EMI Performance of Multilayered Al-CoTaZr Films in Shielded Power Inductors

This paper examines the performance of multilayered Al-CoTaZr films as electromagnetic interference (EMI) shields. The first part of the paper simulates the shielding effectiveness (SE) of several combinations of multilayered stacks of a conductor and magnetic layer of 10 μm thickness. Using the NSA 65-6 standard in the frequency range of 1–100 MHz, multilayered stacks of [Al (2 layers)-CoTaZr (2 layers) and Al (2 layers)-CoTaZr (3 layers)] are shown to provide SE of 10–62 dB. By comparison, commercial EMI shielding such as copper (Cu), shows only 6–41 dB in the same frequency range. Alternatively, using the IEEE 299 standard, the same thickness of Al and CoTaZr samples gives 40–70 dB SE as compared to that of Cu which ranges from 12–46 dB. The second part of the paper studies the impact of various multilayered stacks of Al and CoTaZr to mitigate undesired magnetic radiation from power inductors. The multilayered EMI shielding helps to increase the inductance from 105 to 135 nH in the case of air-core inductors. In the case of magnetic-core inductors, a substantial increment ranging from 390–750 nH was noted.