JP2000261272A - Low pass filter and electronic apparatus using this filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low pass filter, where extents of attenuation in a low frequency area and a high frequency area can be simultaneously secured, and an electronic apparatus using this filter. SOLUTION: A low pass filter 10 is provided with a laminate 11 where dielectric layers 111 to 116 having a low dielectric constant (dielectric constant: 6) are laminated, and inductor electrodes 121 to 123, capacitor electrodes 131 and 132, and a ground electrode 14 are provided in the laminate 11. In this case, only the area between capacitor electrodes 131 and 132 and the ground electrode 14 is formed with a dielectric layer 16 of a high dielectric constant (dielectric constant: 350). External terminals Ta and Tc to which one ends of inductor electrodes 121 and 123 are connected respectively from the upper face to the lower face on the minor axis side of the laminate 11 and external terminals Tb and Td to which the ground electrode 14 are connected from the upper face to the lower face in the major axis side are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pass filter and an electronic apparatus using the same, and more particularly, to improving the noise characteristic by increasing the dielectric constant of a capacitor forming area higher than that of an inductor forming area. The present invention relates to a low-pass filter and an electronic device using the same.

[0002]

2. Description of the Related Art With the rapid spread of electronic devices, there is a strong demand for improvements in the performance of electronic devices. For general electronic circuits, as more and more circuit elements are housed in one chip and miniaturization progresses, unnecessary noise generated from circuit parts of electronic equipment, especially low-pass filters in the tens of MHz band There is a strong demand for miniaturization. In addition, there is a more urgent need to solve existing problems such as reduction of manufacturing costs and simplification of the overall manufacturing process.

FIG. 9 is a sectional view of a conventional low-pass filter. The low-pass filter 50 includes an inductor unit 51 and a capacitor unit 52. The inductor unit 51 includes:
A plurality of inductor electrodes 54 are formed by alternately laminating the magnetic layers 53 and the inductor electrodes 54, and are superimposed in a laminated body composed of the magnetic layers 53. The capacitor section 52 is formed by alternately stacking dielectric layers 55 and capacitor electrodes 56,
A plurality of capacitor electrodes 56 are provided in a laminate made of the dielectric layer 55. The inductor portion 51 and the capacitor portion 52 are joined to each other to form a composite 57, and the side surface of the composite 57 is connected to the inductor electrode 54 of the inductor portion 51 and the capacitor electrode 56 of the capacitor portion 52. An external electrode 58 is provided.

FIG. 10 is a sectional view of another conventional low-pass filter. The low-pass filter 60 includes an inductor section 61 and a capacitor section 62. Inductor section 6
1 is formed by alternately laminating the dielectric layers 63 and the inductor electrodes 64, and is provided with a plurality of inductor electrodes 64 that are superimposed in a laminated body composed of the dielectric layers 63. The capacitor section 62 is formed by alternately stacking the dielectric layers 63 and the capacitor electrodes 65, and a plurality of capacitor electrodes 65 are provided in a stacked body including the dielectric layers 63. Then, the inductor section 61
And the capacitor portion 62 are joined to each other to form a composite 66, and the inductor portion 61
An external electrode 67 is provided for connecting the inductor electrode 64 of FIG. Note that the dielectric constant of the dielectric layer in the region sandwiched between the capacitor electrodes 65 is equal to the dielectric constant of the dielectric layer in the other region.

[0005] The low-pass filters 50 and 60 thus formed can be made smaller than the case where the inductor component and the capacitor component are separately formed, are suitable for high-density mounting, and have a low manufacturing cost. It is also excellent in reduction and simplification of the whole manufacturing process.

[0006]

However, in the above-mentioned conventional low-pass filter, if the frequency characteristic of the magnetic permeability of the magnetic layer constituting the inductor part exceeds 200 MHz, it deteriorates. If an attempt is made to ensure the amount of attenuation, spurious components occur in the low frequency region. As a result, there is a problem that it is difficult to simultaneously secure the attenuation in the low frequency region and the high frequency region.

In another conventional low-pass filter, the inductor portion is provided in a laminate composed of a dielectric layer having the same dielectric constant as the capacitor portion. When the dielectric constant of the dielectric layer forming the capacitor portion is increased, a self-resonant circuit is formed by the inductance component L and the capacitor component C in the inductor portion, and the self-resonant frequency f0 (= 1 /
In a high frequency region of 2π (LC · ^1/2 ) or more, the inductor works not as a coil but as a capacitor. As a result, there is a problem that it is difficult to secure the attenuation in the high frequency region.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a low-pass filter capable of simultaneously securing attenuation in a low-frequency region and a high-frequency region, and an electronic device using the same. The purpose is to provide equipment.

