PCB design technology

1. Why is the PCB file designed by the DOS version of Protel software not the full picture when it is called out in my computer?

Many old electronic engineers have encountered such problems when they first used computers to draw PCB circuit diagrams. Is it because my computer memory is not enough? My computer has 64M memory! Why are the graphics on the screen still missing arms? What about the one with less legs? Yes, there is a problem with the memory configuration. You only need to add the following lines to your CONFIG.SYS file (this file is in the root directory of C:\, if not, create one), save and exit Then restart the computer.

DEVICE=C:\WINDOWS\SETVER.EXE

DEVICE=C:\WINDOWS\HIMEM.SYS

DEVICE=C:\WINDOWS\EMM386.EXE 16000

2. How to determine the line width of the high current wire?

Please see the graphic description in Vol12 of “Manual of Electronic Industry Production Technology” published by National Defense Industry Press in 1989.

3. Why is it necessary to convert the PCB file into a GERBER file and drilling data and submit it to the PCB factory for board manufacturing?

Most engineers are accustomed to sending the PCB file to the PCB factory for processing after the PCB file is designed. However, it is more popular in the world to convert the PCB file into a GERBER file and drill data and then send it to the PCB factory.

Because electronic engineers and PCB engineers have different understandings of PCB, the GERBER file converted by the PCB factory may not be what you want. For example, you define the parameters of the components in the PCB file during design, and you do not want these parameters to be displayed. On the finished PCB, you did not explain, and the PCB factory left all these parameters on the finished PCB. This is just an example. Such incidents can be avoided if you convert the PCB file into a GERBER file yourself.

GERBER file is an international standard optical drawing format file, which includes RS-274-D and RS-274-X two formats, RS-274-D is called the basic GERBER format, and it must be accompanied by a D code file to Completely describe a graphic; RS-274-X is called the extended GERBER format, which itself contains D code information. Commonly used CAD software can generate files in both formats.

How to check the correctness of the generated GERBER? You only need to import these GERBER files and D-code files in the free software Viewmate V6.3, and then you can see them on the screen or print them out through the printer.

Drilling data can also be generated by various CAD software, the general format is Excellon, and can also be displayed in Viewmate. Without drilling data, of course the PCB cannot be made.

4. How to improve the pass rate?

Completing the design of a printed board diagram generally involves the process of schematic diagram input–network table generation–definition of Keepout Layer–network table (component) loading–component layout–automatic (manual) wiring and other processes. Several popular softwares on the market today are not very powerful in the function of automatic layout of components. Manual layout can often improve the placement rate, but please don’t forget to make full use of the Move to Grid function, which can automatically move components To the intersection of the grid, it is of great benefit to improve the routing rate.

5. How to add Chinese characters in the PCB file?

There are many ways to add Chinese characters to the PCB file, and the method I prefer is the one that will be introduced below:

A. Precondition: Protel99 software should be installed in your PC and can run normally.

B. Step: copy the client99.rcs English menu file in the windows directory to another directory and save it; download Protel99cn.zip and unzip it, and copy the client99.rcs to the windows directory; then copy other files to Design In the Explorer 99 directory; after restarting the computer and running Protel99, the Chinese menu will appear, and the function of adding Chinese characters can be realized in the placement|Chinese character menu.

6. How to describe the long slot hole in the PCB file?

As shown in the figure above, it is a relay package, and the section of the relay pin is rectangular, so the corresponding hole on the printed circuit board should be in the shape of a long slot. To describe this slot-shaped hole, you only need to place a Just arrange pads with the same size as the holes, as indicated by the cross cursor in the figure above.

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