JPH07105683B2 - Method for manufacturing series resonator of ladder type electric filter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ladder-type electric filter including a series resonator and a parallel resonator in combination, and a method for manufacturing the series resonator. .

<Prior Art> In a known ladder-type electric filter including a series resonator and a parallel resonator, the parallel resonator has a large capacitance and the series resonator has a small capacitance. I need to come.

The adjustment of the electrostatic capacitance can be achieved by, in addition to the means for changing the thickness, making the electrodes of the series resonator smaller than the electrodes of the parallel resonator.

As shown in FIG. 5, a conventional series resonator a by this means has a partial electrode c formed on one surface of a dielectric element plate b and a full surface electrode d formed on the other surface. .

In the production of the series resonator a of this conventional structure, the entire surface electrode d is formed on the back surface of the large-sized dielectric substrate, and the partial electrodes c are scattered on the surface by screen printing. It is made by cutting into a predetermined shape including.

By the way, since a plurality of small-area partial electrodes c are formed on one surface of the dielectric substrate and the whole surface electrode d is formed on the other surface, the physical loads are different on the front and back sides. For this reason,
During the silver baking, warpage occurs due to the thin dielectric substrate, and element cracks and cracks are likely to occur during application of the polarization electrode or during cutting thereof. Therefore, the yield is deteriorated in the manufacturing process. Further, since the series resonator a itself is warped, there is a drawback that it is difficult to assemble the filter into the housing.

Therefore, the applicant of the present invention, in the manufacturing process, by covering the entire back surface of the large rectangular dielectric substrate with a silver coating, and covering almost the entire surface with an electrode pattern having a large number of annular separating portions, We have proposed a manufacturing method in which the front surface and the back surface have substantially the same physical conditions, so that warpage does not occur during silver baking, and element cracks and cracks are reduced when applying or cutting the polarization electrode. FIG. 6 shows a series resonator x manufactured by such a method. In this series resonator x, a dummy electrode z is formed on the extra surface portion around the partial electrode y.

<Problems to be Solved by the Invention> In this improved series resonator x, as shown in FIG. 4, terminals which are housed in a housing space 21 of a rectangular case 20 and arranged in front of and behind it It makes a part of the filtering circuit by making electrical contact with the raised pressure contact portions 23, 23 of the plates 22, 22. At this time, the raised pressure contact portion 23 needs to contact only the partial electrode y. is there. However, there is a possibility that the pressure contact ridge 23 may contact not only the partial electrode y but also the dummy electrode z due to variations in the stored state. In this case, the dummy electrode z also becomes an effective electrode, the electrostatic capacitance increases, the capacitance ratio with the parallel resonator decreases, and the meaning of the partial electrode is lost.

This contact failure also occurs later due to the fact that the inside of the filter is changed due to the impact of the filter being dropped or the like, and in this case, the generated waveform is changed and the characteristics are changed.

FIG. 7 is a graph in which the vertical axis represents the amount of attenuation and the horizontal axis represents the frequency, and the solid line shows the characteristics of the conventional series resonator a shown in FIG. This characteristic is almost the same even in the improved series resonator x of FIG. 6 when the dummy electrode z and the terminal plate 22 are not short-circuited. The broken line shows the characteristics of the improved series resonator x when the dummy electrode z and the terminal plate 22 are short-circuited. That is, due to this short circuit, the capacitance of the series resonator x increases from the original several tens of PFs to several hundreds of PFs, and as a result, the amount of attenuation decreases as shown in FIG. 8d according to experiments
A decrease in B was seen.

The present invention aims to eliminate such drawbacks as much as possible.

<Means for Solving Problems> The present invention is a method for manufacturing a series resonator of a ladder-type electric filter including the following manufacturing steps.

B) The entire back surface of the large rectangular dielectric substrate is covered with a silver coating, and almost the entire front surface is provided with a large number of annular separating portions that partition the partial electrodes and the dummy electrodes.
Each series resonator cut out by the separation line is covered with an electrode pattern that is electrically separated into two or more divided dummy electrodes, and then baked.

