JPH0323704Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a chip-type piezoelectric filter, and more particularly to a chip-type piezoelectric filter that utilizes energy-trapped multi-mode vibration of a piezoelectric plate.

Prior Art Conventionally, various electronic devices have used filters that utilize energy-trapped multi-mode vibration of piezoelectric plates, and generally, this type of filter has a structure with lead terminals. Incidentally, in recent years, as electronic devices have become smaller, chip-type filters that can be directly attached to printed circuit boards have been desired. For this purpose, the required number of piezoelectric plates each having a divided electrode and a common electrode on their main surfaces, and an insulating plate on the outermost surface of the group of piezoelectric plates, are arranged so that the overlapping surfaces of the piezoelectric plates are separated at least from the vibrating part of the piezoelectric plates. Generally, filters have been proposed that are made into chips by bonding them with adhesive applied to the piezoelectric plate and connecting the necessary terminals of each electrode with external electrodes. The relay capacitor connected between the confinement filters was externally connected.

Purpose of the invention The present invention was devised in view of the above circumstances, and its purpose is to convert the relay capacitance into a capacitor unit in a conventional chip-type piezoelectric filter by attaching it together with the first and second filter units into a chip shape using an adhesive. By bonding, a relay capacitance is incorporated into the filter, thereby eliminating the need for an external capacitor, and obtaining a chip-type piezoelectric filter with a high degree of integration and a small number of parts.

Embodiments Hereinafter, embodiments of the present invention will be described based on the accompanying drawings.

In FIG. 1, 1 is an exterior plate, 2 is a first filter unit, 3 is a second filter unit, and 4 is a capacitor unit.

The exterior plate 1 is made of an insulating material such as ceramic and formed into a rectangular flat plate as shown in FIG. 2a.

As shown in FIG. 2b, the first filter unit 2 has a flat piezoelectric ceramic plate 5 having approximately the same dimensions as the exterior plate 1, and has an energy trapping structure formed on each opposing main surface of the piezoelectric ceramic plate 5. Divided electrodes 6, 7 and a ground electrode 8 of a filter using thickness vibration mode are provided, and these divided electrodes 6, 7 are connected to both ends of one short side of the piezoelectric ceramic plate 5 by extraction electrodes 9, 10 within the plane in which they are formed. On the other hand, the ground electrodes 8 are each drawn out to substantially the center of the long sides of the piezoelectric ceramic plate 5 by means of extraction electrodes 11 and 12 within the plane in which they are formed.

Further, the second filter unit 3 rotates the first filter unit 2 by 180 degrees about a line (not shown) passing through the center of the lead electrodes 11 and 12 of the ground electrode 8, as shown in FIG. 2c. The second filter unit 3 has the same electrode configuration as the first filter unit 2.

As shown in FIG. 2d, the capacitor unit 4 has opposing electrodes 14 and 15 formed on opposing main surfaces of a dielectric substrate 13 having approximately the same dimensions as the exterior plate 1 and the piezoelectric ceramic plate 5, respectively. Electrode 14
are respectively drawn out to the center of each long side of the dielectric substrate 13 by the lead electrodes 16 and 17 within the main surface thereof, while the other counter electrode 15 is drawn out by the lead electrodes 18 and 19 within the main surface thereof. They are drawn out at both ends of one long side of the dielectric substrate 13, respectively.

The above-mentioned exterior plate 1, first filter unit 2, second filter unit 3, and capacitor unit 4 are stacked in this order as shown in FIG.
The respective overlapping surfaces are bonded together using an adhesive 21.

This adhesive 21 is applied to the divided electrodes 6 and 7 of the first filter unit 2 and the second filter unit 3, the ground electrode 8, and their vicinity, that is, except for the vibrating portion of the piezoelectric ceramic plate 5, and the thickness thereof is is the above-mentioned divided electrodes 6, 7 and earth electrode 8.
A space S is formed above the divided electrodes 6, 7 and the ground electrode 8 to allow vibration of the vibrating portion.

By the way, when the exterior plate 1, the first filter unit 2, the second filter unit 3, and the capacitor unit 4 are stacked as described above, the second filter unit 3 overlaps the first filter unit 2. The ground electrode 8 of the first filter unit 2 and its extraction electrode 1 are rotated 180 degrees around the line passing through the extraction electrodes 11 and 12.
1 and 12 overlap the ground electrode 8 of the second filter unit 3 and its extraction electrodes 11 and 12.

