The PCB layout forms the foundation of a well-functioning, robustly designed PCB. Ignoring various PCB layout guidelines could result in added costs, underperforming PCBs, or even failed board.
There are numerous layout tips and guidelines available; however, we have listed the layout tips which we think can be applied to many PCB designs.
1. Leave adequate space between traces. Packing pads and traces too close together increases the risk of creating a short circuit if traces accidentally connect during PCB manufacturing. We suggest leaving a gap of 0.007″ to 0.010″ between all adjacent pads and traces on your board.
2. Balance out the copper on each side of your PCB by using ground fills on the opposite side of the dense copper pattern side.
3. Reduce EMI by implementing a closely-spaced, adjacent, solid plane return path for signal traces.
4. Avoid using 90-degree trace angles. During PCB fabrication, there is a chance that the outside corner of a 90-degree trace is etched narrower than your standard trace width. So, try to use 45-degree angle traces.
5. Widen power and ground traces. Wider power and ground traces allow for more current to flow through them and reduce heat build-up, which could damage your board and wires.
6. Dissipate heat using vias. Vias provide electrical connectivity between layers. But thermal vias can act as a pathway to move heat away from heat-generating components to an area where it can be dissipated.
7. Use solid copper layers to form power planes for EMI shielding and heat sinking.
8. Add fiducials to the same side of the PCB where SMT parts are to be placed. Surface mount assembly machines use fiducial marks to ensure the correct orientation of the PCB, which is necessary for component placement.
9. Use power planes to distribute power to nearly all areas part of the PCB. You can create power planes by adding copper layers to the stack-up and connecting them to power or ground.
10. Consider using buried vias on very dense designs to allow the areas above and below the buried vias to be used for additional routing.
11. Use a unique drill sizing symbol for each type of hole containing the same attributes. For example, if there are several 0.028 diameter holes on a PCB with identical plating requirements and hole diameter tolerance, they can all be assigned the same symbol. However, if there are some 0.028 diameter holes with different characteristics, such as different drill tolerance or plating requirements, a different drill symbol should be used on the drawings.
12. Create a symmetrical stack-up by alternating signal and plane layers symmetrically about the centerline of the PCB.
13. Select trace widths which your PCB manufacturer can easily manufacture.
14. Route all critical signals to establish the shortest path with the fewest possible vias while maintaining adjacent proximity to a solid plane return path.
15. To facilitate board test, have many test points connected to the power and ground nets, which are accessible across the PCB.
16. Avoid placing test points near or adjacent to taller components, which can make assessing test points difficult.
17. Leave space between traces and mounting holes. Consider leaving sufficient space around a mounting hole to avoid contact with surrounding components and traces, which could otherwise result in creating a shock hazard on your board.
18. Reducing trace-width requires a proportional reduction in the trace’s height (or thickness), and the PCB stack-up needs to show this detail.
Not decreasing the copper thickness could result in copper at the base being too narrow and fail. The reason for this is that during the PCB printing and etching processes, the traces in contact with the substrate material is more aggressively attacked by the acids, producing a trapezoidal effect.