Rule 1: select the correct grid – set and always use the grid spacing that can match the most components. Although the utility of multigrid seems significant, if engineers can think more at the early stage of PCB layout design, they can avoid the difficulties in interval setting and maximize the application of circuit boards. Since many devices use a variety of package sizes, engineers should use the products that are most conducive to their own design. In addition, polygon is very important for copper plating on circuit boards. Polygon filling deviation will generally occur when polygonal copper plating is carried out on Multigrid circuit boards. Although it is not as standard as that based on a single grid, it can provide more than the required service life of circuit boards.

Introduction to ten rules of thumb in PCB design

Rule 2: keep the path shortest and most direct. This sounds simple and common, but it should be kept in mind at every stage, even if it means changing the circuit board layout to optimize the wiring length. This is especially applicable to analog and high-speed digital circuits whose system performance is always partially limited by impedance and parasitic effects.

Rule 3: use the power layer to manage the distribution of power lines and ground wires as much as possible. Copper coating on the power layer is a faster and simpler choice for most PCB design software. By sharing a large number of conductors, it is ensured that the current with the highest efficiency and minimum impedance or voltage drop can be provided, and sufficient grounding return path can be provided. If possible, multiple power supply lines can also be operated in the same area of the circuit board to confirm whether the grounding layer covers most layers of a PCB layer, which is conducive to the interaction between operating lines on adjacent layers.

Rule 4: group the relevant components together with the required test points. For example, the discrete components required by OPAMP operational amplifier are placed close to the device, so that the bypass capacitance and resistance can cooperate with it, so as to help optimize the wiring length mentioned in rule 2, and make testing and fault detection easier.

Rule 5: repeatedly copy the required circuit board on another larger circuit board for PCB assembly. Selecting the size most suitable for the equipment used by the manufacturer is conducive to reducing the prototype design and manufacturing cost. First, layout the circuit board on the panel, contact the circuit board manufacturer to obtain their preferred size specifications of each panel, then modify your design specifications, and try to repeat your design many times within these panel sizes.

Rule 6: integrate component values. As a designer, you will choose some discrete components with high or low component values but the same efficiency. By integrating within a small range of standard values, the bill of materials can be simplified and costs can be reduced. If you have a series of PCB products based on the preferred device value, it is more conducive for you to make correct inventory management decisions in the longer term.

Rule 7: perform as many design rule checks (DRC) as possible. Although it takes only a short time to run the DRC function on PCB software, in a more complex design environment, you can save a lot of time as long as you always perform checks during the design process, which is a good habit worth keeping. Every routing decision is critical, and you can be prompted for the most important routing at any time by executing DRC.

Rule 8: flexible use of screen printing. Screen printing can be used to mark various useful information for future use by circuit board manufacturers, service or test engineers, installers or equipment commissioning personnel. Not only clearly mark the function and test point labels, but also mark the direction of components and connectors as far as possible, even if these notes are printed on the lower surface of components used on the circuit board (after circuit board assembly). The full application of screen printing technology on the upper and lower surfaces of circuit boards can reduce repetitive work and simplify the production process.

Rule 9: decoupling capacitor is required. Don’t try to optimize your design by avoiding decoupling power lines and according to the limits in the component data sheet. Capacitors are cheap and durable. You can spend as much time as possible assembling capacitors. At the same time, follow rule 6 and use the standard value range to keep the inventory neat.

Rule 10: generate PCB manufacturing parameters and verify them before submitting to production. Although most circuit board manufacturers are happy to download and verify directly for you, you’d better output Gerber files first and check whether they are as expected with a free reader to avoid misunderstanding. Through personal verification, you will even find some careless errors, so as to avoid losses caused by completing production according to the wrong parameters.

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