Summary: Optimize PCB layout for switching power supplies by minimizing pulse voltage path lengths, directly connecting key components like transformers and rectifier tubes, reducing loop areas, and strategically placing capacitors. Emphasize EMC performance through careful capacitor selection and placement, ensuring adequate spacing for heat dissipation and interference prevention in control circuits. Achieve high reliability by adhering to trace spacing guidelines, optimizing copper trace routing for current density, and selecting suitable board types based on application requirements and safety regulations.