JPH05291802A - Laminated dielectric filter and its manufacture - Google Patents

Abstract

PURPOSE:To prevent exfoliation between a dielectric base and a ground electrode by providing a slit shaped opening to an earth electrode baked simultaneously as the dielectric base. CONSTITUTION:An integrated dielectric base 20 is formed by integrating three rectangular dielectric unbaked sheets 22, 24, 26 and an unbaked electrode provided respectively to the sheets through simultaneous baking. An earth electrode 30 is formed to an upper face and a side face of the dielectric unbaked sheet 22 placed at an uppermost position, and three slit openings 38, 38, 38 are provided to the ground electrode on the upper face so as to be located between the resonance electrodes 28, 28 and at the side of the resonance electrode 38 and in parallel with the resonance element 38. Thus, when the dielectric base 20 and each electrode are baked simultaneously, a stress caused by a difference from contraction of each component and a gas generated from the dielectric base 20 is exhuasted externally.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated dielectric filter used in a microwave band and a method for manufacturing the same, and more particularly, to a dielectric substrate and various electrodes provided on the inner and outer surfaces thereof.
The present invention relates to a laminated dielectric filter integrated by co-firing and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, filters using various types of dielectrics have been used in communication devices using microwaves, such as mobile phones and car phones, in order to reduce loss. Among them, dielectric ceramics are preferably used because they are highly reliable and have a large permittivity ε _r and are suitable for downsizing of filters.

As one of such dielectric filters, a laminated filter having a stripline type transmission line as shown in FIG. 12 is known. Further, as a manufacturing method thereof, a method is known in which a plurality of unfired dielectric sheets provided with different unfired electrodes are laminated and co-fired to integrate them.

Specifically, when three dielectric unfired sheets 4, 8 and 12 are laminated as shown in FIG. 12, the uppermost dielectric unfired sheet 4 has no upper surface. A fired ground electrode 2 is provided, a plurality of unfired resonance electrodes 6 and 6 are provided in parallel with each other on the upper surface of the middle dielectric unfired sheet 8, and the bottom dielectric unfired sheet 12 is provided. Has
A pair of unfired input / output electrodes 10, 10 are provided on the upper surface, while an unfired ground electrode 2 is provided on substantially the entire lower surface. And after stacking each of these sheets in order,
The unfired dielectric sheet and the unfired electrode are simultaneously fired to be integrated. The dielectric unfired sheet is made of a material in which various kinds of known dielectric ceramic powder are mixed with a binder and the like, and each electrode uses a conductor paste such as Ag or Cu. Are formed. The ground electrode 2 is formed on the outer main surface which is the outermost surface of the dielectric substrate as described above, and may be formed on the inner main surface inside the dielectric substrate depending on the structure of the filter.

However, in the case where the dielectric substrate and the electrode are simultaneously fired as described above, there is a problem that peeling easily occurs between the dielectric substrate and the ground electrode provided on the outer main surface and the inner main surface thereof. was there. And the following two points can be considered as the cause. (1) Since the contraction due to sintering during firing occurs earlier in the conductor paste of Ag or Cu than in the dielectric ceramics, the ground electrode contracts before the dielectric substrate contracts, causing peeling. .. (2) While the organic binder contained in the dielectric unfired sheet is not decomposed and scattered, and while a large amount of residual carbon is still remaining, the ground electrode contracts and the lid is covered. Peeling occurs between the dielectric substrate and the ground electrode due to the pressure of the decomposition gas and the oxidizing gas of residual carbon.

By the way, Japanese Laid-Open Patent Publication No. 2-237008 discloses a structure in which a dielectric unfired sheet is arranged on both upper and lower sides of a ground electrode, and a small hole is provided in the ground electrode so that the upper and lower dielectric layers are not exposed through the small hole. A technique for integrally adhering a fired sheet is disclosed. According to this method, the adhesive strength between the dielectric layers above and below the ground electrode becomes strong, and peeling of the dielectric layer is less likely to occur.

Therefore, this method can be adopted only when the unfired dielectric sheets are arranged on both upper and lower sides of the ground electrode, and the dielectric unfired sheet is disposed above the ground electrode 2 as shown in FIG. It cannot be used for filters that do not have a firing sheet. Even if this method is applied to the filter shown in FIG. 12, this method merely adheres the upper and lower dielectric unfired sheets through the small holes to strengthen the adhesive force and forms them on the ground electrode. Even if the peeling of the dielectric layer on the formed surface can be prevented, it is not a measure for eliminating the above-mentioned phenomena (1) and (2). Therefore, it occurs based on the difference in contraction behavior between the ground electrode and the dielectric substrate. Due to stress
Further, the pressure of the decomposition gas or the oxidizing gas causes peeling between the dielectric substrate and the ground electrode.

