Title: Nonreciprocal circuit device, communication device, and method of manufacturing nonreciprocal circuit device
Abstract: A nonreciprocal circuit device, in which metal members which form a metal case can be resistance-welded stably and reliably, having high reliability and satisfactory characteristics, a communication device using the nonreciprocal circuit device, and a method of manufacturing the nonreciprocal circuit device. Protruding portions are formed at two places on each side wall of an upper metal case. The upper metal case and a lower metal case are bonded together by resistance welding the two side walls of the lower metal case to the two side walls of the upper metal case at the protruding portions.
Patent Number: 6,968,609 Issued on 11/29/2005 to Matsuoka, et al.
| Inventors:
|
Matsuoka; Kenichi (Ishikawa-ken, JP);
Chikusa; Hironao (Kanazawa, JP);
Kadooka; Takashi (Ishikawa-ken, JP)
|
| Assignee:
|
Murata Manufacturing Co., Ltd. (Kyoto, JP)
|
| Appl. No.:
|
896960 |
| Filed:
|
July 23, 2004 |
Foreign Application Priority Data
| Mar 01, 2001[JP] | 2001-056593 |
| Current U.S. Class: |
29/601; 333/1.1; 333/24.2 |
| Intern'l Class: |
H01P 001/32; H01F 007/06 |
| Field of Search: |
333/11,242
29/601
|
References Cited [Referenced By]
U.S. Patent Documents
| 4195246 | Mar., 1980 | Izumida et al.
| |
| 5900789 | May., 1999 | Yamamoto et al.
| |
| 6037844 | Mar., 2000 | Makino et al.
| |
| Foreign Patent Documents |
| 51-064442 | Jun., 1976 | JP.
| |
| 53-100143 | Sep., 1978 | JP.
| |
| 64-033796 | Mar., 1989 | JP.
| |
| 10-107513 | Apr., 1998 | JP.
| |
| 10-200307 | Jul., 1998 | JP.
| |
| 10-276011 | Oct., 1998 | JP.
| |
| 10-276011 | Oct., 1998 | JP.
| |
| 2001/-292014 | Oct., 2001 | JP.
| |
Other References
Resistance Spot Welding, Feb. 1999, Safety and Health Fact Sheet No. 21, American
Welding Society, pp. 1-2.
JP10276011A, machine translation.
|
Primary Examiner: Jones; Stephen E.
Attorney, Agent or Firm: Keating & Bennett, LLP
Parent Case Text
This application is a Divisional Application of U.S. patent application Ser.
No. 10/083,429 filed Feb. 26, 2002, now abandon.
Claims
1. A method of manufacturing a nonreciprocal circuit device comprising a permanent
magnet, a magnetic material, and a plurality of center conductors arranged on the
magnetic material, wherein the permanent magnet, the magnetic material, and the
center conductors are housed inside a metal case formed by bonding an upper metal
case and a lower metal case at respective bonding surfaces thereof, said method
comprising the steps of:
forming a protruding portion on a bonding surface of one of the upper metal case
and the lower metal case;
disposing the upper metal case and the lower metal case so that the respective
bonding surfaces including said protruding portion are brought into contact with
each other;
applying pressure to the upper metal case and the lower metal case by electrode
terminals of a resistance welder; and
applying welding current to said case via said electrode terminals so as to resistance-weld
said respective bonding surfaces via said protruding portion; wherein
said pressure is applied to the upper metal case and the lower metal case in
a direction parallel to the bonding surfaces.
2. A method of manufacturing a nonreciprocal circuit device according to claim
1, wherein said protruding portion is formed on said upper metal case.
3. A method of manufacturing a nonreciprocal circuit device according to claim
1, wherein said pressure is also applied to the upper metal case and the lower
metal case in a direction perpendicular to the bonding surfaces.
4. A method of manufacturing a nonreciprocal circuit device according to claim
1, further comprising the step of plating a surface of the upper metal case and
the lower metal case with at least one of Au, Ag, Cu and Ni.
5. A method of manufacturing a nonreciprocal circuit device according to claim
1, wherein said upper metal case is fitted into said lower metal case.
