How to control the minimum loop of an industrial servo power board?

Controlling the current loop area of servo power boards (especially DC buses and IGBT modules) is crucial for reducing parasitic inductance and radiated emissions. Etymotic's control method involves using a "stacked" design during PCB layout, placing power loops (e.g., DC positive - IGBT - motor phase - DC negative) on adjacent layers with overlapping traces, reducing the loop area by over 90%. For multilayer boards, the power layer is placed adjacent to a complete ground plane.

For device mounting, DC bus capacitors and IGBT modules are mounted back-to-back, directly connected using low-inductance busbars (stacked structure). When overlapping traces are not possible, tightly coupled parallel traces with a spacing of <1mm are used. Simulations and measurements show that reducing the loop area between DC+ and DC- from 10cm² to 1cm² reduces the loop inductance from 20nH to 5nH, correspondingly reducing voltage spikes caused by switching by 60% and radiated noise by 10dB in the 30-100MHz range. This design is particularly critical for high-frequency SiC device applications.