Several misunderstandings in pcb layout learning

writer: G March 12, 2018

1. Single panel is simpler than double panel.

Wrong. It is much more difficult to make a single panel in Allegro--PCB Editor than it is to use a dual-panel. PCB LAYOUT is proved to be very low when the automatic routing function is used.

2. The role of ORCAD is mainly to obtain a beautiful circuit diagram.

Wrong. The purpose of the ORCAD drawing is mainly to get a netlist and prepare for the next PCB design. In fact, it is very difficult to get a beautiful and in line with the national standard circuit diagram with ORCAD. Many people only know the simple drawing. Do not understand the norm at all, this has brought a lot of inconvenience to PCB design, and now both understand the circuit design, but also less skilled and less.

3. Allegro--PCB Editor component packaging library is very comprehensive, generally do not need to increase their own packaging library.

Wrong. The packaging of components in Allegro--PCB Editor is indeed a lot, but it is a little less than the packaging of many components we use. Sometimes an electrolytic capacitor will not find a ready-made package. Therefore, designing a printed board using Allegro--PCB Editor, it is common to add a package library. Fortunately, it is very convenient to add a package library to Allegro--PCB Editor. Here we must pay attention to: the package can not only look similar to the shape, we must make the name of the pad and the pin name of the component in the schematic, otherwise it will lose the pin or error in the network table.

4. To use the Edit Router for automatic routing, you must first use ORCAD to draw the circuit diagram.

Wrong. Edit Router Autoroute does not require schematic support, and it is not non-editable with ORCAD. The Edit Router just requires a netlist (.asc) file. The netlist can be drawn by ORCAD as a schematic, generated, and the netlist file can be manually compiled after understanding the netlist.

5. Using Edit Router automatic wiring layout is certainly correct.

Wrong. The use of Edit Router's automatic cabling does not guarantee the correct cabling. Sometimes it can also make ‘serious’ mistakes. For example, the power supply must be short-circuited. It must be inspected after the cabling has been completed and carefully modified.

6. It is reasonable to use the Edit Router automatic routing function to lay out the line.

Wrong. Its practical Edit Router auto-routing function lays out a messy line, which is not as good as the manual wiring of experienced people, especially the wiring of analog circuits, which almost must be manually modified. Even full manual wiring can meet the requirements. PCB LAYOUT training does not recommend automatic routing.

7. When wiring in Allegro, you must ‘formally’ route the wiring according to the wiring method it provides, otherwise you cannot get a complete printed board diagram.

Wrong. In fact, just draw a line on the BOTTOM LAYER or TOP LAYER of Allegro> PCB Editor, or put a solder joint, this wire or the solder joint can be made to the board, no matter how this line is drawn. , or how this solder joint is done, the solder joint can be on a component.


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