Senin, 16 April 2012

How to design pcb in orcad?

Orcad cadence is a popular pcb design software used by professional engineers around the globe. Here how one can learn to design pcb using orcad pcb software quickly is described. First of all you have to download cadence orcad pcb software.

The major general steps to designing a pcb with orcad are:
  1. Start orcad capture and draw the schematics
  2. Perform Simulation and verify result and replace/add components according to your result requirements
  3. Find and assign the footprints(names) for all the schematics symbols
  4. Perform annotation
  5. Perform DRC
  6. Create Netlist
  7. Open orcad PCB Editor
  8.  Define board outline
  9. Place the mechanical components
  10. Place the electrical components
  11. Create layers if multiple layers are required
  12. Place copper pours(multiple layers)
  13. Check electrical rules, physical rules and spacing rules in the constraint manager
  14. Perform manual and automatic routing
  15. Generate Artwork for manufacturing

Once you have downloaded the orcad software, you have to start the orcad schematic capture which is a tool where you can enter the schematics or circuit diagram of the electronics system which you want to design. This requires you to place parts from libraries. There are two kinds of libraries, one that has footprints, part symbol with simulation information and those with only part symbol but without simulation information and/or footprints. Any part used in electronic system design prototyping need its schematic symbol for identification, simulation profile(how it works) and footprints(for pcb generation). If there is no part symbol(and/or simulation profile) then you have to create a new one which you can do so either from orcad capture window or from the model editor application.

Once the schematics of the electronic system to be designed is complete. The next step is to perform simulation. Once the simulation is verified the schematics parts are assigned their footprints. If there is no footprint available then you have to either search for footprint or create a new one using pad designer or using the new part option in the orcad PCB designer.Then the next step is annotation(giving unique identification names to parts) and perfrom DRC(Design Rule Check) to check any error. If there is no DRC then you can create a netlist of your circuit.

This netlist is required by the PCB designing software. During the netlist creation you have the option to automatically open the Orcad PCB editor(or you can independently open the PCB editor and go to open menu to open the netlist file). Once the PCB editor is open you have to create a board outline and start placing components both mechanical components that will hold the pcb board and the electrical components(capacitor, resistors, amplifiers etc).

If it is required to have more than two layers then multiple layers has to defined next. After this pouring of copper planes and construction of vias and the fanout has be carried out. Then the spacing between the copper traces, length width of the copper traces and other electrical and non electrical constraints have to be defined prior to routing the traces using the constraint manager. Once the constraints are defined the next step is to perform routing. The routing can be performed manually for critical nets(for eg power and ground nets) and fixing such nets and then the auto-routing to non-critical nets can be applied for speed-up. The last step is to generate artwork which contains all the information of the pcb to be manufactured, this file(extension usually gerber) is sent to the pcb board manufacturer.

To learn to design pcb in orcad, we recommend you to Download Kraig Mitzner Complete PCB Design Using OrCad Capture and Layout 2007, which you can do so for free

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