JPH07231239A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave device in which miniaturization and low cost are realized by adhering a cap to a surrounding face of a surface acoustic wave element where IDT electrode conductors are formed on a piezoelectric substrate. CONSTITUTION:A cap 6 is adhered to a surface acoustic wave element where interdigital transducer (IDT) electrodes 2 are formed on a piezoelectric substrate 1 by using a sealing agent 5. Through the constitution above, no package is required and no package mount work is required, then miniaturization and low cost are realized. Furthermore, the cap 6 is preferably made up of a substrate 3 made of the same material as that of the piezoelectric substrate 1 whose size is selected so that part of a terminal 2' of the IDT electrode conductor 2 is exposed externally and made up of a metallic plating section 4 applied to a surrounding face of the substrate 3 to form a recessed space 12 to a part corresponding to the IDT electrode conductor 2.

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 element used as an electronic component of a communication device or the like, and more particularly to a surface acoustic wave device hermetically sealed.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view showing an example of a conventional surface acoustic wave device. (A) is a plan view when a cap (upper lid) 23 is removed, and (B) is B of (A). It is a -B 'sectional view. In the figure, reference numeral 20 denotes a surface acoustic wave element, in which an IDT (interdigital transducer) is formed on a piezoelectric substrate such as lithium niobate (LiN _b O ₃ ) or lithium tantalate (LiTaO ₃ ). Reference numeral 21 is a lead wire, 22 is a base, 23 is a cap, and 24 is an external connection terminal portion. Since the surface acoustic wave propagates on the surface of the substrate in the surface acoustic wave element 20, if foreign matter or moisture adheres to the surface, the element characteristics will change. Therefore, as shown in FIG.
After being mounted on No. 2 and connected to the external connection terminal portion 24 by the lead wire 21, an inert gas such as nitrogen gas is injected by the cap 23 and hermetically sealed. Such a surface acoustic wave device,
As with other electronic components, there is a strong demand for miniaturization due to high-density mounting.

[0003]

However, in the above-described conventional surface acoustic wave device, it is necessary to provide the external connection terminal portion 24 on the base 22, and the external connection terminal portion 2 is provided.
4, the lead wire 21 has to be connected from the IDT of the surface acoustic wave element, and there is a problem that the package including the base 22 and the cap 23 becomes considerably larger than the size of the surface acoustic wave element. Further, there is a problem that the package mounting work takes time and becomes an obstacle to cost reduction. It is an object of the present invention to provide a surface acoustic wave device that solves the above problems and realizes downsizing and cost reduction.

[0004]

The surface acoustic wave device of the present invention is a surface acoustic wave element having an interdigital transducer electrode conductor formed on a rectangular piezoelectric substrate, and the interdigital transducer electrode of the surface acoustic wave element. It is characterized in that it is composed of a cap joined to the peripheral surface excluding the conductor.

Further, the cap is formed of a material having the same material as that of the piezoelectric substrate and having an outer dimension in which a part of a terminal portion of the interdigital transducer electrode conductor is exposed to the outside, and a portion corresponding to the interdigital transducer electrode conductor. It is characterized in that it is made of metal plating applied to the peripheral surface of the substrate to form a concave space portion.

[0006]

1 is a structural diagram showing an embodiment of the present invention,
(A) is an exploded perspective view, (B) is an assembly appearance perspective view.
In the figure, 1 is a piezoelectric substrate, 2 is an IDT electrode, 2'is a terminal portion thereof, 3 is a substrate of a cap, 4 is a plated portion, 5 is a sealant, 12 is a concave space portion, and 6 is a cap. The surface acoustic wave device of the present invention comprises a piezoelectric substrate 1 on the surface of which an IDT electrode conductor 2 is formed, and a cap 6. The substrate 3 of the cap 6 is made of the same material as the piezoelectric substrate 1, and has a bottom outer peripheral portion. A low-melting point glass or the like is applied as a sealing agent 5 by screen printing or the like, and is superposed on the surface of the piezoelectric substrate 1 on which the IDT 2 is formed and baked to hermetically seal the piezoelectric substrate 1 and the cap 6. At this time, the concave space 12 is filled with an inert gas such as nitrogen (N ₂ ) gas. The shape of the cap 6 is formed so that the terminal portion 2'of the IDT 2 of the surface acoustic wave element is exposed to the outside.

