| Abstract Scope |
Metals have long been used for electromagnetic interference (EMI) shielding, but their shielding has essentially escaped investigation. Their fractional loss in power indicates reflection dominating over absorption, but the absorption loss is unexpectedly much higher than the reflection loss (Guan and Chung, 2021). The absorption loss per unit thickness increases with decreasing thickness, because of the skin effect. Thus, aluminum foil (0.016-mm thick) is highly effective for shielding. Thick aluminum sheet (0.70-mm thick) (Sorgucu, 2023) is much less effective. Aluminum and steel foils are inferior to exfoliated-graphite-based flexible graphite, due to graphite’s high specific surface area and the skin effect. Flexible graphite (0.127-mm thick) is not available as thin as the aluminum/steel foil, so its absorption-loss/thickness is lower. Steel foil (0.025-mm thick) is not available as thin as aluminum foil, so its absorption-loss/thickness is lower. Therefore, high conductivity, high specific surface area, and small thickness are keys to shielding performance. |