ESD Systems’ ESD Technical Newsletter
Volume 2, April 1999: Issue 4


Sender : ESD SYSTEMS, 19 Brigham Street, # 9, Marlboro, MA 01752-3170
Phone : 508-485-7390
E-mail :

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This is a free monthly newsletter, which specializes on issues in static control in the workplace.

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HOT TIP of the MONTH (Check your Ground)

Conductors are not necessarily ESD safe, especially ungrounded ones. An isolated conductor can hold a significant charge and easily discharge to another conductor (ESDS device). By tying all conductors to the same electrical potential (earth ground), you can minimize the possibility of generating an ESD event.

You can easily check your ground connection by using an ohmmeter between the common point ground snap and a local earth ground point. The ESD Association ANSI/EOS/ESD-S6.1-1991 recommends a hard ground (< 1 ohm) between these two points. NOTE: In lieu of a hard ground, it is acceptable to use a soft ground (1 megohm or other resistance to ground) for purposes other than ESD (such as personnel safety).

According to ANSI/EIA-625, equipment ground should be used instead of earth ground, but when both grounds are used at the same ESD protective workstation, then they shall be bonded together at some point in the ground system.

ESDA’s RTP for 5/19/99

The ESD Association is sponsoring a Regional Tutorial Program (RTP) on electrostatic discharge May 19, 1999 at the Doubletree Hotel—Lloyd Center in Portland, Oregon.

The tutorial is designed for persons who want to learn the basics of static control, as well as for more experienced individuals who want to focus on specific topics. The tutorial is a program designed to meet the specific educational needs and interests in the Northwestern U.S. The tutorial is specifically developed for manufacturers, contract assemblers and users of ESD sensitive electronic parts, assemblies, and equipment. It is targeted for production, design, engineering, technical, quality and reliability, failure analysis, and sales and marketing personnel.

For additional information, contact the ESD Association, 7900 Turin Road, Bldg. 3, Suite 2, Rome, NY 13440-2069. Ph: 315-339-6937, Fax: 315-339-6793. E-mail:


The Northeast's leading source for electronics manufacturing solutions. Exhibition is held between June 15th and 17th, 1999 at the Bayside Exposition Center, Boston, Massachusetts.

Visit the ESD Systems at booth # 2552 between June 15th and 17th, 1999 to see a demo the latest in ESD control products available from ESD Systems.

For additional information, contact Nepcon East @ 1-800-467-5656.


The following questions and answers were selected from our FAQ WEB Page: concerning Questions about Tribocharging.

Q1: If an operator is wearing a 270K wrist strap, conductive shoes or foot straps and is working in an area with conductive flooring and conductive bench tops, what is the maximum potential the operator could be expected to achieve? - Anonymous, York, PA

A1: The maximum potential that an operator could experience from tribocharging whilst wearing a 270K wrist strap and conductive footwear in conjunction with a conductive floor is still dependent on other variables such as RH and skin resistance/capacitance.
Make the following assumptions: the tribocharging rate is 4 milliamps and the equivalent resistance to ground is 1.49 kilohms.

Greatly simplifying the process and using the above assumptions then the maximum potential an operator could be expected to achieve from tribocharging is about 6 volts.


  Static charges are a real problem in the printing industry. Paper picks up a charge when run through the press. When the same paper is rerun through the press, it has enough charge in the paper to make it try to stick together creating a real feed problem. Do you have any experience in this area? - Anonymous, Houston, TX

A2: Your problem is common in the printing industry. You are experiencing triboelectric generation or tribocharging. Every time a surface (material) comes in contact and separates from another surface (material) induces an imbalance of charge on both surfaces, causing the generation of an electrical static charge (electric field). Industrial ionization is one way to handle this problem. This involves using ion bars in close proximity to the web surface (0.5 to 2 inches) which floods the surface with a multitude of both negative and positive ions. This process in essence neutralizes the surface (paper) on one side only and reduces the induced charging. Use of ion bars on both sides of the paper can minimize a lot of the charging problems. Location of the ion bars should be placed after every process involving contact and separation or before every critical process where charging is a problem. Ion bars are available from numerous sources including ESD Systems. Call 1-508-485-7390 for more information.

