Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Reexamination Certificate
2001-06-27
2004-04-13
Sircus, Brian (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
C361S112000, C313S567000, C313S634000
Reexamination Certificate
active
06721157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrostatic discharge devices of the surface mount type and a method of fabricating such devices and, more particularly, to an electrostatic discharge device of the surface mount type designed to be easily installed on a printed circuit board through a surface mounting process and used for protecting electronic circuits or electronic parts from electrostatic damage, and to a method of easily and simply fabricating such devices through a ceramic laminating process.
2. Description of the Prior Art
As well known to those skilled in the art, electronic circuits or electronic elements (herein below commonly referred to simply as “electronic circuits”) of a variety of electronic apparatuses, such as sensors, are electrostatically impacted by an application of static electricity, such as an instantaneously applied high voltage, during an operation. The electronic circuits may be thus seriously damaged, causing operational errors, losing their operational functions, and being broken. As the electronic circuits have become complicated in their construction in accordance with the rapid development of electronic apparatuses in recent years, the electronic circuits become more sensitive to surges. Due to such sensitivity of the electronic circuits to surges, the electronic circuits may be more easily and frequently damaged by static electricity during an operation.
In an effort to overcome such electrostatic damage to the electronic circuits, several techniques have been actively studied and developed in recent years. As an example of such techniques, ESD devices (electrostatic discharge devices) have been proposed and used widely.
An example of conventional ESD devices is shown in
FIGS. 1
a
and
1
b
.
FIG. 1
a
shows an arrangement of the conventional ESD device connected to both an antenna and an electronic circuit.
FIG. 1
b
shows a cross-section of the ESD device.
As shown in
FIG. 1
a
, when the electronic circuit of an apparatus receives signals from an antenna through a signal transmission wire, the circuit may be impacted by an instantaneous application of a high voltage signal. In order to prevent such an application of high voltage signal to the circuit, an ESD device
30
is installed on the signal transmission wire in parallel to the circuit so as to protect the circuit from such a high voltage signal by performing a plasma discharge of static electricity.
As shown in
FIG. 1
b
, the conventional ESD device
30
comprises a hollow cylindrical case
31
, with two holed disc covers
32
a
and
32
b
set in opposite ends of the case
31
to close the ends to form a cavity within the case
31
. Plasma discharge gas is fed into the case
31
through the holes of the two covers
32
a
and
32
b
to fill the cavity of the case
31
. Two signal transmission wires are inserted into the opposite ends of the case
31
through the holes of the two covers
32
a
and
32
b
to reach predetermined positions within the cavity, prior to sealing the gaps between the holes and the wires using insulators
33
a
and
33
b.
When static electricity, having a potential higher than the ionization potential of the plasma discharge gas contained in the ESD device
30
, is introduced into the ESD device, the plasma discharge gas is ionized to perform plasma discharge, thus reducing the voltage of the signal transmitting wires. This protects the electronic circuit from high voltage static electricity surges.
However, the conventional ESD device
30
is manufactured through a complex process. That is, the process of producing the ESD device
30
comprises the steps of setting the two holed covers in the opposite ends of the hollow cylindrical case, feeding plasma discharge gas into the case through the holes of the two covers, inserting two signal transmitting wires into the case through the holes of the two covers, and sealing the gaps between the holes and the wires using insulators. Such a complex manufacturing process undesirably increases the manufacturing cost of the ESD devices. Another problem experienced in the conventional ESD device resides in that the ESD device is too large in its dimension, thus undesirably and excessively consuming the surface area of a printed circuit board (PCB).
FIGS. 2
a
,
2
b
and
2
c
are a perspective view, a plan view, and a sectional view of a conventional ESD device in accordance with another embodiment of the prior art. As shown in the drawings, this conventional ESD device is designed to be improved in its welding-sealed structure including a cylindrical discharge tube
10
containing ionization gas therein. In the ESD device, the discharge tube
10
comprises a cylindrical case
11
, which is made of a conductive metal and is provided with a plurality of axial holes
12
extending in parallel to the axis
15
of the case
11
. Two insulating tubes
16
are set within each of the axial holes
12
such that the two tubes
16
are inserted into each hole
12
from the upper and lower ends of the hole
12
to form a cavity
20
between the inside ends of the two tubes
16
. Ionization gas fills the cavity
20
before an electrode
19
penetrates the communicating holes of the two tubes
16
while passing through the cavity
20
. The above-mentioned construction of this conventional ESD device is expressed in U.S. Pat. No. 5,726,854 in detail.
When a high voltage is applied to the ESD device
10
during an operation, the ionization gas within the case
11
is ionized and responds to the high voltage surge acting on the junctions of the electrodes
19
and the grounds, thus forming conductive passages at the gaps between the electrodes
19
and the case
11
and bypassing the high voltage to the grounds. Therefore, the ESD device
10
protects circuit elements and semiconductor chips operated in conjunction with status reaction sensors from such a high voltage surge.
The above-mentioned ESD device
10
is advantageous in that it is possible to selectively use the electrodes during an operation. However, this ESD device further complicates the process of manufacturing the ESD devices and increases the production costs of the devices. Another problem of this ESD device resides in that it is too large in its dimension, thus undesirably and excessively consuming the surface area of a PCB.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an electrostatic discharge device (ESD device) of the surface mount type, which is designed to be easily installed on a PCB through a surface mounting process and is used for protecting electronic circuits or electronic parts from electrostatic damage, and also provides a method of easily and simply fabricating such ESD devices through a ceramic laminating process.
In order to accomplish the above object, the present invention provides an electrostatic discharge device of the surface mount type, comprising: an upper cover plate made of an insulating material; a middle insulating plate made of an insulating material and laminated on the lower surface of the upper cover plate, and having a discharge opening, with first and second discharge terminals formed in the middle insulating plate at opposite edges of the discharge opening; and a lower cover plate made of an insulating material and laminated on the lower surface of the middle insulating plate, and hermetically sealing the discharge opening of the middle insulating plate in cooperation with the upper cover plate, the lower cover plate having a second signal electrode brought into electric contact with the first discharge terminal of the middle insulating plate, and a second ground electrode brought into electric contact with the second discharge terminal of the middle insulating plate, whereby discharge gas fills the discharge opening of the middle insulating plate sealed by the upper and lower cover plates.
In the electrostatic discharge device, the mi
Lowe Hauptman & Gilman & Berner LLP
Rodriguez Isabel
Samsung Electro-Mechanics Co. Ltd.
Sircus Brian
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