What is PCB layout?

　　The term "layout" generally refers to the arrangement of product components. Therefore, PCB layout is a general term for several interrelated tasks involved in PCB design. Tracing, mounting, cutting, marking, and component placement are all part of this process.

　　Routing is a key idea in printed circuit board design. Software developer Autodesk.com says: "90% of PCB layout design is layout, 10% is routing." After the layout is complete, the next stage is routing. Positioning parts on the PCB is part of the layout process. During routing, wires connect the parts according to specifications. To perform PCB layout, you can do it manually or use a computer program. Most PCB design programs offer autorouting functionality. Many designers use autorouting because it saves time and effort.

　　The autorouting function of PCB design may be faster, but it is not necessarily good. The reason is that it is not always as precise and symmetrical as it should be. Using the correct autorouting settings is crucial for good results, as this allows the automatic function to accurately calculate the routing.

　　 Why is PCB layout important?

　　A well-considered PCB layout can reduce the risk of errors and short circuits. With the rapid development of technology, PCB layout plays an increasingly important role in our daily lives. These PCBs are ubiquitous and are the mainstay of every electronic product.

　 　Difference between PCB schematic and PCB layout

　　In short, the geometry of the actual circuit on the PCB is the reason for the difference between the behavior you find when simulating using a schematic or PCB layout and the actual behavior. PCB design evolves from a circuit diagram to a schematic. Your PCB layout may be based on this important document, which is the foundation of the circuit board. In a standard 2D CAD assembly design, you will depict each circuit and its components in the schematic.

　 　PCB Layout Guidelines

　　Printed circuit board design is far more complex than it first appears. A well-designed PCB layout will physically organize the circuitry to maximize the electrical performance of the board while maintaining complete manufacturability. This requires careful management of library components, CAD configuration and settings, component placement, routing, and power distribution system (PDN) planning. Beyond this, layout designers also need to ensure their work is well-documented and the final output is ready for integration into the larger electronic system for which it was created.

　　This is difficult for engineers, especially those who have never been exposed to PCB layout. A whole set of electronic circuit layout rules for reference may be helpful for this process. Standards within the industry and company will dictate the specifics of the design, although layout principles remain necessary to aid engineers throughout the board creation process. Here are some PCB layout suggestions that you can use as a starting point for standards in this area.

　 　Building Libraries

　　When building libraries for PCB layout, use IPC or manufacturer specifications to determine package dimensions. However, some components may require modification due to individual, business, or technical requirements. For example, packages in RF designs may require narrower pad widths than traditional digital designs. For more information on creating custom PCB component packages, read on!

　　For any library components you create, check the pad pattern dimensions and spacing to ensure they meet standard requirements.

　　Printed circuit boards must include everything from component packages to silkscreen markings and reference designators.

　　Verify with the manufacturer to ensure they can produce the components you are using before finalizing the design.

　　Alternatively, PCB layout diagrams from third-party CAD library providers can be used. Some programs have browsers that allow easy download of manufacturer-made components already compatible with your design system.

　　 Power and Ground Plane Guidelines

　　Using one or more continuous planes on the inner layers is usually the ideal grounding method for current high-speed systems. This provides a high level of EMI shielding and ensures unobstructed signal paths, both of which improve the quality of the transmitted signal.

　　If the ground plane on the board is split due to unusual shapes or features, routing should be avoided through these locations. If the signal does not have a continuous and adjacent ground plane available as a clean return path, your design may generate a significant amount of extra noise. Some rules for power and ground planes are as follows:

　　If the board has high-speed routing, the ground layer must be physically located next to the signal layer. This will protect the high-speed routing from external influences and provide a reliable ground for the signal return path.

　　Power or ground connections for planes require thermal vias and must be carefully maintained. The spokes of the thermal vias need to be large enough to handle high currents without letting the via connection act as a sink.

　　Careful planning of power connections and the division of power planes will provide sufficient power delivery to all components.

　　 Considerations When Designing PCB Layouts

　　Schematic

　　After the conception is complete, the next step is to draw the schematic diagram. The schematic diagram contains information such as component names, values, ratings, and manufacturer part numbers to ensure the proper operation of the circuit board's electrical components.

　　 Component Placement

　　Next is component placement, which is deciding where each component will be placed on the board. Multiple iterations of component placement refinement are not uncommon.

　　 Conclusion

　　No device can function without a well-designed PCB layout. It takes a team of engineers weeks or even months to complete a PCB board design, which is similar to completing a work of art. Creating a PCB layout is not easy, but anyone with the proper resources and expertise can accomplish it.