Further, the extraction electrode 16 of the capacitor unit 4,
17 is each extraction electrode 1 of the filter units 2 and 3.
1 and 12, and the capacitor unit 4
The lead electrode 18 of the capacitor unit 4 is placed above the lead electrode 9 of the filter unit 2.
9 are located above the extraction electrodes 9 of the filter unit 3, respectively.

As described above, the exterior plate 1, the first filter unit 2, the second filter unit 3, and the capacitor unit are bonded together with the adhesive 21.
As shown in the figure, the first filter unit 2,
Each lead electrode 12 of the second filter unit 3 and the lead electrode 17 of the capacitor unit 4 are connected to each other, and each lead electrode 11 of the first filter unit 2 and the second filter unit 3 and the capacitor unit Four extraction electrodes 16 are connected to each other.

The lead electrode 9 of the first filter unit 2 and the lead electrode 18 of the capacitor unit 4 are connected to the connection terminal 24.
Accordingly, the extraction electrode 9 of the second filter unit 3 and the extraction electrode 19 of the capacitor unit 4 are connected through the connection terminal 25, respectively, the extraction electrode 10 of the first filter unit 2 is connected to the input terminal 26, and the extraction electrode 19 of the second filter unit 2 is connected to the input terminal 26. The extraction electrode 10 of the filter unit 3 is connected to the output terminal 27.

By doing the above, as shown in FIG. 4, the first filter unit 2 and the second filter unit 3
A chip-shaped piezoelectric filter having a well-known circuit configuration is obtained in which the filters are successively connected by the ground terminals 22, 23 and the connection terminals 24, 25 with the capacitor unit 4 as a relay capacitor in between.

Effects of the Invention As is clear from the above detailed description, the present invention provides a first filter unit and a second filter unit that constitute an energy trapping type filter.
Since the piezoelectric filter is bonded together with a capacitor unit at intervals that allow the vibration of the vibrating part of the filter unit to form a chip-shaped piezoelectric filter with a relay capacitance, the relay capacitor is incorporated into the filter, making it possible to create a small and highly integrated filter. A chip-type piezoelectric filter can be obtained.

Further, according to the present invention, since the exterior plate, the first filter unit, the second filter unit, and the capacitor unit are stacked in this order,
In addition to functioning as a relay capacitor for the chip-type piezoelectric filter, the capacitor unit also functions as a cover member for the first filter unit and the second filter unit together with the exterior plate, thereby reducing the number of parts.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of a chip-type piezoelectric filter according to the present invention, and FIGS. A plan view of a two-filter unit and a capacitor unit; FIG. 3 is a cross-sectional view for explaining the bonding structure of the chip-type piezoelectric filter in FIG. 1;
FIG. 4 is an equivalent circuit diagram of the chip-type piezoelectric filter of FIG. 1. 1... Exterior plate, 2... First filter unit,
3...Second filter unit, 4...Capacitor unit, 6, 7...Divided electrode, 8...Earth electrode, 9, 10, 11, 12...Extracting electrode, 13...
...Dielectric substrate, 14, 15... Counter electrode, 16,
17, 18, 19... Leading electrode, 21... Adhesive, 22, 23... Earth terminal, 26... Input terminal, 27... Output terminal, S... Spacing.

Claims (1)

[Claims for Utility Model Registration] A divided electrode and a ground electrode of a filter that uses an energy trapping thickness vibration mode are provided on the opposing main surfaces of a flat piezoelectric plate, respectively, and these divided electrodes and the ground electrode are connected to the piezoelectric plate, respectively. A first filter unit and a second filter unit each have an extraction electrode drawn out from the periphery of the filter unit, and counter electrodes are formed on opposite main surfaces of a flat dielectric substrate. A chip-type piezoelectric filter consisting of a capacitor unit drawn out on the periphery and an insulating outer plate, the outer plate, the first filter unit, and the second filter unit.
The filter unit and the capacitor unit are stacked in this order, and the overlapping surfaces of each are adhered with adhesive at least to the upper parts of the divided electrodes and the ground electrode of the piezoelectric plate at intervals, and the input terminals are attached to the outer peripheral surface of the filter unit and the capacitor unit.
An output terminal and a ground terminal are respectively formed, and the divided electrodes of each of the first filter unit and the second filter unit are connected to the input terminal and the output terminal, respectively, and each divided electrode of the other is connected to one of the capacitor units facing each other. A chip-type piezoelectric filter characterized in that the ground electrodes of the first filter unit and the second filter unit and another opposing electrode of the capacitor unit are connected to the ground terminal. .