JPH08186412A - Dielectric resonator - Google Patents

Abstract

(57) [Summary] [Object] The present invention aims to prevent the occurrence of blistering at the interface between a dielectric ceramic and an electroless plating layer of copper during the manufacturing process of a dielectric resonator, particularly during an anilic treatment and formation of an electrolytic plating layer of copper. (EN) Provided is a dielectric resonator which does not cause the occurrence of the above-mentioned phenomenon, and in which the joining position does not shift at all even after the joining process. According to the present invention, a surface of a dielectric ceramic block 1 is electrolessly plated with a thickness of 2 μm or more, a copper plating film 21, an electrolytic plating copper plating film 22, and an electrolytic plating thickness. 1-3 μm silver plated film 23
Was deposited, and the thickness of the entire plating layer was 13 μm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric resonator which constitutes a high frequency filter used in automobile phones, mobile phones, cordless phones and the like.

[0002]

2. Description of the Related Art A high-frequency bandpass filter for communication equipment,
Dielectric filters are often used as filters such as antenna filters. This dielectric filter is configured by coupling a plurality of dielectric resonators.

In this dielectric resonator, a dielectric ceramic material is press-molded to form a block body having a through hole, and the block body is fired to form a conductor film on the inner surface of the through hole or the surface of the block body. , A dielectric ceramic green sheet is laminated and fired, and a conductor film is formed on the outer surface of the laminated body. In addition, there is one in which a plurality of resonators are formed in advance in a block body or a laminated body.

For example, a dielectric resonator using a dielectric block body has a block body having a through hole in which a conductor film serving as an inner conductor is formed on the inner wall surface of the through hole, and the outer surface except one end surface of the block body. A conductor film serving as an outer conductor film was formed on the.

This conductor film was formed by applying a conductive paste containing silver and glass to a block body and baking it. However, since the glass material is contained in the conductor film, there is a problem that high frequency characteristics cannot be sufficiently obtained. Also,
There is a problem that the connection reliability is low at the ridge portion where the surfaces on which the conductor film is formed are mixed.

In order to solve the above problem, there has been proposed a dielectric resonator in which the conductor film formed by the above-mentioned thick film technique is replaced with a conductor film formed by plating.

For example, JP-A-61-121501, JP-A-4-160904, and JP-A-4-185.
In Japanese Patent Laid-Open No. 103, from the surface side of the ceramic, a copper plating layer formed by an electroless plating method, a copper plating layer formed by an electrolytic plating method, and a tin or solder plating layer formed by an electrolytic plating method are deposited. It is disclosed that a conductive film is formed.

The thickness of the electroless plating layer of copper is 0.5-2.
It is described that the thickness including the electroless plating layer of copper of 0 μm and the electrolytic plating layer is 3 μm or more, and the thickness of the plating layer of solder is 1 μm or more.

[0009]

However, in the dielectric resonator having the conductor film having the above-mentioned layer structure, the electroless plating layer of copper is formed into a strong copper having high adhesion in the final step of forming the conductor film. In order to do so, annealing treatment (heat treatment at about 250 ° C.) is performed, but at this time, blisters may occur at the interface between the dielectric ceramic and the electroless copper layer of copper. If such blistering occurs, in the dielectric resonator, the inductance component and the capacitance component in the equivalent resonant circuit change abruptly, resulting in poor characteristics.

Further, such a dielectric resonator requires an assembling step of bonding it to the shield case and bonding the dielectric resonators to each other. Furthermore, it is mounted on an actual printed wiring board. To be done. In the assembly process, heat treatment at about 230 to 240 ° C. is performed using high-temperature solder at the joint portion of the resonator on the premise of the mounting process on the printed wiring board (reflow process at 180 to 200 ° C.). However, when heat of 230 to 240 ° C. is applied to the dielectric resonator, the solder plating layer or the tin plating layer which is the surface layer of the conductor film is softened and melted at 220 to 230 ° C. Although the function is sufficiently derived, the solder plating layer and the tin plating layer, which are the base of the function, may be deteriorated and the joining position may be displaced.

Particularly in a dielectric resonator operating at a high frequency, if the bonding state with the shield case is displaced at a predetermined position or the bonding position between the dielectric resonators is displaced, the resonance frequency immediately fluctuates or the band is changed. Fluctuates, which also becomes a fatal problem.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to provide a dielectric ceramic even in a manufacturing process of a dielectric resonator, especially during an anilic treatment and a copper electrolytic plating layer formation. Dielectric material that does not cause blistering at the interface between the block body and the electroless plating layer of copper, and that the bonding position does not shift during the bonding process, and that stable characteristics can be derived. A resonator is provided.

