JPH0461507A - Electrode lead structure for ultra thin plate piezoelectric resonator - Google Patents

Abstract

PURPOSE:To ensure a variable range of a resonance frequency sufficiently by widening part of an electrode lead pattern prolonged from an electrode of a resonator corresponding to a thick annular surrounding part more than the width of other parts sufficiently. CONSTITUTION:The width of a part 7a of an electrode lead 7 prolonged from an opposite electrode 6 on a face opposite to a full face electrode 5 formed to a side of a recessed part 2 of an ultra thin plate piezoelectric block 1 in an ultra thin piezoelectric resonator corresponding to an annular surrounding part 4 is widened. Thus, the thickness of a vibration part 3 is very thin and forms a capacitor with a large capacitance when a conductor film with a wide area exists on both the front and the rear face of the part 3 opposite to each other, on the other hand, the annular surrounding part 4 is thick and even when a conductor film exists on its front and rear side, a large capacitance is not formed and no detrimental effect is given to the capacitance ratio of the resonator.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention uses fundamental wave vibration to generate waves of several tens to hundreds of M
The present invention relates to an electrode lead structure for an ultra-thin piezoelectric resonator that can obtain a high resonant frequency up to Hz.

(Prior art) In recent years, demands for higher frequencies and higher frequency stability have become stricter in various electronic devices and communication devices. Cut crystal oscillator temperature - circumference e, number 9
Although its resonance frequency is inversely proportional to the plate thickness, from the viewpoint of manufacturing technology and mechanical strength,
The limit was approximately 0 M II z.

Also, so-called overtone oscillation means that extracts harmonic components of an AT-cut crystal resonator to obtain a frequency that is an odd multiple of the fundamental resonance frequency is also widely used, but this method requires an LC tuning circuit that includes a coil in the oscillation circuit. Therefore, it is inconvenient to integrate the oscillation circuit into a semiconductor integrated circuit, and the capacitance ratio is large.
Another drawback is that oscillation may be difficult due to the high impedance level.

On the other hand, surface acoustic wave resonators, whose resonant frequency is determined by the electrode finger pitch of interdigital transducer electrodes, have become
Although it has become possible to achieve a certain level of output, there is a problem in that the temperature-frequency characteristics of the piezoelectric substrate that can be used for this purpose are significantly inferior to that of AT-cut crystal.

In order to solve the above-mentioned problems, conventionally, Fig. 4 (al.
(Piezoelectric resonators as shown in bl are being studied.

That is, this piezoelectric resonator has a concave portion 2 formed by machining or etching in the center of one side of the AT-cut crystal block l.
At the same time, the thickness of the vibrating part 3 located at the bottom surface of the recessed part 2 is set to about 17 μm if a fundamental resonance frequency of 100 MHz is to be obtained, for example.

As a result of forming the concave part 2, a thick annular surrounding part (rib) 4 is formed integrally with the vibrating part 3 on the peripheral edge of the ultra-thin plate-like vibrating part 3 on the block surface on the side of the concave part 2. mechanically supports the ultra-thin plate-shaped vibrating section.

A conductive film 5 is attached to the entire surface of the piezoelectric plate having the above-described structure, including the inner wall of the recess, and a partial electrode 6 and an electrode lead 7 extending therefrom are formed on the surface of the vibrating part 3 on the opposite side by vacuum evaporation or the like. If this method is used for attachment, it is possible to obtain a piezoelectric resonator with an extremely high resonance frequency.

The main reason for attaching the conductor [5] to the entire surface of the piezoelectric plate, including the inner wall of the recess, is that forming a conductor film partially using a special vapor deposition technique using a precision mask is complicated and reduces production efficiency. However, on the other hand, the entire two portions of the concave portion are conductors lI! 1ij partial electrode 6 because it is covered with 25
A capacitor is formed between the piezoelectric resonator and the electrode lead 7 extending from the piezoelectric resonator, increasing the capacitance ratio of the entire piezoelectric resonator, resulting in a problem that the range in which the frequency can fluctuate becomes smaller.

