JPH04192806A - Piezoelectric vibrator and its frequency adjusting method - Google Patents

Abstract

PURPOSE:To facilitate the fine adjustment of a resonance frequency by providing the lower electrode opposed to one upper electrode through a dielectric layer on a substrate, and connecting a capacitor constituted of the upper electrode, the dielectric layer and the lower electrode in series to a piezoelectric vibration element. CONSTITUTION:A substrate 5 is provided with the lower electrode 53 opposed to one upper electrode 51 through a dielectric layer 52, and a capacitor constituted of the upper electrode 51, the dielectric layer 52 and the lower electrode 53 is connected in series to a piezoelectric vibration element 1. Plural substrates 5 in which the capacities of the capacitors are different are prepared in advance. and by selecting suitably the substrate 5 and combining it with the piezoelectric vibration element at the time of executing fine adjustment of a resonance frequency of the piezoelectric vibration element 1, plural kinds of piezoelectric vibration elements 1 whose frequencies are different from each other are constituted. In such a way, the kinds of the piezoelectric vibration elements 1 to be prepared in advance decrease and the management is simplified, and the fine adjustment of the resonance frequency is facilitated.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a piezoelectric vibrator used in a clock signal oscillation circuit, etc., in particular a piezoelectric vibrator whose resonant frequency can be easily finely adjusted, and a method for adjusting its frequency. The purpose is to provide a piezoelectric vibrator and its adjustment method, and it consists of a substrate equipped with a piezoelectric vibrator and a pair of upper electrodes.
A piezoelectric vibrator electrically connected to an extraction electrode or an upper electrode of a piezoelectric vibrating element, wherein the substrate has a lower electrode facing one of the upper electrodes with a dielectric layer interposed therebetween, and the upper electrode, A capacitor including a dielectric layer and a lower electrode is connected in series with a piezoelectric vibrating element.

[Industrial application field]

The present invention relates to a piezoelectric vibrator used in a clock signal oscillation circuit, etc., and more particularly to a piezoelectric vibrator whose resonant frequency can be easily finely adjusted and a method for adjusting its frequency.

An integrated circuit that processes digital signals has a clock signal oscillation circuit built therein, and the clock signal oscillation circuit is formed by adding a piezoelectric vibrator to a semiconductor integrated circuit. However, each semiconductor integrated circuit has a different internal circuit constant. For example, when configuring a circuit that oscillates a 4M7 clock signal, the resonant frequency of the piezoelectric vibrator used therein is not necessarily 4MHz, but is based on the circuit constant of the semiconductor integrated circuit. Therefore, the resonant frequency is required to be slightly shifted.

Therefore, it is desired to realize a piezoelectric vibrator whose resonant frequency can be easily finely adjusted.

[Conventional technology]

Figure 3 is a perspective view showing the main parts of a conventional piezoelectric vibrator;
The figure is a circuit diagram showing an example of a clock signal oscillation circuit.

In FIG. 3, a conventional piezoelectric vibrator has a piezoelectric vibrating element 1 and a substrate 2, and the piezoelectric vibrating element 1 is made of a piezoelectric single crystal such as lithium tantalate (LiTaO=) or lithium niobate (LiNb02). A base plate 11 and a pair of drive electrodes I facing each other with the rectangular piezoelectric base plate 11 interposed therebetween.
2, each drive electrode 12 is composed of a piezoelectric element plate 11
It is connected to extraction electrodes 13 formed at both ends of. Further, the substrate 2 made of ceramic or the like is provided with a pair of electrodes 21, and the lead electrodes 13 of the piezoelectric vibrating element 1 are soldered to the electrodes 21, respectively.

On the other hand, the clock signal oscillation circuit is constituted by a piezoelectric vibrator 3 and a semiconductor integrated circuit 4 which includes a C-MOS inverter 41 and a resistor 42, as shown in FIG.

Such semiconductor integrated circuits 4 have different internal circuit constants depending on the model. For example, when configuring a circuit that oscillates a 4 MHz clock signal, the resonant frequency of the piezoelectric vibrator 3 used therein is not necessarily 4 MHz, and the semiconductor integrated circuit A device whose resonant frequency is slightly shifted depending on the circuit constant No. 4 is required.