6. A method of manufacturing a nonreciprocal circuit device according to claim
5, wherein said protruding portion is formed on said upper metal case.
7. A method of manufacturing a nonreciprocal circuit device according to claim
1, further comprising the step of plating a surface of the upper metal case and
the lower metal case with Cu.
8. A method of manufacturing a nonreciprocal circuit device according to claim
7, further comprising the step of plating Ag on the Cu plating.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nonreciprocal circuit device, such as an isolator
or a circulator, for use in a high-frequency band such as the microwave band, to
a communication device comprising the nonreciprocal circuit device, and to a method
of manufacturing the nonreciprocal circuit device.
2. Description of the Related Art
Generally, nonreciprocal circuit devices, such as isolators or circulators,
used in mobile communication devices such as portable phones, have a function of
allowing signals to pass through in a predetermined transmission direction and
of preventing the transmission in the reverse direction.
This type of nonreciprocal circuit device is constructed by housing a permanent
magnet, a magnetic material (ferrite) to which a DC magnetic-field is applied by
the permanent magnet, and component members such as a plurality of center conductors
arranged on this magnetic material, inside a metal case. The metal case is formed
by bonding an upper metal case made of a magnetic-material metal to a lower metal
case made of a magnetic-material metal.
Nonreciprocal circuit devices, in which an upper metal case and a lower
metal case which form this metal case are bonded by resistance welding, are proposed
in, for example, Japanese Unexamined Patent Application Publication Nos. 10-107513
and 10-276011. In these publications, in the nonreciprocal circuit devices, an
upper metal case and a lower metal case are resistance-welded with their mutually
bonded surfaces in surface contact.
As described in Japanese Unexamined Patent Application Publication No. 10-107513,
as a result of bonding the two metal cases by resistance welding, the problem of
a defective connection caused by remelting of solder, which occurs when the metal
cases are bonded by soldering, can be reduced. Also, it is described in Japanese
Unexamined Patent Application Publication No. 10-276011 that, as a result of bonding
the metal cases by resistance welding, the magnetic resistance of the bonded portions
of the metal cases can be reduced in comparison with conventional bonding by soldering
and crimping, and the external magnetic-field can be made effectively strong.
However, there is a problem in the above-described conventional nonreciprocal
circuit devices, in which the resistance welding of the upper and lower metal cases
is performed with their mutually bonded surfaces in surface contact. Stable and
reliable resistance welding cannot be performed due to processing variations in
their bonded surfaces, and variations in the component members, etc., incorporated
in the nonreciprocal circuit device. Thus, the bonding strength and the electrical
characteristics (insertion loss, isolation, etc.) vary greatly, and as a result,
a desired bonding strength and desired electrical characteristics cannot be obtained.
That is, in a conventional nonreciprocal circuit device, since the two metal cases
are in surface contact at the bonded surfaces, the contact portions, the contact
state, and the contact area are not stable. Also, variations in the bonding process
are large and the bonding strength is decreased under predetermined welding conditions
(a fixed welding current, and a fixed current flowing time). Furthermore, since
the portions which are welded and the bonding strength become unstable, the electrical/magnetic
circuit characteristics change. For example, the magnetic resistance in the bonded
portion may be increased, or the electrical characteristics may vary greatly or
the electrical characteristics may be degraded.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a nonreciprocal circuit
device, in which metal members which form a metal case can be resistance-welded
stably and reliably, which thus has high reliability and satisfactory characteristics,
to a communication device using the nonreciprocal circuit device, and to a method
of manufacturing the nonreciprocal circuit device.
To provide the above-mentioned advantages, the present invention provides a nonreciprocal
circuit device comprising: a permanent magnet; a magnetic material; and a plurality
of center conductors arranged on the magnetic material, the permanent magnet, the
magnetic material, and the center conductors being housed inside a metal case formed
by bonding a plurality of metal members, wherein a protruding portion is formed
on a bonding surface of at least one metal member among the plurality of metal
members, and the protruding portion is bonded to a bonding surface of another one
of the metal members by resistance welding.
