Common Problems in PCB Circuit Layout Design

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

Answer: 

(1) Parts package refers to the appearance and solder joint position indicated when the actual parts are soldered to the circuit board.

(2) The part package is only the appearance of the part and the location of the solder joint. The pure part package is only the concept of space, so different parts can share the same part package; on the other hand, the same kind of parts can also have different packages, such as RES2 stands for resistance, and it is packaged in the form of AXAIL0.4, AXAIL0.3, AXAIL0.6, and so on, so when you use soldered parts, 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 it can be specified when the netlist is introduced. When designing a circuit diagram, you can specify it in the Footprint setting item in the Part Properties dialog box. You can also specify the part package when importing a netlist.

Question 2: What is the difference between wire, fly line, and network?

A: The wire is also called the copper film trace, which is called the wire for connecting the solder joints. It is the most important part of the printed circuit board. The printed circuit board design is based on how to arrange the wire.

Another type of wire associated with a wire, often called a fly wire, is also called a pre-wired wire. After the fly line is introduced into the network table, the system generates according to the rules and is used to guide a kind of wiring of the wiring.

Flying lines and wires are essentially different. Flying line is only a form of connection, it is only a formal representation of the connection between the various solder joints, there is no electrical connection significance. The conductors are arranged according to the connection relationship between the solder joints indicated by the flying lines, and the connection lines are of electrical connection significance.

The network and the wire are different, and the network also includes solder joints, so when referring to the network not only the wire but also the solder joints connected to the wires.

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

A: The middle and inner layers are two confusing concepts. The middle layer refers to the middle plate layer used for wiring. The layer is covered with wires; the inner layer is the power layer or the ground layer. This layer is generally not covered by wiring. It is composed of a whole piece of copper film and is negative. Shown.

Question 4: What is the internal network table and the external network table. What is the difference between the two?

A: The network table has the external network table and the internal network table. The external network table refers to the introduced network table, which is a schematic network table generated by Sch or other schematic design software. The internal network table is based on the imported external network table and is modified to be used by the PCB system for internal wiring. Strictly speaking, these two types of netlists are completely different concepts, but readers do not have to strictly distinguish between them.

Question 5: What is the role of the netlist manager?

A: First, the introduction of a netlist, the introduction of such a netlist is actually the process of loading the schematic design data into the printed circuit board design system PCB. All changes in the data in the PCB design system can be accomplished through the Netlist Macro. The system automatically generates network macros by comparing and analyzing the network table files and the internal data of the PCB system.

Second, the network table manager can be used to directly edit the connection relationships among the various components of the circuit board in the PCB system to form a network table.

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

A: The so-called class refers to a collection of elements that have the same meaning. The definition of the class in the PCB is open to the user. The user can define the meaning of the class and the composition of the class. The introduction of classes in PCB has two main roles:

(1) Convenient wiring in the circuit board wiring process, some networks need special treatment, such as some important data lines in order to avoid the interference of other components on the circuit board, often need to increase these data lines and other components in the wiring The safety spacing between. These data lines can be categorized into a single class. This class can be added to the rules when setting the automatic routing safety clearance rule, and the safety clearance should be increased appropriately. In this case, the safety clearances of all the data lines in this class are automatically Increased; In the circuit board layout process, the power and ground lines often need to be thickened to ensure the reliability of the connection, and the power and ground lines can be classified into one, when setting the Width Constraint rule. You can add this class to the rule, and increase the width of the wire appropriately. When you auto-route, the power and ground lines in this class will be widened.

(2) Easy management of circuit board components For a large circuit board, there are many parts package, there are tens of thousands of networks, very messy, and the use of classes can be very convenient to manage the circuit board. For example, to classify all the input networks in the circuit board, when looking for a certain input network, you only need to search in this input network class; you can also classify the finite resistance in the circuit board, looking for a certain For voltage limiting resistors, simply look in the voltage limiting resistor.

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

A: The solder joints can be added to the circuit board first, then the solder joints can be double-clicked, the solder joint property setting dialog can be opened, and the solder joint placement can be completed by selecting the appropriate network in the Advaced Net item.

Question 8: What is the use of inner segmentation?

A: The split inner layer can be used to connect some important lines, that is, it can improve the anti-interference ability and can also protect important circuits.

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

A: The main role of copper is to improve the circuit board's anti-jamming capability. If you want to make wire or make up teardrops on the circuit, then the copper should be placed at the end.