Conformity Magazine - September 2008 - (Page 18)

ESD Open Forum Disposable ESD Shoe Covers Provided by the ESD Association Q: A: When it comes to disposable ESD shoe covers in a clean (class 10K or 100K cleanroom) ESD protected manufacturing area, does this kind of ESD protective footwear perform as well as ESD shoes? In order to thoroughly answer this question, three key issues will be addressed which include ESD protective properties, particle generation and cost. A comparison has been made in the level of static charge generated on a medium sized person while walking on a grounded, static dissipative floor and wearing one of three different varieties of ESD protective footwear. The footwear varieties tested were disposable ESD protective shoe covers (one on each foot positioned over the wearer’s street shoes) and two varieties of ESD cleanroom shoes, each from different ESD shoe manufacturers. One of the potential issues with disposable or reusable ESD protective shoe covers is the possibility of one or both conductive straps not making adequate contact to the body of the person wearing the shoe covers. This problem also exists with heel/toe grounding apparatus. The conductive straps on the disposable ESD protective shoe covers are meant to connect the body of the person (either through direct contact to the skin or through the sweat layer between the person’s socks and the inside of their “street shoes”) to the bottom or conductive section of the shoe cover. The bottom of the shoe cover then makes contact to the grounded ESD floor for the purpose of draining charge from the person to the ESD floor. The electrical continuity between the wearer’s body and the bottom of the disposable shoe cover can be verified with an ESD footwear testing system. Figure 1 shows the body voltage generation comparisons. The sample subject is a medium sized person walking on a static dissipative floor with no other means of personal grounding. © Ali Ender Birer | Dreamstime.com r A—ESD shoe covers with both conductive straps making good body contact B—ESD shoe covers with only one conductive strap making good body contact C—ESD shoe covers with neither conductive strap making good body contact D—ESD shoe sample from shoe manufacturer X E—ESD shoe sample from shoe manufacturer Y Figure 1: Body voltage generation for ESD footwear 18 Conformity September 2008 http://Dreamstime.com

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Conformity Magazine - September 2008 Contents Editor’s Note Commission Adopts Regulations for Internet-Based TRS Services Another Company Fined for Non-Compliance with HAC Requirements FCC Extends “Do-Not-Call” Registry Compliance Requirements Marketing Company Gets $1.4 Million Fine for Junk Faxes EU Commission Codifies Directive on TTE Market Competition EU Commission Releases Updated Standards List for the R&TTE Directive Updated Standards List for the “New” Low Voltage Directive Released New Standards List Released for the EU’s Machinery Directive The ESD Association: Voluntary Standards in Action ESD Open Forum Medical EMC Standards: Towards the 4th Edition of IEC 60601-1-2 iNARTE Informer Pre-Pulse Voltage in the HBM ESD Model Digital Interfaces and EMC Performance ESD Design Buyer’s Guide Product News Commission Publishes Updated Standards List for the EU’s Personal Protective Equipment Directive FDA Links “Human Factors” to Adverse Events with Medical Devices CPSC Actions in the News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2008

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