JP2000124068A - Laminated-type noise filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated-type noise filter, which is compact and is superior in filtering characteristic at a high-frequency band. SOLUTION: This noise filter is constituted by ground electrode layers 7a, 7b and 7c, each constituted of a ground internal electrode 11 which has first extensions 12 and 13 on the inside of a ceramics layers 10 or 21 to arranged directions of outside grounding electrodes, respectively, and which is connected to the external grounding electrodes, a capacitor electrode layer 8 constituted of a pair of capacitor internal electrodes 14 and 15, having extensions 16 and 17 from oppositely facing edge parts in the directions of external electrodes respectively, to the central part on a ceramics layer 10, and an inductor electrode layer 9 constituted by an inductor internal electrode 22, which is connected to outside electrodes arranged opposite on a ceramics layer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized laminated noise filter for protecting electronic equipment from high-frequency noise.

[0002]

2. Description of the Related Art In recent years, with the increase in the frequency of information devices such as personal computers and digital devices and the like, it has become important to prevent high-frequency noise generated from them, and is typified by notebook computers and digital cameras. As described above, various electronic devices have been downsized, and there is a strong demand for downsized electronic components. Therefore, as a noise filter used in these electronic devices, a π-type filter composed of two capacitors and one inductor and a T-type filter composed of one capacitor and two inductors are generally used. It is disclosed in JP-A-5-235680. According to JP-A-5-235680, a capacitor component of a π-type filter is divided, and a ground-side capacitance electrode of the divided capacitor is connected to a plurality of external ground electrodes, which is generated on the external ground electrode side. The impedance of the residual inductance is made relatively small, so that high-frequency noise easily flows to the ground.

[0003]

However, according to the configuration similar to the above-mentioned Japanese Patent Application Laid-Open No. 5-235680, in a small size, the capacitor component and the inductor component, which are laminated, are apt to be electrically coupled, and the capacitor component and the inductor component are easily combined. However, they interfere with each other, so that the filter characteristics are deteriorated, and it is difficult to obtain the target characteristics in the miniaturization.

Accordingly, an object of the present invention is to provide a laminated noise filter which is small and has excellent filter characteristics in a high frequency band.

[0005]

In order to achieve this object, a laminated noise filter according to the present invention comprises a laminated body in which ceramic layers and internal electrode layers are alternately laminated to form a laminated body. Forming an external electrode and forming an external ground electrode on at least one of a front surface and a rear surface, wherein the laminate has a first extension inward on a ceramic layer in a direction in which the ground electrode is provided; A ground electrode layer formed by forming a grounded internal electrode connected to an external grounded electrode; and a pair of second extensions extending from the opposing edges in the direction in which the external electrodes are arranged on the ceramic layer toward the center. A capacitor electrode layer formed by forming a capacitor internal electrode having a portion, and an inductor electrode layer formed by forming an inductor internal electrode connecting the opposed external electrodes on a ceramic layer. The ground electrode layer is provided between the capacitor electrode layer and the inductor electrode layer and on the outer surfaces of the capacitor electrode layer and the inductor electrode layer, whereby a small-sized laminated layer having excellent filter characteristics in a high-frequency band is provided. A type noise filter is obtained.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is characterized in that ceramic layers and internal electrode layers are alternately stacked to form a laminate, and external electrodes are formed on opposing side surfaces of the laminate. An external ground electrode is formed on at least one of the front surface and the rear surface, and the laminate has a first extension inward on the ceramic layer in a direction in which the ground electrode is provided, and is connected to the external ground electrode. A capacitor internal electrode having a ground electrode layer formed with a ground internal electrode, and a pair of second extension portions each extending from the opposing edges in the direction of disposing the external electrodes on the ceramic layer toward the center; And an inductor electrode layer formed on the ceramics layer by forming an inductor internal electrode connecting the opposed external electrodes on the ceramic layer, and the ground electrode layer is formed of the capacitor electrode layer. A stacked noise filter provided between the capacitor electrode layer and the inductor electrode layer and on the outer surfaces of the capacitor electrode layer and the inductor electrode layer. With this configuration, the inductor electrode layer and the capacitor electrode layer are shielded by the ground electrode layer and interfere with each other. Thus, a small-sized multilayer noise filter having excellent attenuation characteristics in a high-frequency band can be obtained.

