Nonreciprocal circuit device

A nonreciprocal circuit device includes a ferrite-magnet element having ferrite provided with first and second central electrodes intersecting each other in an insulated manner and two permanent magnets arranged to sandwich the ferrite to apply a DC magnetic field thereto, a substrate on which the ferrite-magnet element and matching circuit elements are mounted, and a flat plate yoke. A first resin layer made of a cured liquid resin is provided at bonding portions of the ferrite-magnet element to the substrate, and a second resin layer made of a cured soft sheet-shaped resin adhered to a rear surface of the flat plate yoke is provided around the ferrite-magnet element and the matching circuit elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a nonreciprocal circuit device, and particularly, to a nonreciprocal circuit device, such as an isolator or a circulator, used in a microwave band, and also to a manufacturing method of the nonreciprocal circuit device.

2. Description of the Related Art

Nonreciprocal circuit devices, such as an isolator and a circulator, have characteristics to transmit signals only in a specific direction but not in the direction opposite thereto. By using these characteristics, for example, isolators are used in transmission circuit portions of mobile communication apparatuses, such as an automobile phone and a mobile phone.

In International Publication WO 2007/046229, a nonreciprocal circuit device is disclosed in which a first central electrode and a second central electrode are wound around a substantially rectangular parallelepiped ferrite in an electrically insulated manner so as to intersect each other, a pair of permanent magnets is disposed on two primary surfaces of the ferrite to define a ferrite-magnet assembly so as to apply a direct current magnetic field to the ferrite, and side portions of the ferrite-magnet assembly mounted on a circuit board are surrounded by a yoke.

However, in the nonreciprocal circuit device disclosed in International Publication WO 2007/046229, although the periphery of the ferrite-magnet assembly is surrounded by the yoke, since a cavity is provided around the periphery, the device described above is unfavorably influenced by humidity. In addition, since the side portions of the ferrite-magnetic assembly are surrounded by the yoke, the number of components is increased, and a manufacturing process is complicated.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of the present invention provide a nonreciprocal circuit device which eliminates the adverse influence of humidity and which can be efficiently manufactured and, a manufacturing method for the nonreciprocal circuit device.

According to a preferred embodiment of the present invention, a nonreciprocal circuit device includes a ferrite-magnet element which includes ferrite having two primary surfaces on which central electrodes are arranged to intersect each other in an electrically insulated manner and a pair of permanent magnets arranged on the two primary surfaces of the ferrite so as to apply a direct current magnetic field to the ferrite, a substrate having a surface to which the ferrite-magnet element is bonded so that the two primary surfaces of the ferrite are perpendicular or substantially perpendicular to the surface of the substrate, a flat plate yoke arranged to cover a top surface of the ferrite-magnet element, a first resin layer which is disposed at least at a bonding portion of the ferrite-magnet element bonded to the substrate and which is a cured liquid resin, and a second resin layer which is adhered to a rear surface of the flat plate yoke and which is a cured soft sheet-shaped resin.

According to another preferred embodiment of the present invention, a manufacturing method for a nonreciprocal circuit device includes the steps of bonding a ferrite-magnet element, which includes ferrite having two primary surfaces on which central electrodes are arranged to intersect each other in an electrically insulated manner and a pair of permanent magnets arranged on the two primary surfaces of the ferrite so as to apply a direct current magnetic field to the ferrite, to a surface of a substrate so that the two primary surfaces of the ferrite are arranged perpendicular or substantially perpendicular to the surface of the substrate, disposing a liquid resin at a bonding portion of the ferrite-magnet element bonded to the substrate, followed by curing to form a first resin layer, and disposing a flat plate yoke provided with a soft sheet-shaped resin adhered to a rear surface thereof on a top surface of the ferrite-magnet element, and after the soft sheet-shaped resin is softened, curing the soft sheet-shaped resin to form a second resin layer.