[0013]

According to the present invention, a dielectric ceramic surface is electroless plated with a copper plating film having a thickness of 2 μm or more, an electrolytic plating copper plating film, and an electrolytic plating process. A dielectric resonator comprising a silver-plated film having a thickness of 1 to 3 μm and having a conductor layer having a total thickness of 13 μm or less.

[0014]

According to the present invention, since the conductor layer is basically formed by plating, there is no need to use a conductive paste having a glass frit as in the prior art, so that high frequency characteristics can be improved. .

The copper electroless plating layer is an underlayer for performing a plating process on the dielectric ceramic. By setting the thickness of the copper electroless plating layer to 2 μm or more, this copper electroless plating layer can be used particularly in a later step. Even if an annealing treatment for strengthening the electroless plating layer is performed, it is possible to prevent the occurrence of blistering with the dielectric ceramic.

Further, the copper electroplating layer becomes a conductor layer of the dielectric resonator together with the above-mentioned copper electroplating layer.

The silver electrolytic plating layer has a thickness of 1
By setting the thickness to 3 μm, it is possible to prevent the copper plating layer from being oxidized, and the copper plating layer is formed so that it can be joined by the solder for joining in the joining process. In particular, even if heat for melting the solder is applied at the time of joining, since the state of the silver plating layer can be maintained in a very stable state, no positional displacement at the time of joining occurs. It should be noted that such improvement of the effect cannot be expected even if the thickness is 3 μm or more, the plating time becomes long, and the plating solution deteriorates.

Furthermore, the total of all these plating layers is 1
It is set to be 3 μm or less.

This is because as the film thickness increases, the stress generated at the interface between the dielectric ceramic and the copper plating layer increases, and when it becomes 13 μm or more, it occurs before the annealing treatment or the anneal treatment. The peeling phenomenon at this interface can be effectively suppressed.

As described above, since the copper plating layer is used, high frequency characteristics are excellent, blisters do not occur between the dielectric ceramic and the copper plating layer, and copper oxidation is prevented. As a result, the junction of the dielectric resonator can be extremely stabilized, and as a result, the dielectric resonator has a good manufacturing yield and can suppress fluctuations in characteristics.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The dielectric resonator of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an external perspective view of the dielectric resonator, and FIG. 2 is a sectional view showing the layer structure of the conductor layers of the dielectric resonator. Although there are various structures of dielectric resonators,
In the examples, a dielectric resonator using a dielectric block having one through hole will be described.

In the figure, a resonator 10 is made of a dielectric ceramic, and is formed on a block body 1 having openings at a pair of end faces where through holes 3 face each other, and on all outer surfaces except one face of the end faces. It is composed of a conductor film layer.

The block body 1 is formed by press-molding a dielectric ceramic material such as BaTiO ₃ system using a metal mold having a predetermined shape, molding it into a predetermined shape having a through hole 3, and firing it. .

The shape of the end face having the opening of the through hole 3 is, for example, 2 m × 2 m, and its height is determined corresponding to the wavelength λ of the resonance frequency, and is, for example, about 8 mm of ¼ λ, The inner diameter of the hole 3 is determined by the dielectric constant of the dielectric ceramic material and the required characteristics, and is, for example, 1.6 mm.

The surface of the block body 1 has a predetermined surface roughness so that the copper electroless plating layer 21 forming the conductor layer 2 can be stably deposited.

The conductor layer 2 is a first copper plating layer 2 formed by electroless plating from the surface side of the block body 1.
1. Second copper plating layer 22 formed by electrolytic plating treatment, silver plating layer 23 formed by electrolytic plating treatment
It has a three-layer structure.

The first copper-plated layer 21 is in contact with the block body 1 and is inevitably electroless plated. The thickness of the copper plating layer 21 is 2 μm or more.

The copper plating layer 22 is, together with the copper plating layer 21, a main conductor layer for substantially passing the high frequency current of the conductor layer 2. In order to sufficiently satisfy the high frequency characteristics, the copper plating layer 21 is Are formed to have a total of 5 μm or more.

The silver-plated layer 23 prevents the copper-plated layer 22 from being oxidized, and when soldering a dielectric resonator to another dielectric resonator or a shield case, the wettability of the solder is improved. Is a layer for improving.

Next, a method of manufacturing the dielectric resonator having such a structure will be briefly described.

First, the block body 1 made of the above-mentioned dielectric ceramic is formed.

Next, the first copper plating layer 21 is formed to a thickness of 2 μm or more, for example 3 μm, on the entire surface of the block body 1 by electroless plating.

Subsequently, the second copper plating layer 22 is formed on the surface of the first copper plating layer 21 by, for example, 4 μm by the electrolytic plating method.

Subsequently, a silver plating layer 23 is formed on the surface of the second copper plating layer 22 by electroplating to have a thickness of 1 to 3 μm.
m, for example 2 μm.

