Advantages of Copper Laying on the Surface and Bottom of PCB High Frequency Board
Do you know the advantages of copper coating on the surface and bottom of PCB high-frequency board? In the whole process of pcb board design, engineers want to ignore the process of laying copper on the whole board at the surface and bottom to save time. Is this right? Is it necessary to lay copper on the surface and bottom of PCB high-frequency board? What are the advantages of laying copper on the surface and bottom of PCB high-frequency board?
First of all, we need to make it clear that it is benefICial and necessary to lay copper on the surface and bottom of the PCB high-frequency board, but some conditions need to be observed for laying copper on the whole board.
1、 Advantages of copper coating on the surface and bottom of PCB high-frequency board:
From the perspective of heat dissipation, the BGA main chip needs to consider thermal issues more and more because the current PCB high-frequency boards are becoming more and more high-density. The whole board floor copper improves the heat dissipation capacity of the PCB high-frequency board.
2. From the perspective of EMC, the whole board at the bottom of the surface is paved with copper, which provides additional shielding protection and noise suppression for the inner signal and the inner signal, as well as some shielding protection for the devices and signals at the bottom of the surface.
3. From the perspective of process, the whole board is paved with copper, which makes the high-frequency PCB board evenly distributed. The bending and warping of the board are avoided during PCB processing and pressing. At the same time, the warping and deformation of the high-frequency PCB board caused by the different stresses generated during reflow soldering of the high-frequency PCB board due to the uneven copper foil are avoided.
On the one hand, because the double-sided circuit board does not have a complete reference plane, the flooring can provide a return path and can also be used as a coplanar reference to achieve the purpose of impedance control. We can generally use the bottom floor to lay the ground plane, and the top floor to put the main devices and take the power and signal lines. For high impedance circuits, analog circuits (analog to digital conversion circuits, switching mode power conversion circuits), copper coating is a good practice.
2、 Conditions for surface and bottom copper coating:
Although copper laying on the surface and bottom is beneficial to PCB high-frequency board, some conditions should be followed:
In particular, consider the thermal balance of small devices, such as 04020603 and other small packages, to avoid the monument effect.
Cause: If the whole board is covered with copper for full connection of component pins, the heat loss will be too fast, resulting in difficulty in desoldering and repair welding.
2. At the same time, try to pave by hand instead of one time to avoid broken copper skin. Properly add vias in the copper paving area to the ground level.
Cause: The copper clad plane on the surface must be separated and broken by the components and signal lines on the surface. If there is copper foil with poor grounding (especially the thin and long copper scrap), it will become an antenna and cause EMI problems.
3. The whole board flooring should be continuous, and the distance from the flooring to the signal should be controlLED to avoid discontinuous transmission line impedance.
Cause: The copper sheet too close to the ground will change the impedance of the microstrip transmission line, and the discontinuous copper sheet will also cause a negative impact on the impedance discontinuity of the transmission line.
Cause: In addition to the need to cover the ground for sensitive signals, if there are many high-speed signal lines and components, many small and long copper scraps will be generated, and the wiring channel is tight, it is necessary to avoid the connection between the surface copper sheet and the ground plane as far as possible. At this time, the surface layer can choose not to lay copper. These are the advantages of copper coating on the bottom surface of PCB high-frequency board, and I hope to help you. PCB manufacturers, PCB designers and PCBA manufacturers will explain to you the advantages of copper laying on the surface and bottom of PCB high-frequency boards.