That is, when the area of the electrode lead portion is increased in order to provide sufficient conductivity to the electrode lead 7 extending from the partial electrode 6, a large capacitance C is constructed due to the ultra-thin thickness of the vibrating member plate. When the large capacitance C is formed, the parallel capacitance C8 in the equivalent circuit of the piezoelectric resonator shown in FIG. 5 increases, and the capacitance ratio γ=C, /C of the piezoelectric resonator increases. This type of resonator would have limited application to oscillation circuits that require the oscillation frequency to vary within a predetermined range, such as a voltage controlled crystal oscillator (VCXO), and would not be applicable to multimode filter elements. However, if a relatively wide bus band is required, it is expected that the problem will be difficult to accommodate.

In order to solve this problem, a method can be considered in which the conductor film is not attached to the part corresponding to the lead of the full-surface electrode, but this requires vapor deposition using a mask, and it is said that a mask is not required for vapor deposition. This results in a complete loss of the advantages of the full-surface electrode configuration.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems predicted in ultra-thin plate piezoelectric resonators, and it is an object of the present invention to convert the bottom surface of a recess formed on the surface of a piezoelectric block such as a crystal into an ultra-thin plate piezoelectric resonator. In a piezoelectric resonator with a piezoelectric vibrating part, the electrode and the electrode lead pattern face each other through the ultra-thin vibrating part, forming a capacitor and increasing the parallel capacitance of the resonator. It is an object of the present invention to provide an electrode lead structure for an ultra-thin piezoelectric resonator that can eliminate various problems that occur.

(Summary of the Invention) In order to achieve the above object, the resonance f according to the present invention corresponds to an annular surrounding portion with a thickness of L in a 'Fih lead pattern extending from an electrode formed on one surface of an ultra-thin vibrating part. (Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

Before explaining the embodiments, first, to help understand the present invention, we will explain why the ultra-thin piezoelectric resonator, which is the basis of the present invention, has an electrode structure in which a full-surface electrode is provided in the recessed part and a partial electrode is provided on the opposite surface. Let me explain a little bit about whether to adopt .

First, from the viewpoint of vacuum evaporation technology, it is not possible to place a partial electrode on the vibrating part of the recess of the piezoelectric substrate as described above, and to extend a narrow electrode lead from the electrode beyond the inner wall and step of the recess. However, it would be extremely difficult to perform vapor deposition by tilting the piezoelectric substrate with respect to the horizontal plane, and there would be concerns about ensuring continuity of the electrode leads. This ensures continuity.

Second, this type of resonance r originally aimed at ultra-miniaturization of devices, and the size of the piezoelectric substrate was, for example, 3 mm x 3 m.
I want it to be 10 m or more. If this is the case, a manufacturing method will be adopted in which a large number of chips are formed all at once on 11 sheets of electrical engineering hardware by batch processing, and then cut into individual chips after EL. In this case, if the electrode configuration of the type described in 1. is adopted, it is sufficient to simply deposit a conductive film on the entire surface of the wafer, and there is no need for delicate alignment of a photomask or photolithography mask. Therefore, production efficiency, yield can be improved, and costs can be reduced.

It should be noted that for the reasons mentioned above, the ultra-thin plate piezoelectric resonators that have been studied in the past are based on the fact that electrodes are attached all over the surface of the concave side.

However, if the above-mentioned electrode configuration is used, a large capacitance capacitor is formed between the electrode lead portion and the electrode lead portion on the front and back surfaces of the vibrating portion, partly because the plate thickness of the vibrating portion is extremely small, and as a result, resonance occurs. The capacity ratio of the container is increased to 1g!
As mentioned above, this causes various inconveniences.

In order to solve this problem, the ultra-thin plate monoelectric resonance T- according to the present invention has the electrode structure as described above.

FIG. 1 is a plan view showing the basic configuration of the present invention, showing the surface facing the entire surface electrode formed on the recess 2 side of the ultra-thin piezoelectric block L, and the annular shape of the electrode lead 7 extending from the counter electrode 6 of E. The width of the portion 7a corresponding to the surrounding portion 4 is made wider.

