diagram, and mark the problems that you need to pay attention to when laying out each part of the circuit on the schematic diagram, which is a good reminder for yourself or others. The hierarchical schematic diagram divides the circuits of different functions and different modules into different pages, so that whether it is reading the picture or reusing it in the future, it can significantly reduce the workload. Using a mature design is always less risky than designing a new circuit. Every time I see all the circuits on one drawing, a densely packed device, my head will be bigger.

(5) Carry out the circuit layout well
The anxious engineer finished the schematic diagram, and after importing the netlist into the PCB, he could not wait to put the device away and began to pull the cable. In fact, a good PCB layout can make the cable work behind you simple, and make your PCB work better. Each board will have a signal path, and the PCB layout should follow this signal path as much as possible, so that the signal can be smoothly transmitted on the board. People don't like to go through the maze, and the signal is the same. If the schematic diagram is designed according to the module, the PCB can be the same. According to different functional modules, the board can be divided into several areas. Separate the analog and digital, separate the power signal, separate the heating device and the susceptible device, the larger device should not be too close to the edge of the board, pay attention to the shielding of RF signals, etc. Spending one more minute to optimize the layout of the PCB can save more time when pulling the wire.

(6) Try to do simulation
Simulation is often something that PCB design engineers are reluctant to touch. Some people may say that even if I simulate, the actual PCB and simulation results will be different, so why waste time doing simulation? The board I made without simulation doesn't work as well? Very helpless to this idea. There is no problem with the design once or twice, it does not mean that there will be no problems in the future. Although the simulation results are different from the actual results, the simulation can show the correct change trend, and we can make our own judgment according to the trend. It may be difficult at first, and it is normal to be confused about the simulation model of the simulation parameters. Just start, do it slowly, and accumulate it slowly, you will realize the importance of simulation. Before the board is completed, determine the location of the problem in advance, solve it in advance, and avoid the problem. If you do more simulations, you will understand the root cause of the problem, and it will also help you improve your design capabilities.