JPH04115706A - Electrode lead structure for ultra thin plate piezoelectric resonator - Google Patents

Abstract

PURPOSE:To form an element in an ultra small size and to reduce spurious radiation by forming a part adhered to the surface of a vibration section among electrode lead patterns extended from the electrode formed to one face of the vibration section with plural electrode lead patterns with a narrow width. CONSTITUTION:A part placed on a surface of a ultra thin vibration section 3 in an electrode lead extended from a partial electrode 6 on a face opposite to a full face electrode formed to the surface of a recessed part 2 of an ultra thin plate piezoelectric block 1 is formed by plural narrow electrode lead patterns 7c, 7c... and the sum of the cross sections of each pattern 7c is to be a value sufficiently to prevent the increase in the ohmic loss. Thus, the spurious radiation caused between a full face electrode and the electrode lead patterns divided appear at a point much apart from the resonance point of the resonance by the true electrode, the level is small and no special fault is provided to various characteristics of the resonator.

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention uses fundamental wave vibrations to
The ultra-thin plate piezoelectric resonator has a ':lf pole lead structure which can obtain a high resonance frequency of up to 1000 nm.

(Prior art) In recent years, demands for higher frequencies and higher frequency stability have become stricter in various electronic devices and communication devices. Although the AT-cut crystal resonator has extremely excellent temperature-frequency characteristics, its resonance frequency is inversely proportional to the plate thickness, so from the viewpoint of manufacturing technology and mechanical strength, 40M
The limit was around Hz.

In addition, so-called overtone oscillation means that extracts the harmonic components of an AT-cut crystal oscillator to obtain a frequency that is an odd multiple of the fundamental resonance frequency is also widely used (although it is widely used, it is not possible to use an LC tuned circuit that includes a coil in the oscillation circuit). This is inconvenient when converting 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, the surface acoustic wave resonator, whose oscillation frequency is determined by the electrode finger pitch of the interdigital transducer electrodes, has become 1 GH due to advances in photolithography technology.
Although it has become possible to achieve outputs up to about Z, there is a problem in that the temperature-frequency characteristics of the piezoelectric substrate that can be used for this are significantly inferior to that of AT-cut crystal.

In order to solve the above-mentioned problem, conventionally, the method shown in Fig. 4(a)
(Piezoelectric resonators as shown in bl are being studied.

That is, this piezoelectric resonator has a concave portion 2 formed in the center of one side of the AT-cut crystal block 1 by machining or etching.
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 portion 2, the outer peripheral portion of the block on the side of the concave portion 2 constitutes a thick annular surrounding portion 4 that mechanically holds the peripheral portion of the ultra-thin plate-like vibrating portion 3. A conductive film 5 is attached to the entire surface of the concave side of the piezoelectric plate having the above-described structure, including the inner wall thereof, and a partial electrode 6 and an electrode lead 7 extending from this are attached to the surface of the vibrating part 3 on the opposite side. If it is deposited using a method such as vacuum evaporation, a piezoelectric resonator with an extremely high resonance frequency can be obtained.

The main reason for attaching the conductor film 5 to the entire surface of the piezoelectric plate, including the inner wall of the recess, is simply to facilitate manufacturing and improve yield.
One surface of the piezoelectric substrate 1 is used as a full-surface electrode 5, and the electrode attached to the opposite surface is a partial electrode 6, and the width (cross-sectional area) of the electrode lead portion 7 extending from the partial electrode is determined so that ohmic loss (electrode resistance) does not become a problem. If the value is set to a sufficiently large value, resonance occurs near the resonance point of the above-mentioned resonance caused by the real electrode, with the electrode lead portion serving as a pseudo electrode, and this has the disadvantage that it becomes a high-level spurious.

(Object of the Invention) The present invention has been made to eliminate the above-mentioned defects in an ultra-thin piezoelectric resonator, and the present invention is aimed at eliminating the above-mentioned defects in an ultra-thin piezoelectric resonator. In a piezoelectric resonator having a 1F pole on the entire surface of the concave side, if the width of the electrode lead extending from the partial electrode facing the entire surface electrode is sufficiently wide to avoid ohmic loss, the portion may be simulated. It is an object of the present invention to provide an electrode lead structure for an ultra-thin piezoelectric resonator that can prevent spurious waves generated as electrodes.

(Summary of the Invention) In order to achieve the above-mentioned object, the resonator according to the present invention has a width of a portion of the electrode lead pattern extending from the electrode formed on one surface of the ultra-thin vibrating portion, which is attached to the surface of the thin-walled vibrating portion. Consists of multiple narrow electrode lead patterns.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

Before explaining the embodiments, in order to help understand the present invention, we will explain why the ultra-thin plate 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 possible to extend a partial W pole to the vibrating part on the side of the piezoelectric substrate recess as described above, and to extend a narrow electrode lead from the electrode beyond the inner wall and step of the recess. It would be extremely difficult to perform vapor deposition by tilting the piezoelectric substrate with respect to the horizontal plane, but it would be extremely difficult to ensure continuity between the electrodes.
This ensures continuity at any part.

Second, this type of resonator was originally intended for ultra-miniaturization of devices, and the planar size of the piezoelectric substrate was, for example, 3 mm x 3 mm.
I want it to be less than mm. If this is the case, a manufacturing method will be adopted in which a large number of chips are formed all at once on a single piezoelectric wafer by batch processing, and then the chips are finally cut into individual chips. In this case, if the above-mentioned type of electrode configuration is adopted, it is sufficient to simply deposit a conductor film on the entire surface of the wafer, and delicate alignment of a photomask or photoringraph mask is not required. Production efficiency and yield can be improved and costs can be reduced.

