Copper coating is a crucial aspect of PCB design. Whether utilizing domestic PCB design software or foreign tools like Protel or PowerPCB, the intelligent copper coating function is invaluable. In this article, I will share some insights on how to effectively apply copper coating, with the hope of benefiting my colleagues.
Copper pouring refers to using the unused areas of the PCB as a reference surface and filling them with solid copper, often referred to as copper filling. The purpose of copper coating includes reducing ground impedance and enhancing the circuit’s ability to resist interference; minimizing voltage drop to improve power supply efficiency; and connecting to the ground wire to reduce loop areas. Additionally, to ensure that the PCB remains as undistorted as possible during soldering, most manufacturers require designers to fill open spaces with copper or grid-like ground wires. Improper handling of copper can lead to detrimental effects—whether the advantages outweigh the disadvantages or vice versa is a key consideration.
It is well-known that at high frequencies, the distributed capacitance of traces on a printed circuit board can significantly affect performance. When the trace length exceeds 1/20 of the corresponding wavelength of the noise frequency, an antenna effect may occur, leading to noise emission through the traces. If the copper coating on the PCB is poorly grounded, it can inadvertently serve as a conduit for noise. Thus, in high-frequency circuits, simply connecting the ground wire to a ground plane is insufficient. The ground line must be less than λ/20, with properly punched through-holes in the traces, ensuring a strong connection with the ground plane of multilayer boards. When managed correctly, copper coating not only enhances current capacity but also provides effective shielding against interference.
**PCBA Board**
There are generally two fundamental methods of copper coating: large-area copper coating and grid copper. A common question arises: is large-area copper coating superior to grid copper coating? It’s not advisable to make a blanket statement. Why is that? Large-area copper coating serves dual purposes—enhancing current capacity and providing shielding. However, when employing large-area copper coating during wave soldering, the board may lift and even develop blisters. Consequently, for large-area copper coatings, it’s common to incorporate several grooves to mitigate the blistering of the copper foil. In contrast, grid copper is primarily utilized for shielding, with less emphasis on current enhancement. From a heat dissipation standpoint, grid configurations are advantageous (as they reduce the heating surface of the copper) and contribute to electromagnetic shielding to some extent.
It’s important to note that the grid consists of traces arranged in staggered directions. In circuit design, the trace width correlates to a specific “electrical length” at the operational frequency of the circuit board (actual dimensions divided by the actual size). For lower operational frequencies, the influence of the grid may not be very pronounced. However, once the electrical length aligns with the operational frequency, issues can arise. You may find that the circuit fails to function properly, with signals that interfere with system operations radiating indiscriminately. Therefore, for those utilizing grids, my advice is to choose based on the operational conditions of the designed circuit board, rather than fixating on one particular method. High-frequency circuits necessitate multi-purpose grids for effective interference reduction, while low-frequency circuits often involve larger current capacities, such as those using complete copper.
That being said, we must pay attention to several considerations in copper plating to achieve the desired outcomes:
1. When the PCB features multiple grounds, such as SGND, AGND, and GND, it is crucial to use the main “ground” as a reference for independent copper pouring while separating digital and analog grounds. Prior to copper coating, ensure the power connections (5.0V, 3.3V, etc.) are adequately thickened, forming various deformable structures.
2. For single-point connections between different grounds, consider using 0-ohm resistors, magnetic beads, or inductors for connection.
3. When copper coating near the crystal oscillator, remember that the crystal oscillator acts as a high-frequency emission source. The strategy is to apply copper around the oscillator and separately ground its shell.
4. Address the island (dead zone) issue; if you find it too extensive, defining a ground via and adding it can be a cost-effective solution.
5. At the outset of routing, treat the ground wire equally. Ensure proper routing of the ground wire rather than relying solely on covering after copper application.
6. It’s best to avoid sharp corners (<=180 degrees) on the board, as these can act as transmitting antennas from an electromagnetic perspective. I recommend utilizing rounded edges instead.
7. Avoid applying copper in the open areas of the middle layer in multilayer boards, as achieving effective grounding in these regions can be challenging.