B) A polarization electrode is applied on the electrode pattern, and a DC voltage is applied to the silver coating and the polarization electrode to subject the dielectric substrate to polarization treatment.

C) Dissolve the polarization electrode.

D) A dielectric substrate is cut into a rectangular shape, and each piece thereof is used as a series resonator including a partial electrode partitioned by a ring-shaped separating portion and a dummy electrode.

<Operation> In this manufacturing means, the substantially rectangular front surface of the large rectangular dielectric substrate having a square or rectangular shape is covered with the electrode pattern including the partial electrodes and the dummy electrodes. The front and back have almost the same physical conditions, and the occurrence of warpage during baking is reduced.

Further, the dummy electrode is electrically divided into two or more divided dummy electrodes. Therefore, in the case where the dummy electrode is housed in the case and constitutes a part of the filtering circuit, even if the pressure contact portion of the adjacent terminal plate is displaced and comes into contact with the dummy electrode side, the dummy electrode is electrically connected. Since it is divided into, the entire surface is not effective, and only the divided dummy electrodes that are in direct contact are effective electrodes. Therefore, even if contact failure occurs,
It is possible to suppress the increase in capacitance as much as possible.

<Example> FIG. 1 shows a series resonator 1 manufactured by the method of the present invention.
An example is shown.

Here, in the series resonator 1, a full surface electrode 3 is formed on the back surface of a dielectric element plate 2, a circular partial electrode 4 and an annular separation portion 5 are placed on the front surface, and a dummy formed on the remaining surface thereof. Electrode 6
And are formed.

Incidentally, the partial electrodes 4 may be square such as square, and in this case, the annular separating portion 5 is naturally in the shape of rectangular annular or the like.

Here, in the dummy electrode 6, separation lines 7a are radially formed from the partial electrodes 4 to form a plurality of separation dummy electrodes 8. Each separation dummy electrode 8 is electrically divided by a separation line 7a and is non-conductive.

As shown in FIG. 4, the series resonator 1 is housed in a housing space 21 of a rectangular case 20 made of an insulating material, and the raised pressure contact portions 23 of the terminal plates 22, 22 arranged before and after the housing space 21, When 23 contacts the whole surface electrode 3 and the partial electrode 4, a part of the filtering circuit is formed in the case 20. still,
The parallel element 24 is adjacent to the terminal plate 22 via an insulating plate, a terminal plate or the like.

The manufacturing process of the series resonator 1 having the above structure will be described with reference to FIG.

Here, FIG. 2 (a) shows a rectangular dielectric substrate 10 consisting of a large square or rectangle, and as shown in FIG. 2 (b), silver is applied to the entire back surface by screen printing means. A coating film 11 is formed, and the entire front surface thereof is covered with an electrode pattern 12 having a large number of annular separating portions 5 that partition the partial electrodes 4 and the dummy electrodes 6. On the electrode pattern 12, in addition to a large number of annular separating portions 5 based on a predetermined pattern, radial separating lines 7a radiating from the annular separating portion 5 at equal angles or at equal angles are formed. Then, after coating both surfaces, baking processing is performed (see the form of FIG. 2D).

Next, as shown in FIG. 2C, a polarization electrode 13 is applied on the electrode pattern 12, and a DC voltage is applied to the silver coating 11 and the polarization electrode 13 to polarize the electric substrate 10. Apply processing. After that, the polarization electrode 13 is dissolved away with a solvent such as trichlorethylene. By doing so, polarization becomes possible even after the baking.

Then, as shown in FIG. 2D, the dielectric substrate 10 is cut into a square shape along a cutting line l, and each of the pieces is used as a plurality of separation dummy electrodes 8 as a series resonator 1.