[0008]

The present invention has been made against the background of such circumstances, and a problem to be solved by the present invention is that when a dielectric substrate and an electrode are simultaneously fired, the dielectric substrate and the ground electrode are separated. The stress generated due to the difference in contraction behavior is relaxed, and the decomposition gas and the oxidizing gas generated from the dielectric substrate are effectively released to the outside. It is to prevent peeling between the and.

[0009]

In order to solve the above problems, according to the present invention, a plurality of resonance electrodes are built in a dielectric substrate, and a ground electrode is provided on the main surface of the dielectric substrate. Has a triplate structure, and the dielectric substrate is
A dielectric filter formed by co-firing with these electrodes, wherein the ground electrode co-firing with the dielectric substrate is provided with a slit-shaped opening, a laminated dielectric filter, This is the summary. The term “main surface of the dielectric substrate” as used herein includes not only the outermost outer surface of the dielectric substrate but also the inner main surface inside the dielectric substrate.

Further, in such a laminated dielectric filter, it is advantageous that the slit-shaped opening has a longitudinal / horizontal ratio of 3/1 or more and a lateral direction when the extending direction is the longitudinal direction. Is 0.5 mm or less, and the length in the vertical direction is 10% or more of the surface length of the dielectric substrate in the same direction.

Further, the present invention uses a plurality of dielectric green sheets that are laminated together to provide a dielectric substrate,
For a given one of these sheets, a conductor is provided according to the pattern of the resonance electrode on the surface facing the adjacent sheet at the time of lamination to form a plurality of unfired resonance electrodes, while at the time of lamination. After providing a conductor having a slit-shaped opening on the sheet surface constituting the main surface of the laminate to form an unfired ground electrode, the dielectric unfired sheets are laminated in a predetermined order, and then, A gist of the present invention is also a method for manufacturing a laminated dielectric filter, which is characterized by simultaneously firing a green sheet and a green electrode to integrate them. In addition, the main surface of the laminate referred to here is
In addition to the outermost outer surface of the laminate, the inner principal surface inside the laminate is also included.

[0012]

In the laminated dielectric filter and the method for manufacturing the same according to the present invention, since the ground electrode is provided with the slit-shaped opening, the ground electrode having a large area is effectively divided. When the dielectric substrate and the ground electrode are co-fired, the stress generated due to the difference in their contraction behavior can be effectively relieved. Moreover, since the slit-shaped opening has a large opening area as much as possible while not affecting the characteristics of the filter, the gas generated from the dielectric substrate during firing is passed through the opening, It can be effectively released to the outside. As a result, peeling of the ground electrode, peeling of the dielectric layer inside the dielectric layer near the ground electrode, or on the surface of the dielectric unbaked sheet,
It can be prevented very effectively, and the residual stress between the dielectric substrate and the electrode is very small, so that the reliability is improved for long-term use.

Further, when the shape of the slit-like opening is such that the extending direction is the longitudinal direction, the aspect ratio / aspect ratio = 3.
/ 1 or more, the width in the horizontal direction is 0.5 mm or less, and the length in the vertical direction is 10% or more of the surface length of the dielectric substrate in the same direction, which may adversely affect the filter characteristics. While reducing the number as much as possible, stress relaxation due to the difference in shrinkage behavior and gas degassing effect are advantageously enhanced to more effectively separate the ground electrode, and the inside of the dielectric layer near the ground electrode or the dielectric unbaked sheet lamination. The peeling of the dielectric layer on the surface can be prevented.

[0014]

EXAMPLES In order to clarify the present invention more specifically, representative examples of the present invention will be described in detail with reference to the drawings.

First, FIGS. 1 to 3 show an example of a laminated dielectric filter having a structure according to the present invention. This filter has three rectangular plate-shaped dielectric unsintered sheets 22, 24, 26 shown in FIG. 1 and unsintered electrodes provided on them, which are integrated by co-firing to obtain the structure shown in FIG. It is manufactured by forming an integral dielectric substrate 20 as shown. The unfired dielectric sheet is composed of various known dielectric ceramics. As a method of forming electrodes on the unfired dielectric sheet, various known electrode forming methods such as a conventionally known dipping method, a conductive paste brush coating method, and a transfer method such as screen printing can be employed.

Of the three dielectric unfired sheets, the middle dielectric unfired sheet 24 has two quarter-wavelength resonance electrodes 28, 28 arranged in parallel on the upper surface thereof. Thus, the so-called comb line structure is formed. That is, the resonance electrode 28 has its front end in FIG. 1 connected to the ground electrode 30 to be a short-circuit end, while the end on the other side in FIG.
An electrode 3 connected to the ground electrode 30 formed on the side surface of 4
It is made to be an open end by being opposed to 2 at a predetermined interval. As a result, two quarter-wavelength triplate resonators are provided corresponding to each resonance electrode 28.

