Wave transmission lines and networks – Coupling networks – Wave filters including long line elements
Reexamination Certificate
2001-03-15
2003-04-15
Tokar, Michael (Department: 2819)
Wave transmission lines and networks
Coupling networks
Wave filters including long line elements
C333S206000
Reexamination Certificate
active
06549101
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a dielectric filter which comprises a plurality of resonators disposed side by side and is suitable for forming input/output terminal electrodes on a side surface.
There have hitherto been proposed various types of dielectric filters, in which terminal electrodes are formed on a side surface perpendicular to an open end face of a dielectric porcelain block
42
(i.e., an exposed-dielectric surface having conductors exposed thereon).
Terminal electrodes formed on the side surface perpendicular to an open end face of the dielectric porcelain block
42
are soldered to another circuit board and act as I/O terminals of the dielectric filter. Another electrode placed on the same plane where the terminal electrodes are provided acts as a ground electrode.
Commonly-used terminal electrodes include a terminal electrode formed by means of printing and sintering conductive material, and a terminal electrode formed by means of plating (see, for example, Japanese Patent Publication 8-307119/(1996) and 9-260903/(1997)). The terminal electrode assumes a structure such as that shown in FIG.
13
.
In a dielectric porcelain block
2
of the dielectric filter
1
shown in
FIG. 13
, a plurality of resonators
10
are provided side by side, wherein each resonator
10
is formed by coating the interior surface of a through hole
11
with an interior conductor
12
. I/O terminal electrodes
20
are provided on a side surface
4
perpendicular to an open end face
3
of the dielectric porcelain block
2
having the through holes
11
formed therein. The remaining side surfaces and bottom (i.e., a surface opposite the open end face
3
) of the dielectric porcelain block
2
are covered with an exterior conductor
22
such that the I/O terminal electrodes
20
are isolated from the exterior conductor
22
by means of an exposed-dielectric section
21
.
There have also hitherto been proposed a method of forming independent I/O terminal electrodes, by means of metallizing the entire side surfaces of a dielectric porcelain block; forming recesses in one of the side surfaces by means of sandblasting, laser, or etching; and masking electrodes with resist before the dielectric porcelain block is metallized.
As is evident from an enlarged portion shown in
FIG. 13
, the terminal electrode
20
and the ground electrode (i.e., the exterior conductor
22
) are higher than the exposed dielectric porcelain block
2
located therebetween by an amount corresponding to the thickness of the electrodes.
The terminal electrodes
20
are located at the highest position above amount surface of the dielectric porcelain block
2
. When a dielectric filter is soldered to another circuit board by use of cream solder, the dielectric filter is mounted on a circuit board by means of squeezing cream solder, since no gap exists between a circuit board and a terminal electrode. Accordingly, if the amount of solder is greater than appropriate, a solder bridge arises between adjacent terminals, thus causing a short circuit. Occurrence of a short circuit will be described specifically by reference to
FIGS. 14A through 14C
.
FIGS. 14A through 14C
show an example solder bridge arising in a dielectric filter having a related-art terminal electrode. As shown in
FIG. 14A
, a cream solder layer
33
a
is applied over an electrode
32
a
, and a cream solder layer
33
b
is applied over an electrode
32
b
. When the dielectric porcelain block
2
is mounted on the electrodes
32
a
and
32
b
laid on a circuit board
31
and is pressed against the electrodes
32
a
and
32
b
, the cream solder layers
33
a
and
33
b
squeeze out in a manner as shown in
FIG. 14B
, because no gap exists between a terminal electrode
20
, a ground electrode (i.e., an exterior conductor
22
), and a circuit board
31
of the dielectric porcelain block
2
.
So long as a sufficient space exists between the electrodes
32
a
and
32
b
, occurrence of solder bridges between the electrodes
32
a
and
32
d
can be prevented. However, in a high-frequency dielectric filter which is to be used for higher frequencies and miniaturization, an interval between electrodes becomes narrower, and a short circuit due to solder bridges becomes apt to arise between the electrodes
20
and
22
, as shown in FIG.
14
C.
In connection with a dielectric filter, a dielectric porcelain block per se is greater in area than electrodes. Hence, the strength of a connection must be enhanced by means of increasing the area of a place to be soldered, and the amount of solder to be used must be increased. An increase in the amount of solder eventually results in ease of occurrence of a short circuit.
When terminal electrodes and a ground electrode of a dielectric filter are formed, by means of electric plating, areas where terminal electrodes are to be formed assume island-shaped geometries, and as a result plating of the terminal electrodes becomes thinner. A pattern is formed by means of resist, and hence variations may arise in positions where terminals are to be formed, depending on the precision of printing of resist, thereby adversely affecting a filtering characteristic of the dielectric filter.
In a case where electrodes are formed by means of plating, a plating bridge (elongation of plating) may arise between a terminal electrode
20
and a ground electrode (i.e., an exterior conductor
22
) formed on the dielectric porcelain block
2
of the dielectric filter
1
, thereby resulting in a short circuit such as that shown in FIG.
15
. After removal of resist, the bridge still remains, thereby inducing a short circuit.
When molded bodies which are to become dielectric porcelain blocks are sintered, a maximum number of molded bodies are put into a furnace as close to each other as possible. If contact of large area arises between molded bodies, the molded bodies will stick to each other after sintering, thus resulting in occurrence of defectives.
SUMMARY OF THE INVENTION
The present invention is aimed at obviating drawbacks of a dielectric filter having a related-art structure and at providing a dielectric filter which is easy to mount and provides a high manufacturing yield and stable quality, as well as a method of manufacturing the dielectric filter.
Other objects and novel features of the present invention will be manifest by reference to embodiments to be described later.
To this end, the present invention provides a dielectric filter formed from a dielectric block and a plurality of resonators formed in the dielectric block side by side, each resonator being formed by coating an interior surface of a through section with an interior conductor, wherein, on a side surface of the dielectric block perpendicular to an open end face having the through sections formed therein, there are formed protrusions having a height lower than that of the through sections.
By means of such a construction, when terminal electrodes are provided on a side surface of a dielectric block, dielectric protrusions are located between the electrodes. Hence, when the dielectric porcelain block is mounted on a circuit board by means of cream solder, the amount of solder which enters the exposed dielectric of the protrusions from electrodes becomes less, thereby eliminating squeezing out of solder to adjacent electrodes. Consequently, there can be prevented occurrence of a short circuit, which would otherwise be caused by solder bridges.
One or more protrusions are provided on at least one of the side surfaces of the dielectric porcelain block during molding. As a result, there can be prevented occurrence of contact between molded bodies over a wide area. Consequently, there can be prevented failures, which would otherwise be caused when molded bodies come into contact with each other over a wide area during sintering.
Preferably, each of the protrusions is formed so as to spread across two or more side surfaces.
By means of such a construction, a terminal electrode can be provided at a corner of the dielectric block.
Preferably, a plurality of pr
Gotoh Masashi
Tashiro Kouji
TDK Corporation
Tokar Michael
Tran Ahn
LandOfFree
Dielectric filter, and method of manufacturing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Dielectric filter, and method of manufacturing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dielectric filter, and method of manufacturing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3030042