According to preferred embodiments of the present invention, since the periphery of the ferrite-magnet element is sealed with the first and second resin layers, the influence of humidity is eliminated. Since the permanent magnets are provided on the respective primary surfaces of the ferrite which is provided with the central electrodes, a yoke surrounding the side portions of the ferrite is not always required. In addition, the first and second resin layers can be easily formed, respectively, by automatically applying a liquid resin and by pressing and softening a sheet-shaped resin adhered to the flat plate yoke. Furthermore, when the substrates and the flat plate yokes are manufactured in the form of a mother substrate, manufacturing can be efficiently performed using a multiple-elements forming method.

Other features, elements, steps, processes, characteristics and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the attached drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a nonreciprocal circuit device and a manufacturing method thereof according to the present invention will be described with reference to the accompanying drawings.

First Preferred Embodiment

FIG. 1is an exploded perspective view showing a two-port isolator1according to the first preferred embodiment of a nonreciprocal circuit device of the present invention. This two-port isolator1preferably is a lumped constant isolator and includes a flat plate yoke10, a substrate20, a ferrite-magnet element30composed of ferrite32and a pair of permanent magnets41, a first resin layer50, and a second resin layer60.

As shown inFIG. 2, a first central electrode35and a second central electrode36, which are electrically insulated from each other, are arranged on a front first primary surface32aand a rear second primary surface32bof the ferrite32. In this preferred embodiment, the ferrite32is a substantially rectangular parallelepiped having the first primary surface32aand the second primary surface32b, which are parallel or substantially parallel to each other.

In addition, the permanent magnets41are adhered to the primary surfaces32aand32bof the ferrite32with epoxy adhesives42provided therebetween so as to apply a direct current magnetic field to the primary surfaces32aand32bin a direction perpendicular or substantially perpendicular thereto (seeFIG. 4), so that the ferrite-magnet component30is provided. Primary surfaces41aof the permanent magnets41each have the same or substantially the same dimension as that of each of the primarily surfaces32aand32bof the ferrite32and are arranged to face the respective primary surfaces32aand32bso that their peripheries coincide or substantially coincide with each other.

The first central electrode35is made of a conductive film. That is, as shown inFIG. 2, the first central electrode35is arranged from a right bottom side of the first primary surface32aof the ferrite32, is extended while being divided into two portions to a left top side at a relatively low inclined angle with respect to a long side of the first primary surface32a, is then extended to the second primary surface32bthrough an interconnection electrode35aprovided on a top surface32c, and is arranged on the second primary surface32bwhile being divided into two portions so as to be overlapped with the central electrode35on the first primary surface32athrough the ferrite32, and one end of the first central electrode35is then connected to a connection electrode35bprovided on a bottom surface32d. In addition, the other end of the first central electrode35is connected to a connection electrode35cprovided on the bottom surface32d. As described above, the first central electrode35is wound one turn around the ferrite32. In addition, the first central electrode35and the second central electrode36which will be described below intersect each other so as to be insulated from each other with an insulating film provided therebetween. The intersection angle between the central electrodes35and36is determined in accordance with requirements, so that input impedance and insertion loss are adjusted.

The second central electrode36is preferably made of a conductive film. The second central electrode36includes a first half turn portion36aarranged obliquely on the first primary surface32afrom the right bottom side to the left top side at a relatively large angle with respect to the long side of the first primary surface32aso as to intersect the first central electrode35and is extended to the second primary surface32bthrough an interconnection electrode36bprovided on the top surface32c, and a first turn portion36cextended from the first half turn portion36ais provided on the second primary surface32bso as to perpendicularly or substantially perpendicularly intersect the first central electrode35. A lower end portion of the first turn portion36cis extended to the first primary surface32athrough an interconnection electrode36dprovided on the bottom surface32d, and a first-and-half turn portion36eextended from the first turn portion36cis provided on the first primary surface32aparallel or substantially parallel to the first half turn portion36aso as to intersect the first central electrode35and is extended to the second primary surface32bthrough an interconnection electrode36fprovided on the top surface32c. Subsequently, in the same manner as described above, a second turn portion36g, an interconnection electrode36h, a second-and-half turn portion36i, an interconnection electrode36j, a third turn portion36k, an interconnection electrode36l, a third-and-half turn portion36m, an interconnection electrode36n, and a fourth turn portion36oare provided on the surfaces of the ferrite32. In addition, the two ends of the second central electrode36are connected to the connection electrode35cand a connection electrode36pprovided on the bottom surface32dof the ferrite32. As described above, the connection electrode35cis used as the connection electrodes at the end portions of the first and the second central electrodes35and36.