According to a second aspect of the present invention, the pair of extension portions of the capacitor electrode layer forms a gap without contacting on the ceramic layer, and the first and second extension portions are provided between the capacitor electrode layer and the ground electrode.
2. The multilayer noise filter according to claim 1, wherein a second capacitor is formed, and electric field coupling is performed in the gap, and an attenuation pole is formed by anti-resonance with an inductor component of the inductor electrode layer. As a result, the amount of attenuation in the high frequency band can be further increased, and a multilayer noise filter having excellent attenuation characteristics can be obtained.

According to a third aspect of the present invention, at least one of the first extension portions of the pair of capacitor electrode layers has a narrowed electrode width between both ends of the extension portions. With this configuration, a sudden change in impedance occurs at the constricted portion, and a capacitance component is added equivalently, so that the capacitor electrode layer can be reduced in size and the inductor component of the inductor electrode layer can be reduced. Interference is prevented, and a small stacked noise filter is obtained.

According to a fourth aspect of the present invention, a pair of extensions of the capacitor electrode layer are formed in a similar shape.
In this configuration, the impedance of the pair of extension portions is matched with each other, so that a multilayer noise filter having excellent noise attenuation characteristics without damaging a desired signal can be obtained.

According to a fifth aspect of the present invention, the inductor internal electrode layer of the inductor electrode layer is formed of a wide portion at both ends and a middle narrow portion, and the wide portion does not overlap with the internal electrode layer of the capacitor electrode layer. 2. The multilayer noise filter according to claim 1, wherein the characteristic impedance is changed abruptly at the portion where the width of the internal electrode of the inductor is changed, and a series inductor component is formed in an equivalent circuit. A large inductor can be obtained in the band, and the generation of stray capacitance between the inductor electrode layer and the ground electrode layer can be reduced, so that a small-sized laminated noise filter having excellent attenuation characteristics can be obtained.

According to a sixth aspect of the present invention, the external ground electrodes are formed on a pair of front and back surfaces of the laminate, and the first extension of the ground electrode layer is opposed to the pair of external ground electrodes. The internal electrodes are formed in a cross shape, and the pair of first electrodes
2. The multilayer noise filter according to claim 1, wherein said pair of external ground electrodes are connected to an edge of an extended portion of said multilayer body. Has the effect of shielding with the ground electrode,
Interference due to unnecessary radiation between the external electrodes can be reduced, and a multilayer noise filter having excellent attenuation characteristics can be obtained.

According to a seventh aspect of the present invention, the ceramic layer vertically adjacent to the inductor internal electrode of the inductor electrode layer is formed of a dielectric material having a lower dielectric constant than the ceramic layer of the capacitor electrode layer. 1. The laminated noise filter according to item 1, wherein the configuration further enhances the functions of the capacitor and the inductor, suppresses mutual electromagnetic field interference, and provides a compact laminated noise filter having excellent attenuation characteristics.

The invention according to claim 8 is the multilayer noise filter according to claim 1, wherein the ceramic layer of the inductor electrode layer is formed of a magnetic material. Since an inductor can be configured and deterioration of characteristics due to electromagnetic field interference can be suppressed, a small-sized laminated noise filter having excellent attenuation characteristics can be obtained.

According to a ninth aspect of the present invention, the inductor electrode layer is formed of one of a dielectric material and a magnetic material, and the ceramic layer of the capacitor electrode layer is formed of a varistor material. This is a multilayer noise filter. With this configuration, a surge absorber function is added to the frequency selection filter function, and a multilayer noise filter excellent in noise removal can be obtained.

