Placement strategy: connectors first
Placement, more than routing, decides 80% of PCB quality. Place in the order: mechanical constraints, power flow, then separating fast and analog sections.
Placement order
- Mechanical constraints: board outline, mounting holes, height limits
- Connectors, switches, LEDs: parts that must line up with openings in the case
- Power section: one direction of flow, input connector → protection → converter → output
- MCU and crystal
- Fast / high-current parts: motor driver, MOSFETs
- Analog parts: current sensing and ADC inputs, far from noise sources
- Passives: decoupling right next to the chip pins
Dividing into areas
| Area | Principle |
|---|---|
| High-current power | Short, wide traces, at one end of the board |
| Digital | Centred on the MCU |
| Analog | Opposite the power section, so ground return does not cut across it |
| RF / antenna | At the board edge, with ground removed underneath |
Practical tips
- Aligning polarised parts (diodes, electrolytic capacitors) in the same direction reduces assembly mistakes and inspection effort.
- Place test points and the debug connector from the start. There is no room to add them later.
- Check part clearances and connector heights in the 3D view.