JP2000151350A - Surface acoustic wave device - Google Patents

Abstract

(57) [Summary] To accommodate a plurality of dual mode SAW filters in a package, a means for maintaining a large guaranteed attenuation is obtained. SOLUTION: When a SAW device in which two sets of two-stage cascade connection type dual mode SAW filters are arranged on a piezoelectric substrate is accommodated in a package, the output pad of each filter and the output terminal of the package are bonded in the shortest distance. In this case, the output terminal and the input terminal are on opposite sides of the package, and a filter is cascade-connected so that the output bonding wire does not cross another grounding bonding wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave device (hereinafter, referred to as a SAW device) with an improved guaranteed attenuation.

[0002]

2. Description of the Related Art In recent years, SAW devices have been widely used in the field of communications, and have been used particularly in mobile phones and the like because of their excellent features such as high performance, small size, and mass productivity. One of the above SAW devices is a primary-tertiary longitudinally coupled double-mode SAW filter (hereinafter, referred to as a dual-mode SAW filter). FIG. 3 is a plan view of an electrode pattern showing a configuration of a conventional dual mode SAW filter, and shows three IDTs on a main surface of a piezoelectric substrate 11 along a propagation direction of a surface wave.
Electrodes 12, 13, and 14 are arranged close to each other, and reflectors 15a and 15b are arranged on both sides of the electrodes. Each of the IDT electrodes 12, 13, and 14 is composed of a pair of comb-shaped electrodes having a plurality of electrode fingers interposed therebetween. The electrodes are grounded. on the other hand,
One of the IDT electrodes 13 and 14 is connected to the output terminal OUT while being connected to each other, and the other comb electrode is grounded.

[0003] As is well known, the operation of the dual mode SAW filter shown in FIG. 3 is that acoustic waves excited by the IDT electrodes 12, 13, 14 are confined between the reflectors 15a, 15b. , And the two longitudinal resonance modes of the first and third order are strongly excited by the electrode pattern. By appropriately terminating, the device operates as a dual mode SAW filter using these two modes. It is well known that the pass bandwidth of the dual mode SAW filter is determined by the frequency difference between the primary resonance mode and the tertiary resonance mode.

FIG. 4 shows two double-mode SAW filters as shown in FIG. 2 arranged side by side on the same piezoelectric substrate in order to further increase the guaranteed attenuation and steepen the attenuation gradient near the passband. This is an example in which these input / output terminals are electrically connected to form a two-stage cascade connection type dual mode SAW filter. That is, three IDT electrodes 1 on the piezoelectric substrate 11
6, 17 and 18 are arranged close to each other along the propagation direction of the surface wave, and grating reflectors 19 are provided on both sides thereof.
a and 19b are arranged to form the filter A. further,
Almost like the filter A, the IDT electrodes 16 ', 17',
18 'are arranged close to each other, and grating reflectors 19'a and 19'b are arranged on both sides thereof to form a filter A'. The output terminal of the filter A and the input terminal of the filter A 'are connected by lead electrodes. They are electrically connected to form a two-stage cascade connection type dual mode SAW filter.

The electrode patterns shown in FIGS. 3 and 4 are mainly drawn on the assumption that lithium tantalate (LiTaO ₃ ), lithium niobate (LiNbO ₃ ) or the like is used for the piezoelectric substrate.
The actual size of the dual mode SAW filter (one stage) is
As shown in FIG. 3, the intersection length W is 10λ to 40λ (λ is the wavelength of the surface acoustic wave to be excited), and the length L of the dual mode SAW filter is 250λ including the grating reflector.
３５０350λ.