According to a tenth aspect of the present invention, a ground electrode layer is arranged between the capacitor electrode layer and the inductor electrode layer, and their outer shapes overlap one another, and the ground electrode layer and the inductor electrode layer overlap each other. The multilayer noise filter according to claim 1, wherein the multilayer noise filter is a diffusion prevention layer between the electrode layers, and the multilayer noise filter can prevent deterioration of characteristics due to mutual diffusion of different materials.

[0016] In the eleventh aspect of the present invention, the uppermost layer and the lowermost layer of the laminate are formed of the same material layer selected from one of a magnetic substance, a dielectric substance, and a semiconductor, and are fired. The multilayer noise filter according to claim 1, wherein the configuration prevents damage such as warpage and delamination caused by a difference in shrinkage and sintering between different kinds of materials. can get.

According to a twelfth aspect of the present invention, in the laminate, an electrode paste mainly composed of Ag containing Ag or glass frit is used for the external electrode, and an electrode paste mainly composed of Ag is used for the internal electrode. The multilayer noise filter according to claim 1, wherein the external electrode is formed on the laminate before firing, and the external electrode and the laminate are fired simultaneously, and Ag having a high dielectric constant is used. Thereby, the conductor loss can be reduced and the insertion loss of the filter can be reduced. Further, by using the electrode material having a small insertion loss, the width of the internal electrode of the inductor electrode layer can be further reduced, and the size can be reduced.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an exploded perspective view of a laminated noise filter according to an embodiment of the present invention. FIG. 2 is an external view of the embodiment, FIG. 3 is a perspective view of the embodiment, and FIG.
Is an equivalent circuit diagram of the embodiment, FIG. 5 is a characteristic diagram of the embodiment, and FIG. 6 is a measurement circuit diagram of the characteristic evaluation.

First, the ceramic layer is made of a high dielectric constant ceramic layer made of a Bi-Zn-Cu-O-based powder having a dielectric constant of 100 and having a material composition that sinters at about 900 ° C. A low dielectric constant ceramic layer prepared by adding a forsterite glass component to a powder of a Bi-Zn-Cu-O-based material composition of Example 1 is prepared, and these components are used to form components. The condition of 900 ° C. is used in combination with an electrode paste described later (an electrode paste containing Ag as a main component) to improve workability.

In the external view of FIG. 2, reference numeral 1 denotes a multilayer noise filter. External noise electrodes 3 and 4 are formed on opposing side surfaces of a multilayer body 2 in the multilayer noise filter 1, and are provided on the front and rear surfaces, respectively. External ground electrodes 5 and 6 are formed. The specific configuration will be described with reference to the exploded perspective view of FIG.

In FIG. 1, 7a, 7b and 7c are ground electrode layers, 8 is a capacitor electrode layer, and 9 is an inductor electrode layer. The ground electrode layers 7a, 7b, 7c are arranged between the capacitor electrode layer 8 and the inductor electrode layer 9 and on the outer surface,
A capacitor that serves as a common ground electrode for the capacitor electrode layer 8 and has a function of preventing unnecessary interference between the inductor and the capacitor, and also has a function of preventing diffusion between the capacitor electrode layer 8 and the inductor electrode layer 9. It is.

The ground electrode layers 7a and 7c are printed on the above-described ceramic layer 10 having a high dielectric constant, and the ground electrode layer 7b is printed on the ceramic layer 21 having a low dielectric constant by printing an Ag paste inward. The grounding internal electrode 11 is formed in a cross shape by providing first extension portions 12 and 13 in the direction in which the external grounding electrodes 5 and 6 are arranged. The edge portions 12 and 13 are connected to the external ground electrodes 5 and 6 in an assembling process described later.

