Measurement and Simulation Methodology for Characterizing the Shielding Effectiveness of Coating Materials for Optical Sensors

Effective shielding of radiated emissions of ICs is of vital importance in today's densely packed mobile devices. Since space is very limited in most applications, the mounting of large shielding caps with appropriate grounding is not an efficient solution. This paper investigates the shielding efficiency of space-saving coating materials for optical sensor lids with apertures. The shielding efficiency of coating materials is evaluated for functional sensor devices as well as for simple test structures by means of measurements according to the respective standard. The simple test structures are also used to investigate the influence of the grounding path of the shield. It is shown that solid grounding is crucial for effective RF shielding. Furthermore, a simulation strategy is presented which allows the prediction of the shielding effectiveness of coated sensor lids by means of full wave finite element simulations.