Therefore, conventionally, a plurality of types of piezoelectric vibrating elements 1 each having a certain resonant frequency are prepared in advance, and piezoelectric vibrating elements 1 corresponding to the customer's requirements are combined with a substrate 2 to form a piezoelectric vibrator. If there is no piezoelectric vibrating element 1 that meets the customer's requirements among the prepared elements, the frequency is adjusted by, for example, reducing the size of the drive electrode 12 on the piezoelectric element plate 11.

[Problem to be solved by the invention]

However, the conventional method of preparing a plurality of types of piezoelectric vibrating elements with slightly different resonant frequencies in advance and combining the piezoelectric vibrating elements corresponding to the customer's requirements with a substrate to form a piezoelectric vibrator is as follows.
For example, multiple types of piezoelectric vibration elements for 2MHz, 4MHz
Having multiple types of piezoelectric vibrating elements for 6MHz, multiple types of piezoelectric vibrating elements for 8M&, making managing the piezoelectric vibrating elements complicated and making it difficult to adjust the frequency. There was a problem.

An object of the present invention is to provide a piezoelectric vibrator whose resonant frequency can be easily finely adjusted and a method for adjusting the piezoelectric vibrator.

[Means to solve the problem]

FIG. 1 is a side sectional view showing a piezoelectric vibrator according to the present invention. The same objects are represented by the same symbols throughout the figures.

The above-mentioned problem is a piezoelectric vibrator consisting of a substrate 5 equipped with a piezoelectric vibrating element l and a pair of upper electrodes 51, and in which extraction electrodes 13 provided at both ends of the piezoelectric vibrating element l are electrically connected to the upper electrode 51. It has a lower electrode 53 that faces either the upper electrode 51 via the substrate 5 or the dielectric layer 52, and includes the upper electrode 51, the dielectric layer 52, and the lower electrode 5.
A piezoelectric vibrator according to the present invention, in which a capacitor constituted by 3 is connected in series with a piezoelectric vibrating element 1.

A plurality of substrates 5 having different capacitances are prepared in advance, and when finely adjusting the resonant frequency of the piezoelectric vibrator, the substrate 5 is appropriately selected and combined with the piezoelectric vibrating element 1. This is achieved by a frequency adjustment method.

[For production]

In FIG. 1, the substrate has a lower electrode facing one of the upper electrodes through a dielectric layer, and a capacitor composed of the upper electrode, the dielectric layer, and the lower electrode is connected in series with the piezoelectric vibrating element. The piezoelectric vibrator of the present invention is connected to
By preparing in advance a plurality of substrates with different capacitor capacities, selecting the appropriate substrate when finely adjusting the resonant frequency of the piezoelectric vibrator, and combining it with a piezoelectric vibrator for 4 MHz or 6 MHz, for example, the piezoelectric vibrator for 4 MHz can be adjusted. A plurality of types of piezoelectric vibrators each having a different frequency are configured for 6MHz and 6MHz.

That is, the number of types of piezoelectric vibrating elements to be prepared in advance is reduced, management is simplified, and it is possible to realize a piezoelectric vibrator and its adjustment method that allows fine adjustment of the resonant frequency.

〔Example〕

FIG. 2 is a diagram for explaining the present invention in detail. The principle and effects of the present invention will be explained below with reference to FIG.

The piezoelectric vibrator according to the present invention can be replaced with the equivalent circuit shown in FIG. That is, the piezoelectric vibrating element consists of a resistor R, a coil L, and a capacitor C1 connected in series, and a capacitor C6 connected in parallel to R, L, and C8. C
are connected in series.

The resonant frequency of the series part of R, L, and 08 is f's.If the composite resonant frequency of the piezoelectric vibrating element is f, then Ct + C5 = f, ・(-)"" (3) C4 Also, C is applied to the piezoelectric vibrating element. Let f be the composite resonant frequency when C is connected in series, that is, C connected in series as shown in equations (5) and (6)
The resonant frequency of the piezoelectric vibrator changes depending on C.
As the value increases, the resonant frequency of the piezoelectric vibrator decreases.

