JPS60185416A - Surface acoustic wave element - Google Patents

Abstract

PURPOSE:To suppress electrode multiple reflection by using a reed screen electrode where a bonding pad for a common electrode end is provided at the midpoint between the common electrode end and an effective aperture end at the outside of the effective aperture exciting a surface acoustic wave or receiving a wave. CONSTITUTION:A pair of wave transmission/reception reed screen electrodes are provided on a surface acoustic wave substrate including a piezoelectric substance. The reed screen electrodes consist of a bonding pad 16, a common electrode end 17, non-crossing apertures 18, 18' and the effective aperture 19. It is desirous to increase the electrode finger resistance for the suppression of electrode multiplex reflection (TTE). Thus, the non-crossing apertures 18, 18' are sized large. Since the non-crossing aperture is not directly related to the excitation or reception of the surface acoustic wave, when the bonding pad 16 is provided between the end of the effective aperture 19 and the common electrode end 17, the chip size in the direction perpendicular to the surface acoustic wave propagation is decreased without giving any effect on the surface acoustic wave at all.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a small surface acoustic wave device in which multiple electrode reflections are well suppressed.

[Background of the invention]

One of the problems with surface acoustic wave devices is electrode multiple reflection (Tri
ple Transit Echo, 111% T
There is a T E ). TTE causes ripples in the amplitude and phase frequency characteristics of surface acoustic wave devices, and in particular in devices that require flat frequency band characteristics, 1.) is TTE.
TE suppression is essential.

FIG. 1 is a schematic diagram of a conventional surface acoustic wave element. Hunting 1
On a surface acoustic wave substrate 1 made of a surface acoustic wave body, a surface acoustic wave transmitting blind-shaped electrode 2 and a wave receiving blind-shaped electrode 2' are formed, and the transmitting blind #0. An input 1 and a force signal source 4 are connected to the electrode 2, and an output load impedance 5 is connected to the receiving interdigital electrode 2'. Further, between the transmitting interdigital IM @2 and the receiving interdigital electrode 2', there is a direct wave prevention electrode 7 for preventing electromagnetic waves from inputting from the input end to the surface output end.
, surface acoustic wave sound absorbers 6° 6' are formed to suppress surface reflected waves. Normally, the length of the transmitting stranded electrode 2 or the receiving stranded electrode 2' has a structure in which the intersecting width of the electrode fingers is weighted in order to satisfy amplitude and phase characteristics. In addition, 3 is the Honda pin pad at the common electrode end of the electrode □ finger.
It's Tsudo.

In addition, FIG. 2 is a diagram showing a normal interdigital electrode (single), where 8 is a common electrode, an extreme electrode, and 9 is a bonding electrode thereof.

As a method for suppressing TTE, the power source or 111 is a load conductance Ge and a surface acoustic wave element.

A common method is to increase the ratio of the radiation conductance Ga of the droop-like electrode. However, this method reduces the degree of freedom in designing the opening. Therefore, the present inventors proposed the third
As shown in the figure, non-intersecting 1-.

T'J'B suppression was performed by extending the lid opening 10,10' and increasing the resistance of each electrode finger.

However, this conventional method of the present inventors does not.

It is necessary to make the cross opening considerably large (usually 300 to 1000 μm), and in addition, the outside of the common electrode end 11, 1,
Since the ponting pad 12 was provided in the chip, there was a drawback that the chip size became large.

Further, in order to reduce the chip size, as shown in FIG. 4, if the honting pad 13 is provided inside the common electrode end 14 so that a part thereof overlaps the effective opening 15,
Reflection of surface acoustic waves occurs at the bonding pad,
Unnecessary delayed signals are generated, which appear as thick ripples in the amplitude and phase frequency characteristics of the surface acoustic wave device, and when this device is used in a television receiver, ghosts occur.111
He had the disadvantage of being very talented.

[Purpose of the invention]

An object of the present invention is to provide a small surface acoustic wave element that is free from the various drawbacks and problems described above, and in which T'[''E is well suppressed. 1. [Summary of the Invention] Achievement of the above object In order to avoid this, in the present invention, electrode fingers of different polarity do not intersect with respect to the surface acoustic wave propagation direction and are out of the effective opening for excitation or reception of the surface acoustic wave.
At the midpoint between the common t a = end and the effective opening 0.1° end,
A honding pad is provided for the common electrode end, and is placed outside the common electrode end as before.

The chip size in the direction perpendicular to the surface wave propagation direction is made smaller compared to the case where a bonding pad is provided on the surface. FIG. 5 is a schematic diagram of the interdigital electrode according to the present invention, in which 16 is a honding pad, 17 is a common electrode end, and 18
．． 18' is a non-intersecting opening, and 19 is an effective opening. As mentioned above, TTE suppression.

