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Printed Circuit Board Level ElectroStatic Discharge Protection for Concurrence Maintenances

IP.com Disclosure Number: IPCOM000105220D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Related People

Brown, CW: AUTHOR [+3]

Abstract

Disclosed is a protective cover and circuit combination for preventing damage to printed circuit boards (PCBs) from electrostatic discharge (ESD) during installation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 86% of the total text.

Printed Circuit Board Level ElectroStatic Discharge Protection for Concurrence Maintenances

      Disclosed is a protective cover and circuit combination for
preventing damage to printed circuit boards (PCBs) from electrostatic
discharge (ESD) during installation.

      ESD damage occurs when a PCB makes contact with objects at
different potentials, and a high current is discharged through the
I/O circuits and interface bus.  By providing a conductive cover and
bleeding circuit to the PCB, such damage can be avoided by
discharging the damaging current before any I/O connection is made.

      The ESD protection scheme consists of conductive plastic PCB
covers, each having an average resistivity of about 50 Kohms.
Coupled to each sheet and to the PCB grounding systems is a
self-activating bleeding circuit.  The bleeding circuit switches on
in the presence of sufficient ESD during installation, and switches
off during normal operations to keep the AC and DC grounding systems
separate.

      The bleeding circuit consists of two diodes connected in
parallel and biased in opposite directions.  The diodes will conduct,
or switch the bleeding circuit on, when the forwarding bias exceeds
the turn-on threshold voltage (typically 0.7 V).  When the forwarding
bias is 200-300 mV below the turn-on threshold, the diodes exhibit
very high resistance (over 5 Gohms).  A 450-860 Kohm resistance
provided by a 2.6 Mohm resistor and the conductive plastic card cover
is co...