[0009]

In order to solve the above-mentioned problems, a low-pass filter according to the present invention comprises: a laminate formed by laminating dielectric layers; an inductor electrode provided inside the laminate; A capacitor electrode and a ground electrode provided to face each other with the dielectric layer interposed therebetween in the multilayer body, an inductor is formed by the inductor electrode, and a capacitor is formed by the capacitor electrode and the ground electrode. In the low-pass filter, a dielectric layer in a region between at least one of the capacitor electrodes and the ground electrode has a higher dielectric constant than a dielectric layer in another region.

[0010] Further, a laminate formed by laminating dielectric layers,
An inductor electrode provided inside the laminate, a capacitor electrode and a ground electrode provided opposite to each other with the dielectric layer interposed inside the laminate, forming an inductor with the inductor electrode; In a low-pass filter in which a capacitor is formed by a capacitor electrode and the ground electrode, a dielectric layer in a region between at least one of the capacitor electrodes and the ground electrode has a dielectric constant in another region. Higher than the dielectric constant of
The dielectric constant of the dielectric layer in a region between the rest of the capacitor electrode and the ground electrode is the same as the dielectric constant of the dielectric layer in the other region.

An electronic device according to the present invention is characterized by using the above-mentioned low-pass filter.

According to the low-pass filter of the present invention, the dielectric constant between at least one of the capacitor electrodes forming the capacitor and the ground electrode is higher than the dielectric constant of the dielectric in other regions. , A large-capacity capacitor can be formed. In addition, the inductor can be formed inside a laminate composed of a dielectric layer having a low dielectric constant.

According to the electronic apparatus of the present invention, since a low-pass filter capable of obtaining sufficient attenuation from a low frequency region of several tens of MHz to a high frequency band of several GHz is used, signals in unnecessary bands such as noise are used. Can be removed, and as a result, an electronic device having excellent noise characteristics can be provided.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are a perspective view and a sectional view, respectively, of a first embodiment of a low-pass filter according to the present invention.
The low-pass filter 10 includes a barium oxide having a dielectric constant of 6,
A laminated body 11 is formed by laminating dielectric layers 111 to 116 made of a dielectric ceramic containing aluminum oxide and silica as main components.

An inductor electrode 12 is provided inside the laminate 11.
1 to 123, capacitor electrodes 131 and 132, and a ground electrode 14. The inductor electrode 121 and the capacitor electrode 131, the inductor electrode 122 and the capacitor electrode 132, the inductor electrode 121 and the inductor electrode 12 are provided.
2, the inductor electrode 122 and the inductor electrode 123
Are connected by via-hole electrodes 15, respectively. The capacitor electrodes 131 and 132 and the ground electrode 14 face each other.

At this time, only the region between the capacitor electrodes 131 and 132 and the ground electrode 14 is
It is formed by a dielectric layer 16 made of a dielectric ceramic mainly composed of barium oxide, neodymium oxide, and titanium oxide having a dielectric constant 350 higher than the dielectric constant 6 of の 116.

External terminals Ta to Td are provided from the upper surface to the lower surface of the multilayer body 11, and one ends of inductor electrodes 121 and 123 are connected to the external terminals Ta and Tc on the short axis side of the multilayer body 11, respectively. Although not provided, the ground electrode 14 is connected to the external terminals Tb and Td on the long axis side of the multilayer body 11.

With the above-described configuration, the dielectric constant of the dielectric layer 16 in the region between the capacitor electrodes 131 and 132 and the ground electrode 14 within the multilayer body 11 is changed to the dielectric layer in the other region. A low-pass filter 10 having a dielectric constant higher than 111 to 116 can be formed.

As shown in FIG. 3, the low-pass filter 10 includes an inductor L composed of inductor electrodes 121 to 123 provided on dielectric layers 113 to 115 having a low dielectric constant, and an inductor L having a high dielectric constant. An equivalent circuit is obtained in which the capacitors C1 and C2, which include the capacitor electrodes 131 and 132 and the ground electrode 14 with the dielectric layer 16 interposed therebetween, are connected in a π-type. The size of the low-pass filter 10 is
It is extremely small, 4.5 × 3.2 × 0.9 (mm).

FIG. 4 shows the attenuation characteristics of the low-pass filter of FIG. At this time, the inductor L of the low-pass filter 10 is about 150 nH, and the capacitors C1 and C2 are about 445 pH.
F.

