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Browse Prior Art Database

IMPROVED CART GROUNDING CHAIN

IP.com Disclosure Number: IPCOM000009675D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-10
Document File: 2 page(s) / 88K

Publishing Venue

Motorola

Related People

William James Grubb Jr.: AUTHOR

Abstract

The cart grounding chain is a device that pro- vides ESD protection for mobile conductive carts. Mobile conductive carts are used extensively throughout the electronic industry to transport and process ESD sensitive electronic components. These mobile carts must have ESD protection to eliminate electro-static build up which could dam- age ESD sensitive devices.

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0 M MOTOROLA Technical Developments

IMPROVED CART GROUNDING CHAIN

by William James Grubb Jr.

DEFINITION OF CART GROUNDING CHAIN

  The cart grounding chain is a device that pro- vides ESD protection for mobile conductive carts. Mobile conductive carts are used extensively throughout the electronic industry to transport and process ESD sensitive electronic components. These mobile carts must have ESD protection to eliminate electro-static build up which could dam- age ESD sensitive devices.

  The cart grounding chain provides ESD protec- tion by creating an electrical commction between the cart and the grounded (dissapative) floor. With the cart at a dissapative ground potential, there is no chance for electro-static buildup or damage caused by an ESD event.

PROBLEM

  The industry standard cart grounding chain is intermittant in its operation and therefore is ineffec- tive for cart grounding. This intern&ant operation is caused by two factors.

  1. An electrical "open circuit" occurs between chain lengths when slack is present in the chain. The open circuit between chain lengths is much like flipping a light switch off. If there is an open circuit

between chain lengths, then the cart is electrically disconnected from the grounded floor and therefore not properly grounded for ESD protection.

  2. An electrical "open circuit" occurs between the chain and the conductive floor surface. Most conductive or dissapative floors utilize conductive

fiber strands randomly spaced throughout the sur- face of the floor tile. The industry standard cart grounding chain does not contact much flo...