Therefore, in FIG. 1, the area of the lower electrode 53 may be changed while keeping the material and thickness of the dielectric layer 52 constant, or
By changing the material and thickness of the dielectric layer 52 while keeping the area of 3 constant, the capacitance of the capacitor composed of the upper electrode 51, the dielectric layer 52, and the lower electrode 53 can be changed, and the size of C can be changed. A plurality of different types of substrates 5 are prepared in advance.

Then, when forming a piezoelectric vibrator, a substrate 5 having a capacitor of an appropriate capacity is selected, and for example, a resonance frequency of 4
．． By combining with the 0MHz piezoelectric vibrating element 1,
A piezoelectric vibrator with a resonant frequency slightly lower than 4.0 MHz can be formed. Note that the substrate 5 prepared in advance
If there is no suitable one, use a laser or the like to scrape off a part of the upper electrode 51 facing the lower electrode 53.
It is also possible to appropriately adjust the capacitance of the capacitor to an optimal value.

Similarly, when forming a piezoelectric vibrator, a substrate 5 having a capacitor of an appropriate capacity is selected, and the resonance frequency is, for example, 6.
．． By combining with the 0MHz piezoelectric vibrating element 1,
It is possible to form a piezoelectric vibrator with a resonant frequency slightly lower than 6.0 MHz), for example, a resonant frequency of 8.0 MHz.
By combining this with the piezoelectric vibrating element 1, a piezoelectric vibrator having a resonant frequency slightly lower than 8.0 MHz can be formed.

In this way, the substrate has a lower electrode facing one of the upper electrodes via the dielectric layer, and the upper electrode, the dielectric layer,
In the piezoelectric vibrator of the present invention, in which a capacitor composed of a capacitor and a lower electrode is connected in series with a piezoelectric vibrating element, a plurality of the substrates having different capacitances are prepared in advance, and when forming the piezoelectric vibrator, By selecting an appropriate substrate and combining it with a piezoelectric vibrating element, 4M1 (for z and 6
A plurality of types of piezoelectric vibrators each having a different frequency for MHz are configured. That is, the number of types of piezoelectric vibrating elements to be prepared in advance is reduced and management is simplified, and it is possible to realize a piezoelectric vibrator and its adjustment method in which the resonant frequency can be easily finely adjusted.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a piezoelectric vibrator whose resonance frequency can be easily finely adjusted, and a method for adjusting the piezoelectric vibrator.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a piezoelectric vibrator according to the present invention, FIG. 2 is a diagram for explaining the present invention in detail, and FIG. 3 is a perspective view showing the main parts of a conventional piezoelectric vibrator. FIG. 4 is a circuit diagram showing an example of a clock signal oscillation circuit. In the figure, 1 is a piezoelectric vibrating element, 5 is a substrate, 11 is a piezoelectric element plate, 12 is a drive electrode, 13 is an extraction electrode, 51 is an upper electrode, 52 is a dielectric layer, 5
3 is the lower electrode;

Claims (1)

[Claims] 1) A substrate (5) comprising a piezoelectric vibrating element (1) and a pair of upper electrodes (51), and lead-out electrodes (13) provided at both ends of the piezoelectric vibrating element (1). However, the upper electrode (51)
A piezoelectric vibrator electrically connected to a substrate (5), the substrate (5) having a lower electrode (53) facing one of the upper electrodes (51) via a dielectric layer (52). , a capacitor composed of the upper electrode (51), the dielectric layer (52), and the lower electrode (53) is connected in series with the piezoelectric vibrating element (1). vibrator. 2) A plurality of substrates (5) according to claim 1 having different capacitances are prepared in advance, and the substrates (5) are appropriately selected when finely adjusting the resonance frequency of the piezoelectric vibrator, and the piezoelectric vibrator ( A method for adjusting the frequency of a piezoelectric vibrator, characterized in that it is combined with 1).