Reduction of EMI for ECU with Alumina Multilayer Substrates

Several techniques have been studied for reduction of radiation noise from an ECU (electronic control unit) made of alumina multilayer substrates. Some of them were proven to be effective for the RFI (radio frequency interference) reduction through the development of the ECU. The effective methods were separating the analog and digital power planes, increasing the analog ground area, and using common mode chokes. To reduce the electromagnetic radiation, we have also proposed another technique of a multilayer substrate with the power/ground planes of lossy structure, for dispersing the high frequency electromagnetic radiation energy into the multilayer substrate. Power/ground plane structures in the substrate were evaluated using test modules. We have confirmed that the noise level was fairly reduced by these techniques, in the wide range of frequency, comparing with the conventional design.