Further, the dielectric unfired sheet 26 located at the bottom is provided with a pair of input / output electrodes 3 at a position corresponding to the open ends of the resonance electrodes 28, 28 on the upper surface thereof.
4, 34 are formed. Then, the input / output electrode 3
4, 34 are respectively connected to a pair of input / output terminals 36, 36 formed on a pair of opposite side surfaces of the sheet 26. Further, on the side surface and the lower surface of the sheet 26, in a state of being electrically disconnected from the input / output terminals 36, 36,
The ground electrode 30 is formed (see FIG. 2).

A ground electrode 30 is formed on the upper and side surfaces of the dielectric unfired sheet 22 located at the top, and the resonance electrodes 28, 28 are formed on the ground electrode 30 on the upper surface. The slit-shaped openings 38, 3 are located between the resonance electrode 28 and the resonance electrode 28 and are parallel to the resonance electrode 28.
8, 38 are provided. As a result, the ground electrode 30 having a large area is divided into four in the width direction (left and right direction in FIG. 1), and the opening area is as large as possible while not affecting the characteristics of the filter. There is. When forming the ground electrode 30 having such an opening 38 on the dielectric unfired sheet 22, pattern formation by a screen printing method is preferably adopted among various known electrode forming methods. It

By the way, the shape of the slit-shaped opening 38 is not particularly limited, but (a) the shape of the filter has little influence on the characteristics of the filter and is easy to design, and (b) stress relaxation. To have sufficient effect,
(C) It is necessary to consider that a large area opening can be obtained and the gas release property is good. Therefore, it is advantageous that the slit-shaped opening 38 has a longitudinal / lateral ratio of 3/1 or more and a lateral width of 0.5 mm when the extending direction is the longitudinal direction.
It is desirable that the length in the following and in the vertical direction be 10% or more of the surface length of the dielectric substrate in the same direction. More preferably, the aspect ratio is 5/1 or more, and the width in the horizontal direction is 0.
The length is 01 mm or more and 0.3 mm or less, and the length in the vertical direction is 30% or more of the surface length of the dielectric substrate in the same direction.

Also, as for the position where the slit-shaped opening 38 is provided, it is desirable to select a position that has little influence on the characteristics of the filter. Specifically, as shown in FIG. 3, avoiding above the resonance electrode 28 built in the dielectric substrate 20, between the resonance electrodes 28 and 28 and above the resonance electrode 28 laterally. It is good to provide. Further, it is preferable that the extension direction of the resonance electrode 28 (long axis direction) and the extension direction of the slit-shaped opening 38 (long axis direction) are aligned with each other. However, such a slit-shaped opening 3
Since the effect of 8 on the filter characteristics can be calculated by design, the opening 38 is formed in a direction perpendicular to the extending direction (long axis direction) of the resonance electrode 28 after sufficiently considering the effect. It may be arranged in a diagonal direction, or may be located above the resonance electrode 28.

Then, the dielectric unfired sheets 22, 24, and 26 on which the various unfired electrodes are formed are laminated in a predetermined order, and then simultaneously fired according to a conventional method to form an integral dielectric substrate 20. By forming it, the intended laminated dielectric filter can be obtained.

In the thus-obtained filter, when the dielectric substrate 20 and each electrode are simultaneously fired, the stress caused by the difference in shrinkage behavior between them can be effectively alleviated by the presence of the opening 38. Together with the dielectric substrate 2
Since the gas generated from 0 can be effectively released to the outside through the opening 38, the ground electrode 30
It is possible to very effectively prevent peeling of the dielectric layer and peeling of the dielectric layer inside the dielectric layer near the ground electrode or on the surface where the dielectric unbaked sheet is laminated. Further, since the residual stress between the dielectric substrate 20 and the electrodes is extremely reduced, the reliability is improved for long-term use.

Although the representative embodiments of the present invention have been described in detail above, it is needless to say that the present invention is not limited by the description of such embodiments. Further, in the present invention, in addition to the above-mentioned embodiments, unless departing from the gist of the present invention,
It should be understood that various changes, modifications, improvements, etc. can be made based on the knowledge of those skilled in the art.

For example, the shape and arrangement of the slit-shaped opening 38 provided in the ground electrode 30 can be variously changed, and other than the pattern shown in the above embodiment, for example,
It can be provided in a shape and form as shown in FIGS. Further, in the above-described embodiment, the slit-shaped opening 38 is provided only in the ground electrode 30 on the upper surface of the dielectric substrate 20, but the ground electrode 30 on the lower surface (bottom surface) of the dielectric substrate 20 is similarly provided. Needless to say, it is better to provide the slit-shaped opening 38.

