Electrostatic discharges. Application to electronic industry and other domains

Any material can carry static charges after electrification (charge acquisition) due to various causes, such as friction (triboelectricity), charging by influence (or electrostatic induction), charge transfer by contact, and so on. Electrostatic discharges (ESD) are characterized by the passage of an impulse current between two charged bodies at different potentials, either by direct contact or by disruptive discharge in air. This article briefly describes the phenomena that generate electrostatic charges, and the characteristics of materials according to their ability to generate such charges.

In the case of electronic equipment, the prevention of ESD is based on the control and grounding of static charges that may be generated at every stage of the manufacturing process, from receipt of components and equipped boards to delivery of the equipment. To achieve this, a whole range of protective measures are implemented: creation of protected, marked-out areas with dissipative floors, with dissipative clothing and footwear worn by personnel having access to these areas; grounding of operators, worktops and tools; use of static packaging (material which minimizes any generation of charges) or dissipative packaging, etc.

In the case of electronic components, the continuous reduction in their size increases their sensitivity to ESD, and therefore the risk of malfunction or destruction of these components, and failure of user equipment. For example, in the thin-film transistors (TFTs) used in flat-panel displays, the drain current rises rapidly with the drain-source voltage, leading to the risk of destruction in the event of overvoltage. Passive components (resistors, inductors, capacitors, etc.) are also affected. The use of electrostatic discharge models in the various scenarios encountered in industry is therefore necessary to implement means of protecting component inputs/outputs and electronic boards, and to experimentally validate their resistance.

The aim of this article is to raise awareness of the risks (material, financial, human, etc.) associated with electrostatic discharges, which are omnipresent in an industrial environment. These risks have been heightened by the widespread use of insulating materials capable of accumulating static charges, and by the massive introduction of electronics in many fields (aeronautics, automotive, etc.).