ESD Introduction - Static Equipment Manufacturer

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History & Background

For many people, Electrostatic Discharge (ESD) is only affected when you touch the metal door handle after passing through the carpet floor or sliding over the car seat. However, static electricity and sustainable development are serious industrial problems for centuries. As early as the beginning of the fourteenth century, the military fortress in Europe and the Caribbean used static control procedures and devices to try to prevent accidental electrostatic discharge from the powder shop. By the 1860s, the entire US paper mill used basic grounding, flame ionization techniques and steam drums to dissipate static electricity from the web during the drying of the paper through the drying process. Each of the imaginable commercial and industrial processes has one or more times the problem of electrostatic charge and discharge. Arms, explosives, petrochemicals, pharmaceuticals, agriculture, printing, graphic arts, textiles, paints, plastics, etc. are just some of the industries that are important for electrostatic control. The electronic age has brought new problems related to static electricity and electrostatic discharge. Moreover, as electronic devices become faster and faster, circuits are getting smaller and smaller, and their sensitivity to ESD is usually increased. This trend may be accelerating. ESD Association's "Electrostatic Discharge (ESD) Technology Roadmap" was revised in April 2010, including "As the equipment becomes more sensitive in 2010 and 2015, companies must begin to review the ESD capabilities of their processing processes." Today, ESD affects almost every aspect of the global electronics environment for productivity and product reliability.

Despite the efforts of the past three decades, ESD still affects production costs, manufacturing costs, product quality, product reliability and profitability. Damage the cost of the device itself from the simple diodes to a few cents to complex integrated circuits for thousands of dollars. There are obviously significant opportunities for improvement when the costs associated with repairs and rework, transport, labor and overhead costs are included. Almost all companies involved in electronics manufacturing today note the basic acceptance of static control in the industry. ESD Association Industry Standards today can be used to guide manufacturers to establish basic static charge mitigation and control techniques. Any company that neglects static control can not successfully manufacture and deliver undamaged electronic components.

Static Electricity: Creating Charge

Static charge is defined as "static charge". Electrostatic is an imbalance in the surface or surface charge of the material. This imbalance of electrons produces an electric field that can be measured and can affect other objects. Electrostatic discharge (ESD) is defined as "rapid spontaneous transfer of electrostatic charge caused by a high electrostatic field." Note that the charge passes through a different electrostatic potential through the spark between the two objects because they are close to each other. Electrostatic discharge can change the electrical characteristics of semiconductor devices, degrade or destroy semiconductor devices. Electrostatic discharge may also disturb the normal operation of the electronic system, resulting in equipment failure or malfunction. The charged surface can attract and maintain contaminants and it is difficult to remove the particles. Airborne particles may cause random wafer defects and reduce product yield when attracted to the surface of a silicon wafer or device circuit.

First control the electrostatic discharge begins with the understanding of the occurrence of electrostatic charge. Electrostatic charge is most common through contact and separation of both materials. The materials may be similar or dissimilar, although different materials tend to release higher levels of electrostatic charge. For example, people who pass through the floor produce static electricity because the sole touches and then separates from the floor surface. As the shell and metal leads of the device form a plurality of contacts and separations with the surface of the container, the electronic devices that slide or remove bags, magazines or tubes generate static electricity. Although the magnitude of the electrostatic charge in these examples may be different, static electricity is indeed formed in each case.

The electrostatic charge generated by contact and separation of the material is called "triboelectric charge". The word "rubbing electricity" comes from the Greek, rubbing - meaning "rubbing" and elektros - meaning "amber" (fossil resin from the prehistoric tree). It involves electron transfer between materials. The atoms of the material without static charge have an equal number of positive (+) protons in their nuclei and negative (-) electrons running on the nucleus. In Fig. 1, the material "A" consists of atoms of equal amount and electrons. Material B is also composed of atoms that have equal (though different) amounts of protons and electrons. Both materials are electrically neutral.

When two materials are in contact and separated, the negatively charged electrons are transferred from the surface of one material to the surface of another material. Which materials lose electrons and that electrons will depend on the nature of the two materials. The lost material becomes positively charged, and the material that gets the electron is negatively charged. as shown in picture 2.

Electrostatic measurement with coulombs. The charge "q" on the object is determined by the product of the capacitance of the object "C" and the voltage potential (V) on the object:

Q = CV

However, we usually talk about the electrostatic potential on the object, which is expressed as voltage.

The process of such material contact, electron transfer and separation is a more complex mechanism than described herein. The amount of charge generated by the frictional electricity is affected by factors such as contact area, separation speed, relative humidity and material chemical properties, surface functions and the like. The charge is generated on the material and it becomes an electrostatic charge if it is retained on the material. The charge can be transferred from the material, resulting in electrostatic discharge or ESD events. Additional factors, such as the resistance of the actual discharge circuit and the contact resistance at the interface between the contact surfaces, also affect the actual charge released. Typical charge generation conditions and the resulting voltage levels are shown in Table 1. In addition, moisture contribution to reduce charge accumulation is also shown. It should be noted, however, that static charge generation occurs even at high relative humidity.

The charge may also be produced on the material by other means such as by induction, ion bombardment or contact with another charged object. However, triboelectric charging is the most common.

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