Common Problems in PCB Circuit Layout Design

Question 1: What is part packaging and what is the difference between it and parts?

Answer: (1) Parts packaging refers to the appearance and solder joint position indicated when the actual parts are welded to the circuit board.

(2) Parts encapsulation is only the appearance and solder joint location of parts. Pure parts encapsulation is only the concept of space, so different parts can share the same part encapsulation.

On the other hand, the same kind of parts can also have different packaging, such as RES2, which represents resistance. Its packaging forms are AXAIL 0.4, AXAIL 0.3, AXAIL 0.6 and so on. So when using welded parts, we should not only know the name of the parts, but also the packaging of the parts.

(3) The package of parts can be specified when designing circuit diagrams or when introducing network tables. When designing a circuit diagram, you can specify it in the Footprint settings in the Part Properties dialog box, or you can specify the part package when introducing a network table.

Question 2: What are the differences between wires, flying wires and networks?

Answer: Conductors, also known as copper film wiring, are used to connect solder joints. They are the most important part of printed circuit boards (PCBs). PCBs are designed around how to arrange conductors.

Another kind of wire related to wires is often called flying wire, also known as pre-tensioned wire. Flight line is a kind of connection which is generated by the system according to rules after the introduction of network table and used to guide the routing.

Flying wire is essentially different from wire. Flying wire is only a formal connection, it is only a formal expression of the connection between solder joints, there is no electrical connection significance. The conductors are arranged according to the connection relationship between solder joints indicated by flying wires, which has the meaning of electrical connection.

Network and wire are different. There are also solder joints on the network. So when referring to the network, not only the guide wire but also the solder joints connected with the wire 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 confusing concepts. The middle layer refers to the middle plate layer used for wiring, in which wires are distributed; the inner layer refers to the power supply layer or ground layer, which is not wiring in general. It is composed of a whole piece of copper film, which is negative phase display.

Question 4: What are internal network tables and external network tables? What are the differences between them?

Answer: Network tables are divided into external network tables and internal network tables. The network table guided by the external network table is the schematic network table generated by Sch or other schematic design software; the internal network table is the network table used for wiring in PCB system after modification according to the introduced external network table. Strictly speaking, these two kinds of network tables are completely different concepts, but readers need not strictly distinguish.

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

Answer: Firstly, the introduction of network tables is actually the process of loading schematic design data into PCB. All data changes in PCB design system can be accomplished by Netlist Macro. The system automatically generates network macros by comparing and analyzing network table files and internal data of PCB system.

Secondly, network table manager can be used to edit the connection relationship between components of PCB directly in PCB system to form network table.

Question 6: What are classes and what are the benefits of introducing the concept of classes?

Answer: The so-called class refers to a set of units with the same meaning. Class definition in PCB is open to users. Users can define the meaning of classes and the composition of classes themselves. Introducing classes into PCB has two main functions:

(1) Easy wiring

In the process of PCB routing, some networks need special processing, such as some important data lines, in order to avoid interference from other components on PCB, it is often necessary to increase the safe distance between these data lines and other components.

These data lines can be grouped into a class, which can be added to the rules when setting the rules of safe distance of automatic routing, and the safety distance can be increased appropriately, then the safety distance of all data lines in this class will be increased when automatic routing is carried out. In the process of circuit board routing, the power supply and grounding lines are often required. To ensure the reliability of the connection, the power supply and grounding wires can be grouped. When setting the Width Constraint rule, the class can be added to the rule, and the wire width can be increased appropriately, then the power supply and grounding wires in this class will be widened.

(2) Easy to manage PCB components

For a large circuit board, there are many parts encapsulated on it, as well as thousands of networks, which are very messy. Classes can be used to manage circuit boards easily. For example, all the input networks in the circuit board can be classified into two categories: when looking for an input network, it is only necessary to find it in the input network class; or it can classify all the voltage limiting resistors in the circuit board. When looking for a voltage limiting resistor, it is only necessary to find it in the voltage limiting resistor class.

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

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

Question 8: What is the use of inner segmentation?

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

Question 9: What role does copper play and what should we pay attention to?

Answer: The main function of copper coating is to improve the anti-interference ability of circuit board. If we want to wrap wires or make up teardrops, copper coating should be carried out at the end.