The transfer of a circuit design to a Printed Circuit Board or PCB is a multistep process. First the schematic of the circuit is created using a suitable PCB design software. The same software is then used to translate this schematic into a PCB layout. A layout is simply a map of the components and routings as they will occupy the space on the real PCB. These two steps require part symbols of all the electronic components in the circuit design. A part symbol is simply a set of files containing all electronic and geometrical information about the component. If the part symbol of a component is not available, it must be generated before the schematic and layout can be made.
Instructions
1 Open a new schematic drawing window in the PCB design software. In most software packages this can be done by selecting Edit -> New -> Schematic from the top menu. A new blank schematic drawing window will open up. Save it on your hard disk before moving on to the next step. It is a good practice to give the file a name that corresponds to the part you are creating the symbol for.
2 Using the utilities in the drawing menu, draw the outline of the top view of the part. Although most electronic chips are rectangular in shape, you can essentially draw any shape. The actual shape and size of the part are important for the layout symbol only, which will be created later on.
3 Open up the pin assignment drawing on the component's data sheet. This drawing shows the component's pins around the periphery of the component with names beside each pin. Draw the first pin at the corner of the component outline you drew earlier using the pin drawing utility that is generally available on the left menu bar. Repeat this process for all component pins. A good practice is to try to replicate the pin assignments as given in the component's data sheet.
4 Double click on the first pin. A dialog will open up with details about the pin. Enter its name as it shows on the component's data sheet, such as VCC. Repeat this for all pins.
5 Browse through the component library of the PCB software to find a component with dimensions and number of pins the same as the component for which you are creating the symbol. You can find the exact dimensions of your component from its data sheet. All manufacturers follow packaging standards, and therefore you should be able to find at least one component that matches your component. Save the matching component you just found as a new symbol with the name of your component.
6 Go to the schematic symbol workspace you were working on earlier, and double click on the symbol. A properties window will open up. There will be an option to link this to the layout symbol. Browse to the layout symbol you saved earlier and click OK.
7 Browse through the component library and double click on the layout symbol you saved earlier. This will open up the symbol in the layout view.
8 Double click on the first pin and assign it the name corresponding to the schematic symbol you created earlier. Repeat this process for all pins. Save the file. Your PCB component symbol has been created.