According to this construction, since a protruding portion is formed on
at least one of the bonding surfaces of the metal members to be bonded, and contact
between this protruding portion and the bonding surface of the other metal member
is made possible, a welding current can be concentrated in only this protruding
portion in order to weld the two metal members at this portion. That is, since
the bonding surfaces to be bonded together are in contact with each other only
at the protruding portion or portions, the contact resistance is stable. Thus,
stable and reliable resistance welding is possible under predetermined welding
conditions (a fixed welding current, and a fixed current flowing time), making
it possible to obtain a metal case having a predetermined bonding strength and
having small variations in bonding strength. Furthermore, since the portions to
be welded are limited to the protruding portions, suitable electrical/magnetic
circuits can be obtained.
Preferably, one to three protruding portions are formed on each of the
bonding surfaces of the metal members which are to be bonded together. Furthermore,
the height of each protruding portion is preferably 150 μm or less. As a
result of forming the metal case with the upper metal case and the lower metal
case, the assembly of the nonreciprocal circuit device and the resistance welding
of the metal case are made easier.
The resistance welding of the upper metal case and the lower metal case may be
performed by bringing the surfaces to be bonded into contact with each other at
the protruding portion, and applying pressure to the upper metal case and the lower
metal case by the electrode terminals of a resistance welder.
Furthermore, preferably, the resistance welding of the metal cases may
be performed by applying pressure in a direction perpendicular to the surfaces
to be mutually bonded.
The communication device according to the present invention comprises a nonreciprocal
circuit device having the above-described features.
Further features and advantages of the present invention will become apparent
from the following description of embodiments of the invention with reference to
the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of an isolator according to a first embodiment
of the present invention;
FIG. 2A is a side view of an upper metal case of the isolator; and FIG. 2B is
a plan view of the upper metal case of the isolator;
FIG. 3 is a simplified sectional view showing a method of resistance-welding
the upper metal case and the lower metal case of the isolator;
FIG. 4 is a simplified sectional view showing another method of resistance-welding
the upper metal case and the lower metal case of the isolator;
FIG. 5A is a side view of an upper metal case according to a second embodiment
of the present invention; and FIG. 5B is a plan view of the upper metal case;
FIG. 6A is a side view of an upper metal case according to a third embodiment; and
FIG. 6B is a plan view of the upper metal case; and
FIG. 7 is a block diagram of a communication device according to a fourth embodiment
of the present invention.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The construction of an isolator, and methods of manufacturing the same according
to a first embodiment of the present invention, will be described below with reference
to FIGS. 1 to 4. FIG. 1 is an exploded perspective view showing the overall construction
of an isolator. FIG. 2A is a side view of an upper metal case thereof. FIG. 2B
is a plan view of the upper metal case thereof. FIGS. 3 and 4 are simplified sectional
views showing a method of resistance-welding the upper metal case and the lower
metal case, in which only the two metal cases are shown.
The isolator of this embodiment is constructed by bonding corresponding metal
members of an upper metal case
2 and a lower metal case
8. A permanent
magnet
3, a terminal case
7, a magnetic assembly
5 having
center conductors
51,
52, and
53 arranged on a magnetic material
55, matching capacitor elements C
1, C
2, and C
3, and
a termination resistor element R are housed inside the metal case thus formed.
The upper metal case
2 and the lower metal case
8 are formed by
stamping and bending a metal plate having a predetermined thickness of about 0.2
mm, made of a magnetic metal such as soft iron, and, thereafter, the surface thereof
is plated with Au, Ag, Cu, Ni, etc. The metal case formed of the upper metal case
2 and the lower metal case
8 forms a magnetic circuit, and also serves
as an external case for housing and holding other component members. This isolator
has external dimensions with a length and width of approximately 7.0 mm, and a
height of approximately 2.0 mm. The upper metal case
2 has a height of about
1.0 mm and the lower metal case
8 has a height of approximately 2.0 mm.
The upper metal case
2 has two pairs of opposing side walls
2b
and
2c depending from an upper wall
2a which is
substantially rectangular in a plan view. The external surfaces of the two opposing
side walls
2b are bonded respectively to the side walls
8b
of the lower metal case
8. A protruding portion
21 substantially
in the shape of a hemisphere or a segment of a sphere is formed at two places on
each side wall
2b. Each protruding portion
21 is integrally
formed in the side wall
2b by pressing, in such a manner as to protrude
toward the corresponding side wall
8b of the lower metal case
8.
