JPH0481013A - Saw resonator - Google Patents

Abstract

PURPOSE:To suppress unnecessary resonance, to improve accuracy and to miniaturize the surface acoustic wave(SAW) resonator by providing the pattern of a metallic face on a face (rear face) facing to a face forming a reflecting electrode. CONSTITUTION:The pattern of the metallic film is provided on the face opposed to the face forming an electrode 2 and a reflecting electrode 3 of two terminals composed of IDT electrodes. Namely, the exciting electrode 2 is commonly called as the IDT electrode, and used for exciting the SAW, and the reflecting electrode 3 is provided for reflecting the wave which is excited by the exciting electrode 2 and propagated to both sides of a SAW resonator 1 in the longitudinal direction to return the wave to the side of the exciting electrode 2 by a periodical perturbation effect generated as the result of forming a strip-shaped electrode array 5 by metal such as Au, Ag and Al, etc. Thus, a pattern 5 of the metallic film on the rear face of the resonator 1 absorbs bulk waves and eliminates reflection, the unnecessary resonance at the exciting electrode 2 is suppressed, the accuracy is improved, and the SAW resonator miniaturized by suppressing the warp of the substrate can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a SAW resonator using SAW waves (surface acoustic waves).

[Conventional technology]

A conventional SAW resonator is as shown in FIGS. 2(a) and 2(b). Figure 2(a) is an external view, and Figure 2(b)
indicates the SAW resonator piece, 21 is the airtight case, 22 is the SA
23 is a base of an airtight terminal, 24 is a lead terminal, 25 is a mounting member, and 26 is a wire bonding line. It is fixed to the upper surface of the base 23 of the SAW resonant resonant two-wire terminal with a mounting member 25, and is sealed with an airtight case 21, and the inside is replaced with a vacuum or nitrogen gas. The upper flat portion of the lead terminal 24 is connected to a SAW resonant single wire 2 binding terminal 29 via a wire bonding line 26 .

Figure 2 (Jl) sAW resonance 1t, 2nd rM (b)
As shown in the figure, an excitation electrode 28 with a thickness of about 1,000 to 10,000 and a bonding terminal 29 made of metal such as Au, Ag, or AI are formed on one side of a piezoelectric substrate 20 with a thickness of about 400 to 500 μm. The SAW wave excited by the excitation electrode formed by etching or lift-off and whose back surface is bonded to the heath 23 is reflected by the reflective electrode and returns to the excitation electrode.

[Problem to be solved by the invention]

However, in the above-mentioned conventional technology, vibrations of bulk waves other than 5AWI excited by the excitation IE pole are reflected on the back surface, causing unnecessary resonance at frequencies other than the intended frequency at the excitation electrode on the front surface, or interfering with the SAW waves and causing frequency It was inevitable that the accuracy would deteriorate due to jumps. In addition, since the substrate warps due to the stress of the metal films such as the excitation electrode and the reflective electrode, the thickness of the piezoelectric substrate is made approximately 400 μm to suppress the warping.The present invention solves such conventional problems and eliminates unnecessary resonance. The object of the present invention is to provide a SAW resonator for the lj field, which is highly accurate by suppressing the noise and is miniaturized.

[Means to solve the problem]

The SAW resonator of the present invention has a long SAW resonance and an ID
It is characterized by having a metal film pattern on the surface opposite to the surface on which the two-terminal electrode 2 consisting of a pole and the reflective electrode 3 are formed.