The capacitor electrode layer 8 is formed on the ground electrode layer 7.
a and 7b, and has a function of forming a large distributed capacitance and also forming an electric field coupling on the capacitor electrode layer 8. The capacitor electrode layer 8 is formed by printing an Ag paste on the above-mentioned ceramic layer 10 having a high dielectric constant to form a pair of internal electrodes 14 and 15. Second extension portions 16 and 17 extending from the disposition direction of 3 and 4 toward the center portion are provided, and the second extension portions 16 and 17 are respectively provided.
Reference numeral 17 designates constrictions 18 and 19 at the intermediate portion, and second extension portions 16 and 17 thereof are not connected at the central portion on the ceramic layer 10 to form a gap portion 20. The constriction 1
The formation of 8, 19 causes a rapid change in impedance and equivalently adds a capacitance component, whereby the size of the capacitor electrode layer 8 can be reduced. Also, by forming the gap 20, two capacitances are formed between the ground electrode layers 7a and 7b, and electric field coupling occurs in the gap 20, thereby causing interference of the inductor electrode layer 9. A sub-transmission line which is not affected by the noise is formed, and the anti-resonance with the inductor component of the inductor electrode layer 9 forms a still larger attenuation pole in the filter characteristic, thereby having an excellent effect of removing noise. In addition, since the internal electrodes 14 and 15 have similar shapes, impedance matching can be achieved, so that a desired signal is not impaired and noise attenuation characteristics are good.

The inductor electrode layer 9 includes the external electrodes 3 and
It has the function of forming an inductor between the four.
The inductor electrode layer 9 is formed by printing an Ag paste on the above-mentioned low dielectric constant ceramic layer 21 to form external electrodes 3 and 4.
Are formed at the edges where the internal electrodes 22 are arranged, and the inductor internal electrodes 22 are connected to the external electrodes 3 and 4 at a very narrow width.
An intermediate portion is formed by forming a narrow portion 25 having a narrow electrode width. As described above, a sudden change in impedance is caused by changing the electrode width, so that a series inductor component is added to the equivalent circuit, thereby enhancing the inductor function and preventing electromagnetic interference with the capacitor.

The uppermost layer 26 is an ineffective layer having no internal electrode layer, and is the ceramic layer 1 of the lowermost ground electrode layer 7c.
0 and the same ceramic layer constituting the ground electrode layers 7a and 7b, the capacitor electrode layer 8, the inductor electrode layer 9, etc., and the same material selected from any one of a dielectric material, a magnetic material, and a semiconductor. With this configuration, damages such as warpage and delamination due to the shrinkage ratio and sintering difference between different materials can be prevented, and the reliability is excellent.

The ground electrode layers 7a to 7 configured as described above
c, the capacitor electrode layer 8, the inductor electrode layer 9, and the ineffective layer 26 are stacked and pressurized to obtain the laminate 2 shown in FIG. 2, and thereafter, the external electrodes 3, 4 and the external ground electrode 5 of the laminate 2 are obtained. , 6 are coated with an electrode paste containing Ag or Ag containing glass frit as a main component and dried, and then the external electrodes 3, 4 and the external ground electrodes 5,
6 and the laminated body 2 are simultaneously fired to form a laminated noise filter 1.
Get. In this firing step, the laminate 2
Since the sintering temperature with the electrode paste containing Ag as a main component is adjusted by using each of the ceramic layers described above, simultaneous sintering can be performed at the same time, the manufacturing process can be shortened, and the productivity is good.

FIG. 3 is a perspective view of the same embodiment, showing ground electrode layers 7a, 7b. 7c shows an arrangement relationship between the inductor electrode layer 9 and the wide portions 23, 2 of the inductor electrode layer 9.
4 is a capacitor internal electrode 1 of the capacitor electrode layer 8
4 and 15 are arranged outside so as not to overlap with each other to reduce the occurrence of stray capacitance between the inductor electrode layer 9 and the ground electrode layers 7a, 7b and 7c, thereby obtaining a small-sized multilayer noise filter having excellent attenuation characteristics. It is configured as follows.

