Routing Power, Ground & Copper Pours in ORCAD, courtesy Connexions.org

                            In any design, it is usually wise to route all power and ground connections before anything else. On a thru-hole technology board, this is very easy because connections can be made to the solid plane as the pin passes through the board. The pin will be “flashed” to power or ground. We need to set up our design so that OrCAD knows that the two planes are associated with nets. Open the nets spreadsheet and find the net GND. Double-click to open the Edit Net dialog and click the button labeled Net Layers… Under the section Plane Layers, check the box labeled GND. This will inform OrCAD that the net GND is associated with the solid plane on layer 2. Do the same thing for the netVCC5. When you close the spreadsheet, click the Refresh All button. The ratsnests for VCC5 and GND will disappear. This is because they are now connected to the plane layer. To see this, press Backspace to clear the screen, then press ‘3’ (the shortcut key for the ground layer) to view the ground layer.

You can now see all of the connections to the ground plane. You can do the same thing for the power plane. Press ‘F5’ or the Refresh All button to make the whole design visible again.

We still have one voltage net to route, and that is the input voltage from an external power supply. This net only touches a few components, so we could just put a trace to connect all the components. However, we can also draw a solid piece of copper and associate it with that net. This is especially useful for high-current traces or small voltage planes. We do this using the Obstacle Tool just like when drawing obstacles for footprints. Turn the Obstacle Tool on and then right-click anywhere in your design. SelectNew… and then right-click again and select Properties… to bring up the Edit Obstacle dialog. Name this obstacle VCC_IN, leave the Width at 10 mils. Set the Clearance to 15 mils Change the Obstacle Type to Copper pour. Finally, set the Net Attachment to the name of the net, which should be V_IN. Click OK and you are ready to draw your copper pour. Draw a rectangle around the power connector and other components that are attached to this net. When you are done, click Refresh All to redraw the ratsnests.

    

You have now routed all the power and ground connections. That was easy, right? Let’s look a little bit at some of the tools that OrCAD gives you to check on the progress of your design. Click the View Spreadsheets icon and choose Statistics. The statistics spreadsheet gives you information on time in layout, percent of components placed, percent of traces routed, and some other information.

100% of your components should be placed, and you can also see that a majority of your traces have been routed (power and ground make up the majority of connections in most designs). You are well on your way to completing your design.