JP2620840B2 - Manufacturing method of coaxial laminated dielectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a coaxial dielectric filter in a laminated form, and more specifically, to an internal electrode pattern corresponding to a cross section of a resonator on each green sheet. The present invention relates to a method for manufacturing a laminated dielectric filter in which a via connection portion for connecting between the layers is formed, and after lamination and integration, firing is performed to form an inner conductor. The laminated dielectric filter is suitable for a mobile communication device for microwaves, for example.

[0002]

2. Description of the Related Art One type of microwave filter is a coaxial dielectric filter. The conventional coaxial dielectric filter has a substantially rectangular parallelepiped dielectric block in the longitudinal direction,
It has a structure in which a plurality of resonator holes are provided, and an inner surface of the resonator holes is metallized to form an inner conductor. For example, in the case of a comb-line quarter-wavelength resonance type, one of the surfaces of the dielectric block where the resonator hole is opened is an open surface, and the other outer surface is metallized to increase the height of the resonator hole. It has an integral structure in which a plurality of resonance elements having a resonance wavelength four times as long as the resonance element are formed. In this dielectric filter, each resonator hole corresponds to each individual resonance element, and a coupling adjustment hole is provided between the resonator holes, or a coupling adjustment pattern is provided on the open surface, whereby the resonators are connected to each other. Are adjusted to achieve desired filter characteristics. In addition, there is an interdigital type in which an open surface and a short-circuit surface are alternately provided on the end face of the resonator hole of the dielectric block.

In these dielectric filters, a dielectric block serving as a base is made of a high dielectric constant ceramic material such as barium titanate. Forming process. After firing, a conductive paste is applied to the inner surface and the outer surface of the resonator hole and baked to form a metallized layer.

[0004]

With the recent miniaturization of communication equipment, this type of dielectric filter is also required to be significantly miniaturized. Theoretically, miniaturization is possible by using a material having a high dielectric constant. However, of course, this also makes the cavity smaller, which makes not only difficult to press-mold, but also makes it extremely difficult to apply a conductive paste with a uniform thickness to the wall surface of the small cavity. Further, when the model is changed, the shape of the dielectric block also changes, and a press die corresponding to the shape is required, so that the manufacturing cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coaxial laminated dielectric filter which is suitable for miniaturization, can incorporate a circuit pattern and the like therein, can achieve high functionality, and can reduce the cost.

[0006]

According to the present invention, a green sheet made of a high dielectric material is provided with an internal electrode pattern having a size corresponding to a cross section of a coaxial resonator, and a through hole located in the internal electrode pattern. A via connection part with embedded material is formed, a large number of the green sheets are laminated and press-integrated, fired, and coaxial to form an inner conductor by conducting each internal electrode mutually at the via connection part. This is a method for manufacturing a multilayer laminated dielectric filter. Here, it is preferable that a recess slightly larger than the internal electrode pattern is provided on the surface of the green sheet, and the internal electrode pattern is formed in the recess.

[0007]

[Function] An internal electrode pattern is provided on a green sheet,
Simply laminating and firing does not function as a dielectric resonator. However, when the internal electrode patterns are connected to each other by a conductor, a resonator having a half-wavelength is obtained in an open-ended structure or a short-circuited structure, and a resonator having an open end and a short-circuited end is formed.
It becomes a four-wavelength resonator. When a plurality of stages are arranged in parallel, a multistage filter is obtained by adding a coupling circuit or the like.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory drawing showing an embodiment of the method of the present invention, and is an example of a two-stage filter. Although the method of the present invention is actually carried out in a multi-cavity system, a single-cavity system will be described below in order to simplify the description and the drawings. This dielectric filter is manufactured by stacking a large number of green sheets 10 made of a high dielectric constant material, integrating them under pressure, and then firing. Green sheet 1
0 is, for example, a mixture of a high-permittivity material powder for microwaves such as barium titanate and an organic binder and the like, formed into a sheet (eg, about 80 to 200 μm thick) by a doctor blade method, a roll rolling method, or the like. It is a molded unsintered product.

The green sheet 10 has two internal electrode patterns 12 each having a size corresponding to the cross section of the coaxial resonator.
Nine via connection portions 14 (one at the center and eight at the periphery) are formed at the positions in both internal electrode patterns 12 respectively. FIG. 2 shows the details of this part. The internal electrode pattern 12 is obtained by printing a silver paste or the like on the green sheet 10 by a screen printing method. Here, the internal electrode pattern 12 is a circular pattern, but may be a rectangular pattern.
The via connection portion 14 is formed by forming a minute through hole in the green sheet 10 and filling the inside thereof with a conductive material (actually, a paste containing a conductive material powder such as silver particles).
The manufacturing order is arbitrary. The internal electrode pattern 12 may be provided first, then the through hole may be formed, the conductive material may be filled to form the via connection portion 14, or the through hole may be formed first. The application of the internal electrode pattern and the filling of the through-hole may be performed simultaneously with the same material (eg, silver paste). For example, when the thickness of the green sheet 10 is about 80 μm, the diameter of the through hole is about 0.1 to 0.2 mm. If the hole diameter is too large, the filler will fall off. On the other hand, if the hole diameter is too small, complete filling cannot be performed. Such a hole can be accurately formed at once by a punch or the like.

