Creating a printed circuit board, or PCB, is an important step of an electrical design project. Although designing the schematic and circuitry is key to a functioning product, a well-designed PCB is crucial to the correct operation of a device. PCBs must be carefully designed to fit all components on the board and arranged properly to prevent electrical noise from causing problems.
Instructions
1 Create a board file from your schematic using the built-in tool of your layout software. An unrouted board will be presented. The board will contain all of the part decals that your schematic used and wire lines connecting the pins of the parts together.
2 Move the part decals off the board and group them by part type-resistors, capacitors, inductors and so on-and adjust the size of the blank PCB to fit your required dimensions.
3 Define subsystems for your circuit. This is done by referencing your schematic and grouping similar parts together that connect to each other. Not all parts that connect should be grouped together, though. Typical subsystems include the power supply, input/output circuitry and logic circuitry. The parts in these groups are connected and work together to provide some higher function to the device.
4 Think about how you want the board to be arranged when it's completed. Mentally picture the board, concentrating on where each subsystem will be placed and how it will connect to other subsystems. Consider how tracks will physically flow between subsystems. If the PCB will reside in an enclosure, consider any height limitations that will impose on circuit component placement.
5 Create mounting holes and any other features that will impact part placement on your PCB. Calculate the amount of heat dissipated by components and add heat sinking, if required.
6 Begin placing subsystems on the PCB. It's easier to start with larger subsystems first. Try and place subsystems so they can be easily connected from one to another. Group analog circuitry away from high-speed digital circuitry to avoid electrical noise. Isolate heat-producing components to prevent heat clustering and overheating.
7 Consider adding a ground plane on a one- to two-layer PCB. This will significantly ease routing of ground signals and may reduce the amount of noise in your circuitry. PCBs with four or more layers should have at least one power and ground plane. Avoid having planes too close to sensitive analog and high-speed digital circuitry, as the capacitance and inductance created can affect those signals negatively.
8 Route the tracks between components inside each subsystem. These should flow together since the parts inside subsystems are mostly internally connected. Power tracks should be routed first, following with signal tracks. Make sure tracks are wide enough to handle the current running through them. Insure the clearance between tracks is high enough for the voltage present on them. Avoid 90 degree bends in tracks, opting for 45-degree corners instead. This will prevent noise sources from being created in your circuit.
9 Take a look at the PCB and determine if any subsystems should be moved around. Fix any troublesome routing issues that may arise.
10 Finish your PCB by routing the subsystems together. Keep track width and clearance in mind.
