JPH0884009A - Production of coaxial dielectric resonator - Google Patents

Abstract

PURPOSE: To provide a resonator which has a high plating film adhesive strength and a small dielectric loss by specifying the film thickness of an Ni-P film formed on high frequency dielectric ceramics by electroless plating. CONSTITUTION: The Ni-P film is formed on high frequency dielectric ceramics by electroless plating, and a Cu or Ag film is formed on this Ni-P film as an electrode by electroless plating. The film thickness of this Ni-P film is set to 0.01 to 1.50μm. Thus, the plating film adhesive strength is about 1.0kg/nm<2> with respect to perpendicular tensile stress, and the resonator of high Q is obtained. It is good that they are subjected to heat treatment in the atmosphere of inert gas at <=5500 deg.C after formation of the electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a coaxial dielectric resonator used for a high frequency filter, a high frequency oscillator, etc., which is mounted in mobile communication or the like.

[0002]

2. Description of the Related Art In recent years, the development of mobile communication has advanced, and PHS
(Personal Handy phone Sys
Tests such as tem) are also actively conducted. Since various vendors participate in this mobile communication and the like in the high frequency band, it is expected that segregation of frequencies among the vendors will become an increasingly important issue in the future.

On the other hand, the coaxial dielectric resonator using the dielectric ceramic has an advantage that the resonance frequency can be freely set according to the length of the resonator itself and can be applied to a high frequency band of about 1 GHz or more. Therefore, it is expected that demand will increase significantly in the future.

The coaxial dielectric resonator is generally constructed as shown in FIG. In FIG. 1, 1 is BaO-
A dielectric ceramic made of a material containing Nd ₂ O ₃ —TiO ₂ as a main component and Bi ₂ O ₃ added for the purpose of promoting sinterability and improving the dielectric constant, and has a cylindrical through hole 2 in the center. Is sintered into a rectangular parallelepiped shape. 3 is an electrode layer,
In the conventional method, the outer conductor 4, the inner conductor 5, and the short-circuited end 6 are Ag.
It was formed by coating, baking, electroless plating, or the like by a paste method or the like. In addition, 7 is an open end.

[0005]

The Ag paste method is generally carried out in the steps of applying Ag paste to a product, dipping, drying or baking the product, in which case the viscosity of the Ag paste must be adjusted. However, variations in viscosity in the viscosity adjustment process cause variations in the film thickness on the ceramic surface, and when continuously applying or dipping treatment,
There have been many manufacturing problems such as changes in viscosity due to evaporation of the solvent. In the firing process in the Ag paste method, A
Since the g particles are fired, the Ag electrode layer becomes a porous sintered body, a dense metal layer cannot be obtained, and there are many problems in mass production or in quality such as electrical characteristics.

In order to solve this problem, it has been proposed to form an electroless Cu plating layer on the surface of the dielectric ceramic (Japanese Patent Laid-Open No. 63-13504, etc.).

A high Q is required for a high frequency dielectric resonator. Generally, the unloaded Q of the dielectric resonator
Q _U and Q due to the dielectric loss of the dielectric ceramic material
_{If M} and Q due to conduction loss of the electrode are Q _C , then Q _U is
It is given by Equation 1 below.

[0008]

[Equation 1]

[0009] usually Q _M is about 4,000~200,000 (1GHz equivalent), Q _C is 200 to 1,000
Since it is a degree, Q _C has a great influence on Q _U. Here, Q _C increases in proportion to the conductivity σ of the metal forming the electrode, as expressed by the following mathematical formula 2.

[0010]

[Equation 2]

Here, ω = 2πf _θ (f _θ : resonance frequency), μ _θ = 4π × 10 ⁻⁷ [H / m] (μ _θ : magnetic permeability in vacuum), and A, B and L are cylindrical. In the case of, it is the inner diameter, outer diameter, and height of the dielectric resonator.

On the other hand, when electroless Cu plating is performed as an electrode, Cu has a high electric conductivity and Q _C is large, and Q _U is in a sufficiently practical range. However, unless the ceramic surface is greatly roughened by etching or the like. The vertical tensile strength of the plated film is about 1.0 kg / mm ² , which is not practical. Conversely, the effective conductivity of the electrode metal is reduced by roughening the ceramic surface, there is a drawback of deteriorating the Q _C.

