What ESD is.
Electronic failures due to ESD.
Proper handling procedures for ESDS.
Wrist straps can control static charges on the personnel handling ESDS components
Electrostatic discharge, or ESD, is a bolt of mini lightning that is capable of damaging electronics. Most electronic components, ICs, power modules, and computer boards are sensitive to ESD and are considered electrostatic discharge sensitive (ESDS). If a component is ESDS, it will be marked on the datasheet or package of the component.
Failing to adhere to ESD precautions and proper handling procedures as requested by component manufacturers can result in performance degradation or, in extreme cases, failures. As electronic parts get downsized, their sensitivity or susceptibility to ESD increases. Ignoring the ESD susceptibility of electronic components and circuits can result in monetary losses. Therefore, everyone, from the personnel working in inventory to engineers who are using the components for hardware realization, must follow proper ESD precautions and handling instructions to prevent ESD damages. In this article, we will discuss a few recommendations and procedures that can limit the failures caused by ESD.
ESD is the release of static electricity between two electrically charged objects in contact. In ESD, there is a building up of charges between two surfaces. When surfaces rub against each other, the charges move and cause excess charges on one surface and deficiency on another.
All objects are capable of generating electrostatic charges. The movement of charges due to electrostatic discharge causes current to flow in objects. In sensitive electronic circuits, ESD induces ESD currents when a charged conductor comes in contact with it. Otherwise, the ESDS component discharges to the human body or packaging materials and causes ESD. In rare cases, field-induced ESD also occurs in electronic circuits.
Usually, ESD currents in electronic circuits take low impedance paths to the ground to balance potentials. Repeated electrostatic discharge and current flow subsequently disrupt the operation of the electronic component or device. When an electronic component or circuit is repeatedly subjected to electrostatic discharge, the internal components cross threshold values frequently, degrade over time, and, finally, fail.
Electronic Failures Due to ESD
Electronic circuits, devices, or components fail due to ESD in two ways:
Catastrophic failures - Catastrophic failures in electronic components exposed to ESD are noticeable failures due to physical damages such as melting, burning, or explosions. These failures are immediate when subjected to ESD and end the useful life of the component.
Latent failures - Compared to catastrophic failures, latent failures are less noticeable. These failures are slow, where the component gets internally damaged without any physical flaws. Since the damage is not visible externally, there can be repeated exposure to ESD and subsequent damage. Latent failures cause the device to partially degrade and ultimately undergo complete failure after time.
To avoid these failures, it is important to consider ESD precautions and proper handling procedures when dealing with sensitive electronics. Let’s discuss some of the recommendations to avoid the ill effects of ESD.
ESD Precautions and Proper Handling Procedures
While setting up an electronic system or handling electronic components, certain precautions and proper handling procedures should be followed to prevent ESD-induced failures. There are specific standards, such as IEC 61340-5-1 or ANSI/ESD S20.20, that are devised for establishing the ESD control program to prevent ESD failures when working with electronic components.
Some of the important ESD precautions and proper handling procedures are below:
There should not be any hand contact while transporting or storing ESDS components. This can be achieved by placing components in static-safe containers.
It is important to place ESDS components in static-protected areas before taking them from their packages.
Be careful to keep ESDS components in their respective anti-static containers until they are moved to static-protected workstations.
No human touch is permitted on the pins and leads of ESDS components or ESDS circuitries.
While touching ESDS components or circuits, personnel should be properly grounded.
There is no plastic, foam, or vinyl allowed in static-protected workstations.
Proper Handling Procedures
The personnel handling ESDS components are recommended to wear wrist straps, proper clothing, and gloves as part of proper handling procedures.
Wrist straps - Wrist straps can control the static charge on the personnel handling ESDS components. The user should wear the wrist strap on his or her wrist. The strap connects the person to the ground through a 1MΩ resistor, thus maintaining the potential equal to that of the grounded components in the work station. Wrist straps prevent the accumulation of static charges by dissipating charges from the personnel to the ground.
Dissipative material clothing - Wearing appropriate clothing made of dissipative material can alleviate the effect of ESD. Smocks should be closed to protect the body.
Gloves - It is always preferable to touch ESDS components and circuits while wearing gloves. It is recommended to pull or take ESDS components sideways to avoid touching the pins and leads. Touching the connecting terminals of ESDS components can result in the accumulation of oil, which can be a cause of failure. Gloves prevent the contamination of pins and lead in ESDS components and circuits, thus preventing the dysfunction that can be caused by oil.
Careless handling of ESDS components can degrade their reliability and life expectancy. While handling ESDS components, ESD precautions and proper handling procedures should be followed to prevent ESD failures. In mission-critical circuits, ESD control recommendations are strictly followed, as ESD-induced failures in such circuits cannot be tolerated at any cost. Cadence software offers ESD analysis tools that help with electrostatic discharge prevention in mission-critical electronic systems.