Soft-Failures Induced by System-Level ESD

Hundreds of static discharges were directed to a circuit board containing a custom test chip, and the resulting soft-failures were recorded. The large time-derivative of the ESD current is the primary cause of soft-failures in this system. Magnetic coupling between traces and bondwires produces glitches at IO pins; the magnitude of these glitches is increased by the bounce of the on-chip supply net relative to the on-board supply. Additionally, logic upsets due to substrate current collection are observed when the equipment-under-test is tethered, i.e., when it has a low impedance path to Earth-ground.