FIG. 5A is a plan view of a practically-used filter in which two sets of two-stage cascade-type double-mode SAW filters used for an RF filter of a cordless telephone or the like are arranged on the same piezoelectric substrate. FIG. 2B is a cross-sectional view taken along line AA. It has a configuration of one input (IN) and two outputs (OUT1, OUT2), and IDT electrodes 16 to 18, 19a surrounded by a dotted line,
19b and IDT electrodes 16 'to 18', 19'a, 19 '
b constitutes a first filter F1. Further, the IDT electrodes 20 to 22, 23a and 23b surrounded by dotted lines and the IDT electrodes
The electrodes 20 'to 22', 23a ', and 23'b constitute a second filter F2. The center frequency of each of the first filter F1 and the second filter F2 is in a 900 MHz band,
The difference is about 26 MHz.

[0007]

However, in the example shown in FIG. 5, the bonding wire BW1 connecting the output pad Pd1 of the first filter F1 and the hatched output terminal OUT1 is connected to the input terminal IN. (hatching)
And the input terminal IN and the output terminal OUT1 are arranged on the same side of the package, so that they are electromagnetically or electrostatically coupled between the input / output terminals or between the input terminals and the bonding wires. , The guaranteed attenuation deteriorates,
There was a problem that it was extremely difficult to maintain the guaranteed attenuation. When the output pad of the first filter F1 and the output terminal OUT1 on the opposite side to the input terminal IN are connected to each other using a bonding wire BW1 as shown in FIG. Although possible, the bonding wire BW1 intersects with another bonding wire for grounding, and there is a risk that the bonding wires intersecting with each other due to vibration, shock, aging, etc., may cause a problem that the reliability of the filter is significantly reduced. . SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and has as its object to provide a filter that increases the guaranteed attenuation and increases the reliability of the filter against vibration, impact, and the like.

[0008]

According to a first aspect of the present invention, there is provided a surface acoustic wave device according to the present invention, in which two or more sets of two-stage cascaded double-mode SAW filters are arranged on the surface. A surface acoustic wave device for connecting the input / output pad of the filter and the input / output terminal of the package by wire bonding, wherein the output terminal and the input terminal of the package are connected to each other. The two double-mode SAW filters that are arranged on the opposite side of the piezoelectric substrate as a boundary and that constitute the two-stage cascade-connected double-mode SAW filter are SAW
Are arranged so that the propagation directions are located on the same straight line with each other.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a plan view showing the positional relationship between hatched input / output terminals IN, OUT1, and OUT2, a ground terminal (no hatching), a filter element, and a bonding wire. FIG. 3 is a plan view showing a configuration of a filter having two outputs (OUT1, OUT2). The first filter F1 has IDT electrodes 2 to 2 which are juxtaposed such that the SAW propagation directions of the two filters are substantially on the same line as surrounded by a dotted line.
4, 5a, 5b and IDT electrodes 2 'to 4', 5a ',
5'b and two-stage cascaded dual mode SA
It is a W filter. Furthermore, the IDT electrodes 6 to 6 which are juxtaposed such that the SAW propagation directions of the two filters are substantially on the same line as the second filter F2 is also surrounded by the dotted line.
8, 9a, 9b and IDT electrodes 6 'to 8', 9'a, 9 '
b) is a two-stage cascade-connected double-mode SAW filter composed of B.

FIG. 2 is a schematic plan view showing the arrangement of the IDT electrode and the grating reflector shown in FIG. 1 in detail.
Where IDT electrodes and grating reflectors are the same. That is, the IDT electrodes 2, 3, and 4 are arranged close to each other along the propagation direction of the surface acoustic wave on the piezoelectric substrate 1, and the grating reflectors 5a,
5b is provided to configure the dual mode SAW filter A. Then, IDT electrodes 2 ', 3', 4 'are arranged close to each other in the horizontal direction in parallel with the filter A on the same piezoelectric substrate, and grating reflectors 5'a, 5'b are arranged on both sides thereof. A dual mode SAW filter A 'is constructed. Further, IDT electrodes 6, 7, and 8 are disposed close to each other on the same piezoelectric substrate 1 as in the case of the filter A, and grating reflectors 9a and 9b are disposed on both sides of the IDT electrodes 6, 7, and 8 to provide a dual mode SAW
Construct filter B. The IDT electrodes 6 ', 7', 8 'are arranged close to each other in the horizontal direction in parallel with the filter B, and the grating reflectors 9'a, 9'b
To form a dual mode SAW filter B ′.