As a result, three plating layers 21 to 23 (total thickness of 9 μm, for example) are formed on the entire surface of the block body 1, that is, the inner wall surface of the through hole 3 and all six surfaces of the block body 1. Become.

Next, the plating layers 21 to 23 attached to the end surface having the opening on one side of the through hole 3 are removed by polishing. The removed surface becomes the open end surface of the dielectric resonator 10, and the surface facing the open end surface becomes the short-circuited end surface, forming a 1 / 4λ dielectric resonator.

Incidentally, this polishing not only removes the plating layers 21 to 23, but also reduces the wavelength of the predetermined resonance frequency by 1 /.
The resonance frequency may be adjusted so as to correspond to No. 4.

Next, in particular, the first copper plating layer 21 is subjected to heat treatment (annealing treatment) in order to improve the adhesion strength with the dielectric block body 1. Specifically, the treatment at 200 to 300 ° C., for example 250 ° C., is performed in the air atmosphere, and FIG.
The dielectric resonator 10 shown in is achieved.

Next, the present inventor investigated the film thickness of the first copper plating layer 21 that can sufficiently withstand the above-mentioned annealing treatment.
The thickness of the second copper plating layer 22 is 4 μm and the thickness of the silver plating layer 2 is 4 μm.
The film thickness of 3 was 2 μm.

The thickness of the first copper plating layer 21 is 1.0 μm.
When the total of the plating layers 21 to 23 is 7 μm, voids are generated at the interface between the block body 1 and the first copper plating layer 21 after the annealing treatment at a rate of 20% of the whole sample, and blisters are generated. Resulting in.

The film thickness of the first copper plating layer 21 is 1.
In the case of 5 μm (the total is 7.5 μm), 5% is added to the interface between the block body 1 and the first copper plating layer 21 after the annealing treatment.
The voids are generated and blisters are generated.

The thickness of the first copper plating layer 21 is 2.
In the case of 0 μm (the total is 8.0 μm), no blistering occurred at the interface between the block body 1 and the first copper plating layer 21 after the annealing treatment.

Furthermore, the film thickness of the first copper plating layer 21 is 2.5 μm (the same total is 8.5 μm), 3.0 μm (the same total is 9.0 μm), 4.0 μm (the same total is 1.0 μm). )
In this case, no blistering occurred at the interface between the block body 1 and the first copper plating layer 21 after the annealing treatment.

That is, the block body 1 in the annealing treatment
The blistering phenomenon that occurs at the interface between the first copper plating layer 21 and the first copper plating layer 21 depends on the thickness of the first copper plating layer 21, and it is important to be at least 2 μm.

As a result of measuring the Q value, it is 285 when the thickness of the first copper plating layer 21 is 1 μm, 281 when it is 1.5 μm, and 286 when it is 2.0 μm. And 284 in the case of 2.5 μm, 283 in the case of 3.0 μm, and 279 in the case of 4.0 μm, and there is a general tendency for the phenomenon to occur when the thickness of the first copper plating layer 21 increases. The thickness is 4 μm
There is no big change to the extent.

Therefore, the thickness of the first copper plating layer 21 is
It is important to set the thickness to 2 μm or more, which can prevent the blistering phenomenon, and the upper limit of the thickness is considered to be about 4 μm in consideration of the plating time and the deterioration of the plating solution due to the increase of the thickness. Further, if it is less than 2.0 μm, the first copper plating layer 21 that completely covers the surface of the block body 1 cannot be formed, and the second copper plating layer 22 is formed due to this. It is considered that the electrolytic plating treatment (not directly applied to the surface of the ceramic) cannot be uniformly performed.

Next, the thicknesses of all the plated layers 21 to 23 which can sufficiently withstand the above-mentioned annealing treatment were examined. The thickness of the first copper plating layer 21 is 3 μm and the thickness of the silver plating layer 23 is 2 μm.
The thickness of the second copper plating layer 22 was variously changed, and the limit was examined.

When the second copper plating layer 22 had a thickness of 3 to 8 μm, that is, when the total thickness of the second copper plating layer 22 and the plating layers 21 to 23 was 13 μm, the blistering phenomenon did not occur during the annealing treatment.
The second copper plating layer 22 exceeds 8 μm, and the plating layers 21 to 21
If the total of 23 and 23 exceeds 13 μm, the block body 1 of the dielectric ceramic and the first copper plating layer 2 before the annealing treatment.
The blistering phenomenon occurred at the interface with No. 1 and the blistering phenomenon began to occur at the interface after the treatment.

