Common Problems in PCB Circuit Layout Design

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Common Problems in PCB Circuit Layout Design [Copy link]

Frequently Asked Questions in PCB Circuit Layout Design
Question 1: What is a component package and how is it different from a component?

　　Answer: (1) The part package refers to the appearance and solder joint position of the actual part when it is soldered to the circuit board.
　　(2) The part package is only the appearance and solder joint position of the part. Pure part package is just a concept of space, so different parts can share the same part package; on the other hand, the same part can also have different packages. For example, RES2 represents a resistor, and its package forms include AXAIL0.4, AXAIL0.3, AXAIL0.6, etc. Therefore, when taking a soldering part, you must know not only the part name but also the part package.
　　(3) The part package can be specified when designing the circuit diagram or when importing the network table. When designing the circuit diagram, you can specify it in the Footprint setting item in the part properties dialog box, or you can specify the part package when importing the network table.

Question 2: What is the difference between wires, flying leads and networks?

　　Answer: Wires are also called copper film traces, or simply wires. They are used to connect various solder joints and are the most important part of printed circuit boards. Printed circuit board designs are all based on how to arrange wires.
　　Another type of wire related to wires is often called flying wires, also known as pre-stretched wires. Flying wires are generated by the system according to rules after the network table is introduced, and are used to guide wiring.
　　There is an essential difference between flying wires and wires. Flying wires are just a formal connection, which only formally indicates the connection relationship between various solder joints and has no electrical connection meaning. Wires are arranged according to the connection relationship between solder joints indicated by flying wires, and are connecting lines with electrical connection meaning.
　　Networks and wires are different. Networks also include solder joints. Therefore, when referring to networks, not only guide wires but also solder joints connected to wires are included.

Question 3: What is the difference between the inner layer and the middle layer?

　　Answer: The middle layer and the inner layer are two concepts that are easily confused. The middle layer refers to the middle board layer used for wiring, in which the wires are laid; the inner layer refers to the power layer or ground layer, which is generally not wired and is composed of a whole piece of copper film.

Question 4: What are internal network tables and external network tables, and what is the difference between them?

　　Answer: Network tables can be divided into external network tables and internal network tables. External network tables refer to the introduced network tables, that is, the schematic network tables generated by Sch or other schematic design software; internal network tables are modified based on the introduced external network tables and are used for wiring in the PCB system. Strictly speaking, these two network tables are completely different concepts, but readers do not need to strictly distinguish them.

Question 5: What is the function of the Network Table Manager?

　　A: First, introduce the network table. The process of introducing this network table is actually the process of loading the data of the schematic design into the printed circuit board design system PCB. All changes in the data in the PCB design system can be completed through the network macro (Netlist Macro). The system automatically generates the network macro by comparing and analyzing the network table file and the internal data of the PCB system.
　　Second, the network table manager can be used to directly edit the connection relationship between the various components of the circuit board in the PCB system to form a network table.

Question 6: What is a class? What are the benefits of introducing the concept of class?

　　A: A class is a collection of units with the same meaning. The class definition in PCB is open to users, and users can define the meaning and composition of the class. There are two main functions of introducing classes in PCB:
　　(1) Facilitating wiring. During the wiring process of the circuit board, some networks need special processing. For example, some important data lines need to be wired to avoid interference from other components on the circuit board. When wiring, it is often necessary to increase the safety spacing between these data lines and other components. These data lines can be grouped into a class. When setting the automatic wiring safety spacing rule, this class can be added to the rule and the safety spacing can be appropriately increased. Then, during automatic wiring, the safety spacing of all data lines in this class will be increased. During the wiring process of the circuit board, the power and ground lines often need to be thickened to ensure the reliability of the connection. The power and ground lines can be grouped into a class. When setting the automatic wiring wire width (Width Constraint) rule, this class can be added to the rule and the wire width can be appropriately increased. Then, during automatic wiring, the power and ground lines in this class will become wider.
　　(2) Easy to manage circuit board components. For a large circuit board, there are many parts packages and thousands of networks, which are very messy. Classes can be used to easily manage the circuit board. For example, all input networks in the circuit board can be classified. When looking for a certain input network, you only need to search in this input network class; you can also classify all voltage-limiting resistors in the circuit board. When looking for a certain voltage-limiting resistor, you only need to search in this voltage-limiting resistor class.

Question 7: How to add additional solder joints to the network?

　　A: You can first add the solder joint to the circuit board, then double-click the solder joint to open the solder joint property setting dialog box, select the appropriate network in the Net item in Advaced, and then complete the placement of the solder joint.

Question 8: What is the use of inner segmentation?

　　Answer: The separated inner layer can be used to connect some important lines, which can improve the anti-interference ability and also protect important circuits.

Question 9: What is the function of copper plating and what should we pay attention to?

　　Answer: The main function of copper plating is to improve the anti-interference ability of the circuit board. If the circuit needs to be wrapped with wires or teardrops are to be filled, the copper plating should be done last.