JPH0818390A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To reduce the size and cost of the surface acoustic wave device. CONSTITUTION:At the peripheral edge part of the IDT electrode surface of a surface acoustic wave element, a circumferential metallic film 4 which is thicker than the film of the IDT electrode 2 is provided and is subjected to plane junction to a terminal conductor 9 provided on the side of a substrate 12 opposite the terminal electrode 3 of the IDT 2 and a circumferential ground conductor 10 provided opposite the circumferential metallic film 4. Consequently, the need for a package is eliminated, so the device is reduced in size and thickness and the fixation of the element, the connection of the electrode and their hermetic sealing are performed by one process at the same time, so that the man-hours are decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device used as a high frequency functional component of communication equipment.

[0002]

2. Description of the Related Art A device utilizing surface acoustic waves, for example, a surface acoustic wave device accommodating a surface acoustic wave element (chip) such as a resonator or a filter has a hollow and airtight electrode surface of the element. In order to maintain the above, the device is housed in a package such as ceramic and sealed by welding. FIG. 4 is a cross-sectional view showing a conventional structure example. In the figure, reference numeral 13 is a surface acoustic wave element, on which an interdigital transducer electrode and its terminal electrode are provided on the upper surface. Reference numeral 17 is a package, and 14 is a terminal electrode inside the package 17, which is connected to a terminal electrode of the element 13 by a bonding wire 16. 15 is a cap.

[0003]

Generally, in a conventional surface acoustic wave device, a ceramic package or the like is expensive and occupies a large proportion of the cost of the device. Further, in the case of the conventional surface mount type ceramic package shown in FIG. 4 as well, one chip of the surface acoustic wave device is accommodated in one package, and therefore the limit of miniaturization is determined by the size of the package 17. Further, with respect to the height of the device, there is a limitation in reducing the thickness because a space is required to prevent the bonding wire 16 and the cap 15 from contacting each other and the thickness of the bottom surface of the package 17 itself. Furthermore, when the surface acoustic wave element (chip) 13 is accommodated in a package together with other IC circuits and sealed, the sealing resin comes into contact with the vibrating electrode surface when the chip is left bare. The electrical characteristics may not be obtained. On the other hand, the above-mentioned device mounting manufacturing process is roughly divided into three processes of die bonding, wire bonding, and hermetic sealing, and it is desirable that the number of processes is smaller in terms of manufacturing cost and man-hours.

The object of the present invention is to eliminate the expensive package, which is a problem of the prior art, and to secure a vibrating space on the vibrating electrode surface of a surface acoustic wave element or the like. The object of the present invention is to provide a surface acoustic wave device which can be made more compact and has fewer manufacturing steps.

[0005]

In the surface acoustic wave device of the present invention, the same or another metal film as the IDT electrode or another metal film is provided around the vibrating IDT electrode or around the vibrating IDT electrode. The gist of the invention is that a conductive adhesive such as a silver (Ag) paste can be used to simultaneously fix the element, connect the electrodes, and hermetically seal.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. As a typical example, a case where the element is a surface acoustic wave resonator will be described. FIG. 1 is an explanatory perspective view showing a first embodiment of the present invention. In the figure, 1 is a piezoelectric substrate, and 2 is an interdigital transducer formed on the piezoelectric substrate 1.
r, hereinafter abbreviated as IDT), 3 is a connecting terminal electrode, 4 is an I
It is a peripheral metal film provided so as to surround the periphery with a metal of the same material as the DT electrode 1 or the terminal electrode 3 or another metal. On the other hand, 9 is a terminal conductor, and 10 is a surrounding ground conductor, which are arranged on an insulating mounting substrate 12. Reference numeral 11 is a wiring conductor, which is arranged in the inner layer of the mounting substrate 12 having a multi-layered structure and used for connection with an external circuit. A conductive adhesive is applied to the terminal conductor 9 and the surrounding ground conductor 10 of the mounting substrate 12 by screen printing or the like, and the surface acoustic wave element is placed with the electrode surface down.
The terminal electrode 3 and the terminal conductor 9, and the surrounding metal film 4 and the surrounding ground conductor 10 are made to face each other and accurately aligned and bonded.
Then, it is heat-cured and the chip and the substrate are brought into close contact with each other to be mounted. Through the above process, the chip is fixed, the electrodes are connected,
Hermetically sealed mounting can be performed at the same time.

At this time, 10 is provided between the IDT 2 and the substrate 12.
A space above 00Å is secured. That is, the substrate 12
Of the terminal conductor 9 and the surrounding ground conductor 10 are dug down in a portion facing the IDT2, or the structure in which the terminal electrode 3 and the surrounding metal film 4 are thicker than the thickness of the IDT2, or the thickness of the conductive adhesive. This space is secured by.

FIG. 2 is a plan view of the element side showing the second embodiment of the present invention. In this embodiment, the periodic metal film 5 is connected to one terminal electrode 3 of the IDT 2 formed on the piezoelectric substrate 1 and the other terminal electrode. Also in this case, FIG.
In the same manner as in the first embodiment described above, a terminal conductor and a surrounding ground conductor are provided and joined to a portion of the substrate 12 facing the element-side electrode, and 1000 Å is provided between the IDT 2 and the opposing substrate 12.
The above space is provided.