For the reasons mentioned above, it should be noted that the ultra-thin plate piezoelectric resonators that have been studied by the inventors of the present invention are based on the fact that electrodes are attached all over the surface of the concave side.

However, in order to prevent an increase in ohmic loss in the armpit by giving a sufficiently large cross-sectional area to the electrode lead portion of the partial electrode that faces the entire surface electrode as described above, the size of the partial electrode 6 itself must be extremely small. As shown in FIG. 5, the width of the electrode lead part 7b on the ultra-thin vibrating part 3 is about the same as that of the part 1f pole 6, and as a result, the entire surface facing the ultra-thin vibrating part 3 is As mentioned above, there is a defect in that the electrode and the 1i pole part 7b function as a pseudo 1it pole, and a high-level spurious is generated near the resonance point of the real electrode 6 due to the resonance of the electrode lead part. be.

In order to solve this problem, the ultra-thin plate piezoelectric resonator according to the present invention has the following t-pole structure.

FIG. 1 is a plan view showing the basic configuration of the present invention, in which the electrode lead extends from the partial electrode 6 on the surface facing the recess 2 side surface of the ultra-thin piezoelectric block 1, and The part located on the surface of the thin vibrating part 3 is composed of a plurality of small-width electrode lead patterns 7c, 7c, ..., and the total cross section of each '4N lead pattern 7c prevents an increase in ohmic loss. The structure is such that it has a sufficient value.

As a result, the spurious generated between the entire surface electrode and these subdivided electrode lead patterns appears at a point quite far away from the resonance point of the real electrode, and its level is small, and the It does not cause any particular damage to the characteristics.

In this embodiment, three electrode lead patterns 7C are extended in a blind shape from the partial electrode 6 toward the pad 7a on the outer periphery of the piezoelectric block 1, but this is merely an example. First, the number of electrode lead patterns 7c may be two or more. Further, the electrode lead patterns do not need to be parallel to each other.

The pad 7a is located on the thick annular surrounding portion 4 and is attached to the vibrating portion 3.
Since it is a part that does not participate in resonance (even if it resonates, the resonance frequency is significantly lower than that of the vibrating part), its f
The product can be set arbitrarily.

As shown in FIG. 2, the piezoelectric resonator as described above is housed in a dish-shaped package 8 made of sintered ceramics, for example, with its concave 2 side facing the conductor film 10 provided on its inner bottom surface. The second side full surface electrode 5 is adhesively fixed to the conductive film 10 on the edge surface of the annular surrounding portion 4 with a conductive adhesive 11, and is connected to the external lead terminal 12 of the package via the conductor g10. On the other hand, the wide NI 7 a of the electrode lead 7 extending from the partial electrode 6 connects it to the lead terminal 13 on the outer wall of the package and the conductor pad 14 provided on the stepped part of the inner wall of the package 8 and the bonding wire 1 .
It is convenient to connect 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, the dual-mode piezoelectric filter, which is the most widely used of the multi-mode filters, has a ground electrode on the entire surface of one main surface of the piezoelectric substrate (in this case, the recess 2 side), and a divided adjacent electrode on the opposite surface. , an alternating electric field is applied to these picture electrodes to create acoustic coupling between the two electrodes, and as a result, two vibration modes with different resonance frequencies are excited to form a bandpass filter.

It is obvious that in such a filter element, if the ohmic loss of the electrode leads extending from the electrodes on both sides is large, the insertion loss of the filter will increase. If it is made too large, a problem arises in that spurious noise due to armpit resonance occurs near the filter passband, making it impossible to obtain the desired stopband attenuation. Therefore, as shown in FIG. 3, the portion 17.17 of the lead drawn out from the divided electrode 16.16, which is attached to the surface of the vibrating section 3, may be composed of a plurality of thin electrode lead patterns 17c.

In this way, a vibrator that obtains a resonant frequency of several tens to 100 MHz through fundamental wave vibration or a filter element having approximately this frequency as its center frequency is formed into an ultra-compact size.
Furthermore, spurious components can be reduced.

(Effects of the Invention) Since the present invention is constructed as described above, by only slightly changing the shape of the vapor deposition mask or photomask for forming the partial electrode, spurious signals can be minimized or even present. Even if the ultra-thin plate piezoelectric resonator has an electrode on one side, which is easy to manufacture, the equivalent resistance can be increased because it can be made to appear at a position quite far from the resonance point of the vibrator or the passband of the filter. (It has a remarkable effect on maintaining its spurious characteristics.)

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of the structure of the electrode lead 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. 4(a) and 4(b) are perspective views showing the structure of ultra-thin piezoelectric resonators that have been studied in the past, respectively. The figure, its XX sectional view, and FIG. 5 are plan views showing electrode leads having the same width as the 1f pole. 1...Ultra-thin piezoelectric block 2...Concavity 3...Vibrating part 4...Annular surrounding part 5...Full surface electrode 6...
・Partial electrode 7... Electrode electrode 7a... Wide part
7b...Narrow width part 7C...Narrow electrode lead pattern patent applicant Toyo Tsushinki Co., Ltd.

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 and an electrode lead extending from it to the edge of the blank are provided, and the electrode lead is
An electrode lead structure for an ultra-thin piezoelectric resonator characterized by being composed of a lead pattern as narrow as a book or more.