A large number of the green sheets 10 having the internal electrode patterns 12 and the via connection portions 14 formed thereon are laminated, pressed and integrated by a press, and then fired. And it becomes the inner conductor of the coaxial resonator. An outer conductor of the coaxial resonator is formed by applying and baking a conductive paste to the outer surface of the integrally sintered product. In a structure in which both ends of the inner conductor are open or short-circuited, a resonator of １ ／ wavelength is provided. In a structure in which one end is opened and the other end is short-circuited, a resonator of １ ／ wavelength is provided.

When the internal electrode pattern 12 is formed on the surface of the green sheet 10, as shown in FIG. 3, a recess 16 slightly larger than the internal electrode pattern 12 is provided, and the internal electrode pattern 12 is formed in the recess 16. Preferably, it is formed. The depth of the depression 16 may be substantially the same as the printing thickness of the internal electrode pattern 12. FIG. 4A shows a cross section before sintering. Although the printing thickness is exaggerated here, the printing thickness of the internal electrode pattern 12 is actually 10 μm.
m. In screen printing, an internal electrode pattern having a clear and clean edge is obtained (FIG. 4B).
The edge flows and spreads because it melts a little in the sintering process (Fig. 4
C). If there is no dent, the expansion is not regulated because it is not regulated. It will be easier to obtain. Further, since the electrodes are embedded in the depressions on the sheet, they do not expand even when they are laminated, and the outer surface can be formed flat.

FIGS. 5 to 12 show an embodiment of a comb line type dielectric filter according to the present invention. Since the basic configuration is the same as that of FIG. 1, corresponding portions are denoted by the same reference numerals, and description thereof will be omitted. In the example shown in FIG. 5, a coupling adjustment pattern 18 is provided at a position between the internal electrode patterns 12 of the uppermost green sheet 10. Both coupling adjustment patterns 18 have a shape in which one end reaches the side surface and the other end extends toward the center. The coupling adjustment pattern 18 may be formed by a screen printing method at the same time when the internal electrode pattern is provided on the green sheet.
As for the sintered product, as shown in FIG. 6A, the surface on which the coupling adjustment pattern 18 is formed (upper surface) is an open surface, and the outer conductor 20 is provided on the other outer surfaces (lower surface and four side surfaces). FIG. 6B is a longitudinal section thereof. The inner conductor is indicated by reference numeral 21. When the coupling adjustment pattern 18 is formed on the open surface,
A coupling capacitance is generated between the ground electrode formed by the coupling adjustment pattern 18 and the outer conductor 20 and each inner conductor open end, and these are coupled to each other. Therefore, desired filter characteristics can be realized by adjusting the shape (length and width) of the coupling adjustment pattern 18 without providing coupling holes.
The green sheet having the bonding adjustment pattern is
It may be arranged not only at the uppermost part of the laminated body but also at a lower layer.

FIG. 7 shows an example in which a coupling portion with an input / output line is integrated with the dielectric filter. As a further uppermost layer of the configuration shown in FIG. 5, another green sheet 24 provided with a bonding pattern 22 on its surface is placed and integrated. In this configuration, the green sheet 24 is interposed between the coupling pattern 22 and the inner conductor to form an input / output coupling capacitor.
Therefore, coupling with the input / output line is achieved by this capacitor. The green sheet 24 may be made of a material (a material having a dielectric constant suitable for a coupling capacitor) different from the material constituting the dielectric filter main body, or a plurality of green sheets 24 instead of one may be interposed. It is good also as a structure to be made.

FIG. 8 shows an example in which a polarized circuit pattern 26 is used in addition to the coupling adjustment pattern 18. A linear pattern is provided in the longitudinal direction of the surface of the green sheet and in the vicinity of the internal electrode pattern to form a polar structure. FIG. 9 and FIG. 10 show examples in which coupling holes are formed at positions between the internal electrode patterns 12 of each green sheet 10. In FIG. 9, a plurality of small holes 28 are formed in a line, and in FIG.
0 is formed. It is necessary to prevent these holes from being crushed when the layers are integrated by pressing. For that purpose, for example, the pressure may be integrated by passing through a pin or the like. In the case of the small hole shown in FIG. 9, another low dielectric constant material can be buried in the small hole, and in such a case, there is no fear that the small hole is crushed.

