Research on the Equivalent Circuit Model of Electromagnetic Shielding and the Critical Thickness of the Metal Grid.

The thickness of a metal grid represents a significant factor in electromagnetic interference shielding effectiveness (SE), and the skin depth of the uniform metal surface does not represent the critical thickness of the metal grid. In this study, the influence of Cu grid thickness on the electromagnetic interference SE and critical thickness was assessed using a theoretical model, followed by simulation analysis. According to the equivalent circuit model theory, the skin depth in the equivalent resistance was replaced by the actual thickness of the grid, and the equivalent reactance was corrected by changing the coefficient. A physical field model was established, considering the effects of different grid structures on the SE, using the finite element method. The Cu grids were fabricated in line with the simulation results, and we found that the tested electromagnetic interference SE values of the Cu grids with different thicknesses were generally consistent with the equivalent circuit model when the thickness was less than the critical thickness. The simulation demonstrated that the critical thickness of the Cu grid was constant for different periods and line widths, and the critical thickness of the Cu grid was approximately 170 nm at 1–12 GHz. When the thickness of the Cu grid was 170 nm, the average electromagnetic interference SE was 24.8 dB at 1–12 GHz. In engineering applications, grid thickness greater than the critical thickness should be preferentially designed, and the period or line width should be optimized to further improve the electromagnetic interference SE of the target frequency band. In addition, the electromagnetic interference SE of a metal grid can be quickly estimated by the equivalent circuit model, thus guiding future design work. [ABSTRACT FROM AUTHOR]