Next, a method of forming the cap 6 and a method of attaching the cap 6 to the piezoelectric substrate 1 will be described. FIG. 2 is a partial external perspective view of a strip-shaped cap row 11 formed by connecting a plurality of caps 6 of the present invention. That is, the strip-shaped cap row 11 is in a state before cutting (dicing) in which a plurality of caps 6 are connected. Reference numeral 12 is a concave space portion. FIG. 3 is an external view showing a state in which the strip-shaped cap row 11 is mounted on the wafer 10 on which a large number of surface acoustic wave elements are formed.
(A) is a plan view and (B) is a sectional view taken along line AA '. In the figure, 10 is a wafer of a piezoelectric substrate, 11 is a strip-shaped cap row, 5 is a sealant such as an adhesive, 4 is a plated portion, and 12 is a concave space portion.

First, a method of forming the cap row 11 will be described. In FIG. 2, the strip-shaped cap row 11 is formed by evaporating or sputtering a metal such as copper (Cu) on the elongated strip-shaped substrate 3 made of a material having the same thermal expansion coefficient as that of the piezoelectric substrate 1 while leaving the space 12. Thereafter, plating 4 is applied to form the concave space portion 12.

Next, a method of attaching the cap row 11 to the wafer 10 will be described. In FIG. 3, in the strip-shaped cap row 11, a low melting point glass or the like is applied as an adhesive 5 to the outer peripheral portion of the plated concave space portion 12 by screen printing or the like. Then, with the adhesive surface facing down, the piezoelectric substrate wafer 10 on which the IDT is formed is stacked and heated to melt the adhesive agent 5 and hermetically seal it. At this time, the space 12 to be sealed is sealed with an inert gas such as nitrogen (N ₂ ) gas.

The surface acoustic wave device is cut out one by one by dicing the wafer in which a large number of surface acoustic wave elements are formed in this way together with the cap row. According to the present invention, a package which has been conventionally required is not required, so that the packaging work is eliminated and the surface acoustic wave device can be provided at low cost. Further, since the external dimensions are almost the same as the surface area of the surface acoustic wave element chip, the size can be greatly reduced as compared with the conventional one.

[0011]

As described in detail above, by implementing the present invention, it is possible to obtain a small-sized surface acoustic wave device at low cost, and the practical effect is great.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a structure of an embodiment of the present invention (A).
It is an external perspective view (B).

FIG. 2 is a partial external view of a strip-shaped cap row of the present invention.

FIG. 3 is a plan view of the wafer (A) and an AA ′ cross-sectional view (B) after the strip-shaped cap row of the present invention is attached.

FIG. 4 is a plan view and a BB ′ cross-sectional view of a conventional device.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 IDT Electrode Conductor 2'IDT Terminal Part 3 Cap Substrate 4 Plated Part 5 Sealant 6 Cap 10 Wafer 11 Strip Cap Row 12 Recessed Space 20 Surface Acoustic Wave Element 21 Lead Wire 22 Base 23 Cap 24 External connection terminal

Claims (2)

[Claims] 1. An elastic structure comprising a surface acoustic wave element having an interdigital transducer electrode conductor formed on a rectangular piezoelectric substrate and a cap joined to the surface of the surface acoustic wave element excluding the interdigital transducer electrode conductor. Surface wave device. 2. A substrate having the outer dimensions of the cap, which is made of the same material as that of the piezoelectric substrate, such that a part of a terminal portion of the interdigital transducer electrode conductor is exposed to the outside.
2. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is made of metal plating applied to the peripheral surface of the substrate to form a concave space in a portion corresponding to the interdigital transducer electrode conductor.