When the dielectric resonator is mounted on a mobile communication device or the like, the performance of the dielectric resonator is substantially impaired if the plating film peels off due to a drop impact of the mobile communication device itself. The plating film adhesion strength is required to be high. At this time, the plating film adhesion strength is required to be about 2.0 kg / mm ² or more in vertical tensile stress.

In order to solve this problem, a method of performing electroless Ni-P plating on the surface of the dielectric ceramic as a Cu plating base can be considered. It is known that the deposition mechanism of electroless Ni-P plating is different from that of electroless Cu plating, and that the adhesion strength to ceramics is higher in Ni-P plating (for example, Osaka, Tamura et al .: Surface Technology). , Vol. 40, No. 7 (1989), 835-3.
9). However, since the conductivity of Ni is lower than that of Cu,
A problem that Q _C is deteriorated occurs.

Therefore, a technical object of the present invention is to form a Ni-P plating film as a base layer on the surface of the dielectric ceramic in the coaxial type dielectric resonator, and the adhesion strength of the plating film is 2.0 kg in vertical tensile stress. / mm ^2, and is to provide a method for producing a practically sufficient large coaxial Q _U is obtained dielectric resonator.

[0016]

According to the present invention, (1)
Ni-on high frequency dielectric ceramic by electroless plating
In a coaxial dielectric resonator formed by forming a P film and further forming a Cu film or an Ag film, or both of them as electrodes by electroless or electrolytic plating, Ni is used.
-P film thickness is 0.01 to 1.50 μm, (2)
In the coaxial dielectric resonator, a Ni-P film is formed on the high frequency dielectric ceramic by electroless plating, and a Cu film or an Ag film, or both of them are electrolessly or electrolytically plated. A coaxial dielectric resonator having a vertical tensile strength of ² kg / mm ² or more and a sufficiently large Q _U for practical use by applying heat treatment in an inert gas atmosphere at 500 ° C. or less after being formed as an electrode. Can be obtained.

[0017]

The function of the present invention will be specifically described below.

As described above, when electroless Ni-P plating is applied to the surface of the dielectric ceramic in the coaxial type dielectric resonator, the adhesion strength of the plating film is 2.0 kg / mm ² or more. Is too thick, the Q _U deteriorates because the Ni-P conductivity is low.

Therefore, the inventors of the present invention have variously changed the Ni-P plating film thickness of the electrode layer, and further have a Cu film or an Ag film on the Ni-P plating film in order to give the electrode practical conductivity.
The film, or both, was formed as an electrode by electroless or electrolytic plating. As a result, the Ni-P plating film thickness is set to 0.01 to 1.50 μm, and Ni + P
+ Cu plating film thickness or Ni-P + Cu + Ag plating film thickness is about 5.0 μm, the adhesion strength of the plating film is 2.0 kg / mm ² or more in vertical tensile stress, and is sufficiently large for practical use. I found that _U can get.

Further, a Ni-P + Cu plated film, or
It has been found that there is a temperature range in which the adhesion of the plating film is improved by forming a Ni-P + Cu + Ag plating film thickness and then performing a heat treatment in an inert gas atmosphere, and a sufficiently large Q _U can be obtained in practical use. .

[0021]

EXAMPLES Examples of the present invention will be described below with reference to the attached tables and the like.

First, 3 mm × 3 mm × having a circular hole centered on a BaO—Nd ₂ O ₃ —TiO ₂ system dielectric ceramic.
After forming into a 10 mm rectangular parallelepiped, it was sintered at a temperature of 1200 to 1400 ° C. for 2 hours or more. Next, after the surface of the dielectric ceramic was etched using hydrofluoric nitric acid, phosphoric acid, etc., Ni-P plated layers of various thicknesses were formed on the dielectric ceramic by electroless Ni-P plating. Then, a Cu plating layer is formed on the Ni-P plating layer by electrolytic plating, and further 0.1 μ is formed on the Cu plating layer by electrolytic plating.
m Ag plated layer was formed. At this time, Ni-P + C
The u + Ag plating film thickness was 5 μm in total.

Further, in order to improve the adhesion strength of the plated film to the coaxial type dielectric resonator thus produced,
Heat treatment was performed at a temperature of up to 600 ° C. for about 1 hour in an atmosphere of an inert gas such as N ₂ or Ar.

The adhesion strength of the plated film at each heat treatment temperature of the coaxial dielectric resonator manufactured as described above is shown in Table 1 below.

