A study of esd damage to a device inside a metal enclosure

The ESD immunity of a system consisting of a metal box with an ESD sensitive device that is coupled to the inside and outside of the box is studied experimentally and through SPICE and 3D electromagnetic simulations. It is found that the combination of wire feedthroughs and an impedance imbalance across the terminals of the device results in significant current flow through the device. It is concluded that simulations combined with experimental measurements open up the possibility of predicting the ESD immunity of a system containing an extremely ESD sensitive device.