From this figure, it can be seen that an attenuation of 40 dB or more is obtained at 50 MHz, and an attenuation of about 30 dB is obtained even at around 3 GHz. That is, the spurious in the low frequency region is suppressed, and the low frequency region of several tens MHz is reduced to several GHz.
Sufficient attenuation is obtained up to the high frequency band.

FIG. 5 is a manufacturing process diagram of the low-pass filter of FIG. First, as shown in FIG. 5A, six dielectric layers 111 to 116 made of a dielectric ceramic containing barium oxide, aluminum oxide and silica as main components are prepared.

Next, as shown in FIG. 5B, a via hole 17 is punched in the dielectric layers 113 to 115. At the same time, punching of the dielectric layer forming holes 18 is performed on the dielectric layer 112. Next, the dielectric layer forming hole 18 of the dielectric layer 112 is filled with a dielectric ceramic paste containing barium oxide, neodymium oxide, and titanium oxide as main components to form the dielectric layer 16 having a high dielectric constant.

Next, as shown in FIG. 5C, a conductive paste such as copper or a copper alloy is filled in the via holes 17 of the dielectric layers 113 to 115 to form via hole electrodes 15. Next, on the upper surfaces of the dielectric layers 111 to 115,
A conductor paste such as copper or a copper alloy is screen-printed, and the inductor electrodes 121 to 123 and the capacitor electrode 1 are printed.
31 and 132 and the ground electrode 14 are formed.

Next, as shown in FIG. 5D, after sequentially stacking the dielectric layers 111 to 116, the layers are baked at a temperature of about 900 ° C. in a reducing atmosphere while applying pressure from above to obtain a laminate. 11 is formed. Then, a conductor paste such as copper or a copper alloy is screen-printed and baked on the side surfaces of the laminate 11 to form the external terminals Ta to Td, thereby completing the low-pass filter 10.

According to the low-pass filter of the first embodiment, the dielectric constant of the dielectric between at least one of the capacitor electrodes forming the capacitor and the ground electrode is different from that of the dielectric in other regions. Therefore, a large-capacity capacitor can be formed. Also, the inductor can be formed inside a dielectric having a low dielectric constant.

Therefore, the spurious in the low frequency region can be suppressed, and the inductor can work as a coil in the low frequency region and the high frequency region. Therefore, sufficient attenuation can be provided from a low frequency region of several tens of MHz to a high frequency band of several GHz. Obtainable. That is, deterioration of the attenuation characteristic of the low-pass filter can be prevented.

Further, since the dielectric constant between the capacitors is low due to the high dielectric constant, the stray capacitance between the capacitors can be suppressed, and the characteristics of the low-pass filter can be improved. it can.

Further, by setting the dielectric constant of the dielectric layer in a region between the capacitor electrode and the ground electrode to a desired value, the value of the capacitor of the low-pass filter can be controlled. Can easily be controlled to desired characteristics.

Further, since the low-pass filter includes a laminated body formed by laminating dielectric layers, the number of dielectric layers is increased or decreased to reduce the number of dielectric layers and the inductor electrodes and capacitors constituting the inductor of the low-pass filter. The number of constituent capacitor electrodes can be increased or decreased, and the characteristics of the low-pass filter can be easily set to desired characteristics.

Furthermore, if this low-pass filter is used in an electronic device, signals in unnecessary bands such as noise can be removed, so that an electronic device having excellent noise characteristics can be provided.

FIG. 6 is a sectional view of a second embodiment of the low-pass filter according to the present invention. Low-pass filter 20
Has a laminated body 21 formed by laminating dielectric layers 211 to 216 made of a dielectric ceramic mainly composed of barium oxide, aluminum oxide, and silica having a dielectric constant of 6.

An inductor electrode 22 is provided inside the laminate 21.
1 to 225, capacitor electrodes 231 to 233, and a ground electrode 24. The inductor electrode 221 and the capacitor electrode 231, the inductor electrodes 222 and 223 and the capacitor electrode 232, the inductor electrode 225 and the capacitor electrode 233, the inductor electrode 221 and the inductor electrode 2
22, an inductor electrode 222 and an inductor electrode 223,
In addition, the inductor electrode 224 and the inductor electrode 225 are connected by the via hole electrode 25, respectively. The capacitor electrodes 231 to 233 and the ground electrode 24 face each other.