Each protruding portion
21 is formed substantially in a hemispherical shape
such that, for example, the diameter on the bonding surface is 60 μm and
the height from the bonding surface to the tip is 30 μm.
The lower metal case
8 has a bottom wall
8a, and a pair
of side walls
8b. The internal surface of each side wall
8b
is bonded with the corresponding side wall
2b of the upper metal
case
2.
The distance between the side walls
2b of the upper metal case
2 and the distance between the side walls
8b of the lower
metal case
8 are such that, when the upper metal case
2 is fitted
into the lower metal case
8, the tip portion of each protruding portion
21 of the upper metal case
2 is brought into pressure-contact with
the corresponding side wall
8b of the lower metal case
8.
For the isolator of this embodiment, as will be described later, the upper metal
case
2 and the lower metal case
8 are then bonded by resistance welding
the protruding portions
21 of the side walls
2b of the upper
metal case
2 to the two side walls
8b of the lower metal case
8.
The magnetic assembly
5 is formed by arranging center conductors
51,
52, and
53 on the top surface of a magnetic material (ferrite)
55
in the shape of a rectangular plate in such a manner as to mutually intersect each
other substantially every 120 degrees with insulation sheets (not shown) being
provided in between. Port sections P
1, P
2, and P
3 extend outward
from one end of each of these center conductors
51 to
53. A common
grounding portion is connected to the other ends of the center conductors
51
to
53 and is disposed in contact with the underside of the magnetic material
55. The center conductors
51 to
53 and the common grounding
portion are integrally formed by stamping and etching a metal conductor plate such
as copper.
A resin case
7 is formed from a resin material having heat resistance
and
insulating properties, and is such that a bottom wall
7b is integrally
formed on a side wall
7a in the shape of a rectangular frame. An
insertion hole
7c is formed in substantially the central portion
of the bottom wall
7b, and capacitor housing recesses for housing
the capacitor elements C
1 to C
3, and a resistor housing recess for
housing a resistor element R are formed around the peripheral edge of the insertion
hole
7c. Input/output terminals
71 and
72 which are
external connection terminals, and a grounding terminal
73 are insert-molded
to the resin case
7. The input/output terminals
71 and
72
and the grounding terminal
73 are formed by stamping a metal conductor plate
into a predetermined shape and bending it. One end of each of the input/output
terminals
71 and
72 is exposed on the external surface of the side
wall
7a and the bottom wall
7b of the resin case
7,
the other ends of the input/output terminals
71 and
72 are exposed
on the inner surface of the bottom wall
7b of the resin case
7,
and the other end of the grounding terminal
73 is exposed on the inner surface
of each housing recess.
The magnetic assembly
5 is inserted into the insertion hole
7c
of the resin case
7, the capacitor elements C
1 to C
3 are
housed in the capacitor housing recesses of the resin case
7, and the resistor
element R is housed in the resistor housing recess of the resin case
7.
The grounding portion which is common among the center conductors
51 to
53 on the underside of the magnetic assembly
5 substantially covers
the underside of the magnetic material
55, and is connected to the bottom
wall
8a of the lower metal case
8. The port sections P
1
and P
2 of the center conductors
51 and
52 on the input/output
sides are connected to the top-surface (hot side) electrodes of the capacitor elements
C
1 and C
2 and to the portions of the input/output terminals
71
and
72 that are exposed inside the bottom walls
7b. The port
section P
3 of the center conductor
53 is connected to the top-surface
(hot side) electrode of the capacitor element C
3 and to the hot side electrode
on one end of the resistor element R. The underside (cold side) electrodes of the
capacitor elements C
1 to C
3 are connected to the capacitor housing
recesses of the grounding terminal
73, and the electrode on the other end
(cold side) of the resistor element R is connected to the portion exposed on the
inner surface of the resistor housing recess.
A method of manufacturing an isolator of this embodiment will be described below.
