PCB circuit board layout design of the common seven questions seven answers

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

A: (1) Parts package refers to the appearance and solder spot position indicated when the actual parts are welded to the circuit board.

(2) Parts packaging is only the appearance of parts and solder joint location, pure parts packaging is just a concept of space, so different parts can share the same parts packaging; On the other hand, the same parts can also have different packages, such as RES2 stands for resistance, its package form AXAIL0.4, AXAIL0.3, AXAIL0.6 and so on, so in the use of welding parts, not only to know the name of the part but also know the package of the part.

(3) The package of parts can be specified in the design of the circuit diagram, can also be specified in the introduction of the network table. The circuit diagram can be specified in the Footprint setting item in the Part Properties dialog box, or the part package can be specified when the network table is introduced.

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

A: Wire, also known as copper film wiring, referred to as wire, used to connect the solder joints, is the most important part of the printed circuit board, printed circuit board design is around how to arrange wire to carry out.

The other kind of wire associated with the conductor is often called the flying wire or the pre-drawn wire. Fly wire is a kind of wire generated by the system according to the rules after the introduction of the network table, which is used to guide the wiring.

There is a fundamental difference between a flying wire and a conductor. Flying wire is just a formal connection, it is just a formal expression of the connection between the solder joints, no electrical connection significance. The wire is arranged according to the connection relationship between the solder joints indicated by the flying line, and has the connection line of electrical connection significance.

A network is different from a wire. A network also includes solder joints, so when we talk about a network, we don't just refer to the wire but also to the solder joints connected to the wire.

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

A: The middle layer and the inner layer are two confusing concepts. Intermediate layer refers to the intermediate plate layer used for wiring, the layer is distributed in the wire; The inner layer refers to the power layer or ground layer, the layer is generally not wired, it is composed of the whole piece of copper film, is negative phase display.

Question 4: What is an internal network table and an external network table, and what are the differences between the two?

A: There are external network tables and internal network tables. The external network table guides the incoming network table, namely, the schematic network table generated by Sch or other schematic design software; The internal network table is the network table used for wiring inside the PCB system after modification according to the imported external network table. Strictly speaking, these two types of network tables are completely different concepts, but the reader may not have to make a strict distinction.

Question 5: What does the network table manager do?

A: First, the introduction of the network table, which is actually the process of loading the schematic design data into the printed circuit board design system PCB. All the changes of the data in the PCB design system can be completed through the Netlist Macro. The system generates the network macro automatically by comparing and analyzing the network table file and the internal data of the PCB system.

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

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

A: A class is a collection of units that have the same meaning. PCB class definition is open to users, users can define the meaning of the class and the composition of the class. The introduction class in PCB has two main functions:

(1) Easy wiring In the circuit board wiring process, some networks need to make special processing, such as some important data lines in order to avoid the interference of other components on the circuit board, in the wiring often need to increase the safety distance between these data lines and other components. These data lines can be classified into a class, when setting the safety spacing rules for automatic wiring, this class can be added to the rules, and appropriately increase the safety spacing, then automatic wiring, the safety spacing of all data lines in this class is increased; In the process of circuit board wiring, the power supply and ground wire often need to be bold, to ensure the reliability of the connection, you can classify the power supply and ground wire into one class, in setting the automatic wiring wire width (WidthConstraint) rules, you can add this class to the rules, and increase the wire width appropriately, then automatic wiring, Both the power and ground wires in this class will be widened.

(2) Easy to manage circuit board components for a large circuit board, it has a lot of parts package, there are thousands of networks, very messy, the use of the class can be very convenient to manage the circuit board. For example, all the input networks in the circuit board are classified. When looking for an input network, only the input network class can be searched; You can also classify all the finite voltage resistors in the circuit board. When you are looking for a voltage limiting resistor, you only need to look for it in the voltage limiting resistor class. Question 7: How can external solder joints be added to the network?

A: You can first add the solder joints to the circuit board, then double click the solder joints, open the solder joints properties dialog box, and select the appropriate network in the Advaced Net TAB to complete the solder joints placement.

Question 7: What is the use of inner division?

A: The segmented inner layer can be used to connect some important lines, which can improve anti-interference ability and can also protect important circuits. Question 9: What is the effect of applying copper and what should we pay attention to?

Answer: The main role of copper is to improve the anti-interference ability of the circuit board, if you want to pack wire or tear drop on the line, then copper should be put in the last.