Wave transmission lines and networks – Coupling networks – Frequency domain filters utilizing only lumped parameters
Reexamination Certificate
2002-07-17
2004-08-17
Young, Brian (Department: 2819)
Wave transmission lines and networks
Coupling networks
Frequency domain filters utilizing only lumped parameters
C361S302000, C361S306100
Reexamination Certificate
active
06778040
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to feed-through filters arranged in power lines and signal lines to cut off noise transmitted through those lines, and more particularly to a feed-through filter, which can improve filtering performance by assigning a shielding function to a bottom surface, on which filter devices are not mounted, of the insulating substrate having a plurality of through holes into which lead terminals are respectively inserted and by improving the shielding function, and which can achieve reduction of production cost of a feed-through filter and increase the convenience in use by assigning an elastic adhesion function to the insulating substrate on which filter devices are mounted.
2. Description of the Prior Art
Generally, electromagnetic interference (EMI) is a phenomenon wherein electromagnetic waves directly radiated or conducted from electric/electronic appliances interfere with the reception of electromagnetic waves from other appliances. Alternatively, EMI also is a phenomenon wherein the reception of desired electromagnetic signals is prevented by undesirable electromagnetic signals or electromagnetic noise.
Typically, a feed-through filter is a filter in which external electrodes are grounded and conductors of internal electrodes penetrate through holes, and which cuts off noise occurring on the conductors penetrating the through holes. A feed-through capacitor mounted on the feed-through filter is problematic in that it is expensive and it is difficult to manufacture a capacitor to obtain desired capacitance when the capacitor is realized as a device for a filter. In order to solve the above problems, chip capacitors or plate capacitors, which are inexpensive and are easily mounted on a substrate, must be used. In this case, the feed-through filter can be implemented by arranging a circuit unit on an insulation resin substrate or an insulation ceramic substrate, and then mounting chip capacitors on the substrate using a surface mounting device machine. The feed-through filter implemented according to the above procedure is inserted into a metal housing or a ferrule formed in one of various shapes, thus completing the manufacturing of the feed-through filter.
In the past EMI was mainly treated within a range of electromagnetic wave noise interference. Thereafter, the handling range of EMI is extended to radiated EMI directly radiated from electric/electronic appliances, and conductive EMI conducted along power lines. With the large increase in numbers of various electronic appliances and development of digital technologies and semiconductor technologies, application fields of precision electronic appliances are widened. Therefore, EMI generated from the precision electronic appliances results in mutual malfunctioning of the precision electronic appliances, biological hazard affecting organisms such as the human body, etc., as well as electromagnetic wave noise interference. That is, the influence of electromagnetic energy on biological ecosystems is a serious issue.
Hereinafter, a conventional feed-through filter is described in detail with reference to
FIGS. 1
to
3
.
FIG. 1
is a perspective view of a conventional feed-through filter. Referring to
FIG. 1
, a ground part
11
and lead terminal connection parts
12
are formed on an insulating substrate
13
such as an alumina ceramic substrate, on which one or more lead terminal through holes
14
are formed, using a printing method. Chip capacitors
15
are disposed between the ground part
11
and the lead terminal connection parts
12
, such that they are mounted on the insulating substrate
13
. The construction of such a feed-through filter is disclosed in detail in U.S. Pat. No. 5,959,829.
In the conventional feed-through filter, if the insulating substrate is used as shown in
FIG. 1
, the lead terminal connection parts
12
and the ground part
11
surrounding the lead terminal connection parts
12
are disposed on the top surface of the insulating substrate, and the chip capacitors
16
are mounted between the lead terminal connection parts
12
and the ground part
11
. However, the recent trend toward miniaturization and integration of electronic parts is rapidly spreading. Therefore, provided a filter with a narrow interval between neighboring lead terminals is produced using the conventional method of
FIG. 1
, it is difficult to dispose the chip capacitor between lead terminals.
FIG. 2A
is a perspective view of another conventional feed-through filter and
FIG. 2B
is a sectional view of a conventional feed-through filter shown in FIG.
2
A. Referring to
FIGS. 2A and 2B
, an insulator
23
through which a lead terminal
24
penetrates is disposed within an outer conductive metal ferrule
22
. A chip capacitor is mounted between the lead terminal
23
and the outer conductive metal ferrule
22
, and the outer conductive metal ferrule
22
is sealed with insulating resin
21
. The construction of such a feed-through filter is disclosed in detail in U.S. Pat. No. 5,650,759.
However, the conventional feed-through filter of
FIGS. 2A and 2B
is problematic in that a shielding effect is decreased by the provision of plural lead terminals, it is difficult to manufacture the component parts of the filter, and a plurality of capacitors must be mounted by a manual operation.
FIGS. 3A
to
3
D are views showing the construction of a substrate for a conventional feed-through filter. Referring to
FIGS. 3A
to
3
D, a conventional feed-through filter employs an insulating substrate
30
in which one or more lead terminal through holes
33
are formed.
FIG. 3A
is a top view of the insulating substrate
30
,
FIG. 3B
is a sectional view of &agr;-&bgr; line of FIG.
3
A,
FIG. 3C
is a bottom view of the insulating substrate
30
, and
FIG. 3D
is an equivalent circuit diagram of the feed-through filter.
Referring to
FIGS. 3A
to
3
D, in the conventional feed-through filter, one end electrodes C
1
b
and C
2
b
of chip capacitors C
1
and C
2
are electrically connected to lead terminal connection parts
32
. Further, the other end electrodes C
1
a
and C
2
a
of the chip capacitors C
1
and C
2
are electrically connected to a top surface ground part
31
. Further, a bottom surface ground part
35
is formed along the border of the bottom surface of the insulating substrate
30
.
However, in the conventional feed-through filter shown in
FIGS. 3A
to
3
D, a conductive layer is restrictedly formed only at some portion of the bottom surface of the insulating substrate
30
, that is, the border of the bottom surface. Therefore, noise cannot be bypassed to the ground through the bottom surface of the insulating substrate
30
of the filter, and passes through the insulating substrate
30
, so the filter cannot perform a shielding function.
As described above, in conventional feed-through filters, various methods are proposed so as to use chip capacitors, which are inexpensive and can be easily mounted, in a manufacturing process of filters. However, the conventional filters perform only a filtering function and cannot perform a shielding function through a bottom surface of an insulating substrate. That is, the conventional feed-through filters can hardly provide shielding measures.
Meanwhile, there are proposed methods of improving the shielding effect while assigning a filtering function to a feed-through filter by manufacturing metal structures and insulator structures in various shapes without using an insulating substrate. However, such methods are problematic in that they cause several difficulties, such as increase of costs, etc., due to their complicated manufacturing processes.
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 a feed-through filter, which can improve filtering performance by assigning a shielding function to a bottom surface, on which filter devices are not mounted, of t
Law Office of Marc D. Machtinger, Ltd.
Nguyen John B
Young Brian
LandOfFree
Feed-through filter having improved shielding and mounting... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Feed-through filter having improved shielding and mounting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Feed-through filter having improved shielding and mounting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3356157