[0025]

[Table 1]

In Table 1, the plating film adhesion strength means that the coaxial dielectric resonator has a plating film having a cross section of 2 × 2 mm, and
Cut out to have a thickness of 1.0 μm, solder a wire of φ0.5 mm on the plated film, fix the other ceramic cross section with an adhesive, etc., pull the wire vertically and peel the plated film Indicates the stress when

The Q _U value of the coaxial dielectric resonator manufactured in the same manner as in Table 1 is shown in Table 2 below.

[0028]

[Table 2]

As can be seen from Table 1, the adhesion strength of the plated film of the coaxial dielectric resonator after the plating is gradually improved at a Ni-P film thickness of 0.01 μm to 0.05 μm, and is 0.05.
It becomes almost constant above μm. At this time, if the Ni-P film thickness is 0.01 μm or more, it exceeds the target value of the adhesion strength of 2.0 kg / mm ² (Nos. ² to 14). In addition, when heat treatment is applied to a coaxial dielectric resonator having a Ni-P film thickness of 0.01 μm or more in an inert gas atmosphere of 500 ° C. or less, the plating film adhesion strength is improved and 2.0 kg /
It exceeds mm ² . From the above, the Ni-P film thickness is
It may be 0.01 μm or more, and if it is 0.05 μm or more, it can be evaluated as more desirable from the viewpoint of adhesion strength.

By the way, the dielectric resonator has a required Q _U value depending on its size as shown in Equation 2, and in the case of the coaxial dielectric resonator of 3 mm × 3 mm × 10 mm shape prepared this time, It is generally required that Q _U ≧ 250.

On the other hand, as is clear from Table 2, the Q _U value of the coaxial dielectric resonator after plating is N
When the i-P film thickness is 1.50 μm or less, it is 250 or more, but when it exceeds 1.50 μm, it is less than 250 (No. 1).
2-14). Further, even when the coaxial dielectric resonator having a Ni-P film thickness of 1.50 μm or less is subjected to heat treatment in an inert gas atmosphere of 500 ° C. or less, Q _U exceeds 250 (No. 1). ~ 11), Ni-P film thickness is 1.50μ
When it exceeds m, Q _U falls below 250 (No. 12 to 1)
4). From the above, the Ni-P film thickness may be 1.50 μm or less.

As can be seen from Table 1, a coaxial dielectric resonator having a Ni-P film thickness of 0.01 μm or more has a temperature of 500 ° C.
Heat treatment (550,600
C) is added, the Q _U decreases to below 250 for all coaxial dielectric resonators of Ni-P thickness. From this, it can be evaluated that the heat treatment in the inert gas atmosphere is 500 ° C. or lower, and from the viewpoint of the Q _U value, 400 ° C. or lower is more preferable.

[0033]

As described above, according to the present invention,
Ni-on high frequency dielectric ceramic by electroless plating
In a coaxial dielectric resonator formed by forming a P film and further forming a Cu film or an Ag film, or both of them as electrodes by electroless or electrolytic plating, Ni is used.
-P film thickness is 0.01 to 1.50 μm, and
In the coaxial dielectric resonator, a Ni-P film is formed on the high frequency dielectric ceramic by electroless plating, and a Cu film or an Ag film, or both of them are used as electrodes by electroless or electrolytic plating. After forming
A heat treatment is applied in an inert gas atmosphere at 500 ° C. or less to obtain a method for manufacturing a coaxial dielectric resonator having a vertical tensile strength of ² kg / mm ² or more and a Q _U that is sufficiently large for practical use. The industrial utility value is great.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross-section of a part of a coaxial dielectric resonator which is an object of the present invention.

[Explanation of symbols]

_{1 BaO-Nd 2 O 3 -TiO} 2 based dielectric ceramic 2 cylindrical through holes 3 electrode layer 4 outer conductor 5 within the conductor 6 short-circuited end 7 open end

Claims (2)

[Claims] 1. A Ni-P film is formed on a high frequency dielectric ceramic by electroless plating, and a Cu film, an Ag film, or both are formed as electrodes by electroless or electrolytic plating on the Ni-P film. A coaxial dielectric resonator, wherein the Ni-P film thickness is 0.01 to 1.50 μm, wherein the coaxial dielectric resonator is manufactured. 2. A Ni-P film is formed on the high-frequency dielectric ceramic by electroless plating, and a Cu film or an Ag film, or both are formed as electrodes by electroless or electrolytic plating, The method of manufacturing a coaxial dielectric resonator according to claim 1, wherein the heat treatment is applied in an inert gas atmosphere at 500 ° C or less.