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| ESD Technical e-Newsletter |
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May 2000
Issue 5, Volume 3
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STATIC ELECTRICITY
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"Static electricity" appears when two dissimilar materials are placed into intimate contact and then separated. This is a charge separation or an IMBALANCE between quantities of positive and negative particles. During contact electrification, it is usually only the negative electrons, which are moved. As negative particles are pulled away from the positive particles, equal and opposite areas of imbalance are created. In one place, you'll have more protons than electrons, and this spot will have an overall positive charge. Elsewhere you'll have more electrons than protons, for an overall negative charge. "Static electricity" exists whenever there are unequal amounts of positive and negative charged particles present. It doesn't matter whether the region of imbalance is still or is flowing; only the imbalance is important.
All solid objects contain vast quantities of positive and negative particles whether the objects are electrified or not. When these quantities are not exactly equal and there is a tiny bit more positive than negative (or vice versa), we say that the object is "electrified" or "charged," and that "static electricity" exists. When the quantities are equal, we say the object is "neutral" or "uncharged." "Charged" and "uncharged" depends on the sum of opposite quantities. Since "static electricity" is actually an imbalance in the quantities of positive and negative, it is wrong to believe that the phenomena has anything to do with lack of motion, with being "static." In fact, "static electricity" can easily be made to move along conductive surfaces. When this happens, it continues to display all it's normal characteristics as it flows, so it does not stop being "static electricity" while it moves along very non-statically!
In a high voltage electrical system, the wires can attract lint, raise hair, etc., even though there is a large current in the wires and all the charges are flowing. Last, when any electric circuit is broken and the charges stop flowing, they do not turn into "static electricity" and begin attracting lint, etc. A disconnected wire contains charges, which are not moving; yet, it contains no "static electricity!"
For more information on Static Electricity visit our Web Site or William J. Beaty's web page Articles on "Electricity".
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DATA LOGGER TESTING SYSTEM (Item # 41211)
- System is a complete unit designed for fast, frequent testing of ESD personnel grounding devices
- Incorporates a unique dual test circuit design, which improves accuracy of testing and eliminates the need for separate wrist strap and foot grounder test units
- This complete unit will automatically log in test results from either your wriststrap and footwear test. Simply swipe card and test
- This system helps comply with ISO 9000 requirements and audits
- It also saves hours of supervisor's time collecting and analyzing data
Get more information from about the Data Logger here.
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22nd Annual International EOS/ESD Symposium and Exhibits
Click here for more EOS/ESD Symposium Info or the EOS/ESD Symposium Program
September 24-28, 2000 at Disneyland Hotel, Anaheim, CA USA
- "ESD Workshops" dozens of Technical Seminars
- "ESD Exhibits" visit us at our Booth, # 202
- "ESD NARTE Certification" become NARTE certified!
- ESD Technical Paper Presentations
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Sponsored by
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Q1: part 1. "Static electricity is NOT a build up of electrons".
As I see it protons & electrons are in balanced numbers in an atom. When charge separation takes place it is usually the electron that is moved from one surface (atom) to another. Using the example of a person walking across a carpeted floor - as they collect electrons they leave behind an equal and opposite charge on the atom that lost the electron but don't the electrons that are collected build up in the recipient? Otherwise how can varying levels of static charges be generated?
part 2. "Electrons in metals move around and between the mass of atoms.."
Does this mean that on the surfaces the electrons are whizzing round in orbit but underneath the surface they are held in check by the protons? Or does it mean that throughout the metal the electrons are whizzing about but that they are not connected to any particular atom, so they move from end to end at random but always maintaining the balance with protons within any one atom?
see ANSWER 175.1
Q2: If two charged dielectric materials, of opposite or same polarity, are brought to close proximity of each other, will there be a transfer of charge from one material to the other. And, does the introduction (contact) of a reference ground impact the decay time of the ESC on these materials? - Anonymous, San Jose, CA see ANSWER 168
Find more ESD Q&As here
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It is possible to touch a charged object which is a real concern when it relates to ESD Sensitive devices and grounded operators. This is due to the fact that the Charge Device Model (CDM) is commonly left out of a good ESD control program (in favor of the Human Body Model (HBM)).
When it comes to "Charged Devices", the wearing of a grounded wrist strap does not ensure the complete safety of an ESD Sensitive device. Whether you are wearing a wrist strap or not, a discharge can still occur. Increasing the contact resistance is the only way to control the speed of the discharge. One way to accomplish this is by wearing Static Dissipative Gloves or Finger Cots.
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This is a free monthly e-newsletter, which specializes on issues in static control in the semiconductor/electronics workplace and is best viewed while connected to the Internet.
Let us know what you think. Tell us what you would like to see in future issues. Want to contribute articles or other related information to our Newsletter? If you have any comments, suggestions or feedback about this newsletter, please send them directly to the editor@esdsystems.com, thanks.
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Copyright © 2000 ESD Systems.com. All rights reserved.
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