Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1998-08-06
2001-02-06
Gaffin, Jeffrey (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S763000, C361S764000, C361S765000, C361S766000, C174S260000, C174S262000, C174S263000, C228S180100
Reexamination Certificate
active
06185105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to printed circuit boards widely used in various electronic equipments, and particularly relates to a discharge structure of a printed circuit board for discharging static electricity to a ground pattern when static electricity is generated upon supply of input signals or upon connection of the other component.
The present application is based on Japanese Patent Application No. Hei. 9-213424, which is incorporated herein by reference.
2. Description of the Related Art
In various electronic equipments, for example, in an electronic equipment for car control, miniaturized electronic components or integrated circuits (ICs) are formed on a printed circuit board for making the size compact and making the weight light. Such an IC has a tendency that they may be broken easily by static electricity as disclosed in Unexamined Japanese Patent Publication No. Hei. 3-261087 or the like. For example, an IC mounted on a printed circuit board may be broken by static electricity when a finger or the like touches the printed circuit board, when an input signal is supplied to an input terminal of the printed circuit board, or when other electronic components are connected to the printed circuit board.
Therefore, conventionally, various measures have been taken to cope with generation of static electricity, as follows.
First, referring to
FIG. 4
, a first example of such a conventional measure against static electricity will be described. Input terminals T
21
and T
22
are provided on a printed circuit board
31
, and electronic circuits
32
and
33
constituted by ICs are connected to the input terminals T
21
and T
22
through resistors R
21
and R
22
respectively.
Discharging capacitors C
21
and C
22
are connected between the input sides of the resistors R
21
and R
22
and a ground pattern (not shown) respectively.
In such a configuration, static electricity generated at or asserted to the input sides of the resistors R
21
and R
22
are discharged to the ground through the capacitors C
21
and C
22
respectively. The capacitors may be replaced by discharging surge absorbers or the like.
Next, referring to
FIG. 5
, a second example of the measure against static electricity will be described. In a printed circuit board
41
, a belt-like ground patten
43
of a copper foil portion is formed on one side surface of an insulating substrate
42
, and a resist layer
44
of an insulating material is formed on the ground pattern
43
. Insertion holes
45
are formed through the printed circuit board
41
, so that connection terminals of connectors or the like are inserted through the insertion holes
45
so as to be connected to a circuit pattern (not shown).
The resist layer
44
is partly removed to form removed portions
46
in positions corresponding to lower portions of components (in the vicinity of input terminals). Accordingly, the ground pattern
43
is partly exposed through the removed portions
46
.
Next, referring to
FIG. 6
, a third example of the measure against static electricity will be described. In a printed circuit board
41
, a belt-like ground patten
43
of a copper foil portion is formed on one side surface of an insulating substrate
42
, and a resist layer
44
of an insulating material is formed on the surface of the ground pattern
43
. Insertion holes
45
are formed through the printed circuit board
41
, so that connection terminals of connectors or the like are inserted through the holes
45
so as to be connected to a circuit pattern (not shown).
The resist layer
44
is partly removed to form a belt-like removed portion
47
in a position corresponding to a lower portion of components (in the vicinity of input terminals). Accordingly, the ground pattern
43
is slenderly exposed through the removed portion
46
.
In the first example of the discharge measure against static electricity, however, it is necessary to provide components such as the capacitors C
21
and C
22
, surge absorbers, or the like, so that the number of components and the number of work steps increase. Further, static electricity often exhibits a high voltage instantaneously so that the capacitors may be broken by such a high voltage applied thereto. Thus, there is a problem in durability.
On the other hand, in the printed circuit boards
41
illustrated as the second and third examples of the discharge measure against static electricity, the removal portions
40
and
47
are formed to expose the ground pattern to allow discharge. However, since the impedance of the input terminals is low, discharge can not be generated from the input terminals to the ground pattern.
Further, with respect to prevention of breaking of electronic equipments due to static electricity, the above-mentioned Unexamined Japanese Patent Publication No. Hei. 3-261087 discloses “Electrostatic Breaking Preventing Apparatus” and Unexamined Japanese Patent Publication No. Hei. 3-297199 discloses “Electric Apparatus”.
In the above “Electrostatic Breaking Preventing Apparatus”, a ground pattern is formed on a printed circuit board and a protrusion for accelerating discharge of static electricity is formed at a position of a part of the ground pattern facing an input pattern. However, the input pattern and the ground pattern do not face each other three-dimensionally but only portions of the thin patterns formed on one and the same plane are made adjacent to each other. Accordingly, the discharge effect with respect to the input pattern is not good. In addition, there is a possibility that static electricity due to approach of a finger, a component or the like cannot be discharged.
Further, in the above “Electric Apparatus”, an electrostatic come-flying copper foil portion (circuit pattern) is formed on a printed circuit board so that static electricity generated when operating components are mounted is discharged to the electrostatic come-flying foil. However, no consideration is given to discharge of static electricity due to input signal supply.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a discharge structure of a printed circuit board which is attained in view of the above problems so that static electricity in a high impedance circuit of an electronic apparatus can be discharged surely to a ground pattern so that the printed circuit board is never affected by static electricity.
In order to achieve the above object, according to an aspect of the present invention, there is provided a discharge structure for discharging static electricity which comprises: a printed circuit board comprising: an insulating substrate, an electrically conductive layer formed on the insulating substrate, the electrically conductive layer including a circuit pattern, and a resist layer by which the printed circuit board is partially covered; and an electronic component including a body and at least two terminal portions in electrical contact with the circuit pattern; wherein a ground pattern of the circuit pattern is partially exposed through a removed portion which is formed in vicinity of one of the terminal portions connected through the body and the other one of the terminal portions of the electronic component to a high-impedance side on the circuit pattern.
In the above discharge structure of a printed circuit board, the resist layer covering the electrically conductive layer formed as a ground pattern is partially removed to form the removed portion so that the ground pattern is exposed partially in the vicinity of one of leading portions or one of electrodes of the electronic component connected to a high impedance portion on the circuit pattern.
Accordingly, the high-impedance side leading portion or the electrode is in opposition to the ground pattern exposed through the removed portion, without interposition of the insulating resist layer, and further, the opposing positions are arranged three-dimensionally. Accordingly, when an input signal is applied to the printed circuit board or when any other components are approac
Foster David
Gaffin Jeffrey
Sughrue Mion Zinn Macpeak & Seas, PLLC
Yazaki -Corporation
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