Basic concepts > ElectroStatic Discharge (ESD) Explained
Date: Saturday, May 28, 2011 - 19:55
Difficulty: Intermediate
Views: 4939
Pages: 11

Author: Saeid Yazdani

ESD is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide. Either of these materials can suffer permanent damage when subjected to high voltages; as a result, there are now a number of antistatic devices that help prevent static build up.  
Page 1:  ESD Definition and history

What does ESD Means?

ESD stands for ElectroStatic Discharge. A common explain for an ESD event is often described as the sudden transition of electric current that flows between two objects at different electrical potential, while in terms of electronics and semi conductors it refers to momentary unwanted currents that may cause damage to components and equipments.

EOS, Electrical Over Stress, is commonly the most frequently occurring failure mode in semiconductor devices of all types. ESD is actually a subset of the more general range of failures associated with EOS. However, EOS is generally associated with over-voltage and over-current stress of rather long time durations which usually associated with events that occur during normal circuit operation, screening or test conditions.

On the other hand, an ESD event counts as a short, fast and high amplitude pulses that are inevitable part of the day to day environment.

ESD is a miniature lightning bolt (spark) of charge that moves between two surfaces that have different potentials. It can occur only when the voltage differential between the two surfaces is sufficiently high to break down the dielectric strength of the medium separating the two surfaces. When a static charge moves, it becomes a current that damages or destroys gate oxide, metallization, and junctions.

ESD can occur in any one of four ways: a charged body can touch an integrated circuit (IC), a charged IC can touch a grounded surface, a charged machine can touch an IC, or an electrostatic field can induce a voltage across a dielectric sufficient to break it down.

What makes an ESD event important in electronics is that ESD is a relatively important cause of device (component) failure, whether in production line or at the user side. So it is vital to predict and prevent this type of failure as much as possible. There is growing interest in the effects of ESD on the performance of semiconductor ICs because of the impact ESD has on production yields and product quality.

ESD problems are increasing in the electronics industry because of the trends toward higher speed and smaller device sizes. ESD is a major consideration in the design and manufacture of ICs.

The story begins with a phenomenon that almost everybody has experienced already. This phenomenon is known as Static Electricity. This should be explained before continuing with ESD and its rule in reliability of components, integrated circuits and complex electronic systems.

NOTE: It is recommended to read our article about Static Electricity before going through rest of this article.

History & Background

For many people, static electricity is nothing little more than the shock experienced when touching a metal doorknob after walking across a carpeted room or sliding across a car seat. However, static electricity has been a serious industrial problem for centuries.

As early as the 1400’s, European and Caribbean forts were using static control procedures and devices to prevent electrostatic discharge ignition of black powder stores. By the 1860's, paper mills throughout the U.S. employed basic grounding, flame ionization techniques, and steam drums to dissipate static electricity from the paper web as it traveled through the drying process.

Every imaginable business and industrial process has issues with electrostatic charge and discharge at one time or another. Munitions and explosives, petrochemical, pharmaceutical, agriculture, printing and graphic arts, textiles, painting, and plastics are just some of the industries where control of static electricity has significant importance.

The age of electronics brought with it new problems associated with static electricity and electrostatic discharge. And, as electronic devices become faster and smaller, their sensitivity to ESD increases. Today, ESD impacts productivity and product reliability in virtually every aspect of the global electronics environment.

Despite a great deal of effort during the past decades , ESD still affects production yields, manufacturing costs, product quality, product reliability, and profitability.

The cost of damaged devices themselves ranges from only a few cents for a simple diode to thousands of dollars for complex integrated circuits. When associated costs of repair and rework, shipping, labor, and overhead are included, clearly the opportunities exist for significant improvements.

Nearly all of the thousands of companies involved in electronics manufacturing today pay attention to the basic, industry accepted elements of static control.

Industry standards are available today to guide manufacturers in establishing the fundamental static mitigation and control techniques. It is unlikely that any company which ignores static control will be able to successfully manufacture and deliver undamaged electronic parts.

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