That is, the block body 1 in the annealing treatment
Blisters generated at the interface between the first copper plating layer 21 and
It depends on not only the thickness of the first copper plating layer 21 but also the thicknesses of all the plating layers 21 to 23.
This is because even with copper, which is a relatively soft material, as the film thickness increases, the block body 1 and the first copper plating layer 2
It is considered that a mechanical stress is applied to the interface with No. 1 and this stress exceeds the adhesion between the block body 1 and the first copper plating layer 21 before and after the annealing treatment.

The thickness of the silver plating layer 23 is 1 μm and 3 μm.
Even if m, the total thickness of the plated layers 21 to 23 is 13 μm.
It was confirmed that the blistering phenomenon as described above occurs when it exceeds m.

The thickness of the silver-plated layer 23 should be 1 μm or more in order to prevent the copper-plated layer 22 from being oxidized and to keep the silver-plated layer 23 stable even during the following bonding process. Good. Regarding the upper limit, as described above, there is an upper limit of the thickness of all the plated layers 21 to 23, and when considering the time required for the plating treatment due to the thickness of the plating film, the deterioration of the plating solution, etc., about 3 μm. Is enough.

Dielectric resonator 1 thus formed
When used as a resonant circuit, one terminal is connected to the inner conductor and the outer conductor is grounded. When used as a dielectric filter, for example, two or more dielectric resonators 1 are connected and the inner conductor (through hole 3) of the input / output side resonator is connected.
The input / output terminals are connected to the conductor layer 2) formed on the inner surface of the resonator 1, and the inner conductors of the resonators 1 are connected to each other via the capacitive element. In any case, the shield case is joined via solder, and in the case of a filter, the outer conductors of the resonators are joined together via solder.

As the solder for joining, the melting temperature is 220
Use high temperature solder of about ℃. This is because the shield case and each terminal are solder-bonded to the blind wiring board by reflow treatment at a maximum of about 200 ° C., but the bonding solder is not melted even at the temperature at this time.

Here, since the conductor layer 2 of the present invention is composed of the first copper plating layer 21, the second copper plating layer 22 and the silver plating layer 23, the heat of the high temperature solder bonding during the bonding process ( 220 to 230 ° C.) or the heat of soldering (180 to 200 ° C.) during mounting on a printed wiring board, the respective plating layers 21 to 23, especially the surface silver plating layer 23 are stable. Since it can be maintained, the plating layer (solder plating layer, tin plating layer) on the surface is never softened or melted unlike the conventional case, so that stable bonding can be achieved at a predetermined bonding position. For example, there is no change in resonance frequency or band.

Further, the above-mentioned joining of the dielectric resonators 10 and the joining to the shield case can be easily assembled by a reflow process using high temperature solder.

In the above-mentioned embodiment, the dielectric resonator having the conductor layer 2 formed on the surface of the block body 1 made of the dielectric ceramic having the through holes 3 has been described, but it has a plurality of through holes. The present invention can be applied to a structure in which a plurality of dielectric resonators are integrated by forming a block body made of a dielectric ceramic. Further, in a ceramic laminate substrate (block body) formed by laminating a plurality of ceramic layers, two ceramics are used. It can also be used in a tri-plate dielectric resonator in which an inner conductor film is formed between layers and a conductor film is formed on the surface of a laminate substrate.

[0058]

As described above, according to the present invention, a copper plating film having a thickness of 2 μm or more electrolessly plated or a copper plating film electrolytically plated on the surface of a block body made of a dielectric ceramic. , Electroplated thickness is 1
Since a silver plating film of ˜3 μm is deposited and the thickness of all the plating layers is 13 μm or less, blistering that occurs between the dielectric ceramic and the first copper plating layer during the annealing treatment during the manufacturing process. The phenomenon can be completely suppressed.

Further, since the conductor layer itself can maintain a stable state even when heat of about 220 to 230 ° C. is applied,
Even if the resonators are joined via high-temperature solder, or even if the resonators are joined to the shield case with high-temperature solder, the state does not change to the silver plating layer that is the plating layer on the surface. The junction state can be maintained stably, and a dielectric resonator having very stable characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is an external perspective view of a dielectric resonator of the present invention.

FIG. 2 is a schematic view showing a layer structure of a conductor layer of the dielectric resonator of the present invention.

[Explanation of symbols]

 10 ... Dielectric resonator 1 ... Block body 2 ... Conductor layer 3 ... Through hole 21 ... First Copper plating layer 22 ... Second copper plating layer 23 ... Silver plating layer

Claims (1)

[Claims] 1. A dielectric ceramic surface is electrolessly plated with a copper plating film having a thickness of 2 μm or more, an electrolytic plating copper plating film, and an electrolytic plating film having a silver plating thickness of 1 to 3 μm. It consists of a membrane and the total thickness is 1
A dielectric resonator comprising a conductor layer having a thickness of 3 μm or less.