For soil, it is desirable to increase the electrode finger resistance. Therefore, the non-intersecting openings 18 and 18' are made thicker. Since these non-intersecting openings are not directly involved in excitation or reception of surface acoustic waves, the common electrode end 17 and the end of the effective opening 19 are similar to each other.

By providing the honding pad 16 between them, the surface acoustic waves can be transmitted without affecting the surface acoustic waves at all.

The chip size in the direction perpendicular to the propagation direction can be reduced, and the cost can be reduced accordingly. Also, this.

In this case, the electrode finger resistance can be increased relatively easily, so that a surface acoustic wave element with good TTE suppression characteristics can be obtained.

As mentioned above, increasing the electrode finger resistance of non-crossing apertures is effective in suppressing TTE, so it is possible to The electrode finger can be bent once or more, and the electrode finger can be split into an effective aperture to suppress 3TTE.

Better results can be obtained with a solid type for non-intersecting openings. Figure 6 is a schematic diagram of an electrode constructed in this way.
8a and 18a' are non-intersecting openings made of bent solid electrode fingers, and 19a is an effective opening made of sublit 1 [1-shaped electrode fingers]. Of course, you can just bend the non-intersecting openings and make the effective openings solid, which is great.

The part is a solid type that does not bend and has an effective opening.

It may also be a split type. 1. [Embodiment of the Invention] FIG. 7 is a diagram showing an embodiment of the present invention. The electrode configuration is input/output interdigital electrodes 20 and 20', and the specific electrode structure is as shown in FIGS. It has a structure with

The electrode material was A1, and the film thickness was 500'h.

The effective aperture length was 300 μm, and the non-intersecting aperture length was 450 μm. The surface acoustic wave substrate is made of LiNbO3, the filter center frequency is 403 M, Hz, the 3 dB bandwidth is -30 MHz, the number of electrode pairs on the transmitting side (regular type) is 15, and the number of electrode pairs on the receiving side (weighted) is 15 pairs. There are 60 pairs. this.

The sample was prepared using photolithography technology, the Alt electrode was formed by chemical etching, and the lead wire was made of Au.
H1 was performed by wire bonding.

Measurements were conducted using a network analyzer using a 50Ω system, and the results showed that it had good characteristics.

won. The chip size is also smaller by 300×2=600 μm in the direction perpendicular to the surface wave propagation direction.

I was able to do it.

〔Effect of the invention〕

As explained above, according to the present invention, multiple electrode reflections can be well suppressed, and surface acoustic wave transmission can be effectively suppressed.

An elastic surface wave element having a reduced element size in a direction perpendicular to the vibration direction is obtained.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the general configuration of a conventional surface acoustic wave element, Fig. 2 is a diagram showing a conventional normal interdigital electrode, and Fig. 3 is a diagram showing a conventional interdigital electrode. A diagram showing a conventional interdigital electrode in which the non-intersecting portions of the electrode fingers are lengthened. Figure 4 shows an interdigital electrode placed at the common electrode end honding pad or at a location inside the common electrode end overlapping the effective opening. Figures 5 and 6 are diagrams showing Suda 1 () according to the present invention.
A schematic diagram of a curved electrode, FIG. 7 is an embodiment of the present invention. It is a diagram. 1...Surface acoustic wave substrate 2, 2', 20, 20'...Surface acoustic wave transmitting/receiving interdigital electrode. 3.9,12,13.16...Honding Bad
l. 8.11, 14.17, 178... Common electrode end 4...
- Input signal source 5... Output load impedance 6.6'... Surface acoustic wave sound absorber 7... Direct wave prevention electrode 7 - 10.10', 18.18', 18a, 18a'.
・Electrode finger non-crossing opening 15.19.19a...Effective opening ・ 8 ・ 42 Figure 2 Figure 4 Scabbard 5 Figure G

Claims (1)

[Claims] 1) On a surface acoustic wave substrate containing a piezoelectric material, at least one
In an elastic □ surface wave element having two poles of a pair of wave transmitting/receiving interdigital boxes, electrode fingers of different polarity do not intersect with respect to the surface acoustic wave propagation direction, and the surface acoustic wave element or the effective opening for wave reception is A surface acoustic wave element characterized in that a common-to-extreme honding pad is installed at an intermediate location between the detached end of the common electrode and the end of the effective opening. 2) Using interdigital electrodes in which the frost pole fingers are bent one or more times at an intermediate point from the common type to the extremes. The surface acoustic wave device according to section 1. 3) The surface acoustic wave according to claim 1 or 2, which uses interdigital electrodes in which the electrode fingers are of a split type at the effective opening and solid at positions outside the effective opening. element. ,.