In the manufacturing process, since the silver film 11 and the electrode pattern 12 were adhered to the front and back of the series resonator 1 and the front and back were made to have substantially the same physical condition, the warpage was almost eliminated. The radial separation line 7a has a small removal area because the electrodes are removed linearly, and therefore has little influence on the warp. The piezoelectric characteristics of the series resonator 1 and the series resonator x of FIG. 6 were almost the same.

Further, since the area of the separation dummy electrode 8 is about 1/4 of that of the dummy electrode 6 which is not separated, the raised pressure contact portion 23 of the terminal plate 22 and the dummy electrode 6 contact each other. However, the change in the capacitance can be made as small as possible.

FIG. 3 is a plan view showing another means for separating the dummy electrode 6.

Here, in FIG. 3 (I), the dummy electrode 6 is connected to the radial separation line 7b.
It is divided into eight parts. In FIG. 3 (II), the dummy electrode 6 is divided by the separation line 7c. Further, in FIG. 3 (III), the dummy electrode 6 is connected to the concentric separation line 7d.
It is divided by.

<Effects of the Invention> As described above, according to the present invention, the entire back surface of the large rectangular dielectric substrate 10 is covered with the silver coating 11 in the manufacturing process, and substantially the entire front surface is covered with the annular separating portion 5 and the separating line. It is covered with the electrode pattern 12 having 7a to 7b, and since the electrode removal area of the annular separation portion 5 and the separation lines 7a to 7d is small, the front and back surfaces thereof have substantially the same physical condition, and therefore the silver No warpage occurs during baking, and element cracks and cracks are less likely to occur during application of the polarization electrode or subsequent cutting. Therefore, defective products can be reduced as much as possible, and the yield in the manufacturing process can be improved. Further, when the series resonator 1 made by this manufacturing method is accommodated in the case 20, the pressure contact portion 23 of the terminal plate 22 is changed to the partial electrode 4 by the variation of the accommodated state.
However, even if the dummy electrode 6 comes in contact with the dummy electrode 6 side, the dummy electrode 6 is electrically divided into a plurality of separation dummy electrodes 8 by the separation lines 7a to 7d. Since only the separating dummy electrode 8 is involved, there is an excellent effect that an increase in electrostatic capacity can be prevented as much as possible.

[Brief description of drawings]

FIG. 1 is a perspective view of a first embodiment of the present invention, FIG. 2 is an explanatory view showing a manufacturing step of the series resonator 1, and FIG.
(III) is a plan view of a modified embodiment of the series resonator 1 with separation lines 7b to 7d of another example, and FIG. 4 is a longitudinal section of a main part showing an example of a storage state of the series resonator 1 in a case 20. It is a side view. Further, FIG. 5 is a perspective view of a series resonator a having a conventional structure, FIG. 6 is a perspective view of an improved series resonator x, and FIG. 7 is a graph showing problems of the improved series resonator x. is there. 1; series resonator, 2; dielectric element plate, 3; full surface electrode, 4; partial electrode, 5; annular separating portion, 6; dummy electrode, 7a to 7d; separating line, 8;
Separation dummy electrode, 12; electrode pattern

Claims (1)

[Claims] 1. A method of manufacturing a series resonator of a ladder type electric filter comprising the following manufacturing steps. B) The entire back surface of the large rectangular dielectric substrate is covered with a silver coating, and almost the entire front surface is provided with a large number of annular separating portions that partition the partial electrodes and the dummy electrodes.
Each series resonator cut out by the separation line is covered with an electrode pattern that is electrically separated into two or more divided dummy electrodes, and then baked. B) A polarization electrode is applied on the electrode pattern, and a DC voltage is applied to the silver coating and the polarization electrode to subject the dielectric substrate to polarization treatment. C) Dissolve the polarization electrode. D) A dielectric substrate is cut into a rectangular shape, and each piece thereof is used as a series resonator including a partial electrode partitioned by a ring-shaped separating portion and a dummy electrode.