In addition, the connection electrodes35b,35c, and36pand the interconnection electrodes35a,36b,36d,36f,36h,36j,36l, and36nare formed by applying or filling an electrode conductor, such as silver, a silver alloy, copper, or a copper alloy, in concave portions37(seeFIG. 3) provided in the top and the bottom surfaces32cand32dof the ferrite32. Furthermore, dummy concave portions38are also provided in the top and the bottom surfaces32cand32dparallel or substantially parallel to the concave portions37, and dummy electrodes39a,39b, and39care provided therein. This type of electrode is formed such that, after a through-hole is formed in advance in a mother ferrite substrate, the through-hole is filled with a conductive conductor, and the substrate is then cut so as to divide the through-hole. In addition, the connection and interconnection electrodes may preferably be made of conductive films provided in the concave portions37and38.

As the ferrite32, YIG ferrite or other suitable ferrite may preferably be used, for example. The first and second central electrodes35and36and the other electrodes may preferably be formed of a thick film or a thin film of silver or a silver alloy, for example, by a printing, a transfer, or a photolithographic method. As the insulating film provided between the central electrodes35and36, a dielectric thick film formed, for example, from glass or alumina or a resin film formed from polyimide may preferably be used, for example. These films described above may also preferably be formed, for example, by a printing, a transfer, or a photolithographic method.

In addition, the ferrite32may preferably be simultaneously fired together with the insulating film and the electrodes. In this case, the various electrodes are preferably made using Pd, Ag, or Pd/Ag, each of which can withstand high-temperature firing, for example.

As the permanent magnet41, a strontium-based, a barium-based, or a lantern-cobalt-based ferrite magnet is preferably used, for example. As the adhesive42which adheres the permanent magnet41to the ferrite32, a one-component type thermosetting epoxy adhesive is most preferably used, for example.

The substrate20is preferably made of the same type of material that is commonly used for a printed circuit board, for example, and the terminal electrodes21ato21dfor soldering the connection electrodes35b,35c, and36pof the ferrite-magnet element30and chip type matching circuit elements CS1and R (seeFIG. 5), input and output electrodes (not shown), and a ground electrode (not shown) are provided on the surface of the substrate20. In addition, inside the substrate20, matching circuit elements C1, C2, and CS2(seeFIG. 5) are preferably defined by internal electrodes.

The ferrite-magnet element30is disposed on the substrate20, the connection electrodes35b,35c, and36P provided on the bottom surface32dof the ferrite32are integrally connected to the terminal electrodes21a,21b, and21con the substrate20by reflow soldering, and the bottom surfaces of the permanent magnets41are integrally adhered to the substrate20with an adhesive, for example. In addition, the matching elements CS1and R are reflow-soldered to the terminal electrodes21b,21c, and21d.

The flat plate yoke10functions as an electromagnetic shield and is adhered to the top surface of the ferrite-magnet element30with the second resin layer60provided therebetween, which will be described below.

One circuit example of the isolator1is shown by an equivalent circuit inFIG. 5. An input port P1is connected to the matching capacitor C1and the terminal resistance R through the matching capacitor CS1, and the matching capacitor CS1is connected to one end of the first central electrode35. The other end of the first central electrode35and one end of the second central electrode36are connected to the terminal resistance R and the capacitors C1and C2and are further connected to an output port P2through the capacitor CS2. The other end of the second central electrode36and the capacitor C2are connected to a ground port P3.