Next, an equivalent circuit diagram of the present embodiment will be described with reference to FIG. In FIG. 4, 3T and 4T correspond to FIG.
External electrode terminals corresponding to the external electrodes 3 and 4 of FIG.
T and 6T indicate external ground electrode terminals corresponding to the external ground electrodes 5 and 6, respectively. The external ground electrode terminals 5T, 6T
Between the pair of internal electrodes 14 and 15 of the capacitor electrode layer 8 to form an electrostatic capacitance C3.
Between the external ground electrode 5 and the external ground electrode terminal 5T, and between the external ground electrode 6 and the external ground electrode terminal 6T, a pair of capacitor internal electrodes 1 formed on the capacitor electrode layer 8 is provided.
4 and 15 constitute the capacitances C1 and C2 developed through the ceramic layer 10 having a high dielectric constant.

Reference numeral 7T (broken line) denotes a shield, which is formed by the ground electrode layers 7a, 7b, and 7c, electrically shields between the inductor L1 and the capacitances C1, C2, and C3. Capacitance C1, C2
Since the entire C3 is shielded so as to surround it, interference due to unnecessary radiation which is extremely important for handling high-frequency signals can be prevented, and a small stacked noise filter can be obtained.

The filter characteristics of the present embodiment are measured based on the measurement circuit diagram of FIG. 6, and the results are shown in FIG. 5 as characteristic examples. FIG. 5 shows that the frequency of 100 MHz to 10 GHz is passed through the multilayer filter of the present embodiment, and the voltage attenuation at each frequency is shown continuously. The attenuation curve A has an attenuation pole B, and the attenuation amount C is about 55 dB, which indicates an extremely excellent filter characteristic. Further, the frequency of the connection cord attenuating pole B can be adjusted by the distance of the gap 20 between the capacitor internal electrodes 14 and 15 of the capacitor electrode layer 8, so that the productivity is extremely good.

In the above-described embodiment, the ceramic layer 10 of the capacitor electrode layer 8 is described as a ceramic layer having a high dielectric constant. However, by using a material having a varistor characteristic, a surge of a voltage peak value selection type of noise can be obtained. A composite function as an absorber can be provided. If a magnetic material is used for the ceramic layer 21 of the inductor electrode layer 9, a larger inductor can be obtained, and the inductor electrode layer 9 can be reduced in size.

[0032]

As described above, according to the structure of the present invention, the capacitor component and the inductor component, which are laminated, do not interfere with each other to impair the filter characteristics, the insertion loss can be reduced, and the noise removal effect in the high frequency band can be reduced. Thus, a small-sized laminated noise filter having excellent characteristics can be obtained. Also, the frequency of the attenuation pole in the filter characteristics can be easily adjusted. It is possible to cope with filter characteristics unique to various electronic devices.

Further, by using the material for the ceramic layer of the present invention, damages such as warpage and delamination can be prevented in the laminating step, and a laminated noise filter excellent in reliability can be obtained. In addition, by using together with the prescribed electrode paste, after lamination, the laminate and the electrode paste can be simultaneously sintered to obtain predetermined characteristics, so that the productivity is extremely good.

Therefore, the multilayer noise filter of the present invention greatly contributes to miniaturization of various electronic devices and miniaturization and high performance of digital devices.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a laminated noise filter according to an embodiment of the present invention.

FIG. 2 is an external view of the embodiment.

FIG. 3 is a perspective view of the embodiment.

FIG. 4 is an equivalent circuit diagram of the embodiment.

FIG. 5 is a characteristic diagram of the embodiment.

FIG. 6 is a measurement circuit diagram of the characteristic evaluation.