At this time, only the region between the capacitor electrodes 231 and 232 and the ground electrode 24 is
The dielectric layer 26 is made of a dielectric ceramic containing barium oxide, neodymium oxide, and titanium oxide having a dielectric constant 350 higher than the dielectric constant 6 of ６216.

External terminals Ta to Td are provided from the upper surface to the lower surface of the multilayer body 21, and one ends of inductor electrodes 221 and 225 are connected to the external terminals Ta and Tc on the short axis side of the multilayer body 21, respectively. However, the ground electrode 24 is connected to the external terminals Tb and Td on the long axis side of the laminate 21.

With the above-described structure, the dielectric constant of the dielectric layer 26 in the region between the capacitor electrodes 231 and 232 and the ground electrode 24 inside the multilayer body 21 is reduced. A low-pass filter 20 having a higher dielectric constant than 211 to 216 can be formed.

As shown in FIG. 7, the low-pass filter 20 includes inductors L1 and L2 formed of inductor electrodes 221 to 225 provided on dielectric layers 213 to 215 having a low dielectric constant, and high dielectric constants. Electrodes 231 and 232 and the ground electrode 2 sandwiching the dielectric layer 26
4 and a capacitor electrode 233 with a low dielectric constant dielectric layer 212 interposed therebetween.
And a low-capacitance capacitor C3 composed of the ground electrode 24 and an n-type capacitor.

The method for manufacturing the low-pass filter 20 is the same as the method for manufacturing the low-pass filter 10 shown in FIG.

FIG. 8 shows the attenuation characteristics of the low-pass filter of FIG. At this time, the inductor L1 of the low-pass filter 20 is about 150 nH, the inductor L2 is about 10 nH, the capacitors C1 and C2 are about 445 pF, and the capacitor C3 is about 4 pF.

From this figure, in addition to the characteristics of the low-pass filter 10 of the first embodiment, an attenuation of 50 dB or more is obtained near 3 GHz, and 40 dB from 50 MHz to 3 GHz.
It can be seen that the above attenuation is sufficiently obtained. That is, more sufficient attenuation is obtained from a low frequency region of several tens of MHz to a high frequency band of several GHz.

According to the low-pass filter of the second embodiment, the inductor and the small-capacitance capacitor of the low-pass filter are formed inside the laminated body composed of the dielectric layers having the low dielectric constant. Therefore, the amount of attenuation in the high frequency region can be secured by the LC resonance circuit including the inductor and the small-capacity capacitor, and as a result, the attenuation in the high frequency region can be further improved. Therefore, more sufficient attenuation can be obtained from a low frequency region of several tens of MHz to a high frequency band of several GHz.

In the low-pass filters of the first and second embodiments, the dielectric layer having a high dielectric constant is made of a dielectric ceramic containing barium oxide, neodymium oxide and titanium oxide as main components. Although the case has been described, the dielectric layer is not limited to these materials,
Dielectric ceramics having a dielectric constant of about 10 to 20 containing magnesium oxide as a main component, and dielectric ceramics containing bismuth oxide as a main component having a dielectric constant of about 400 to 500 have higher dielectric constants than dielectric layers constituting a laminate. Is higher, the same effect can be obtained.

Further, the case where the dielectric layers having a high dielectric constant are formed of the same dielectric ceramic has been described. However, even if the dielectric layers are formed of different dielectric ceramics, the dielectric layers have higher dielectric constants than the dielectric layers forming the laminate. The same effect can be obtained if it is high.

[0044]

According to the low-pass filter of the first aspect,
Since the dielectric constant of the dielectric between the capacitor electrode and the ground electrode is higher than the dielectric constant of the dielectric in other regions, a large-capacity capacitor can be formed. In addition, the inductor can be formed inside a laminate composed of a dielectric layer having a low dielectric constant.

Therefore, the spurious in the low frequency region can be suppressed, and the inductor can function as a coil in the low frequency region and the high frequency region. Therefore, sufficient attenuation can be provided from the low frequency region of several tens of MHz to the high frequency band of several GHz. Obtainable.

In addition, since the dielectric constant between the capacitors is low due to the high dielectric constant, the stray capacitance between the capacitors can be suppressed, and the characteristics of the low-pass filter can be improved. it can.

Further, by setting the dielectric constant of the dielectric layer in the region between the capacitor electrode and the ground electrode to a desired value, the value of the capacitor of the low-pass filter can be controlled. Can easily be controlled to desired characteristics.