8. Ensure that metal components within devices, such as radiators and reinforcement strips, have solid grounding.
9. The heat-dissipating metal block of the three-terminal regulator requires proper grounding, as does the ground isolation strip near the crystal oscillator. In summary: effectively addressing grounding issues related to copper on the PCB will yield more advantages than disadvantages. This approach can reduce the return area of signal lines and decrease the electromagnetic interference emitted to the surroundings.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
Copper pouring refers to using the unused areas of the PCB as a reference surface and filling them with solid copper, often referred to as copper filling. The purpose of copper coating includes reducing ground impedance and enhancing the circuit’s ability to resist interference; minimizing voltage drop to improve power supply efficiency; and connecting to the ground wire to reduce loop areas. Additionally, to ensure that the PCB remains as undistorted as possible during soldering, most manufacturers require designers to fill open spaces with copper or grid-like ground wires. Improper handling of copper can lead to detrimental effects—whether the advantages outweigh the disadvantages or vice versa is a key consideration.
It is well-known that at high frequencies, the distributed capacitance of traces on a printed circuit board can significantly affect performance. When the trace length exceeds 1/20 of the corresponding wavelength of the noise frequency, an antenna effect may occur, leading to noise emission through the traces. If the copper coating on the PCB is poorly grounded, it can inadvertently serve as a conduit for noise. Thus, in high-frequency circuits, simply connecting the ground wire to a ground plane is insufficient. The ground line must be less than λ/20, with properly punched through-holes in the traces, ensuring a strong connection with the ground plane of multilayer boards. When managed correctly, copper coating not only enhances current capacity but also provides effective shielding against interference.
**PCBA Board**
There are generally two fundamental methods of copper coating: large-area copper coating and grid copper. A common question arises: is large-area copper coating superior to grid copper coating? It’s not advisable to make a blanket statement. Why is that? Large-area copper coating serves dual purposes—enhancing current capacity and providing shielding. However, when employing large-area copper coating during wave soldering, the board may lift and even develop blisters. Consequently, for large-area copper coatings, it’s common to incorporate several grooves to mitigate the blistering of the copper foil. In contrast, grid copper is primarily utilized for shielding, with less emphasis on current enhancement. From a heat dissipation standpoint, grid configurations are advantageous (as they reduce the heating surface of the copper) and contribute to electromagnetic shielding to some extent.
It’s important to note that the grid consists of traces arranged in staggered directions. In circuit design, the trace width correlates to a specific “electrical length” at the operational frequency of the circuit board (actual dimensions divided by the actual size). For lower operational frequencies, the influence of the grid may not be very pronounced. However, once the electrical length aligns with the operational frequency, issues can arise. You may find that the circuit fails to function properly, with signals that interfere with system operations radiating indiscriminately. Therefore, for those utilizing grids, my advice is to choose based on the operational conditions of the designed circuit board, rather than fixating on one particular method. High-frequency circuits necessitate multi-purpose grids for effective interference reduction, while low-frequency circuits often involve larger current capacities, such as those using complete copper.
That being said, we must pay attention to several considerations in copper plating to achieve the desired outcomes:
1. When the PCB features multiple grounds, such as SGND, AGND, and GND, it is crucial to use the main “ground” as a reference for independent copper pouring while separating digital and analog grounds. Prior to copper coating, ensure the power connections (5.0V, 3.3V, etc.) are adequately thickened, forming various deformable structures.
2. For single-point connections between different grounds, consider using 0-ohm resistors, magnetic beads, or inductors for connection.
3. When copper coating near the crystal oscillator, remember that the crystal oscillator acts as a high-frequency emission source. The strategy is to apply copper around the oscillator and separately ground its shell.
4. Address the island (dead zone) issue; if you find it too extensive, defining a ground via and adding it can be a cost-effective solution.
5. At the outset of routing, treat the ground wire equally. Ensure proper routing of the ground wire rather than relying solely on covering after copper application.
6. It’s best to avoid sharp corners (<=180 degrees) on the board, as these can act as transmitting antennas from an electromagnetic perspective. I recommend utilizing rounded edges instead.
7. Avoid applying copper in the open areas of the middle layer in multilayer boards, as achieving effective grounding in these regions can be challenging.
8. Ensure that metal components within devices, such as radiators and reinforcement strips, have solid grounding.
9. The heat-dissipating metal block of the three-terminal regulator requires proper grounding, as does the ground isolation strip near the crystal oscillator. In summary: effectively addressing grounding issues related to copper on the PCB will yield more advantages than disadvantages. This approach can reduce the return area of signal lines and decrease the electromagnetic interference emitted to the surroundings.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