In the two-port isolator1having the above-described equivalent circuit, one end of the first central electrode35is connected to the input port P1, the other end is connected to the output port P2, one end of the second central electrode36is connected to the output port P2, and the other end is connected to the ground port P3. Thus, a two-port lumped constant isolator having a low insertion loss is provided. In addition, during operation, a large high-frequency current flows through the second central electrode36, and a high-frequency current does not significantly flow through the first central electrode35.

In addition, since the ferrite32and a pair of the permanent magnets41are integrated with the adhesives42to define the ferrite-magnet element30, the mechanical properties thereof are stabilized, and thus, a robust isolator that is not deformed or damaged by vibration and/or impact is obtained.

Next, the first and second resin layers50and60will be described. As shown inFIGS. 6 and 7B, the first resin layer50is a liquid thermosetting resin (such as a fine-grain epoxy resin) at room temperature disposed at bonding portions of the ferrite-magnet element30bonded to the substrate20, and after being applied to the bonding portions, the liquid thermosetting resin is cured by heating. InFIGS. 6 and 7Ato7D, reference numeral55indicates bonding solder for the matching elements CS1and R, and reference numeral56indicates bonding solder for the connection electrodes35b,35c, and36pof the ferrite-magnet element30.

As shown inFIG. 7C, the second resin layer60is formed from a soft sheet-shaped thermosetting resin60′ (such as an epoxy resin) adhered to a rear surface of a mother yoke10′, which is a base material for the flat plate yokes10, and is obtained such that the thermosetting resin60′ is disposed on the surface of the substrate20while pressure is applied, is then softened, and is finally cured.

Next, a manufacturing process for the isolator1according to the first preferred embodiment including the steps of forming the first and the second resin layers50and60will be described.

First, a plurality of the ferrite-magnet elements30is bonded to a surface of a mother substrate20′ in a matrix so that the primary surfaces32aand32bof each ferrite32are disposed perpendicular or substantially perpendicular to the surface of the mother substrate20′, and the matching elements CS1and R are also bonded to the surface thereof (seeFIG. 7A). Next, a liquid resin is applied to the bonding portions of the ferrite-magnet elements30and the matching elements CS1and R which are bonded to the mother substrate20′ and is then cured, so that the first resin layer50is formed (seeFIG. 7B). The liquid resin is a liquid at room temperature and is cured, for example, by heating at approximately 165° C. for approximately 90 minutes. The first resin layer50is filled in gaps formed on the surface of the substrate20′ between the solder bonding portions of the ferrite-magnet elements30and the matching circuit elements CS1and R.

Next, as shown inFIG. 7C, after the mother yoke10′ provided with the soft sheet-shaped resin60′ which is adhered on the rear surface thereof is disposed on the upper surfaces of the ferrite-magnet elements30, the soft sheet-shaped resin60′ is softened and is then cured, so that the second resin layer60is formed. The soft sheet-shaped resin60′ is softened and is then cured by heating at approximately 150° C. for approximately 180 minutes while pressure is applied. When being softened, the soft sheet-shaped resin60′ enters gaps formed between the ferrite-magnet elements30and the matching circuit elements CS1and R and seals these elements from the outside (seeFIG. 7D).

In particular, the step of forming the second resin layer60is performed such that an oven in which an inside pressure can be set at a high level is used, and the inside pressure of the oven is increased, for example, to approximately 4 to 5 atmospheric pressure.

Subsequently, the mother substrate20′ and the mother yoke10′ are cut together along the dotted lines Y shown inFIG. 7D, and each unit obtained by cutting is used as the isolator1. In this step, cutting is also performed for each unit in a direction perpendicular or substantially perpendicular to the dotted lines Y.

As described above, according to this first preferred embodiment, since the periphery of the ferrite-magnet element30is sealed with the first and the second resin layers50and60, the influence of humidity is eliminated. Since the permanent magnets41are provided on the first and second primary surfaces32aand32bof the ferrite32which is provided with the central electrodes35and36, a yoke surrounding the side portions of the ferrite32is not always necessary. In addition, the first and the second resin layers50and60can be easily formed, respectively, by automatically applying a liquid resin and by applying a pressure to the sheet shaped resin60′ adhered to the mother yoke10′, followed by softening. Furthermore, since the substrates20and the flat plate yokes10are formed from the mother substrate20′ and the mother yoke10′, respectively, manufacturing can be efficiently performed by a multiple-elements forming method.

