Electrostatic Discharge (ESD) is the cause of most component level or subsystem level electrical overstress (Electrical Overstress, EOS). This type of damage will disrupt the ICs functions causing malfunctioning which leads to the destruction of semiconductors and even computer systems.
Electrostatic discharges are often cause by humans, which undoubtedly is impossible to prevent. During manufacturing, production, assembly, testing, storage, and shipping, static electricity will accumulate in humans, instruments, and storage equipments as well as in ICs. Unknowingly, people often will let off this discharge when coming in contact with the device resulting in circuit flow, unwilling exposing the components to an electrostatic discharge. There are four types of ESD testing defined in IEC 61000-4-2: Contact Discharge, Air Discharge, Horizontal Coupling Planes (HCP) Contact Discharge, and Vertical Coupling Planes (VCP) Contact Discharge.