A simple application can be done with a two-layer board. You can run the wiring on the TopLayer and BottomLayer. However, for a more complicated circuit or a circuit with higher performance requirements, the two-layer board may not work. In my personal opinion, a multi-layer board and a double-layer board are the same. It does not mean that the higher the number of layers, the more "advanced". For example, to complete the same function, engineer A uses a 6-layer board to achieve it, and engineer B uses a 6-layer board to achieve it. It is achieved using 4-layer boards, and Engineer S only uses 2-layer boards, and the performance of the boards made by the three engineers is the same, so obviously Engineer S has the highest level, not Engineer A. Of course, we have not reached the height of engineer S. When encountering a PCB design that cannot be achieved by a double-layer board, we can only use a multi-layer board design. Generally speaking, multi-layer boards refer to boards with even-numbered layers such as 4-layer boards, 6-layer boards, and 8-layer boards, but there are indeed applications of 3-layer boards and 5-layer boards, but it seems that the manufacturing difficulty and cost of 3-layer boards are different from 4-layer boards are not much different, so since 4-layer boards can be used, why use 3-layer boards. Next, let's try the PCB design of the multi-layer board.
First create a project, create a new schematic file and a PCB file, use DR to set the rules of the PCB file, set the line width, aperture, spacing and other rules, and then draw a 5CM*5Cm board shape. Let's start to draw the schematic diagram, and extract some schematic diagrams from other projects, as shown below:
This is a minimal system of STM32 plus CAN chip, 485 chip, EEPROM chip, power chip and other parts. Compile and import into the PCB file.
By default, the newly created PCB file has only two signal layers TopLayer and BottomLayer. If we need to draw a multi-layer circuit board, we need to add layers ourselves. Use DK to open the Layer Stack Manager window as shown below:
From top to bottom are Top Overlay, Top Solder, Top Layer, Dielectric 1, Bottom Layer, Bottom Solder, Bottom Overlay. There are only two signal layers in it. We can click "Add Layer" to add a power layer or a signal layer. We first draw a 4-layer board, the middle two layers are the GND and VCC layers, click Add Internal Plane to add two power layers, and then rename them to GND and VCC, as shown in the figure below:
The board we draw has 4 layers. Here we should pay attention to the difference between the power supply layer and the signal layer, which can be specific to Baidu. Generally speaking, the signal layer is a positive film output, and the power supply layer is a negative film output. That is to say, the line drawn on the signal layer actually becomes a line. The copper wire is actually processed by drawing a wire on the power layer. To put it bluntly, drawing a wire on the power layer is equivalent to deducting copper, and drawing a wire on the signal layer means drawing a copper wire. The benefits of this design method can be Baidu. In this way, when we draw the power layer, we actually perform a division operation, that is, we use lines to divide the copper skin of the power layer into a piece of area, which is "power division". We first lay out the signal lines on the top and bottom layers, as shown in the figure below:
Then connect the remaining power supplies on the middle power supply layer and enter the GND layer. We use Place Line to draw a dividing line for power division, and divide all the power The GND vias are all divided into one area:
this way all the GNDs are connected together, just like copper on the top layer. Then we divide the power supply on the VCC layer, where the VCC layer has two power supplies of 5V and 3.3V. When we divide, we divide the vias corresponding to the power supply together:
the above picture is the 5V power supply area.
The picture above is the 3.3V power supply area.
Hmm, that does the power splitting. In fact, there is still a lot of attention to power splitting. For details, please go to the blog of the expert.
The above is basically the drawing of the 4-layer board, but the middle two layers of the 4-layer board can also be a lot of power layers, which can be signal layers. It is very simple. When adding layers, use "Add Layer" to add signal layers, as follows Figure:
Then we can perform wiring in the two intermediate signal layers, and it is the signal layer of the positive output, and the signal lines can be drawn directly without dividing, so that if the wiring of the top and bottom layers is very tight, it can be directly in the middle signal layer. Do the wiring. Then we route the first signal layer in the middle. We can use copper or thicker wires to connect all GND vias, as shown in the figure below:
the thicker wire above is the GND wire, and the thinner wire is the signal wire . Then perform wiring on the second signal layer in the middle, and connect the 5V and 3.3V vias on this layer, as shown in the figure below:
OK, the board with the 4-layer signal layer has also been drawn here, which is a bit rough, but it doesn't matter. I have a big heart.
Well, since we've come this far, let's go a little longer and try a 6-layer board. On the basis of the above board with two layers of signal layer and two layers of power layer, DK is used to add two more signal layers:
now there are 6 layers, presumably everyone already understands that it will be easier to use 6-layer boards for circuits of the same difficulty. Just put the wires that cannot be routed on other layers on the other two layers for wiring. It is easier to use an 8-layer board. If you use a 100-layer board, I will use one wire for each layer. Here I chose two for demonstration, as shown below:
In general, the drawing of multi-layer boards is not difficult, but when using multi-layer boards, it means that the circuit is complex enough, and the difficulty lies in the circuit.
Reference article: https://www.cnblogs.com/raymon-tec/p/5631318.html