{"id":1915,"date":"2026-10-05T09:00:00","date_gmt":"2026-10-05T01:00:00","guid":{"rendered":"https:\/\/www.jingpengpcb.com\/?p=1915"},"modified":"2026-09-30T09:25:49","modified_gmt":"2026-09-30T01:25:49","slug":"pcb-anti-interference-design-basics","status":"publish","type":"post","link":"https:\/\/www.jingpengpcb.com\/en\/blog\/pcb-anti-interference-design-basics\/","title":{"rendered":"How to Design a PCB for Electromagnetic Interference (EMI) Protection? Layout of Power Lines, Ground Lines, and Decoupling Capacitors"},"content":{"rendered":"

Printed circuit boards (PCBs) are one of the core components of modern electronic devices. However, once the design is complete, interference issues\u2014such as mobile phone signal interference\u2014often arise. These interferences can affect the user experience; therefore, interference-resistant design has become crucial in PCB manufacturing. Next, we will introduce the principles and methods of interference suppression to help you create more reliable PCB designs.
\n\"Analysis<\/p>\n

I. Power Cord Layout<\/h2>\n
    \n
  1. Avoid arranging wires in parallel<\/strong>: Between the input and output terminals, avoid using parallel wires as much as possible; it is best to use a ground wire between the wires to reduce feedback coupling.<\/li>\n
  2. Selecting the Wire Width<\/strong>: The minimum width of a conductor is primarily determined by the adhesion strength between the conductor and the insulating substrate, as well as the current flowing through them. Typically, for copper foil with a thickness of 0.05 mm, the width is 1Wires between 15 mm in length can carry a current of 2 A without heating up by more than 3 \u00b0C. However, for integrated circuits\u2014especially digital circuits\u20140.02 is typically chosen.<\/del>0.3 mm wire width. When selecting wire width, it is best to use wider wire, especially for power and ground wires.<\/li>\n
  3. Design of Wire Bends<\/strong>: When routing traces around bends, it is best to use curved paths rather than right angles or sharp angles. This helps minimize the impact on electrical performance in high-frequency circuits. In addition, try to avoid using large areas of copper foil, as prolonged exposure to heat can cause the copper foil to expand and delaminate. If large areas of copper foil must be used, it is best to employ a grid-like pattern to help vent volatile gases between the copper foil and the substrate.<\/li>\n<\/ol>\n

    II. Grounding Arrangement<\/h2>\n
      \n
    1. Separate digital ground from analog ground<\/strong>: Keep the digital ground and analog ground separate to prevent mutual interference between them.<\/li>\n
    2. Thicker Grounding Wire<\/strong>: Ground traces should be as wide as possible, capable of carrying at least three times the allowable current on the PCB. Typically, their width should be 2 to 3 mm.<\/li>\n
    3. Forming an Infinite Loop<\/strong>: The grounding wires should be arranged to form closed loops as much as possible, which helps reduce potential differences in the grounding system.<\/li>\n<\/ol>\n

      III. Device Configuration<\/h2>\n
        \n
      1. Clock Signal Processing<\/strong>: The clock generator, crystal oscillator, and CPU clock input should be placed as close together as possible and kept away from other low-frequency components.<\/li>\n
      2. Separation of Current Circuits and Logic Circuits<\/strong>: Whenever possible, separate low-current circuits from high-current circuits and keep them away from logic circuits.<\/li>\n
      3. Heat Distribution<\/strong>: In PCB layout, ensure that components that generate a significant amount of heat are placed on top to minimize the impact of heat on other components.<\/li>\n<\/ol>\n

        IV. Decoupling Capacitor Configuration<\/h2>\n
          \n
        1. Adding Electrolytic Capacitors<\/strong>: Connect a 10\u2013100 \u03bcF electrolytic capacitor across the power input terminal of the PCB; a larger capacitance is preferable if possible.<\/li>\n
        2. Decoupling capacitors for each integrated circuit<\/strong>: A 0.01 should be added between Vcc and GND on each integrated circuit.A 0.1 \u03bcF ceramic capacitor. If space is limited, you can use one for every 4<\/del>Each of the 10 chips is equipped with a 1\u201310 \u03bcF tantalum capacitor.<\/li>\n
        3. Devices with poor noise immunity<\/strong>: For components with low noise immunity or significant variations in turn-off current, as well as ROM and RAM, decoupling capacitors should be added between Vcc and GND.<\/li>\n
        4. Lead Length of Decoupling Capacitors<\/strong>: The lead lengths of decoupling capacitors should not be too long; in particular, high-frequency bypass capacitors should not have leads.<\/li>\n<\/ol>\n