FIG. 3A is a plan view of the element side showing the third embodiment of the present invention. In this embodiment, one terminal electrode 6 of the IDT 2 provided on the piezoelectric substrate 1 is provided at a position where it forms a part of the periodic metal film 7. A gap 8 of 100 μm or less is provided between the terminal electrode 6 and the surrounding metal film 7. In the case of this embodiment, the terminal electrode 6
Since it is not surrounded by the surrounding metal film 7, it is not necessary to have a multilayer structure because the opposing substrate 12 can easily connect wiring conductors. Also in this case, as in the embodiment shown in FIGS. 1 and 2, a space of 1000 Å or more is provided between the IDT 2 and the opposing substrate 12. Further, in this case, when the conductive adhesive is used to mount on the substrate 12, the airtight sealing cannot be achieved due to the gap 8, but the gap 8 is 10
Since it is 0 μm or less, it can be put to practical use by resin-sealing it simultaneously with other IC circuits and the like.

FIG. 3B is a plan view of the element side showing the fourth embodiment of the present invention, in which both of the terminal electrodes 6 of the IDT 2 are insulated from the ground. Therefore, the surrounding metal film 7 ′ is divided at the portion of the terminal electrode 6.

[0011]

As described in detail above, according to the present invention, a conventional package is not required, so that the cost can be reduced and the external dimensions can be made smaller and thinner. Further, since the fixing of the element, the connection of the electrodes, and the hermetic sealing can be performed at the same time, there is an advantage that the number of steps is significantly reduced and the manufacturing cost is reduced.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a first embodiment of the present invention.

FIG. 2 is a plan view of an element showing a second embodiment of the present invention.

FIG. 3 is a plan view of an element showing third and fourth embodiments of the present invention.

FIG. 4 is a sectional view of a conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 IDT 3 Terminal electrode 4 Surrounding metal film 5 Surrounding metal film 6 Terminal electrode 7,7 'Surrounding metal film 8 Gap 9 Terminal conductor 10 Surrounding ground conductor 11 Wiring conductor 12 Board 13 Surface acoustic wave element 14 Terminal electrode 15 Cap 16 bonding wire 17 package

Claims (8)

[Claims] 1. A piezoelectric substrate, a comb-shaped electrode provided on the piezoelectric substrate, two terminal electrodes connected to the comb-shaped electrode and thicker than the comb-shaped electrode, and a thickness of the terminal electrode. A surface acoustic wave element having an equal thickness, which is composed of the interdigital transducer and a peripheral metal film which is disposed on the peripheral portion of the piezoelectric substrate so as to surround the periphery of the two terminal electrodes, and the surface acoustic wave element. An insulating mounting substrate for mounting, wherein the mounting substrate is provided with a terminal conductor and a surrounding ground conductor in portions facing the two terminal electrodes and the surrounding metal film, respectively. A surface acoustic wave device, characterized in that an electrode surface of an element and a conductor surface of the mounting substrate are opposed to each other and are surface-bonded with a conductive adhesive. 2. The one terminal electrode of the two terminal electrodes is connected to the surrounding metal film.
The surface acoustic wave device described. 3. One of the two terminal electrodes is connected to the surrounding metal film, and the other terminal electrode is provided with a gap so as to form a part of the surrounding metal film. The surface acoustic wave device according to claim 1, wherein: 4. The surface acoustic wave device according to claim 1, wherein the two terminal electrodes are provided at positions so as to form a part of the surrounding metal film with a gap therebetween. 5. A piezoelectric substrate, a comb-shaped electrode arranged on the piezoelectric substrate, two terminal electrodes connected to the comb-shaped electrode, and surrounding the comb-shaped electrode and the two terminal electrodes. A surface acoustic wave element formed of a peripheral metal film disposed on the peripheral portion of the piezoelectric substrate as described above, and an insulating mounting substrate for mounting the surface acoustic wave element. A terminal conductor and a peripheral ground conductor are respectively arranged in the portions facing the two terminal electrodes and the surrounding metal film, and the portions facing the interdigital electrodes are not dug down to prevent surface acoustic wave vibration. A surface acoustic wave device, characterized in that a space is provided, and an electrode surface of the surface acoustic wave element and a conductor surface of the mounting substrate are opposed to each other and are surface-bonded with a conductive adhesive. 6. The terminal electrode of one of the two terminal electrodes is connected to the surrounding metal film.
The surface acoustic wave device described. 7. One of the two terminal electrodes is connected to the surrounding metal film, and the other terminal electrode is provided at a position so as to form a part of the surrounding metal film with a gap therebetween. The surface acoustic wave device according to claim 5, wherein 8. The surface acoustic wave device according to claim 5, wherein the two terminal electrodes are provided with a gap between them so as to form a part of the surrounding metal film.