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Talking about PCB wiring adjustment
PCB News
Talking about PCB wiring adjustment

Talking about PCB wiring adjustment

2021-11-09
View:32
Author:Kavie

I would like to ask a question: I feel that the machine cloth is not as good as you want, and it takes time to adjust it. I usually use manual wiring. Most of the PCB boards I make now use SMD with higher pin density to package the chip, and the bus (ABUS, DBUS, CBUS, etc.) May be short. Naturally, very dense signal lines are evenly distributed on a small area of the board. I now feel that it takes more time to adjust these dense signal lines. One is to adjust the distance between the lines to make them as even as possible. Because in the process of wiring, it is generally necessary to change the wiring from time to time. Every time you change it, you must re-even the spacing of each line that has been laid out. The more it goes to the end, the more this happens. The second is to adjust the width of the line so that it can accommodate the newly added line as much as possible in a certain width. Generally, there are many bends in a line, one bend is one section, manual adjustment can only be adjusted one by one, and it takes time to adjust. I think if in the process of wiring, if I can manually pull the wire roughly according to my idea, after the completion, the software can help me automatically adjust from these two aspects. Or even if the cloth is finished, if you want to change the thread, change it roughly, and then let the software adjust it. Even, in the end, I felt the need to adjust the package of the components, that is to say, the entire wiring needs to be adjusted and let the software do it. That would be much faster. I use Protel98. I know that this software can automatically adjust the distance of the component packaging but not the line spacing and line width. It may be that some of these functions are not yet available to me, or there are other ways. I would like to ask here.


 PCB


answer: Line width and line spacing are two important factors that affect trace density. Generally, when designing a board with a higher operating frequency, it is necessary to determine the characteristic impedance of the trace before wiring. In the case of a fixed PCB stack, the characteristic impedance will determine the line width. The line spacing has an absolute relationship with the size of crosstalk (Crosstalk). The minimum acceptable line distance depends on whether the influence of crosstalk on signal time delay and signal integrity is acceptable. The minimum line distance can be obtained by pre-simulation by simulation software. In other words, before wiring, the required line width and minimum line distance should have been determined, and can not be changed at will, because it will affect the characteristic impedance and crosstalk. This is why most EDA wiring software does not change the line width and minimum line spacing when doing automatic wiring or adjustment. If the line width and minimum line distance have been set in the wiring software, the convenience of wiring adjustment depends on the ability of the software winding engine.

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