The process of developing a printed circuit board or PCB starts with designing the circuit. For smaller circuits, this can be done on a piece of paper, but for larger and more complicated circuits, use specialized software programs that have built-in algorithms to help in the design process. For example, to design a filter, it's better to use software than doing the lengthy calculations by hand. After the design process is complete, the schematic and layout of the design are developed using a PCB design software. The layout is then used to etch the PCB.
Instructions
1 Familiarize yourself with the PCB software you will be using. All PCB programs come with tutorials that take you step-by-step through the design process. Designing a PCB is essentially a two-step process: developing the circuit schematic and developing the PCB layout.
2 Go through the PCB software component library and see if it has symbols for all the components of your circuit. The word "symbol" is used to indicate a file that contains the geometry and electrical information about a component. If some component symbols are missing, try to find them on the manufacturer's website. Most electronic component manufacturers provide PCB component libraries for widely used PCB software. If you still can not find the correct PCB symbols, you will have to create those using the same PCB design software. Go through the PCB software tutorial for creating component symbols. Every software has a different methodology and you will have to familiarize yourself with the software you are using.
3 Create the symbols for components, which are absent from the component libraries and manufacturers' websites. You can skip this step if all the required component symbols are already available.
4 Create your schematic using the PCB software. The process involves inserting the components' schematic symbols from the library into the workspace and connecting them together according to the circuit design. To make a connection, first select the wire-connector from the menu, then click and hold with the left mouse button on the first point to be connected and drag it to the second connection point. Releasing the mouse button at the second point will terminate the wire at that point. It is always a good practice to start from the main electronic component, which could for example be a microcontroller, a gate or simply a transistor. Be very careful while connecting components together as any mistake you make here will get translated to the PCB board.
5 Create the layout using the PCB software's schematic-to-layout translation utility. Generally, this can be done in two steps. In the first step, create the layout using the schematic-to-layout translation menu button. In most software packages, this menu button is available on the top menu bar. In this automatically generated layout, the components are not properly positioned inside the PCB space. So, in the second step place the components at their desired locations on the board and all the routing is done.
6 Place all components inside the PCB space one by one so that the input and output pads are at the board edges and the main component with largest number of pins is approximately in the middle. In most PCB software packages, this is done by simply dragging and dropping the components using the mouse. Note that all the connections are represented by thin lines on the board. Do not delete any of these lines even if they seem to be going in random directions all over the board.
7 Perform the routing of pads, that is make electrical connections. In most software packages, this can be done by left-clicking and holding the end of a line and following the path it should take up to the other end. Releasing the mouse button then creates the desired route. If your software has automatic routing capability, you can also use that. However, note that after this automatic routing you may need to make some manual adjustments in routes. Your circuit has now been converted to PCB layout and is ready to be transferred to the PCB for etching and populating.
