Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-04-16
2002-07-30
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C174S034000, C361S800000, C361S816000, C361S818000
Reexamination Certificate
active
06426457
ABSTRACT:
RELATED APPLICATION DATA
The present application claims priority to Japanese Application No. P10-116623 filed Apr. 27, 1998 which application is incorporated herein by reference to the extent permitted by law.
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic wave shielding apparatus and an electromagnetic wave shielding method used for electric circuits, electronic circuits and the like.
In electric circuit arrangements, electronic circuit arrangements and the like, it is necessary to prevent electromagnetic waves generated from electronic parts and the like installed in the circuit arrangement from being leaked to the outside. For example, a circuit board
100
of a related art electronic circuit arrangement shown in
FIG. 7
has electronic parts
101
and
102
which generate electromagnetic waves
103
in the directions shown by the arrows, and which circuit board
100
is covered with a case
104
. In this case, the electromagnetic waves
103
are reflected from the inner surfaces of the case
104
and leaked to the outside through a small gap
105
and/or wiring. The case
104
, if being made from a metal, produces a high-frequency current when it is exposed to the electromagnetic waves, and therefore, the case
104
becomes a re-generating source of electromagnetic wave noise.
To cope with such an inconvenience, in the related art electronic circuit arrangement, as shown in
FIG. 8
, an electromagnetic wave absorbing member
110
is fixed on a surface, facing to the electronic parts, of the inner wall of the case
104
. The electromagnetic wave absorbing member
110
functions to absorb or attenuate the electromagnetic waves
103
and prevent leakage of the electromagnetic waves
103
to the outside as much as possible, to reduce the degree of reflection of the electromagnetic waves
103
and decay the electromagnetic waves
103
, and to prevent re-generating of electromagnetic wave noise from the case
104
.
The related art electromagnetic wave absorbing member
110
, however, has disadvantages that it takes a lot of time to lay out the member
110
because the member
110
must be stuck on the inner surface of the shield case
104
with an adhesive double coated tape or the like by an operator in such a manner as to ensure the optimum absorption of electromagnetic waves, and that the weight of the circuit board
100
becomes very large because the member
110
having a large thickness is stuck on the inner surface of the case
104
with an adhesive double coated tape or the like.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electromagnetic wave shielding apparatus and an electromagnetic wave shielding method, which are capable of simply obtaining an electromagnetic wave shielding function without increasing the weight of the apparatus.
To achieve the above object, according to a first aspect of the present invention, there is provided an electromagnetic wave shielding apparatus for shielding electromagnetic waves generated from a circuit so as to prevent the electromagnetic waves from being leaked to the outside of the circuit, including: a metal member disposed in such a manner as to be opposed to the circuit; and an electromagnetic wave absorbing member disposed on the metal member; wherein the electromagnetic absorbing member is composed of a carbon layer and coil-like carbon fiber structures.
With this configuration, since the electromagnetic wave absorbing member is composed of the carbon layer and the coil-like carbon fiber structures which are formed on the metal member, it can be made lighter than that of the related art electromagnetic wave absorbing member, and since the coil-like carbon fiber structures are electrically conductive, the electromagnetic wave absorbing member is capable of efficiently absorb electromagnetic waves generated from an electromagnetic wave generating source through the coil-like carbon fiber structures.
In the above apparatus, preferably, the carbon layer is formed on a surface, facing to the circuit, of the metal members; one-end portions of the coil-like carbon fiber structures are connected to the carbon layer; and the axial directions of the coil-like carbon fiber structures are substantially perpendicular to an electromagnetic wave generating source. With this configuration, electromagnetic waves generated from an electromagnetic wave generating source can be efficiently absorbed in the carbon layer through the coil-like carbon fiber structures.
According to a second aspect of the present invention, there is provided an electromagnetic wave shielding method for shielding electromagnetic waves generated from a circuit so as to prevent the electromagnetic waves from being leaked to the outside of the circuit, including the steps of: forming an electromagnetic wave absorbing member on a metal member; and disposing the metal member in such a manner that the metal member is opposed to the circuit; wherein the electromagnetic wave member is composed of a carbon layer and coil-like carbon fiber structures produced by a chemical vapor deposition process based on thermal decomposition.
With this configuration, the electromagnetic wave absorbing member can be simply formed on the metal member by chemical vapor deposition, being made lightweight, and is capable of efficiently absorb electromagnetic waves.
In the above method, preferably, the carbon layer is formed on a surface, facing to the circuit, of the metal members; one-end portions of the coil-like carbon fiber structures are connected to the carbon layer; and the axial directions of the coil-like carbon fiber structures are substantially perpendicular to an electromagnetic wave generating source.
With this configuration, since the electromagnetic wave absorbing member is composed of the carbon layer and the coil-like carbon fiber structures which are formed on the metal member, it can be made lighter than that of the related art electromagnetic wave absorbing member, and since the coil-like carbon fiber structures are electrically conductive, the electromagnetic wave absorbing member is capable of efficiently absorb electromagnetic waves generated from an electromagnetic wave generating source through the coil-like carbon fiber structures.
According to the present invention, a shield case for shielding a circuit can be simply prepared by working the metal member on which the electromagnetic wave absorbing member has been formed, into a desired shape.
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patent: 4848566 (1989-07-01), Havens et al.
patent: 5171936 (1992-12-01), Suzuki et al.
patent: 5406026 (1995-04-01), Yamaguchi et al.
patent: 5508889 (1996-04-01), Ii
patent: 5827585 (1998-10-01), Gianetti
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patent: 11-81051 (1999-03-01), None
Serway, Physics for Scientists and Engineers, 1990, p. 877.
Iwashita Sakan
Toyoda Junichi
Oliva Carmelo
Reichard Dean A.
Sonnenschein Nath & Rosenthal
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