First, the isolator is assembled as follows. The resin case
7 is mounted
on the bottom wall
8a of the lower metal case
8, and the capacitor
elements C
1 to C
3, a resistor element R, and the magnetic assembly
5 are housed inside the resin case
7. A permanent magnet
3
is placed thereon, and the upper metal case
2 is fitted into the lower metal
case
8 in such a manner as to cover the permanent magnet
3. In this
assembly process, a solder cream or solder paste is applied to the connection portions
of the other component members, excluding the connection portion of the two metal
cases
2 and
8, the upper metal case
2 is fitted into the lower
metal case
8, and the component members are soldered together.
Next, as shown in FIG. 3, one of the electrode terminals
61 of a resistance
welder is pressed against the upper wall
2a of the upper metal case
2 and the other electrode terminal
62 is pressed against the bottom
wall
8a of the lower metal case
8. Pressure is applied to
the upper metal case
2 and the lower metal case
8 by the electrode
terminals
61 and
62. At this time, the side wall
2b is
in contact with the corresponding side wall
8b of the lower metal
case
8 only at the respective protruding portions
21 formed in the
side wall
2b of the upper metal case
2. Then welding current
is made to flow so as to melt the protruding portions
21 of the upper metal
case
2, so that the upper metal case
2 and the lower metal case
8
are bonded together by resistance welding at the protruding portions
21.
The welding current is concentrated at the protruding portions
21, so that
the metal cases
2 and
8 are stably and reliably welded to each other
at the protruding portions
21.
In this embodiment, since the side wall
2b which is a bonding surface
of the upper metal case
2 and the side wall
8b which is a
bonding surface of the lower metal case
8 contact each other only at the
protruding portions
21, the contact resistance between the two metal cases
2 and
8 is stabilized. Therefore, stable and reliable welding becomes
possible with a fixed welding current and a fixed current flow time, and variations
of the bonding (welding) strength are small. Furthermore, since the portions to
be welded (bonding portions) are limited to the protruding portions
21,
variations of the electrical/magnetic circuits formed by the metal case are reduced.
Therefore, variations of the electrical characteristics are reduced, and the electrical
characteristics are improved. Furthermore, since pressure is applied to the upper
metal case
2 and the lower metal case
8 by the electrode terminals
61 and
62 of the resistance welder, the contact resistance between
the two metal cases
2 and
8 and the electrode terminals
61
and
62 is decreased. As a result, stable resistance welding becomes possible,
and the height of the nonreciprocal circuit device can be minimized.
In an alternative method, shown in FIG. 4, when performing the resistance welding
of the two metal cases
2 and
8, if pressure is applied to both side
walls
8b of the lower metal case
8 by a pressure jig
63
in the directions indicated by the arrows P, the contact resistance at the protruding
portions
21 can be stabilized even further, allowing more stable and reliable
welding to be performed. In this case, each protruding portion
21 is crushed
during welding, so that the height of the protruding portions
21 after welding
can be made substantially 0 mm, and the outside dimensions can be minimized. Furthermore,
the clearance between the bonded surfaces of the two metal cases
2 and
8
is decreased, the magnetic resistance between the two metal cases
2 and
8 can be decreased, and the electrical characteristics are improved even more.
In a further method, also shown in FIG. 4, the pressure jigs
63 on the
right and left may be used as electrode terminals of a resistance welder, which
abut the lower metal case
8. That is, in FIG. 4, both jigs
63 and
62 may be used as electrode terminals. Further, only one of them may be
used as an electrode terminal.
In the first embodiment, two protruding portions
21 are formed on each
of the two side walls
2b, which are the bonded surfaces of the upper
metal case
2. However, the number of protruding portions to be formed on
the bonded surfaces is not limited to this.
A metal case according to a second embodiment of the present invention is shown
in FIGS. 5A and 5B. A metal case according to a third embodiment of the present
invention is shown in FIGS. 6A and 6B. In the metal case shown in FIGS. 5A and
5B, one protruding portion
21 is formed on each of the side walls
2b
of the upper metal case
2. In the metal case shown in FIGS. 6A and 6B,
three protruding portions
21 are formed on each of the side walls
2b
of the upper metal case
2. Also, in the constructions shown in FIGS.
5A and 5B and FIGS. 6A and 6B, the same advantages and manufacturing methods as
those of the first embodiment can be obtained.
