How to optimize the PCB layout for grounding copper foil in HMI (Human Machine Delivery) systems?

Optimizing grounding copper foil in HMI PCB layout is fundamental to improving EMC performance. Grounding copper foil should ideally form a complete ground plane, especially in multilayer boards, where at least one complete layer should serve as the ground plane. On double-sided boards, the area of the grounding copper foil should be maximized, using a grid pattern or solid copper foil, and providing sufficient vias to the power and ground networks. The key to optimization is controlling the return path of ground current: high-speed signal lines must have a complete ground plane as their mirror return path, and signal lines should not be allowed to cross the ground plane's partition gaps. For circuit areas with different functions, such as analog, digital, and power areas, isolation can be achieved through ground plane partitioning.

However, partitioning must be done carefully, ensuring that signal lines do not cross the partition, or providing return paths for necessary signals through bridging. Grounding copper foil rings can be placed at board edges and interface areas, connected to the inner layer ground plane via multiple vias to absorb edge-radiated fields. Long, thin "islands" or "bottlenecks" on the grounding copper foil should be avoided to prevent increasing grounding impedance. The grounding terminals of decoupling capacitors and filter capacitors must be connected to the ground plane via short, thick traces or direct vias. A well-planned grounding copper foil layout, combined with proper grounding of the audio components, can provide a stable, low-noise reference ground for the HMI circuit.