Further, as shown in FIG. 11, an insulating protective layer 40 may be provided so as to cover the ground electrode 30 provided with the slit-shaped opening 38. In that case, after the unfired ground electrode 30 having the slit-shaped opening 38 is formed on the unfired dielectric sheet 22, the protective layer 4 is further formed.
0 may be formed, and the protective layer 40 may be simultaneously fired together with the dielectric substrate 20 and various electrodes. In addition, such a protective layer 4
0 is for stacking unfired sheets made of insulating material,
It can be formed by applying an insulating material by screen printing, and as the insulating material, for example, a dielectric ceramic similar to that used for the dielectric substrate 20 can be used.

Further, as in the laminated type dielectric filter shown in FIGS. 13 to 15, the earth electrode 3 is formed on the outer main surface constituting the outermost surface (upper surface and lower surface) of the dielectric substrate 20.
0 is formed, and a ground electrode 30 is also formed on the inner main surface of the dielectric substrate 20 so as to be located between the resonance electrode 28 and the coupling electrode 46 provided on different dielectric layers. When the ground electrode 30 on the outer main surface and the ground electrode 30 on the inner main surface are
It goes without saying that it is better to form the slit-shaped opening 38. In these figures, reference numeral 42 denotes a serial capacitance electrode that forms a serial capacitance with the resonance electrode 28, and both ends thereof also serve as input / output electrodes.
In addition, 44 are all through holes, which connect electrodes of different dielectric layers.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a laminated structure of an example of a laminated dielectric filter according to the present invention.

FIG. 2 is a bottom view of the laminated dielectric filter of FIG.

3 is a sectional view showing a section taken along line III-III in FIG.

FIG. 4 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 5 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 6 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 7 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 8 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 9 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 10 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

FIG. 11 is a cross-sectional view corresponding to FIG. 3, showing an example in which a protective layer is provided on the multilayer dielectric filter according to the present invention.

FIG. 12 is an explanatory diagram showing a laminated structure of an example of a conventional laminated dielectric filter.

FIG. 13 is a perspective view showing another example of the laminated dielectric filter according to the present invention.

14 is a sectional view showing a section taken along line XIV-XIV in FIG.

15 is an explanatory view showing a laminated structure of the laminated dielectric filter of FIG.

[Explanation of symbols]

 20 Dielectric Substrate 22, 24, 26 Dielectric Unfired Sheet 28 Resonance Electrode 30 Earth Electrode 34 Input / Output Electrode 36 Input / Output Terminal 38 Opening 40 Protective Layer 42 Series Capacitance Electrode 44 Through Hole 46 Coupling Electrode

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[Procedure amendment]

[Submission date] June 16, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction content]

For example, the shape and arrangement of the slit-shaped opening 38 provided in the ground electrode 30 can be variously changed, and other than the pattern shown in the above embodiment, for example,
It can be provided in a shape and form as shown in FIGS . 4 to 10 and 16 . Further, in the above-described embodiment, the slit-shaped opening 38 is provided only in the ground electrode 30 on the upper surface of the dielectric substrate 20, but the ground electrode 30 on the lower surface (bottom surface) of the dielectric substrate 20 is similarly provided. Needless to say, it is better to provide the slit-shaped opening 38.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] Fig. 16

[Correction method] Added

[Correction content]

FIG. 16 is an explanatory diagram showing an example of the shape and arrangement of slit-shaped openings.

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] Fig. 16

[Correction method] Added

[Correction content]

FIG. 16

Claims (3)

[Claims] 1. A dielectric substrate has a triplate structure in which a plurality of resonance electrodes are built in, and a ground electrode is provided on a main surface of the dielectric substrate, and the dielectric substrate includes the electrodes. A multilayered dielectric filter, characterized in that a dielectric filter is obtained by co-firing together with the dielectric substrate, and a slit-shaped opening is provided in the ground electrode co-firing with the dielectric substrate. 2. The slit-shaped opening has a longitudinal / horizontal ratio of 3/1 or more, a lateral width of 0.5 mm or less, and a longitudinal length when the extending direction is the longitudinal direction. 2. The laminated dielectric filter according to claim 1, wherein is provided so as to be 10% or more of the surface length of the dielectric substrate in the same direction. 3. A plurality of dielectric unfired sheets laminated on each other to provide a dielectric substrate, wherein a predetermined one of these sheets is provided on a surface of a side facing an adjacent sheet at the time of lamination. A conductor is provided according to the pattern of the resonance electrode to form a plurality of unfired resonance electrodes, and a conductor having a slit-shaped opening is provided on the sheet surface that constitutes the main surface of the laminate during lamination. After forming an unfired ground electrode, the dielectric unfired sheets are laminated in a predetermined order, and then the unfired sheet and the unfired electrode are simultaneously fired to be integrated, thereby forming a laminated dielectric. Body filter manufacturing method.