Board-level shielding with magnetic absorber sheet

Abstract

The ongoing trend to miniaturize electronic devices with the aim of providing more advanced functionalities and greater performances makes the detection of electromagnetic interference (EMI) a recurring problem. These requirements result in design restrictions that make it complicated to use basic EMI shielding techniques. Consequently, innovative shielding solutions are needed. Thereby, the board-level shielding (BLS) solutions are widely used in printed circuit board (PCB) applications to reduce the intra-system EMI of integrated circuits (ICs) and improve the immunity of the electronic devices. This contribution focuses on analyzing a magnetic absorber sheet combined with a metal layer as a board-level shield solution. Using this combination is expected to obtain higher shielding effectiveness than using only a magnetic sheet by obtaining the absorbing properties of the magnetic material and the losses mechanism of a metal, such as reflection and eddy current losses. One of the main advantages of using this hybrid structure is that it does not require redesigning the electronics since it can be stuck over the EMI source. Therefore, a magnetic material with different thicknesses is combined with metal layers. These hybrid combinations are compared with the performance of a shielding cabinet in order to determine its performance. The results presented are based on the spectral and spatial magnetic near-field distribution measurement.