Introduction:

Copper coating, also known as copper pour or copper fill, involves using unused space on a printed circuit board (PCB) as a reference surface and filling it with solid copper. This practice is crucial for reducing the impedance of the ground wire, improving the board’s anti-interference ability, reducing voltage drops, and enhancing power supply efficiency. Connecting copper fills with the ground wire can also minimize the loop area, leading to better overall performance of the PCB.

Here are nine important points to consider when applying copper coating on PCBs:

1. Independent Copper Pouring for Different Grounds

If your PCB has multiple grounds, such as SGND (Signal Ground), AGND (Analog Ground), and GND (General Ground), you should independently pour copper for each one based on their positions on the PCB. Use the main ground as a reference. Before starting the copper pour, thicken the corresponding power connections (e.g., 5.0V, 3.3V). This approach creates multiple deformable structures with different shapes, which can enhance the board’s performance.

2. Single-Point Connections to Different Grounds

For single-point connections to different grounds, use 0-ohm resistors or ferrite beads. Ferrite beads have high resistivity and permeability, acting like a resistor and an inductor in series. Their resistance and inductance values vary with frequency, providing better high-frequency filtering characteristics than ordinary inductors. They maintain higher impedance over a wide frequency range, improving FM filtering. In circuits, ferrite beads are often used as power supply filters, converting AC signals into heat, whereas inductors store and slowly release AC. Generally, ferrite beads offer greater resistance to high-frequency signals than inductors.

3. Copper Coating Around Crystal Oscillators

Crystal oscillators are high-frequency emission sources in circuits. To minimize interference, coat copper around the crystal oscillator and ground its shell separately. This practice helps in reducing the high-frequency noise generated by the oscillator.

4. Addressing Island (Dead Zone) Problems

Islands or dead zones can occur in copper pours. If these zones are large, it is advisable to define a ground via and add it to the area. This step ensures proper grounding and avoids potential performance issues.

5. Proper Ground Wire Routing

When starting the wiring process, treat the ground wire with the same importance as signal wires. Properly route the ground wire instead of relying solely on copper pour to eliminate the ground pin connections. This practice ensures better grounding and avoids poor performance.

6. Avoid Sharp Corners

Avoid sharp corners (≥180 degrees) on the PCB. From an electromagnetic perspective, sharp corners can act as transmitting antennas. Using rounded edges or arcs is recommended to minimize electromagnetic interference.

7. Copper Pour on Multi-layer Boards

Do not apply copper in the open areas of the middle layers of multi-layer PCBs. It is challenging to ensure that this copper has proper grounding, which can lead to potential issues.

8. Grounding Metal Components

Ensure that any metal components within the device, such as metal radiators and metal reinforcement strips, are properly grounded. Good grounding of metal parts helps in reducing electromagnetic interference and improving the overall performance of the PCB.

9. Reducing Electromagnetic Interference with Three-Terminal Regulators

The return area of three-terminal regulators should be managed to minimize the electromagnetic interference they can cause to the outside. Proper handling of these areas can significantly enhance the performance and reliability of the PCB.

By paying attention to these nine points, you can optimize your copper coating process, leading to improved performance and reliability of your PCBs. Copper coating is a vital aspect of PCB design, and careful consideration of these factors can make a significant difference in your final product.