Further, since the low-pass filter has a laminated body formed by laminating dielectric layers, the number of dielectric layers is increased or decreased to reduce the number of dielectric layers and the inductor electrodes and capacitors constituting the inductor of the low-pass filter. The number of constituent capacitor electrodes can be increased or decreased, and the characteristics of the low-pass filter can be easily set to desired characteristics.

According to the low-pass filter of the second aspect, the dielectric constant of the dielectric between at least one of the capacitor electrodes and the ground electrode is higher than the dielectric constant of the dielectric in the other region, and Since the dielectric constant of the dielectric between the rest and the ground electrode is the same as the dielectric constant of the dielectric in the other region, large-capacity and small-capacity capacitors can be formed inside the same laminate. . In addition, the inductor can be formed inside a laminate composed of a dielectric layer having a low dielectric constant.

Therefore, the spurious in the low frequency region is suppressed, the attenuation in the high frequency region is improved, and the inductor can function as a coil in the low frequency region and the high frequency region. Since the amount of attenuation in the high frequency region can be secured by the LC resonance circuit, more sufficient attenuation can be obtained from a low frequency region of several tens of MHz to a high frequency band of several GHz.

According to the electronic device of the third aspect, several tens of MHz
Since a low-pass filter that can obtain sufficient attenuation from a low frequency region to a high frequency band of several GHz is used, signals in unnecessary bands such as noise can be removed, and as a result, excellent noise characteristics can be obtained. An electronic device can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a low-pass filter according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the low-pass filter of FIG. 1 taken along line II-II.

FIG. 3 is an equivalent circuit diagram of the low-pass filter of FIG.

FIG. 4 is a diagram illustrating an attenuation characteristic of the low-pass filter of FIG. 1;

FIG. 5 is a diagram showing a manufacturing process of the low-pass filter of FIG. 1;

FIG. 6 is a sectional view of a low-pass filter according to a second embodiment of the present invention.

FIG. 7 is an equivalent circuit diagram of the low-pass filter of FIG.

FIG. 8 is a diagram illustrating an attenuation characteristic of the low-pass filter of FIG. 6;

FIG. 9 is a sectional view showing a conventional low-pass filter.

FIG. 10 is a sectional view showing another conventional low-pass filter.

[Explanation of symbols]

 10, 20 Low-pass filter 11, 21 Electric capacitor 111-116 Dielectric layer 121-123, 221-225 Inductor electrode 131, 132, 231-233 Capacitor electrode 14, 24 Ground electrode 16, 26 High permittivity dielectric Body layer L, L1, L2 Inductor C1-C3 Capacitor

Continued on the front page F-term (reference) 4E351 AA07 BB03 BB17 BB22 BB26 BB49 CC11 CC20 CC31 CC35 DD04 DD21 DD41 EE01 GG09 5E070 AA05 AB07 CB03 CB13 CB17 CB20 DB08 EA01 5E082 AA01 AB03 BB01 BC40 DG60 EG04 FG06 FG06 FG04 FG06 FG04 FG04 FG04 FG04 FG04 FG04 FG04 FG06 5E346 AA02 AA03 AA12 AA13 AA43 BB02 BB04 CC17 CC21 CC32 DD07 DD13 EE01 FF01 FF22 FF28 GG05 GG19 GG28 HH01 HH22 5J024 AA01 BA01 DA04 DA21 DA35 EA01 EA08 KA02

Claims (3)

[Claims] 1. A laminated body formed by laminating dielectric layers, an inductor electrode provided inside the laminated body, and a capacitor electrode provided inside the laminated body so as to face each other with the dielectric layer interposed therebetween. And a ground electrode, wherein the inductor electrode forms an inductor, and the capacitor electrode and the ground electrode form a capacitor. In a low-pass filter, a dielectric in a region between the capacitor electrode and the ground electrode is provided. A low-pass filter, wherein a dielectric constant of a body layer is higher than a dielectric constant of a dielectric layer in another region. 2. A laminate comprising laminated dielectric layers, an inductor electrode provided inside the laminated body, and a capacitor electrode provided inside the laminated body so as to face each other with the dielectric layer interposed therebetween. A low-pass filter comprising: an inductor formed by the inductor electrode; and a capacitor formed by the capacitor electrode and the ground electrode, wherein at least one of the capacitor electrodes is connected to the ground electrode. The dielectric constant of the dielectric layer in the region is higher than the dielectric constant of the dielectric layer in the other region, and the dielectric constant of the dielectric layer in the region between the rest of the capacitor electrode and the ground electrode is
A low-pass filter having the same dielectric constant as the dielectric layer in the other region. 3. An electronic apparatus using the low-pass filter according to claim 1.