FIG. 11 shows an example in which the end of the input / output coupling pattern 32 is drawn out to the side, and a shield layer 34 is further provided thereon. The shield layer 34 is formed by forming a shield pattern 38 on the surface of a green sheet 36. As a result, a dielectric filter which is not easily affected by external factors can be obtained. FIG. 12 shows that a green sheet 40 having no electrode pattern is interposed under the uppermost layer,
This is an example in which the uppermost internal electrode pattern is used as an input / output coupling pattern. The green sheet 40 may be made of a different material from the other green sheets 10. With this configuration, it is not necessary to prepare another green sheet having the input / output coupling pattern, and the number of parts used can be reduced.

In the example shown in FIGS. 13 and 14, a large-diameter internal electrode pattern 12a is formed on the open surface side, and a small-diameter internal electrode pattern 12b is formed on the short-circuit surface side. This corresponds to a step impedance type in which the cavity diameter is changed on the way. Such a configuration can be easily coped with only by changing the shape of the internal electrode pattern formed on the green sheet 10. In this example, the internal electrode patterns are stacked in such a manner that the internal electrode patterns are joined back to back.

FIGS. 15 and 16 show examples of an interdigital dielectric filter. Green sheet 1 in the top layer
0a and the lower surface of the lowermost green sheet 10b,
Open ends and short-circuit ends are formed alternately. In FIG. 15, the electrode pattern 42 is formed on half of the outer surface of the green sheet, and in FIG. 16, the electrode pattern 44 is formed up to the vicinity of the inner conductor open end. In these, it goes without saying that outer conductors are provided on the four side surfaces. The uppermost and lowermost electrode patterns 42 and 44 may be applied to a sintered product as in the case of applying and baking a conductive paste to the four side surfaces.

Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to only these embodiments. Needless to say, the number of the inner conductors (the number of steps of the filter), the shape of each electrode pattern, the number of the laminated green sheets, and the like can be appropriately changed according to the required characteristics, the used band, and the like. The procedure for forming the outer conductor is usually performed by applying and baking to a sintered product. However, depending on the firing temperature and electrode material, it is also possible to apply to the laminate and perform baking simultaneously with firing. is there.

[0019]

According to the present invention, an internal electrode pattern corresponding to a cross section of a resonator and a via connection portion connecting the internal electrode patterns are formed on a green sheet, and after lamination and integration, firing is performed to form an internal conductor. Since this method is used, it is not necessary to press-mold a block having a long and thin through-hole, and it is not necessary to metallize the through-hole. Therefore, high functionality can be achieved.

In the present invention, a complicated circuit pattern such as a polarized circuit, a coupling circuit, and frequency control can be manufactured by printing in the same process as the internal electrode pattern. Also, the internal electrode pattern corresponding to the resonator can be changed inside the laminate. Further, when manufacturing various types of filters, it is possible to cope only by changing the printing screen, so that various types of dies as in the case of conventional press molding are not required. Thus, the method of the present invention can manufacture a dielectric filter at low cost.

[Brief description of the drawings]

FIG. 1 is a manufacturing explanatory view showing one embodiment of the present invention.

FIG. 2 is an enlarged explanatory view of the internal electrode pattern portion.

FIG. 3 is an enlarged explanatory view showing another example of the internal electrode pattern portion.

FIG. 4 is an explanatory sectional view of the same.

FIG. 5 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 6 is a perspective view and a vertical sectional view thereof.

FIG. 7 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 8 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 9 is an explanatory view illustrating another embodiment of the present invention.

FIG. 10 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 11 is an explanatory view of the production showing another embodiment of the present invention.

FIG. 12 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 13 is a manufacturing explanatory view showing another embodiment of the present invention.

FIG. 14 is a longitudinal sectional view thereof.

FIG. 15 is an explanatory view of the production showing another embodiment of the present invention.

FIG. 16 is a manufacturing explanatory view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Green sheet 12 Internal electrode pattern 14 Via connection part 16 Depression

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhisa Yamazaki 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (72) Inventor Yasuo Suzuki 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (72) Inventor Nobuyoshi Kojima 5-36-11 Shimbashi, Minato-ku, Tokyo Inside Fuji Electric Chemical Co., Ltd. (56) References JP-A-59-51606 (JP, A)

Claims (2)

(57) [Claims] 1. A green sheet made of a high dielectric constant material, an internal electrode pattern having a size corresponding to a cross section of a coaxial resonator, and a via connection portion in which a conductive material is embedded in a through hole located in the internal electrode pattern. A plurality of the green sheets are laminated and pressurized and integrated, then fired, and the inner electrodes are connected to each other at the via connection portion to form an inner conductor, thereby forming an inner conductor. Manufacturing method of body filter. 2. The method according to claim 1, wherein a recess slightly larger than the internal electrode pattern is provided on the surface of the green sheet, and the internal electrode pattern is formed in the recess.