          V. Separate Power Cables, AC Cables, and Signal Cables<\/h2>\n

          Try to route power lines and AC lines separately from signal lines to minimize mutual interference. If they must be routed on the same board, ensure that they are routed separately from the signal lines.<\/p>\n

          VI. Making Effective Use of Decoupling Capacitors<\/h2>\n

          Decoupling capacitors between the power supply and ground in an integrated circuit serve two purposes: first, to provide energy storage for the integrated circuit, and second, to bypass high-frequency noise. Select an appropriate decoupling capacitance value based on the circuit\u2019s requirements, and ensure that the pins are connected closely together, especially for high-frequency bypass capacitors.<\/p>\n

          VII. Best Practices for Reducing Noise and Electromagnetic Interference<\/h2>\n

          Some empirical principles in interference-resistant design include:<\/p>\n

            \n
          1. A series resistor is used to reduce the rise and fall times of the control circuit and minimize noise.<\/li>\n
          2. Keep the potential around the clock signal circuit as close to zero as possible, enclose the clock area with a ground plane, and keep the clock lines as short as possible.<\/li>\n
          3. I\/O driver circuits should be placed as close to the edge of the PCB as possible.<\/li>\n
          4. The outputs of unused gate circuits should not be left floating; instead, they should be connected to ground. The positive inputs of unused operational amplifiers should be connected to ground, and the negative inputs should be connected to the outputs.<\/li>\n
          5. Use 45\u00b0 bends instead of 90\u00b0 bends to reduce the radiation and coupling of high-frequency signals to the outside.<\/li>\n
          6. The clock line should be perpendicular to the I\/O lines rather than parallel to them, in order to reduce interference.<\/li>\n
          7. Keep the component leads as short as possible.<\/li>\n
          8. Ground lines around weak-signal and low-frequency circuits should not form current loops.<\/li>\n
          9. A pull-up resistor of about 10K can be added to the bus to help protect against interference.<\/li>\n
          10. Using full-decoding rather than bit-by-bit decoding can improve noise immunity.<\/li>\n<\/ol>\n

            When designing printed circuit boards, following these principles and methods for electromagnetic interference (EMI) mitigation can help you create more reliable and stable electronic devices, thereby enhancing the user experience. Additionally, for electronic devices with special requirements, customized EMI mitigation designs can be developed based on specific circumstances.<\/p>\n

            \n

            Conclusion<\/strong><\/p>\n

            Interference-resistant design is crucial for printed circuit boards. Through proper power and ground trace routing, component placement, the use of decoupling capacitors, and other principles, interference can be effectively reduced, thereby improving the performance and reliability of electronic devices.<\/p>\n

            \n

            Frequently Asked Questions<\/strong><\/p>\n

              \n
            1. What is a decoupling capacitor?<\/strong>\n

              Decoupling capacitors are used to suppress high-frequency noise in circuits and are typically connected between the power supply and ground in integrated circuits.<\/li>\n

            2. Why is it important to separate digital ground from analog ground?<\/strong>\n

              Separating the digital ground from the analog ground reduces mutual interference between them and ensures the stability and performance of the circuit.<\/li>\n

            3. How do you choose the value of a decoupling capacitor?<\/strong>\n

              The value of a decoupling capacitor can be selected based on the circuit's requirements and typically ranges from 0.1 \u03bcF to 10 \u03bcF. When selecting a value, follow the principle C = 1\/F, where F is the data transmission frequency.<\/li>\n

            4. Why should you avoid using large areas of copper foil?<\/strong>\n

              Large areas of copper foil are prone to expansion and delamination when exposed to heat for extended periods, which can cause problems with the PCB; therefore, the use of large areas of copper foil should be avoided in the design.<\/li>\n

            5. What are the key principles of anti-interference design?<\/strong>\n

              Key principles of anti-interference design include proper layout, the use of decoupling capacitors, and the separation of signal and power lines, among others, to minimize interference and improve the performance of electronic devices.<\/li>\n<\/ol>\n

              The above outlines some key principles and methods for interference-resistant design, which we hope will help you improve your printed circuit board designs. If you have any further questions or need additional assistance, please feel free to contact us.<\/p>\n

              Related Reading<\/strong>\uff1aHow to Avoid Common Mistakes in Printed Circuit Board Design<\/a> \u00b7 Analysis and Solutions to Humidity Issues in Printed Circuit Boards<\/a><\/p>","protected":false},"excerpt":{"rendered":"

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