Electricity: electrical systems and devices – Discharging or preventing accumulation of electric charge – Specific conduction means or dissipator
Reexamination Certificate
2000-02-28
2002-07-16
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Discharging or preventing accumulation of electric charge
Specific conduction means or dissipator
C361S816000
Reexamination Certificate
active
06421221
ABSTRACT:
BACKGROUND
The disclosures herein relate generally to computer systems and more particularly to an apparatus and method for redirecting electrostatic discharge currents via an alternate path to a reference voltage node.
Electrostatic discharge (hereinafter referred to as ESD) is a problem in most electronic devices and contributes to field failures that are usually hard to investigate. Desktop computer systems, portable computer systems and other types of electronic devices are especially susceptible to ESD failures. Portable computers and keyboards are particularly susceptible to damage by ESD due to the repeated contact with the hands of a computer user. The hands of the computer user are a potential source of static charge. In addition to ESD failures associated with the use of an electronic device, ESD related failures also occur during manufacturing, shipping and set-up of electronic devices. These types of failures adversely affect the profit margin, manufacturer reputation and product warranty indexes.
The electronic components of many computer systems are highly susceptible to damage by ESD. Such discharges produce conducted transient currents in electronic devices that are carried through the circuitry. These conducted transient currents can occur via discharges through the seams in an enclosure, directly to the pins of a connector, or through secondary discharges from floating metal parts such as enclosure access panels. Catastrophic damage can occur to the circuitry of an electronic device as a result of ESD induced transient currents.
U.S. Pat. No. 4,837,657 discloses a device for conducting electrostatic discharge currents to a protection ground. The device includes an electrically conductive center section mounted on a substrate mounting device with the center section electrically connected to the protection ground. First and second arms, having an electrically conductive coating, extend from opposite sides of the center section. During the installation of a circuit substrate to the substrate mounting device, an associated arm is arranged to contact a metalized edge of the circuit substrate providing an electrical path for discharging electrostatic potentials from the circuit substrate to the protection ground.
U.S. Pat. No. 4,667,266 discloses a printed circuit board mounted inside the plastic housing of a piece of electrical equipment adjacent to a hole in the housing. The printed circuit board has a ground trace adapted to be connected to a source of ground potential. The ground trace is positioned on the printed circuit board so that, when the board is mounted in the housing, a portion of the ground trace is the nearest conductor to the hole. In this way, static discharges through the hole are prevented from damaging the equipment mounted on the printed circuit board.
Electronic devices such as computers must be resistant to, and preferably immune to, certain levels of ESD. This is particularly important for electronic devices sold in countries that maintain regulations for prescribed levels of ESD performance on certain electronic devices. In many instances, it is difficult to meet and maintain the specified levels of ESD performance. Acceptable levels of ESD performance are often difficult and expensive to achieve and maintain. Furthermore, even if the initial system design meets required ESD performance specifications, changes made during the life cycle of a product often adversely affect the ESD performance of the product.
Therefore, what is needed is a retrofitable apparatus for redirecting ESD currents from a current path through one or more electrical components susceptible to be damaged by ESD currents to an alternate, nondestructive current path.
SUMMARY
One embodiment, accordingly, provides an electronic device including an apparatus attachable to an electrically conductive reference voltage member of the electronic device and including a portion for being manually positioned adjacent to a system component of the electronic device. To this end, an electronic device includes a reference voltage member and an ESD susceptible system component. An ESD receiving member is electrically connected to the reference voltage member. The ESD receiving member includes an ESD receiving portion positioned adjacent to the ESD susceptible system component.
A principal advantage of this embodiment is that the apparatus may be used as a cost-effective stop gap solution in the manufacture of an affected electronic device until a long term solution is designed and implemented.
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Tannehill Joseph W.
Thomason Gary S.
Dell Products L.P.
Haynes and Boone LLP
Leja Ronald W.
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