Some pertinent information from ESD Association documents: Per ANSI/ESD S20.20 paragraph 6.2.1.1. Grounding / Bonding Systems Requirements, "Grounding/Bonding Systems shall be used to ensure that ESDS items, personnel and any other conductors (e.g. mobile equipment) are at the same electrical potential. As a minimum, ESDS items, personnel and other related conductors shall be bonded or electrically interconnected." Per S20.20 Table 1 Technical Requirements Recommended Range, Mobile Equipment Recommended Range RTG < 1 x 10^9 ohms. [so put 5# Electrode on cart shelf & lead to equipment ground to verify path-to-ground] ESD Protected Workstations ESD-ADV53.1 Electrical Requirements, "Workstation elements shall be connected to, and maintain electrical continuity to, the common point ground as follows: Surfaces of shelves and drawers intended to be used for unprotected ESD sensitive devices - Resistance: Between 1 x 10^6 ohms and 1 x 10^9 ohms." [so matting should be 10^6 to 10^8 ohms on cart shelves]. Note: most any hard floor [like regular vinyl tiles] can become an ESD Floor using a dissipative floor finish. Gene Felder www.desco.com -----Original Message----- From: Ken Bliss [SMTP:[log in to unmask]] Sent: Thursday, October 02, 2003 8:46 AM To: [log in to unmask] Subject: Re: [TN] Bliss carts with non-ESD flooring Hi technetters I thought I would ensure that is was clear how the tray cart is designed to work. I hope there is no one out there using Bliss tray carts without either an ESD Static Dissipative floor or Conductive floor or properly applied and maintained ESD Static dissipative or Conductive Wax. I am unaware of any research that shows without proper grounding to the floor our cart is ESD safe. How the tray cart does work. The PC Board sits on an ESD static dissipative mat, which is in a Conductive composite reinforced tray, which sits on zinc plated steel rails that are welded to a steel cart frame that has a ground chain attached to the bottom which drags on the floor about 2"-3". This works on the floors mentioned above very well. On a non grounded floor I do not recommend it with one exception. If you use our ground cable connector option on the cart and plug it into a techbench or something else that is grounded to drain any charges, then load the cart, then unplug the cart and move it to the next location and plug it in there, (During this move the employee is touching it so you already have a common ground between the two), when you plug it in at the next location all the charges on the operator and the cart will drain safely, provided you do not touch the PC boards until after you plug it in. (do not leave a tray cart sitting some where that is not plugged in) I would be comfortable that this will work fine. It certainly would require employee training to reduce the chance of someone forgetting to plug it in. For that reason only I do not recommend it. If you have really good people then it would probably work fine. Our products are designed to be virtually worry free, ESD safe and easy to use. This method stretches the "easy to use" part. I would wax the floor properly and eliminate the problem entirely. The tray cart has become the industry standard for a reason, it works better than any other method in the electronics industry to date for handling and processing PC boards offline and in manual assembly and protecting those boards from ESD and physical damage. I would be interested to hear all additional constructive comments good or bad. Ken Bliss President and CEO Engineering Manager Bliss Industries, Inc. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------