Conformity - November 2008 - (Page 24) ESD Open Forum Gloves and Grounding provided by the Esd association For example, suppose there is a cleanliness specification for flexible circuit assemblies that require handling by gloved hands. The objective of the ESD Glove Working Group is to recommend a charge accumulation test method to find the best type of gloves for handling your device or assembly while maintaining cleanliness. It should be noted that the use of ESD protective gloves and finger cots is one part of a multi-parameter ESD control program as outlined in ANSI/ESD S20.20. References • ANSI/ESD S20.20, Protection of Electrical and Electronic Parts Assemblies, and Equipment (excluding Electrically Initiated Explosive Devices). • ANSI/ESD SP15.1, Standard Practice for In-Use Resistance Testing of Gloves and Finger Cots. • ANSI/ESD S1.1, Wrist Straps. • ANSI/ESD STM11.11, Surface Resistance Measurement of Static Dissipative Planar Materials. • ANSI/ESD STM 11.12, Volume Resistance Measurement of Static Dissipative Planar Materials. • ANSI/ESD STM 11.13, Two-Point Resistance Measurement of Dissipative and Insulative Materials. About the Author This month’s ESD Open Forum column was prepared on behalf of the ESD Association by Gene Chase. Chase currently serves as the chairman of the ESD Glove Working Group, and as a member of the Periodic Verification Working Group. He has written Bellcore (Telcordia Technologies) Generic Requirements for Electrostatic Discharge (ESD) Controlling Floor Finishes, ESD Controlling Floor Covering, ESD Protective Workstations, ESD-Protective Chairs and Carts, and has revised the Bellcore ESD Protective Packaging requirements. Chase is a NARTE ESD Engineer and ESD Technical Consultant for Electro-Tech Systems, Inc., Glenside, PA. He received his B.S.E.E. and M.S. degrees from the New Jersey Institute of Technology in 1966 and 1970 respectively. About the ESD Association Founded in 1982, the ESD Association is a not for profit, professional organization dedicated to furthering the technology and understanding of electrostatic discharge. The Association sponsors educational programs, develops ESD standards, holds an annual technical symposium, and fosters the exchange of technical information among its members and others. Additional information may be obtained by contacting the ESD Association, 7900 Turin Rd., Bldg. 3, Rome, NY 13440-2069 USA. Phone: 315-339-6937. Fax: 315-339-6793. Email: info@esda.org. Website: www.esda.org. I assume by “open parts” you mean that your parts may be electronic components that are bare, not in a protected package, or do not have their leads shorted. Therefore, these parts are susceptible to damage from electrostatic discharge (ESD) from handling, or mechanical damage from handling. If all the above is correct, then a grounded operator using ordinary insulated gloves can be an ESD hazard to your parts. The insulating gloves will accumulate charge from contact and separation from handling the parts. The amount of charge on the glove will determine how much charge is induced into the part, and the ESD susceptibility of the part will govern whether it will be damaged. It is suggested that you handle your “open parts” with ESD protective gloves that have an “In-Use” resistance well within the static dissipative range. It is suggested that the “In-Use” resistance of the glove or finger cot be in the range of 1x105 ohms to 1x109 ohms. With a grounded operator using ESD gloves, any charge accumulated on the gloves should be quickly bled to ground. The ESD Association Glove and Finger Cot Working Group has developed an ESD glove test that can measure the “In-Use” properties of gloves and finger cots. The details of this test are contained in ANSI/ESD SP15.1, Standard Practice for In-Use Resistance Testing of Gloves and Finger Cots. Although a planar resistance measurement or a volume resistance measurement will yield the resistance properties of a glove by itself, the “In-Use” resistance measurement will give the user a more accurate result of how a glove will perform. For example, some types of gloves (mainly Nitrile) will hydrate when donned, and will often show an order of magnitude less resistance then the planar resistance. There could be a case where the planar resistance of a Nitrile glove measures above the dissipative range, but the glove performs adequately into the static dissipative range when donned. As described in SP15.1, the “In-Use” resistance test uses an electrode with a fixed diameter flat polished metal button slightly smaller than one’s finger tip. It is designed to be balanced on a person’s finger with a donned glove or finger cot while the resistance measurement is taken. Materials accumulate charge when contacted and separated. Because gloves may accumulate charge from handling items such as devices, tools or materials, the ESD Association ESD Glove Working Group is in the process of developing test methods to determine the charge accumulation properties of gloves when handling items for various applications. The user needs test methods to characterize their combination of gloves and materials in order to choose the best gloves. 2 Conformity november 2008 Q: A: I work on a production line, where we use gloves to work with open parts. I was wondering if we are still grounded when working with parts? http://www.esda.org
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.