Here are 14 common pitfalls or misconceptions in circuit board design:

1. Insufficient Ground Plane: Neglecting the importance of a solid and continuous ground plane, leading to poor signal integrity and increased EMI.

2. Overlooking Signal Integrity: Failing to consider trace impedance, termination, and length matching, which can result in signal degradation and timing issues.

3. Inadequate Decoupling: Not placing enough decoupling capacitors near power pins of ICs, causing power noise and instability.

4. Inefficient Component Placement: Poor component placement leading to longer trace lengths, increased parasitic capacitance, and undesirable signal paths.

5. Improper Trace Routing: Not following good routing practices, such as avoiding sharp bends, crossing traces, or excessive vias, which can lead to signal integrity problems.

6. Thermal Management Issues: Ignoring heat dissipation requirements, resulting in components overheating and reduced reliability.

7. Lack of EMI/EMC Considerations: Neglecting electromagnetic interference (EMI) and electromagnetic compatibility (EMC) measures, causing failures or issues with other nearby devices.

8. Excessive Trace Width/Via Size: Using unnecessarily wide traces or large vias, which can waste PCB space and increase manufacturing costs.

9. Inadequate Silkscreen and Documentation: Neglecting to provide clear component labeling and essential design documentation for future reference and troubleshooting.

10. Ignoring Manufacturing Constraints: Not considering the capabilities and limitations of the PCB manufacturer, leading to fabrication issues or higher costs.

11. Single-Layer Ground Plane: Using single-layer ground planes instead of multi-layer ground planes, which can increase interference and noise.

12. Ignoring Thermal Relief for Copper Pours: Not using thermal relief for copper pours, making it difficult to solder components connected to large copper planes.

13. Using Incorrect Footprints: Employing incorrect or outdated component footprints, causing compatibility and soldering issues.

14. Insufficient Testing and Prototyping: Not thoroughly testing prototypes before mass production, potentially leading to costly design errors.

Avoiding these pitfalls and misconceptions can significantly improve the reliability, performance, and manufacturability of the circuit board design.