Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-06-08
2001-05-29
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S051000, C361S753000
Reexamination Certificate
active
06239360
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a grounding structure for an electromagnetic wave shield including a substrate formed of a resin material and a coated layer formed by coating the substrate with an electromagnetic wave shielding paint, with a metal plate disposed in abutment under pressure against the coated layer for providing a ground connection.
Electronic and electrical appliances, instruments and systems often act as noise sources which cause, or are exposed to, electromagnetic interference. Accordingly there is a need for a conductive electromagnetic wave shield which is capable of preventing such electromagnetic interference. The development of resin materials and the advances in the molding techniques have created a tendency to replace heavy metal materials with lighter resin materials in electronic and electrical appliances.
An electromagnetic wave shield, which is commonly used to block electromagnetic interference, comprises a substrate formed of an electrically insulated resin material, the surface of which is electroplated or coated with an electromagnetic wave shielding paint to render it electrically conductive. The use of an electromagnetic wave shielding paint as a coating on the surface of the substrate is currently the principal way of providing a conductive coating, in view of its versatility of application depending on the variety of the substrate materials and the complexity of configuration thereof as well as the cost consideration. For example,
FIG. 9
shows an electromagnetic wave shield
101
comprising a substrate
102
of a resin material and a coated layer
103
which coats the substrate
102
with an electromagnetic wave shielding paint. A flat metal plate
104
and the shield
101
are secured together as by bolts
105
and nuts
106
so that the metal plate
104
is held in abutment under pressure against the coated layer
103
of the shield
101
. The shield
101
and the metal plate
104
are formed with openings
107
a
and
107
b
, respectively, to pass the bolts
105
therethrough.
The metal plate
104
is connected to a shield cable
108
, whereby the shield
101
is grounded via the metal plate
104
and the shield cable
108
. In this manner, the coated layer
103
of the shield
101
, the metal plate
104
and the shield cable
108
are electrically connected to each other.
FIG. 10
is a microscopic illustration of the abutment of the metal plate
104
against the coated layer
103
. As can be seen, the coated layer
103
partly bites into the metal plate
104
. Specifically, the electromagnetic wave shielding paint which forms the coated layer
103
comprises a binder
109
of a resin material and a conductive filler
110
dispersed in the binder
109
.
When the metal plate
104
is disposed in abutment under pressure against the coated layer
103
, the conductive filler
110
bites into the metal plate
104
. Accordingly, when the conductive coated layer
103
and the metal plate
104
are in contact with each other, in the manner shown in
FIGS. 9 and 10
, the electrical conduction between the coated layer
103
and the metal plate
104
provides a desired conductivity or electromagnetic wave shielding effect.
However, when the assembly shown in
FIG. 10
is subject to a thermal cycle (i.e., a heating and cooling cycle), because the metal plate
104
is held in abutment under pressure against the shield
101
, rubbing stresses occur between the dissimilar materials of the substrate
102
and the metal plate
104
due to their different rates of thermal expansion. In particular, in a region where an edge of the metal plate
104
is in contact with the coated layer
103
or where a force for holding the metal plate
104
in abutment against the coated layer
103
is concentrated, the coated layer
103
cannot follow the substrate
102
, but is exfoliated therefrom, as illustrated in FIG.
11
. As a consequence, exfoliation of the coated layer
103
is accelerated under severely changing thermal conditions, as shown in the dotted region in
FIG. 12
, resulting in poor conduction from point A or C to point B and in a failure to maintain the desired conductivity.
It is an object of the invention to provide a grounding structure for an electromagnetic wave shield and is capable of securing a desired conductivity and suppressing an exfoliation of a coated layer formed on a substrate.
SUMMARY OF THE INVENTION
The present invention provides a grounding structure for an electromagnetic wave shield. The grounding structure includes a substrate formed of a resin material and a coated layer formed on the substrate with a shielding paint. A metal plate is held under pressure against the coated layer for suppressing an exfoliation of the coated layer from the substrate. The metal plate is grounded and has a generally covered surface which is convex toward the coated layer.
The present invention further provides a grounding structure including a substrate formed of a resin material, a coated layer formed on the substrate with shielding paint, a metal plate held under pressure against the coated layer and connected to ground. A suppressor is provided for suppressing an exfoliation of the coated layer.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
REFERENCES:
patent: 3962550 (1976-06-01), Kaiserswerth
patent: 4733013 (1988-03-01), Hemming
patent: 5687453 (1997-11-01), Megregian et al.
Kato Mamoru
Ogisu Yasuhiko
Ngo Hung V
Pillsbury & Winthrop LLP
Reichard Dean A.
Toyoda Gosei Co,., Ltd.
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