In the present invention, as in the above-described first to third embodiments,
it is preferable that one to three protruding portions for welding be formed on
the bonding surfaces of the metal member. The reason for this is that, when four
or more protruding portions for welding are formed on one bonding surface. The
possibility is increased that one or more of the protruding portions will make
poor contact, so that the contact resistance is not stabilized.
Furthermore, it is preferable that the height of each protruding portion
21 be 5 to 150 μm before resistance welding. The reason for this is
that, if the height of the protruding portion
21 exceeds 150 μm, magnetic-force
leakage and insufficient magnetic force may occur, due to the clearance (gap) between
the bonded surfaces of the two metal cases
2 and
8, and it becomes
susceptible to the influence of the temperature and humidity of the outside air
and intrusion of foreign matter. Another reason is that, since the two metal cases
2 and
8 have flatness variations of approximately 5 μm, if
the height of the protruding portion
21 is 5 μm or less, the two metal
cases
2 and
8 cannot reliably be made to contact each other only
at the protruding portions
21.
In each of the above-described embodiments, protruding portions
21 for
welding are provided on the bonding surfaces of the upper metal case
2 of
the isolator. However, the protruding portions
21 may also be provided on
the bonding surfaces of the lower metal case
8.
In either case, in order to obtain stable contact on the protruding portion
21
and in order to reduce the cost of the metal case, it is preferable for the protruding
portions
21 to be provided on only one of the metal cases, rather than on
both of the metal cases.
Furthermore, the shape of the protruding portions is not limited to
that in the above-described embodiments. The protruding portions may have a substantially
cylindrical, prismatic, conical, or pyramidal shape. Regardless of the shape, it
is preferable for the protruding portions to be formed on a surface of a metal
member to be welded by pressing, etc. as in the first to this embodiments.
Furthermore, the shapes of the upper metal case and the lower metal
case are not limited to those of the above-described embodiments, and the present
invention can also be applied to a metal case formed by three or more metal members.
Furthermore, in the above-described embodiments, an isolator is described.
However, of course, the present invention can also be applied to a circulator.
Furthermore, the overall construction and the component members of the
nonreciprocal circuit device are not limited to those of the above-described embodiments,
and, for example, the shape of the permanent magnet may be another shape, such
as a rectangular plate shape, and the shape of the magnetic material may also be
a circular plate shape.
Next, the construction of a communication device according to a second embodiment
of the present invention is shown in FIG. 7. This communication device has an antenna
ANT connected to an antenna end of a duplexer DPX formed of a transmission filter
Tx and a receiving filter Rx. An isolator ISO is connected between the input end
of the transmission filter TX and a transmission circuit, and a receiving circuit
is connected to the output end of the receiving filter Rx. A transmission signal
from the transmission circuit passes through the isolator ISO, and through the
transmission filter Tx, and is transmitted from the antenna ANT. Also, a received
signal received by the antenna ANT is input to the receiving circuit through the
receiving filter RX.
Here, as the isolator ISO, the isolator of the above-described embodiments
can be used. As a result of using the nonreciprocal circuit device according to
the present invention, it is possible to obtain a communication device having high
reliability and satisfactory characteristics.
As has thus been described, according to the present invention, since protruding
portions are formed on the bonding surfaces of a plurality of metal members which
form a metal case, and the bonding surfaces which are to be bonded together can
be made to contact each other only at the protruding portions, the metal members
can be resistance-welded stably and reliably. Therefore, it is possible to obtain
a metal case having a predetermined bonding strength and having a small variation
of a bonding strength, and it is possible to obtain a nonreciprocal circuit device
having high reliability and satisfactory characteristics.
Furthermore, as a result of using a nonreciprocal circuit device according
to the present invention, it is possible to obtain a communication device having
high reliability and satisfactory characteristics.
While the present invention has been described with reference to what are presently
considered to be the preferred or best known embodiments, it is to be understood
that the invention is not limited to the disclosed embodiments. On the contrary,
the invention is intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims. The scope of the following
claims is to be accorded the broadest interpretation so as to encompass all such
modifications and equivalent structures and functions.
*
