High Optical Visibility and Shielding Effectiveness Metal Mesh Film for Microwave Oven Application

A typical microwave oven generates an electromagnetic wave in an ISM band of 2.45 GHz. To prevent this unwanted microwave leakage through its front door, a circular perforated metal sheet is typically used with low shielding effectiveness (<; 27 dB) and with poor visibility (<; 50%) which is usually difficult to check the progress of cooking. In this paper, we investigate sheet resistance (R_S) and optical transparency (OT) for electrical and optical performance of two transparent electrodes (TEs) including metal mesh film (MMF) and indium tin oxide (ITO) and compare those to the currently used perforated copper sheet (PCS) in commercial microwave oven. The measured RS and average OT in visible spectrum of MMF is 0.11 Ω/sq and 68.4%, and its figure of merit (FoM) is 203.8 which is the highest among them. The measured shielding effectiveness of MMF, ITO, and PCS at 2.45 GHz are 31.4, 21.0, and 25.5 dB, respectively. The results indicate that MMF has highest FoM and the best EMC performance among the TEs and PCS, which makes it the most suitable candidate for microwave ovens.