Designing a printed circuit board (PCB) is the delicate process of translating your circuit schematic into a practical application. You need to consider many factors in a practical circuit that will affect your result almost as much as the quality of your schematic. Unlike theoretical components, real world devices generate heat, wires and traces have inherent resistance, and traces that are too close together can become a capacitor or create a short circuit through a manufacturing defect. A carefully designed PCB will be easy to assemble; have a clear, logical flow; and avoid electrical problems.
Instructions
1 Open your PCB layout software and create a new project file. Set the board size to the specifications of your project, and enable the "snap to grid" feature in your software. "Snap to grid" is a standard feature of PCB layout software, and will make it easier to place components in an orderly fashion.
2 Place components that need to have a specific location first. This includes mounting holes, switches, LEDs, heat sinks, or any other component that will connect to an outside location or mount on the enclosure.
3 Separate your components into functional groups to make your layout more logical and easy to understand. For example, make the logic and input/output sections into separate groups. Keep all the power supply components on one area of the board, and separate digital and analog components. High-frequency digital signals can create interference in analog circuits.
4 Place all of your polarized components with the same orientation, and place your ICs facing the same way so that the No. 1 pin is in the same position on each chip. This will make it a lot easier to place components when you're actually putting the board together and help you avoid mistakes.
5 Place components that connect close to each other to minimize trace lengths. Short traces are easier to route and help you avoid complications from noise, inherent resistance and board capacitance. Power filtering capacitors should be placed very close to the IC pins they connect to. Every component should go on the top side of the board, unless there's absolutely no way to avoid placing a few components on the bottom.
6 Set your trace widths based on the amount of current you expect them to carry. Higher current lines need wider traces; 0.01 inches is a good width for low-power digital and analog signals of about 0.3 amps and lower. A 0.7-amp signal should use a 0.02-inch-wide trace, and a 1-amp signal should use a 0.025-inch-wide trace. When a trace has to turn, use a pair of 45-degree corners rather than a single sharp 90-degree turn in order to avoid noise and protect against manufacturing flaws. Use vias, which are feed-through holes from one layer of the board to another, for when traces have to cross without connecting.
7 Place your power and ground rails after placing your components. Make your power rail a single wide trace that branches off as needed rather than running a bunch of traces out of the power supply or daisy-chaining power connections together. Make a large, solid ground plane as well. Good grounding is crucial and helps minimize noise.
8 Simulate the heat dissipation on your board, if your software has this feature. Keep heat-generating components like transformers away from heat-sensitive components like ICs, and place heat sinks if necessary.
