The Effects of Hand-Associated Metal Object Geometry and Hand-to-Object Coupling Impedance on ESD Current Waves

The initial current spike that typically precedes the main discharge wave in a hand/metal electrostatic discharge (ESD) from a human body can he generated in two ways. One is via capacitance to free space of the hand and forearm. The second is via capacitance to free space of the metal object itself, when its geometry makes that capacitance high enough. Another point, also often overlooked, is that the discharge can "access" the capacitance to free space of the fingers and hand that hold the metal object, or on which it is worn, only when the impedance that couples the hand to the metal object is low. Hand-to-metal coupling impedance can therefore be a major factor in determining the magnitude of the initial spike due to the hand/forearm combination. Perhaps somewhat surprisingly, in a similar manner this coupling impedance can also control the sise of the main current discharge or body wave that follows the initial spike, caused by capacitance of the entire human body to its surroundings.