The three issues in designing a four layer circuit board

The three issues in designing a four layer circuit board

Drawing a four layer circuit board is one of the most important steps in the design process. It includes the planning of the circuit board in the early stage, the layout of components, wiring, and the design verification (DRC) after the circuit board design is completed, as well as the subsequent output of gerber, bom tables, and other files. Drawing a four layer circuit board design is the most knowledgeable, skilled, and difficult part of circuit board design. Therefore, in PCB design, beginners also encounter the most problems.

1、 How to add pads to the network Question: How to add pads to the network? Answer: There are two specific methods to add a pad to a network in a circuit board. The first method is to first add a pad to the circuit board, then double-click the pad to pop up the Pad dialog box. Click the Advanced tab with the mouse to enter the Advanced tab, then select the network label of the pad in the drop-down list after the Net option, and finally click 0K confirmation in the dialog box to add the pad to the network. Next, move the modified pad to its current position on the network. The second method is to execute the menu command to place a pad, and then directly place the pad on the network where the pad needs to be placed. At this time, the system will automatically add a network label to the pad. After placing a pad, the system is still in the command state for placing pads, and users can continue to place pads. This method is very convenient for placing multiple pads. 2、 Regarding copper coating question 1: What is the function of copper coating? What should be paid attention to during the copper coating process? Answer: The main function of copper coating is to improve the anti-interference ability of circuit boards and increase the load capacity of wires with excessive current. Among them, copper coating on the ground wire network is the most common operation. On the one hand, it can increase the conductive area of the ground wire and reduce the common impedance introduced by the circuit due to grounding. On the other hand, it can increase the area of the ground wire, improve the anti-interference performance and overcurrent ability of the circuit board. Copper coating should generally follow the following principles. If the layout and wiring of components allow, the safety distance between the copper clad network and other graphics should be limited to more than twice the conventional safety distance; If the layout and wiring of components are relatively tight, the safety distance can also be appropriately reduced, However, it is best not to be less than "0.5mm". The connection method between copper clad boxes and solder pads with the same network label should depend on the specific situation. For example, in order to increase the current carrying area of the solder pads, users should use direct connection. If in order to avoid the rapid heat dissipation of large copper foils during component assembly, radiation should be used for connection. Question 2: Why copper clad (copper clad) Is the file that big? Is there a good solution? Answer: It is normal for the file to have a large amount of data after copper coating. But if it is too large, it may be due to your unscientific settings. Figure 2 shows the copper clad settings dialog box. If the values of Grid Size and Track Width are set too small in this dialog box, the circuit board design file will be large. This is because the copper clad foil is actually covered by countless wires, and the more wires there are, the greater the amount of information stored in the PCB file. The designer wants to make the PCB file after copper clad not too large, You can set the values of the Grid Size and Track Width options to be larger. Question 3: How to remove the separated small copper clad areas in the copper clad area? Answer: These separated small copper coated pieces are commonly referred to as "dead copper". The solution is to open the Polygon Plane dialog box before performing the copper coating operation, select the Remove Dead Copper option, and the system will automatically remove the "dead copper" during the copper coating process.

3、 Question 1: How to make different parts of a wire have different widths and appear continuous and aesthetically pleasing on the same wire? Answer: This operation cannot be completed automatically, but it can be divided into several steps using editing techniques, such as drawing continuous and smooth wires. 1. First place a thin wire with a wire width of 0.5mm, then press the Tab key to modify the wire width to 2mm in the pop-up wire properties dialog box. Then draw a wire with a width of 2mm and place a pad on the newly drawn wire. The outer diameter of the pad is the width of the widest wire, which is 2mm. 3. Use the mouse box selection method to select the added pad. 4. Choose the menu command Tools/teardrops... The Teardrop Options dialog box will pop up. In the Teardrop Options dialog box, users can set the scope of the teardrop repair operation, add/remove teardrops, and the style of the teardrop repair (including two styles: circular arc and wire). 5. In the dialog box, select the teardrop filling operation for the selected object, with the teardrop style being an arc style. Finally, click the OK button to confirm. Teardrop wire is a guide wire that gradually increases in width and forms a teardrop shape when it enters a pad or through hole. The operation of making teardrop wires is called "repairing teardrops". The purpose of repairing teardrops on the wire is to strengthen the connection between the wire and the solder pad (or through hole), in order to prevent stress concentration during the processing of the solder pad or through hole. If the stress concentration is severe, it often causes the wire at the connection between the wire and the solder pad (or through hole) to break. Of course, the goal of smooth and aesthetically pleasing transitions between two sections of wire with different widths can also be achieved before filling the tears. 6. Delete the solder pad to obtain a smooth and natural transition wire.