Reduction of radiated electric fields for ESD immunity design

The finite difference time domain (FDTD) method was used to study the reduction of electric fields radiated from the gap between two screws embedded in a test bar under an ESD event. It is illustrated that the radiated ESD wave is a near-field phenomenon. It is also illustrated that the electric field radiated from an ESD event decays very quickly at high frequencies. From simulation results, it is found that the magnitude of a radiated electric field decreases sharply if the air-filled test bar is filled with properly insulating materials. Especially, a lossy dielectric material with smaller relative dielectric constant and bigger conductivity results in a smaller value of radiated electric fields and has better ESD protection.