The important role of PCB design in power circuit design need not be repeated. The PCB is the physical platform for circuit design and the most flexible part for the design and manufacture of original components. So how can we better use the design software to layout the PCB? What are its design rules? In this article, we will share those golden rules of PCB design that we call "timeless".
1. Choose the right grid - Set and always use the grid spacing that will match the most components. While multigrid may seem like a powerful tool, engineers who think a bit more about the PCB layout early in the design process can avoid space-setting challenges and get the most out of the board. Since many devices are available in a variety of package sizes, engineers should use what works best for their design. In addition, polygons are critical for board copper deposition, and multi-mesh boards generally have polygon fill deviations when polygonal copper is applied, which is not as standard as based on a single mesh, but provides board life beyond what is required.
2. Keep the path the shortest and most direct. This may sound simple, but it should be kept in mind at every stage, even if it means changing the board layout to optimize trace lengths. This also applies especially to analog and high-speed digital circuits where system performance is always partially limited by impedance and parasitics.
3. Use the power layer as much as possible to manage the distribution of power lines and ground lines. Power plane copper is a faster and simpler option for most PCB design software. By connecting a large number of conductors in common, the highest efficiency current with the least impedance or voltage drop is guaranteed, while providing an adequate ground return path. If possible, run multiple power supply lines in the same area of the board to confirm whether the ground plane covers most of a layer of the PCB, which facilitates the interaction between running lines on adjacent layers.
4. Group the relevant components together with the desired test points. For example, placing the discrete components required for an OpAmp op amp closer to the device so that the bypass capacitors and resistors can co-locate with it helps optimize the trace lengths mentioned in Rule 2, while also enabling testing and fault detection made easier.
5. Repeat the required circuit board on another larger circuit board for PCB imposition. Choosing the size that best suits the equipment used by the manufacturer can help reduce prototyping and manufacturing costs. Start by laying out the board on the panels, contact the board manufacturer for their preferred size specifications for each panel, then modify your design specifications and try to repeat your design as many times as possible within those panel sizes.
6. Integrate component values. As a designer, you will choose some discrete components with higher or lower component values, but with the same performance. By consolidating within a smaller range of standard values, bills of materials can be simplified and costs can be potentially reduced. If you have a range of PCB products based on preferred device values, it will also help you make the right inventory management decisions in the longer term.
7. Perform as many Design Rule Checks (DRCs) as possible. Although it takes only a short time to run the DRC function on the PCB software, in more complex design environments it is a good habit to keep in mind that you can save a lot of time as long as you perform checks throughout the design process. Every routing decision is critical, and performing DRC keeps you informed of the most important routings.
8. Flexible use of screen printing. Screen printing can be used to label a variety of useful information for future use by circuit board manufacturers, service or test engineers, installers or equipment debuggers. Not only clearly labeled functional and test point labels, but also the orientation of components and connectors where possible, even if these annotations are printed on the underside of the components used on the board (after board assembly). The full application of screen printing technology on the upper and lower surfaces of the circuit board can reduce duplication of work and streamline the production process.
9. Decoupling capacitors are required. Don't try to optimize your design by avoiding decoupling power lines and sticking to the limits in the component datasheet. Capacitors are inexpensive and durable, and you can take as much time as you can to get them assembled, while following rule number six and using standard value ranges to keep your inventory tidy.
10. Generate PCB manufacturing parameters and verify before submitting for production. While most board manufacturers are happy to just download and verify for you, it's best to output the Gerber file yourself and check with a free viewer that it works as expected to avoid misunderstandings. By verifying for yourself, you may even spot some inadvertent errors, and thus avoid the loss of production by following the wrong parameters.
The last thing I want to say is that the rules shared above are still a feature of printed circuit board design today when circuit design is more and more widely shared, and as long as these basic rules are clarified, even if you are a novice, you will easily master PCB design.
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