The reason for increasing the width of the electrode lead portion 7a located on the back surface of the annular surrounding portion 4 while minimizing the width of the electrode lead portion 7b located on the vibrating portion 3 to the necessary minimum is as follows. The vibrating part 3 has an extremely small wall thickness, and if large-area conductor films exist facing each other on both the front and back sides of the part, it forms a capacitor with a large capacity, whereas the annular surrounding part 4 has a very small wall thickness. is large, and even if there is a conductive film on the front and back sides, it will not have a very large capacitance (this is because it is thought that it will not have a large effect on the capacitance ratio of the resonator. Also, This is because ohmic loss can be reduced by limiting the length of the thin electrode lead portion 7b.

As shown in FIG. 2, the piezoelectric resonator as described in 1. The second side full surface electrode 5 is adhesively fixed to the conductor film 10 on the edge surface of the annular surrounding portion 4- with a conductive adhesive 11, and is connected to the external lead end T-12 of the package via the conductor film 10. On the other hand, the wide part 7a of the electrode lead 7 extending from the partial electrode 6 is connected to the conductor pad 14 provided on the stepped part of the inner wall of the back cage 8, which connects it to the lead terminal 13 on the outer wall of the package.
It is convenient to use for connecting at 5.

Although the present invention has been described above in the case where it is applied to a piezoelectric vibrator, the present invention can be similarly applied to an ultra-thin multi-mode filter. As is well known, in the dual mode JE@ filter, which is the most commonly used multimode filter, the entire surface electrode 5 on one main surface of the piezoelectric substrate (in this case, the recess 2 side) is used as a ground electrode, and the white surface thereof is provided with divided adjacent electrodes. 16 is provided, and an alternating electric field is applied to both electrodes to create acoustic coupling between the two electrodes, and as a result, two vibration modes with different resonant frequencies are excited to form a panned pass filter. It is something.

It is well known that the achievable bandwidth of such a filter element also decreases as the equivalent parallel capacitance C0 increases, that is, as the capacitance ratio γ increases.

Therefore, as shown in FIG. 3, the portion 17.17 of the lead drawn out from the split electrode 16.16 is attached to the surface of the vibrating portion 3.
is thin, and the portions 17a, 17 on the surface 5 of the annular surrounding portion 4
A should be made wider.

In this way, a vibrator that obtains a resonant frequency of several lO to 100 MHz by fundamental wave vibration or a filter element that has approximately this frequency as its center frequency can be formed into an ultra-small size, and these characteristics, especially the resonant frequency Variable width allows the filter bandwidth to be partially secured to a large value.

(Effects of the Invention) Since the present invention is constructed as described above, the capacity:d ratio of the ultra-thin piezoelectric vibrator or filter element can be reduced to 11.
(In addition, in the case of a resonator, a sufficient variable width of the resonant frequency is ensured, and in the case of a filter element, L, which has a wide bass band of 5, has an unpleasant effect.Furthermore, the resonator Since the leet area on the surface of the vibrating part is smaller than that of the electrode, it also has the effect of generating fewer unnecessary waves.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the electrode lead structure of the ultra-thin piezoelectric resonator according to the present invention, FIG. 2 is a cross-sectional view showing an example of the piezoelectric resonator packaging method according to the present invention, and FIG. FIGS. 4(a) and 4(fb) are a plan view showing an embodiment of an ultra-thin multi-mode filter element to which the invention is applied, a perspective view and a perspective view showing the structure of an ultra-thin piezoelectric resonator that has been conventionally studied, respectively. Its XX cross-sectional view, FIG. 5, is an equivalent circuit diagram of the resonator. 3... Vibrating part 4... Annular surrounding part 5-0゜Full surface electrode...Partial electrode 7...°4 positive part

Claims (1)

[Claims] (1) A piezoelectric resonator element that is integrally formed with an ultra-thin vibrating part and a thick-walled annular surrounding part that supports the periphery of the vibrating part has a full-surface electrode on one main surface, and a partial electrode on the opposite surface. An electrode lead structure for an ultra-thin piezoelectric resonator, characterized in that an electrode and an electrode lead extending from the electrode lead to the edge of the blank plate are provided, and a part of the electrode lead that attaches to the surface of the annular surrounding part is wider than the other part. .