PCB Copper Coating Experience

2018/12/27 14:01:52

The so-called copper coating is to use the unused space on the PCB as the reference surface, and then fill it with solid copper, which is also called copper filling. The significance of copper coating is to reduce the ground line impedance, improve the anti-interference ability; reduce the voltage drop and improve the power supply efficiency; and, connect with the ground line to reduce the loop area.


If the PCB has more ground, there are often named as GND, SGND, which are depending on the places in the PCB surface, and for the main "ground" , it is used to separate the copper, and the digital ground and the analog ground.


Before coating the copper, the first step is needed to increase the corresponding for power connection: 5.0V, 3.3V and so on. In this way, a plurality of multi-deformed structures of different shapes will be formed.




Copper clad needs to deal with several problems: First, a single point connection in different places, the method is to connect through 0 ohm resistor or magnetic beads or inductor; second is copper clad in the vicinity of crystal oscillator, the crystal oscillator in the circuit is a high frequency emission source, The copper is applied around the crystal, and then the outer casing of the crystal is grounded separately. The third is the problem of an isolated island (dead zone). If you feel that it is very big, it will not cost much to define a place to add it.


In addition, the large area of copper is good or the grid is copper, it is not easy to generalize. Why? Large area copper clad, if the wave soldering, the board may be tilted up, and even foaming. From this point of view, the heat dissipation of the grid is better. Usually, the high-frequency circuit is used to resist the interference of the multi-purpose grid, and the low-frequency circuit has a large current circuit and the like.



When starting the wiring, the ground wire should be treated equally. When the wire is routed, the ground wire should be taken well. It is not possible to rely on the copper to add the hole to eliminate the ground pin. This effect is very bad. Of course, if you choose the grid copper, these ground connections will affect the appearance, if you are careful, delete it.


1. Large area of copper is applied, which has the dual functions of increasing current and shielding. The simple grid copper is mainly shielded, and the effect of increasing current is reduced. The purpose of adding grid is not necessarily for beauty, but Prevent and alleviates the gas generated when the copper foil adhesive is welded to foam the copper foil. Therefore, it is a large area of copper, and also pay attention to open a few grooves to ease the foaming of the copper foil.


2. The ring ground wire can have shielding effect; can also form the reception of the radiation signal that is similar to the loop antenna. Therefore, the charger has both high current and small signal detection, so it is better to use "tree type ground wire. .


3. Such a general charging control IC is also connected to the ground loop and then connected to the high current ground loop to reduce the interference of the copper foil voltage drop of the large current loop on the small signal.


This is not absolute, you can also see a lot of violations of the above requirements, you can also use. But I will pay attention to these requirements as much as possible in the general layout.


1. The wiring of the middle layer of the multi-layer board is not empty. Because it is very difficult for you to make this copper "good grounding".


2. A PCB, no matter how many kinds of power supply, it is recommended to use power split technology, and only use one power layer. Because the power supply is the same as the ground, it is also the “reference plane”. The “good grounding” of the power supply and the ground is realized by a large number of filter capacitors. Without the filter capacitor, there is no “ground”.


3. The metal inside the equipment, such as metal radiators, metal reinforcement strips, etc., must achieve "good grounding."


4. The heat-dissipating metal block of the three-terminal regulator must be well grounded.


5. The grounding isolation strip near the crystal oscillator must be well grounded.

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