How should the power and signal layers be stacked in an HMI (Human Machine Interface)?

well-designed HMI PCB stack-up is fundamental to controlling power integrity and signal integrity, directly impacting EMC performance. The core principle of multilayer board stack-ups is to provide an adjacent, complete reference plane (power or ground plane) for each high-speed signal layer. A classic 8-layer stack-up example is as follows: Top (signal), GND02, S03 (signal), PWR04, GND05, S06 (signal), PWR07, Bottom (signal). This ensures that both the top and inner signal layers have adjacent ground or power planes as return current references. Power and ground planes should be as adjacent as possible to form a natural parallel-plate capacitor, providing high-frequency decoupling. Avoid placing two signal layers adjacent to each other, as this can lead to severe crosstalk.

For HMI motherboards, digital power, analog power, and core power typically need to be separated onto different power planes. Care must be taken not to disrupt the return current paths of adjacent signal layers during this separation. The ground plane should be kept as intact as possible, serving as the primary shielding and reference layer. Stack-up symmetry helps reduce board warpage. Increasing the number of ground plane layers is always beneficial for EMC, provided cost allows. Once the stack-up scheme is determined, its impedance control and crosstalk levels need to be verified through simulation. A good stack-up design, combined with the correct placement of audio electronic components, can build a solid EMC foundation for the HMI system.