JPH02185101A - Production of dielectric filter - Google Patents

Abstract

PURPOSE:To minimize the variation of dimensions accompanied with actual sintering to improve the accuracy of dimensions after actual sintering by obtaining a half-sintered body by preliminary preparatory sintering at a temperature lower than the temperature of actual sintering and working the shape in this half-sintered state so that each part has prescribed dimensions. CONSTITUTION:A dielectric block 1a in the unsintered state which has a recessed groove 2 and through holes 3a and 3b is generated by press forming, extrusion, or the like. This block is preparatorily sintered at a preparatory sintering temperature T2, at which the dielectric block 1a is not sintered, lower than an actual sintering temperature T1 by DELTAT (=50 to 200 deg.C) to obtain a half-sintered body. The shape is so worked that each part has prescribed dimensions. After side holes 3c and 3d are formed in a dielectric block 1b in the half-sintered state by a drill, a complete sintered body is obtained by actual sintering at the actual sintering temperature T1.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" This invention is applicable to, for example, wireless communication 4! ! The present invention relates to a method of manufacturing a dielectric filter used in a duplexer, etc. of a device.

"Prior Art" Conventionally, this type of dielectric filter has been constructed as shown in FIGS. 4 to 6. In FIG. 4, l is a substantially rectangular parallelepiped dielectric block constituting the dielectric filter main body, and the dielectric block l is connected from the groove bottom surface 2a of the groove 2 formed at 1° on one end surface of the dielectric block l. A pair of through holes 3a and 3b are formed through the back surface, and internal electrodes 4a and 4b are provided on the inner circumferential surface of each of these through holes 3a and 3b, respectively. Also, one end surface l° of the dielectric block l
An external electrode 5 is provided on the outer peripheral surface other than the groove side surface 2b of the groove 2.

Groove side electrodes 68 to 6d are provided on a part of the groove 2c, and groove bottom electrodes 7a to 7d are provided on the groove bottom surface 2a to connect the internal electrodes 4a, 4b and the groove side electrodes 6a to 6d. ing. On the other hand, input/output pins (conductor rods) 8 are provided in the through holes 3a, 3b with a gap between them and the internal electrodes 4a, 4b.
a and 8b are inserted. These output pins 8a,
8b is a fixing member 9 that fits into the groove 2 and a through hole 3.
A fixing member 10a that fits into parts a and 3b.

10b, these fixed members 9.1
0a and 10b are made of an insulator.

In the above configuration, the externally protruding portions of the input/output pins 8a and 8b function as external input/output terminals, the external electrode 5 functions as a ground electrode, and the internal electrodes 4a and 4b form a λ/4 resonant element (a λ/4 resonant element) electromagnetically coupled to each other. 7), there is a ground capacity IICt, c between the groove side electrodes 6a to 6d and the external electrode 5.
t (see FIG. 5), the groove bottom electrodes 78 to 7d serve as connecting electrodes between the internal electrodes 4a and 4b and the groove side electrodes 6a to 6d, and the human output pins 8a and 8b and the internal electrodes 4a and 4b.
and the input/output coupling capacitor 11 between the groove side electrodes 6a to 6d.
By functioning as cs, ci (see FIG. 6), they operate as a combline distributed constant filter as shown in the equivalent circuit of FIG.

Conventionally, such dielectric filters have been used as shown in Fig. 8.
It was manufactured using the process of ■. That is, ■Ba-
■ An organic binder is added to dielectric ceramic material powder such as Ti-based or Ba-Ti-Nd-based, ■ molded by means such as press molding or extrusion molding, and then ■ It is fired at a high temperature to form a sintered body, (1) the final shape is processed to give each part the predetermined dimensions by polishing and cutting, and (3) electrodes are formed in each part of the dielectric block 1, as shown in Figure 4. Internal electrodes 4a, 4b.

External electrode 5, groove side electrodes 6a to 6d, groove bottom electrodes 78 to
7d, and finally insert the input/output pins 8a and 8b to complete the process.

"Problems to be Solved by the Invention" By the way, the above-described conventional method for manufacturing a dielectric filter has the following problems. In other words, the dimensional shrinkage rate of each part in the firing process indicated by ■ in Fig. 8 is approximately 1.
This is as large as 5 to 20%, which results in large variations in dimensions after firing, and also tends to cause deformations such as curvature and curling after firing, as shown in FIGS. 9(a) and 9(b), for example. For this reason, sufficient dimensional accuracy cannot be obtained only by the molding step (2). In addition, when processing into a complicated shape, the desired shape cannot be obtained by press molding or extrusion molding alone, and drilling, polishing, and cutting may be required after the molding process. However, if the dielectric block is processed before firing, as shown in Fig. 1θ, the simply formed dielectric block will be fragile, so even if you try to make a hole with the drill 12, damage 13 will occur due to chucking. , there is a possibility that cracks 14 may occur due to the vibration of the drill I2. On the contrary, after firing. When attempting to process the dielectric block l in the sintered state, it is difficult to process because of its high hardness, and not only does it take a long time to process, but the drill 12 and other tools are subject to severe wear and damage. easy.

This invention was made in view of the above-mentioned circumstances, and aims to provide a method for manufacturing a dielectric filter that can easily be processed into a complex shape and that can obtain sufficient dimensional accuracy. .

