PCB copper knowledge

Copper cladding is a common operation, which is to cover the area on the circuit board with no wiring by copper film. This can enhance the anti-interference performance of the circuit board. The so-called copper clad is to use the idle space on the PCB as a reference surface, and then fill it with solid copper. These copper areas are also called copper filling. Copper cladding can reduce the impedance of the ground wire and improve the anti-interference ability; reduce the voltage drop and improve the efficiency of the power supply; in addition, connect to the ground wire to reduce the loop area.


  Copper needs to deal with several issues:


   1. Different single point connection: The method is to connect through 0 ohm resistance or magnetic beads or inductance.


   2. The copper clad near the crystal oscillator. The crystal oscillator in the circuit is a high-frequency emission source: the method is to apply copper around the crystal oscillator, and then ground the crystal oscillator shell separately.


   3. The isolated island (dead zone) problem: If it feels large, then it is not a big deal to add a ground via to add it.


  What are the benefits of copper clad?


  Improve power supply efficiency, reduce high-frequency interference, and the other is to look beautiful!


   Large area copper or grid copper?


   is not generalized. why? Large area copper clad, if over-wave soldering, the board may warp, or even blisters. From this point, the heat dissipation of the grid is better. It is usually a multi-purpose grid with high requirements for anti-interference in high-frequency circuits, and high-current circuits for low-frequency circuits.


  When you start wiring, you should treat the ground wire equally. When routing, you should run the ground wire well. You can not rely on adding copper vias to eliminate the ground pin connected. This effect is very bad. Of course, if you choose grid copper, these ground connections will affect the appearance, if you are careful, delete it.


Copper filling is intelligent. This operation will actively determine the network properties of the vias and pads in the copper filling area, which is absolutely consistent with the safety distance you set. This is different from drawing copper skin, and drawing copper skin does not This feature.


There are many functions of copper filling. Pouring copper on the reverse side of the double panel and connecting it to the ground ring can reduce interference, increase the laying range of the ground wire, reduce low impedance, etc. Therefore, after the wiring of the PCB board is basically completed, it is often necessary to fill copper.


   Precautions for copper wiring


   1. The setting of pcb copper safety distance:


  Copper's safety pitch is generally twice that of wiring. But before there is no copper cladding, the wiring safety distance is set for wiring, then in the subsequent copper cladding process, the copper safety distance will also default to the wiring safety distance. This is not the expected result.


   A stupid way is to extend the safety distance to twice the original one after wiring, and then copper-clad, and then change the safety distance back to the wiring safety distance after copper-cladding, so that DRC inspection will not report an error. This method works, but if you want to change the copper overlay again, you have to repeat the above steps, which is a little troublesome. The best way is to set the rules separately for the safe distance of the copper overlay.


  Another way is to add rules. In Rule Clearance, create a new rule Clearance1 (the name can be customized), and then select Advanced(Query) in the WheretheFirstObjectmatches option box, click QueryBuilder, and then the BuildingQueryfromBoard dialog box appears. In this dialog box, the first row of the drop-down menu Select the default item ShowAllLevels, select ObjectKindis in the drop-down menu under ConditionType/Operator, and select Ploy in the drop-down menu under ConditionValue on the right, so that IsPolygon will be displayed in QueryPreview, click OK to confirm, the next is not finished, save it completely Will prompt an error:


   Next, just change IsPolygon to InPolygon in the FullQuery display box, and finally modify the copper-clad safety distance you need in Constraints. Some people say that the priority of wiring rules is higher than that of copper. If copper is used, the rules of safe spacing of wiring must be followed. The exception of copper should be added to the rules of safe spacing of wiring. The specific method is in FullQuery NotInPolygon is annotated inside. In fact, it is not necessary to do so, because the priority can be changed. There is an option priority in the lower left corner of the main page of the setting rule to increase the priority of the copper-clad safety clearance rule to be higher than the wiring safety clearance rule. Do not interfere anymore.


   2. PCB copper width setting:


  Copper will notice that there is a place to set TrackWidth when choosing Hatched and None modes. If you choose the default 8mil, and the minimum width of the network connected to your copper ply is greater than 8mil when setting the line width range, then an error will be reported during DRC, and you will not notice this at the beginning. Details, DRC has a lot of mistakes after each copper.