 Our paper lab is controlled to a 50% RH environment. Operators receive many uncomfortable shocks when touching the equipment and anything else metal such as the doorknob. Is a floor mat alone enough anti-static protection? I do not see us ever going to foot straps or wrist straps. Any advice? - Anonymous, Longview, WA

A3: There are two highly probable reasons why your operators are experiencing ESD to metal conductors. One is triboelectric generation specifically caused by walking; the other is triboelectric generation caused by the friction of the cleanroom garments with the body or street clothes. Triboelectric generation (tribocharging) is a building up of an imbalance of charge on an object, caused by the action of contact and separation, and can lead to a physically perceptible ESD event. To minimize the first problem, an ESD floor mat that has the specific property of being antistatic may help as would an ESD floor finish systems such as Statproof's® Zinc Free Floor Finish. The Statproof® floor finish system has excellent antistatic properties, which from our experience does not allow tribocharging over 100 Volts.

To minimize the second problem, have your operators wear cotton clothing versus rayon, nylon, silk, wool, etc. to minimize tribocharging of the body from the clean room garments rubbing on their street cloths or body. Wearing an ESD smock would help even more, providing an isolation of the dissimilar materials, some antistatic properties and being able to conduct charges. Also try clean room garments made from different materials, as the current materials making up the garments may be high (up or down) on the triboseries chart.

As always, proper personnel grounding (ESD floor with foot grounders or wrist straps) is the sure way to eliminate your problems and would be our first recommendation.

Eliminator Jr. Ionizer with Heater, Model # 41360
Dual speed airflow, 77 CFM max
Heater increases ambient air temperature in coverage are by 10oF
Removable back grill makes for easy access to clean emitters
Includes ground point for personal grounding
Audio/Visual alarm indicates emitters need cleaning (off/on)
Optional intake filter assembly with washable screen, re-usable


Topic: Tribocharging

There are 3 common ways to generate static electricity, triboelectric generation, field induction, and direct charging. Triboelectric generation (tribocharging) is the most prevalent method for charge generation is discussed first. The Triboseries in Figure 1 is a direct result of getting a better understanding this method. Electric fields and field induction is discussed next. Direct charging is a result of applying either a current or a voltage directly to the material but only works with conductors. Tribocharging and field induction works with both insulators and conductors.

    1. Triboelectric Series

A listing of materials, with respect to the polarity and magnitude of charge generated during contact and separation is called the Triboelectric Series. The series is arranged so that those materials at the top of the list lose electrons and charge positively when rubbed with materials below them relative to the Series. Conversely, the materials at the bottom of the list gain electrons and charges negatively. The farther away the materials are from each other within the list, the greater the magnitude of the charge is generation by them under tribocharging conditions.

The series should be considered a guide to both polarity and relative charge magnitude for various materials. Frequently, one finds some slight inconsistencies in magnitude between two materials from what the Series indicates. Sometimes complete reversals of material positions have been observed.

Table 1







Walking across carpet




Walking across vinyl floor




Motions of bench worker




Remove DIPs from plastic tubes




Remove DIPs from vinyl trays




Remove DIPs from Styrofoam




Remove bubble pack from PCBs




Pack PCBs in foam-lined box




*Source: AT&T ESD Control Handbook-1989

Click below to link to our Triboelectric Series Chart.


This is a free monthly newsletter, which specializes on issues in static control in the workplace.

Need your own copy? Want to subscribe to this Newsletter? All you or your colleague(s) need to do is simply fill out the subscription form at

This Newsletter is never sent unsolicited. To unsubscribe from this mailing, send an e-mail to and put " UNSUBSCRIBE ESD_Newsletters" in the subject.

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? Send your comments to the

Copyright © Desco Industries, Inc. 1999