[Means for Solving the Problems] This invention provides a method of forming a ceramic material into a predetermined shape, and then
Preliminary firing is performed at a temperature lower than the temperature at which sintering is possible to produce a semi-sintered body. Next, each part is shaped to the specified dimensions, and then main firing is performed at a temperature at which sintering is possible to complete the product. It is characterized in that it is made into a sintered body, which is then subjected to polishing and cutting as necessary.

"Operation" According to the manufacturing method described above, before the main firing, preliminary firing is performed at a temperature lower than the sintering temperature to form a semi-sintered body, and in this semi-sintered body, each part has a predetermined size. Since the shape processing is performed so that Since this process is easier than the subsequent shape processing, the processability is improved in terms of the manufacturing process as a whole.

"Example" FIG. 1 is a process diagram showing a method for manufacturing a dielectric filter according to an embodiment of the present invention, and as shown in this figure,
It consists of the following steps. First, (1) organic binder is added to dielectric ceramic material powder. These materials are the same as those used in conventional manufacturing methods. Next, (1) Shaping is performed by means such as press molding or extrusion molding. As a result, as shown in FIG.
is produced. The steps up to this point are the same as conventional manufacturing steps.

Next, ■ ΔT (-50℃~200℃
The pre-firing is performed at a pre-firing temperature T which is as low as 0.degree. C.) and does not sinter the dielectric block 1a to form a semi-sintered body. Then, ■ each part is shaped to have a predetermined size, and the dielectric block is in a semi-sintered state as shown in Figures 3 (a) to (d)! After forming side holes 3c and 3d using a drill (b), main firing is performed at the main firing temperature T to obtain a complete sintered body. After that, (1) final shape processing is performed to make each part into predetermined dimensions by polishing and cutting as necessary. From then on, as in the conventional method, (1) form electrodes on each part to complete the process.

Here, when pre-calcined at the temperature mentioned above, 15 to 5%
Dimensional shrinkage occurs, and the dimensional shrinkage rate during final firing is approximately 5% ~
It decreases to 15%. In this case, the pre-firing temperature T! When is set to a high value, the dimensional shrinkage rate during the main firing can be suppressed to a low level, and the dimensional accuracy after the main firing can be improved. However, since the hardness increases after pre-firing, shaping becomes somewhat difficult.

Conversely, if the preliminary firing temperature T is set to a low value, processing after the preliminary firing becomes easier, but the dimensional accuracy after the main firing decreases. Furthermore, if the temperature difference ΔT>200°C, the hardness after pre-firing is too low and becomes brittle, making it difficult to process the shape after pre-firing.

Therefore, by setting the pre-firing temperature T as high as possible for shape processing after pre-firing, dimensional changes during main firing are small, and deformations such as curvature and warping are also reduced, making it possible to reduce Compared to the method, the variation in dimensions of each part is about half or less.

In addition, since the dimensional accuracy after the main firing is improved, polishing and cutting after the main firing are unnecessary in some cases, and even if they are necessary, only a small amount is needed, and as a result, polishing and cutting after the main firing, which have poor workability, The number of cutting operations can be reduced.

"Effects of the Invention" As explained above, according to the manufacturing method of the present invention, before the main firing, preliminary firing is performed at a temperature lower than the main firing temperature to form a semi-sintered body. Since the shape processing is performed so that each part has the specified dimensions, it is possible to minimize the dimensional changes caused by the main firing and improve the dimensional accuracy after the main firing. This has the effect of reducing the number of polishing and cutting processes after the main firing, which have poor performance, and can even be omitted in some cases. It is easier than shaping after firing, so
When viewed as a whole in the manufacturing process, it is possible to improve workability, which also has the effect of reducing damage to the molded body and wear of tools during processing.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a dielectric filter according to an embodiment of the present invention, FIG. 2 is a perspective view of an unsintered dielectric block in the manufacturing process of the same embodiment, and FIGS. D)
are a perspective view, a front view, a top view, and a side view when side holes are formed in the same dielectric block, FIG. 4 is an exploded perspective view of a conventional dielectric filter, and FIGS. 5 and 6 are the same conventional example. Figure 7 is an equivalent circuit diagram of each dielectric filter, Figure 8 is a diagram of the manufacturing process of a conventional dielectric filter, and Figure 9 (a) is a diagram of the conventional manufacturing process. 9(B) is a cross-sectional view taken along line A-A in FIG. 9(A), and FIG. 10 is a front view of the dielectric block in the sintered state in the conventional manufacturing process. FIG. 11 is a perspective view showing an example of processing a dielectric block in a sintered state in a conventional manufacturing process. !・・・・・・Dielectric block in sintered state, la...
...Dielectric block in unsintered state, tb...
Dielectric block in semi-sintered state, 'r1...Main firing temperature, T,...Preliminary firing temperature.

Claims (1)

[Claims] After the ceramic material is formed into a predetermined shape, it is pre-fired at a temperature lower than that at which sintering is possible to form a semi-sintered body, and then after being shaped so that each part has the predetermined dimensions,
A method for manufacturing a dielectric filter, which comprises performing main firing at a temperature that allows sintering to obtain a complete sintered body, and then subjecting it to polishing and cutting as necessary.