Electrostatic discharge ( ESD ) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by tribocharging or by electrostatic induction. The ESD occurs when differently-charged objects are bought close together or when the dielectric between them breaks down, often creating a visible spark.

ESD can create spectacular electric sparks ( lighting, with the accompanying sound of thunder, is a large-scale ESD event ), but also less dramatic forms which may be neither seen nor heard, yet still be large enough to cause damage to sensitive electronic devices. Electric sparks require a field strength above approximately 40kV/cm in air, as notably occurs in lightning strikes.

ESD is a serious threat to the industry today. Major cause for the ESD damage in the real world is the human. A study in Semiconductor Reliability news estimated that approximately 60% of device failures are due to ESD. ESD costs the electronic industry millions of dollars each year in damaged components, non-functional circuit board or missing information. ESD can occur in manufacturing, movements in the shop floor, field handling with no visible signs of damage.