〔Example〕

FIG. 1 is a plan view of a SAW resonator according to an embodiment of the present invention, with FIG. 1(a) being a front view and FIG. 1(b) being a back view. To explain each part in the diagram step by step,
First, the names of each part in Fig. 1(a) are: 1 is the voltage board;
2 is an excitation electrode, 3 located on both left and right sides of 2 is a reflective electrode, and 4 is an electrode on the mount part.0As is well known, SA
In the W resonance resonance length match, the elastic wave used as a resonator is a SAW wave (surface acoustic wave), and the SAW wave is a wave that propagates locally on the surface of an elastic body, and the energy of the wave is It exists at a depth of approximately one wavelength. Therefore, SAW
100M, which is the frequency band usually used as a resonator.
In the range from Hz to IGHz, the commonly used L i T
In the case of AOS or crystal, the wavelength λ = approximately 30 μm, and the thickness of the SAW resonant long current substrate 1 is 3 times λ, 100 μm.
A thickness of approximately μm is sufficient. The excitation electrode 2 is commonly called an IDT electrode, and is used to excite the above-mentioned SAW wave. The role of the reflective electrode 3 is to conduct waves (6 in Figure 1 (a)) that are excited by the excitation electrode 2 and propagate to both sides of the SAW resonance longitudinal direction to a strip-shaped electrode array made of metal such as Au, Ag1A1, etc. The purpose is to reflect the periodic perturbation effect generated as a result of the formation and return it to the excitation electrode side. 4
is the electrode of the mounting part on the lead terminal part of the airtight terminal.

Next, FIG. 1(b) will be explained. Reference numeral 5 denotes a bulk liquid absorbing electrode, and the wave (bulk wave) in the depth direction excited by the excitation electrode 2 in Figure 1 (a) is absorbed by the pattern in the longitudinal direction of this electrode, and is absorbed by the back surface. The reason why the pattern on the back side is in the long plane direction is that it is recommended to be reflected and reach the surface.If the pattern on the back side is in the short direction like the pattern on the front side, the bulk wave generated on the front side will cause the electrode on the back side to This is to prevent the resonance from generating a new bulk wave, which is propagated to the surface and interferes with the SAW wave being excited by the excitation electrode on the surface. In addition, if the material and thickness of the metal film on the front surface and the range and area of the electrode pattern are approximately equal to the material and thickness of the metal film on the back surface and the range and area of the electrode pattern,
The stress in the metal film on the front side is offset by the stress in the metal film on the back side,
In addition, the above-mentioned electrode 2. prevents warping of the substrate. 3. 4.
5 is Au with a thickness of about 1000 to 10000A
, Ag, A1, etc., and after forming a metal film by vapor deposition or sputtering, an electrode pattern is formed by corrosion processing by etching.
Alternatively, an electrode pattern is first formed by lift-off, and then a metal film is formed by vapor deposition or sputtering.

[Effects of the Invention] According to the present invention, the pattern of the metal film on the back surface of the resonator absorbs bulk waves and eliminates reflection, suppresses unnecessary resonance at the excitation electrode, improves precision, and prevents warping of the substrate. It is possible to provide the market with a SAW resonator that is smaller and has a lower cost, and is advantageous in increasing the precision of oscillators and making them smaller.

[Brief explanation of the drawing]

Figures 1(a) and 1(b) show the SAW resonator of the present invention.
AW resonance resonator surface plane IA (a) and back plan view (b)
FIGS. 2(a) and 2(b) are an external view (a) showing an example of a conventional SAW resonator and a plan view (b) of the SAW resonator. l...Piezoelectric substrate 2...Excitation electrode 3...Reflecting electrode 4...Mount section 5...Bulk wave absorbing electrode 6...Propagating wave 21...Airtight case 22...SAW resonance Resonator...Airtight terminal 24...Lead terminal 25...Mount member 26...Wire bonding line 27...Excitation electrode 28...Reflection electrode 29...Bonding terminal and above Applicant: Seiko Epson Corporation Company agent Patent attorney Kisanbe Suzuki 1st name Hanbetsu wo board 2 Excitement of Akihiro Matsu Nido SAW Chowegetsu 1) Buddha's death Figure 1) SAW Mourning Figure 1 (Mu) Figure 112 ( 0,n Figure 2 (J)

Claims (3)

[Claims] (1) In the SAW resonator piece, a metal film pattern is formed on the surface (back surface) opposite to the surface on which the two-terminal excitation electrode consisting of the IDT electrode and the reflective electrode for reflecting and confining the SAW wave are formed. A SAW resonator comprising: (2) The SAW resonator according to claim 1, wherein the pattern of the metal film on the back surface of the SAW resonator piece is a stripe pattern in the longitudinal direction. (3) In the SAW resonator piece, the material and thickness of the metal film on the back surface and the range and area of the pattern are approximately equal to the material and thickness of the metal film on the front surface, and the range and area of the pattern. The SAW resonator according to item 1.