Measuring the shielding performance of materials and assemblies

The method of measurement described was originally devised and developed for measuring the shielding performance of materials and packages used for transporting static sensitive semiconductor devices and assemblies through area where static electricity cannot be controlled. Voltages up to 20 or 30 kV can occur as people walk over flooring and move on furniture. A package containing sensitive devices hence needs to be protected against the possibility of spark discharges to or near the package at any voltage up to this level. As 50 to 100 volts may be the maximum permissible in proximity to static sensitive devices the material and package design needs to provide an attenuation of electric field transients by 1000:1 over the frequency range from 10 Hz to 1 GHz. The method of measurement should also have relevance for testing the performance of joins and gaskets used in equipment requiring sealing against electromagnetic radiation