One electrode of the IDT electrode 2 of the filter A is electrically connected to the input terminal IN, and one of the IDT electrodes 3 and 4 is connected to the IDT electrode 3 'of the filter A'.
4 'is electrically connected to one electrode of the IDT electrode 2'.
Is electrically connected to the output terminal OUT1 to form a two-stage cascade connection type dual mode SAW filter F1 (first filter). Next, the filters B and B 'are connected in the same manner as the filters A and A' described above, and the two-stage cascade connection type double mode SAW filter F2 (second filter) is used.
Is configured. However, the filter B and the input terminal IN are connected, and the output of the filter B 'is connected to the output terminal OUT2.

As shown in FIG. 2, the filter A (B) and the filter A '(B') are arranged in the horizontal direction in the figure, that is, in such a manner that the SAW propagation path is located on the same line. A (B) and the filter A '(B') make it possible to form a two-stage cascaded dual-mode SAW filter F1 (F2), and the input terminal IN and the output terminal OUT1,
2 can be arranged at positions facing each other.
Thereby, as shown in FIG. 1, the bonding wire BW1 connecting the output pad of the filter A 'and the output terminal OUT1 (hatched) and the bonding wire BW2 connecting the output pad of the filter B' and the output terminal OUT2 are formed. It can be placed away from the input terminal IN. Further, both the output bonding wires BW1 and BW2 can be provided without intersecting with other ground bonding wires.

[0013]

According to the present invention, as described above, a large amount of guaranteed attenuation can be maintained, and a SAW device excellent in quality can be manufactured because bonding wires do not intersect. Was. The present invention S
When the AW device is used for a mobile phone or the like, there is an excellent effect that a small and high-performance communication device can be configured.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a 1-input / 2-output SAW device according to the present invention.

FIG. 2 is a plan view showing an electrode pattern configuration of a 1-input / 2-output SAW device according to the present invention.

FIG. 3 is a plan view showing an electrode pattern configuration of a conventional primary-tertiary-order longitudinally coupled dual-mode SAW filter (double-mode SAW filter).

FIG. 4 is a plan view showing an electrode pattern configuration of a conventional two-stage cascade connection type dual mode SAW filter.

5A is a plan view showing an example of an arrangement of electrode patterns and bonding wires of a 1-input / 2-output SAW device, and FIG. 5B is a cross-sectional view along AA.

FIG. 6 is a plan view showing another example of the arrangement of the electrode patterns and the bonding wires of the one-input / two-output SAW device.

[Explanation of symbols]

1. Piezoelectric substrates 2, 3, 4, 2 ', 3', 4 ', 6, 7, 8, 6',
7 ′, 8 ′... IDT electrodes 5a, 5b, 5′a, 5′b, 9a, 9b, 9′a,
9'b ... Grating reflector BW1, BW2 ... Output bonding wire F1, F2 ... Two-stage cascade connection type dual mode SAW filter IN ... Input terminal OUT1, OUT2 ... Output terminal A, A ', B, B '... dual mode SAW filter

Claims (1)

[Claims] 1. A two-stage cascaded dual-mode SAW on the surface.
A surface acoustic wave device in which a piezoelectric substrate on which two or more filters are arranged is housed in a package, and input / output pads of the filter and input / output terminals provided on the package are connected by wire bonding. An output terminal and an input terminal are arranged on opposite sides of the piezoelectric substrate as boundaries, and two double-mode SAWs constituting the two-stage cascade-type double-mode SAW filter.
A surface acoustic wave device wherein filters are arranged such that SAW propagation directions are located on the same straight line.