[Explanation of symbols]

 Reference Signs List 1 laminated noise filter 2 laminated body 3, 4 external electrode 5, 6 external ground electrode 7a, 7b, 7c ground electrode layer 8 capacitor electrode layer 9 inductor electrode layer 10 ceramic layer 11 ground internal electrode 12, 13 first extension 14, 15 Capacitor internal electrode 16, 17 Second extension 18, 19 Constriction 20 Gap 21 Ceramic layer 22 Inductor internal electrode 23, 24 Wide part 25 Narrow part 26 Invalid layer

Continued on the front page F term (reference) 5E001 AB03 AC02 AC09 AF06 AH01 AH09 AJ01 AJ02 AJ03 AZ01 5E082 AA01 AB03 BB02 BC14 BC39 DD04 DD08 EE04 EE11 EE23 EE35 FG26 FG54 GG10 GG11 GG28 MM24

Claims (12)

[Claims] 1. A laminate in which ceramic layers and internal electrode layers are alternately stacked to form a laminate, external electrodes are formed on opposing side surfaces of the laminate, and external ground electrodes are formed on at least one of the front and back surfaces. A ground electrode layer formed by forming a grounding internal electrode connected to the external grounding electrode, the laminated body having a first extension inward of the grounding electrode in a direction in which the grounding electrode is provided; A capacitor electrode layer formed by forming a pair of second extension portions from the opposite edge portions in the disposition direction of the external electrodes toward the center portion on the layer, and a ceramic electrode layer; An inductor electrode layer formed by forming an inductor internal electrode connected between the opposed external electrodes,
A multilayer noise filter comprising the ground electrode layer provided between the capacitor electrode layer and the inductor electrode layer and on the outer surfaces of the capacitor electrode layer and the inductor electrode layer. 2. A pair of extensions of a capacitor electrode layer forms a gap without contacting on a ceramic layer, and forms first and second capacitors between the capacitor electrode layer and the grounding internal electrode. 2. The multilayer noise filter according to claim 1, wherein electric field coupling is performed in a gap portion of the extension portion of the first layer, and an attenuation pole is formed by anti-resonance with an inductor component of the inductor electrode layer. 3. The multilayer noise filter according to claim 1, wherein at least one of the pair of first extension portions of the capacitor electrode layer has a narrowed electrode width between both ends of the extension portion. 4. The multilayer noise filter according to claim 1, wherein a pair of extensions of the capacitor electrode layer are formed in a similar shape. 5. An internal electrode layer of the inductor electrode layer is formed of a wide portion at both ends and a narrow portion in the middle, and the wide portion is disposed outside so as not to overlap with the internal electrode layer of the capacitor electrode layer. Item 2. The stacked noise filter according to Item 1. 6. An external ground electrode is formed in a pair of a front surface and a rear surface of the laminate, and a first extension of a ground electrode layer is provided to face the pair of external ground electrodes, and an internal electrode is formed in a cross shape. 2. The multilayer noise filter according to claim 1, wherein the end portions of the pair of first extension portions are connected to the pair of external ground electrodes. 3. 7. The laminated noise according to claim 1, wherein a ceramic layer vertically adjacent to the inductor internal electrode of the inductor electrode layer is formed of a dielectric material having a lower dielectric constant than the ceramic layer of the capacitor electrode layer. filter. 8. The multilayer noise filter according to claim 1, wherein the ceramic layer of the inductor electrode layer is formed of a magnetic material. 9. The multilayer noise according to claim 1, wherein the ceramic layer of the inductor electrode layer is formed of one of a dielectric material and a magnetic material, and the ceramic layer of the capacitor electrode layer is formed of a varistor material. filter. 10. A ground electrode layer is arranged between a capacitor electrode layer and an inductor electrode layer, and their outer shapes are identically overlapped, and the ground electrode layer is provided with a diffusion preventing layer between the capacitor electrode layer and the inductor electrode layer. The stacked noise filter according to claim 1. 11. The laminate according to claim 1, wherein the uppermost layer and the lowermost layer of the laminate are formed of the same material layer selected from one of a magnetic substance, a dielectric substance, and a semiconductor, and are fired. Type noise filter. 12. A laminate before firing, wherein an electrode paste containing Ag or Ag containing glass frit as a main component is used for an external electrode and an electrode paste containing Ag as a main component is used for an internal electrode. The multilayer noise filter according to claim 1, wherein the external electrode is formed on the external electrode, and the external electrode and the laminate are simultaneously fired.