Electricity: electrical systems and devices – Safety and protection of systems and devices – Load shunting by fault responsive means
Reexamination Certificate
2000-02-22
2002-12-10
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Load shunting by fault responsive means
C361S091100, C361S111000, C361S118000
Reexamination Certificate
active
06493198
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to electrostatic discharge protection for electronic circuits, and more particularly to a non-moving electrostatic discharge structure that is readily integrated into the product being protected.
BACKGROUND
Electronic components that are sensitive to electrostatic discharge (ESD) are utilized in a wide range of products including computers, two-way radios and cellular telephones. A common cause of electrostatic discharge is the physical contact or handling by a person of a product containing ESD sensitive electronic components, as in the course of replacing an inkjet print cartridge or a rechargeable battery, for example. In particular, electrostatic charge that may have been accumulated by a person will be discharged upon physical handling of the product. The path of discharge in the product will be the path of least impedance from the location of charge transfer and may include ESD sensitive electronic components. Known techniques for preventing damage as a result of ESD include the integration of protection circuitry into electronic components, anti-static packaging, shielding covers to prevent contact with conductive elements, and static charge dissipating furnishings such as anti-static rugs and table mats. Considerations with integrating protection circuitry into electronic components include difficulty in achieving the requisite level of protection, and the burden of re-designing existing electronic components, particularly those that include integrated circuits. U.S. Pat. No. 4,160,210 attempted to partially solve the problem of ESD by fabricating a serpentine conductor on a printed circuit board (PCB), then mounting the PCB on a grounded metal chassis of the receiver's tuner so that the serpentine conductor and the grounded chassis form a transmission line for matching the impedances of the receiver's antenna network and tuner circuitry. Eyelets that connect the serpentine conductor to the antenna network and tuner circuitry extend through the dielectric material of the printed circuit into cutout areas in the chassis. Tabs extend from the peripheries of the cutout areas toward the eyelets to form spark gaps for discharging excessively high energies which may be induced by lightning.
However, anti-static packaging and shielding covers add cost, and moreover cease to afford ESD protection after removal. The use of static dissipating furnishings can be burdensome and therefore not readily implemented, and moreover may not provide sufficient ESD protection. Adding eyelets and associated connectors to a chassis consumes a great deal of space, and is not a workable solution for today's compact, high density circuitry.
REFERENCES:
patent: 4160210 (1979-07-01), Molinari
patent: 5164880 (1992-11-01), Cronin
patent: 5220489 (1993-06-01), Barreto et al.
patent: 5315472 (1994-05-01), Fong et al.
patent: 5357397 (1994-10-01), Leary
patent: 5828555 (1998-10-01), Itoh
patent: 5933307 (1999-08-01), West
patent: 5963415 (1999-10-01), Johansen
Arledge John K.
Barreto Joaquin
Underwood Jeffrey A.
Crilly Daniel C.
Dorinski Dale W.
Jackson Stephen W.
Motorola Inc.
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