In particular, according to the first preferred embodiment, since the first resin layer50is formed at the bonding portions so as to have a relatively small thickness, the volume of a relatively expensive liquid resin can be decreased, and the mother substrate20′ does not warp as the liquid resin is cured.

Second Preferred Embodiment

FIG. 8is an exploded perspective view showing a two-port isolator2according to the second preferred embodiment of the nonreciprocal circuit device of the present invention. Since the two-port isolator2has substantially the same structure as that of the first preferred embodiment, the same elements and portion as those of the first preferred embodiment are designated by the same reference numerals, and a duplicated description will be omitted. The differences from the first preferred embodiment are that the first resin layer50has a relatively large thickness and the second resin layer60has a relatively small thickness.

That is, as shown inFIG. 9, the first resin layer50extends from the surface of the substrate20to the upper surface of the ferrite-magnet element30including the bonding portions of the ferrite-magnet element30and the matching circuit elements CS1and R which are bonded to the substrate20. The second resin layer60extends between the flat plate yoke10and the upper surface of the ferrite-magnet element30.

In a manufacturing process, first, a plurality of the ferrite-magnet elements30is bonded to the surface of the mother substrate20′ in a matrix so that the two primary surfaces32aand32bof the ferrite32are arranged perpendicular or substantially perpendicular to the surface of the mother substrate20′, and the matching circuit elements CS1and R are also bonded to the surface thereof (seeFIG. 10A). Next, a liquid resin is applied from the surface of the mother substrate20′ to the upper surfaces of the ferrite-magnet elements30and is then cured, so that the first resin layer50is formed (seeFIG. 10B). The height of the ferrite-magnet element30is approximately 0.5 mm, and the liquid resin does not flow out of end portions of the mother substrate20′ and enters gaps between the ferrite-magnet elements30. The heating temperature and the heating time for the liquid resin are approximately equivalent to those of the first preferred embodiment.

Subsequently, as shown inFIG. 10C, after the mother yoke10′ provided with the soft sheet-shaped resin60′ which is adhered to the rear surface thereof is disposed on the upper surfaces of the ferrite-magnet elements30, the soft sheet-shaped resin60′ is softened and is then cured, so that the second resin layer60is formed (seeFIG. 10D). In the step of forming the second resin layer60, an oven in which an inside pressure can be set at a high level may also preferably be used in the second preferred embodiment. However, since the second resin layer60is provided between the flat plate yoke10and the upper surface of the ferrite-magnet element30, the applied pressure, the heating temperature, and the heating time similar to those of the first preferred embodiment are not always necessary.

Next, the mother substrate20′ and the mother yoke10′ are cut together along the dotted lines Y shown inFIG. 10D, and each unit obtained by cutting is used as the isolator2. In this step, cutting is also performed for each unit in a direction perpendicular or substantially perpendicular to the dotted lines Y.

The function and the benefits of the isolator2according to the second preferred embodiment substantially the same as those of the first preferred embodiment. In particular, since the periphery of the ferrite-magnet element30is covered with the liquid resin, gaps are not formed at the above periphery, and since the second resin layer60is formed on a flat upper surface of the ferrite-magnet element30and the first resin layer50, the adhesion properties are greatly improved.

In addition, the nonreciprocal circuit device according to the present invention and the manufacturing method thereof are not limited to the preferred embodiments described above, and any changes and modifications may be made without departing from the spirit and the scope of the present invention.

In particular, the configuration of the matching circuit may be arbitrarily selected and all matching circuit elements may be provided on the substrate or may be embedded therein. In addition, in the ferrite-magnet element, the ferrite and the permanent magnets may be integrally fired.