JPH07321583A - Surface acoustic wave device and manufacture thereof - Google Patents

Abstract

PURPOSE:To simplify the package structure of a surface acoustic wave device, to miniaturize it, to make it thinner and to reduce a cost. CONSTITUTION:A substrate 4 where a wiring conductor 5 is printed is provided with a hollow part 6. A surface acoustic wave element for which a piezoelectric substrate 1 is provided with an IDT electrode 2 and the terminal electrode part 3 is mounted so as to let the surface of the IDT electrode 2 correspond to the hollow part 6 of the substrate 4. A conductive coating material 8 is prepared in the part of the wiring conductor 5 corresponding to the terminal electrode part 3 beforehand, heating is performed and fixing is performed. The surface acoustic wave element is covered and air-tight sealing is performed by resin 7.

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 for communication equipment and a method for manufacturing the same.

[0002]

2. Description of the Related Art A surface acoustic wave device such as a surface acoustic wave resonator or a filter is sealed with a package made of ceramic or the like because it is necessary to keep the excited electrode surface hollow and keep it airtight. ing. FIG. 5 is a sectional view of a conventional surface acoustic wave device having a surface mount type package structure. In the figure, 1 is a piezoelectric substrate, 2 is an interdigital finger electrode (IDT), and 3 is a terminal electrode portion thereof, and a large number of elastic surfaces in which the interdigital electrode and the terminal electrode are formed on a single wafer piezoelectric substrate. It is an element (chip) obtained by dividing the wave element. 12 is a package, 13 is an electrode, 14 is a wire, and 15 is a cap. ID of the surface acoustic wave element inside the package 12
There is a hollow portion between the surface of the T electrode 2 and the cap 15 so that the bonding wire 14 does not contact the cap 15.

[0003]

However, in the above-mentioned conventional structure, the ceramic package or the like is expensive and occupies a large proportion of the cost of the device. Also, in the case of the surface mount type package as shown in FIG. 5, one surface acoustic wave element chip is put in one package, and therefore the size of the package 12 restricts the miniaturization. That is, with respect to the height, a hollow portion is required so that the bonding wire 13 and the cap 15 do not come into contact with each other, and the thickness of the bottom portion of the package 12 also limits the reduction in thickness. If the chip is resin-sealed at the same time as other IC circuits,
Since there is no hollow portion, the desired electrical characteristics cannot be obtained by touching the electrode surface excited by the resin.

An object of the present invention is to solve the above problems of the prior art and to provide an inexpensive, small-sized and thin surface acoustic wave device and a method for manufacturing the same.

[0005]

A surface acoustic wave device according to the present invention has a surface acoustic wave element in which an interdigital electrode and a terminal electrode portion thereof are provided on a piezoelectric substrate, and an area larger than the area of the piezoelectric substrate. And a hollow portion provided in a portion corresponding to the crossing finger electrode portion and having a depth that does not make surface contact when the crossing finger electrode is excited, and is arranged continuously from the portion corresponding to the terminal electrode portion to the peripheral portion. A substrate provided with a wiring conductor, a terminal electrode portion of a surface acoustic wave element mounted on the substrate so that a surface provided with the interdigital electrode faces each other, and the terminal electrode portion of the wiring conductor of the substrate And a conductive coating material interposed between the surface acoustic wave element mounted on the substrate and the peripheral surface portion of the surface acoustic wave element which is hermetically sealed. It is a thing.

Further, in order to manufacture the above device, the surface area of the surface acoustic wave element to be attached is larger than the area of the piezoelectric substrate, and the surface of the surface acoustic wave element is located at a portion corresponding to the electrode portion of the surface acoustic wave. From above the substrate provided with a hollow portion having a depth that does not make surface contact when the electrode is excited, and a wiring conductor continuously arranged from the portion corresponding to the terminal electrode portion of the surface acoustic wave element to the peripheral portion, After placing a mask in which a hole is provided in the portion of the wiring conductor corresponding to the terminal electrode portion of the surface acoustic wave element, and extending the cream-like conductive paint from above the mask with a squeegee to fill the hole with the conductive paint ,
Then, the mask is removed, and then a surface acoustic wave pendulum is mounted on the substrate with the crossing finger electrode portion corresponding to the hollow portion and the terminal electrode portion corresponding to the conductive coating portion. After being placed, it is heated to evaporate and fix the solvent of the conductive paint, and the surface acoustic wave pendulum and its peripheral portion are covered with a resin to hermetically seal them.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the apparatus according to claim 1 will be described in detail with reference to the drawings. FIG. 1 is a perspective view (A) and a sectional view (B) showing an embodiment of the structure of the present invention. FIG. 2 is a perspective view of the element. The surface acoustic wave device including the piezoelectric substrate 1, the IDT electrode 2, and the terminal electrode portion (bonding pad) 3 shown in FIG. 2 is directly attached to the substrate 4 with the surface of the IDT electrode 2 facing downward as shown in FIG. . The substrate 4 is a plate of ceramic, silicon having a SiO ₂ (silicon oxide) film on its surface, or glass epoxy. Reference numeral 5 is a printed wiring conductor of the substrate 4, 6 is a hollow portion, 7 is a resin for hermetic sealing, and 8 is a conductive paint. The conductive paint 8 is used to prevent a conductive defect between the bonding pad 3 of the surface acoustic wave element and the printed wiring conductor 5 of the substrate 4. When forming the conductive paint layer on the wiring conductor 5, a thick film printing technique is used. In addition, a hollow portion 6 is previously formed in the substrate 4 so as not to interfere with the vibration of the surface acoustic wave. The hollow portion may have a depth that does not prevent vibration of the wave mode used. After heating in an oven or the like to evaporate the solvent of the conductive paint, the element 7 and the substrate 4 around it are covered with a resin 7 for hermetic sealing.

Next, the manufacturing method according to claim 2 will be described. 3 and 4 are perspective views showing the manufacturing method of the present invention during the assembling process. FIG. 3 (A) to FIG. 4
The outline of the assembly process is shown up to (F). FIG. 3A is a perspective view of the substrate 4 provided with the hollow portion 6 and the wiring conductor 5. FIG. 3B is a perspective view showing that the mask 9 having the holes 10 at the positions corresponding to the terminal electrode portions 3 of the surface acoustic wave element is placed on the substrate 4. In FIG. 3 (C), a cream-like conductive paint 8 (for example, silver-palladium) is placed on the mask 9, and the squeegee 11 is strongly pressed on the hole 10 and pulled toward the arrow to draw the conductive paint on the hole 10. 8 shows a mode in which 8 is filled. FIG. 4D shows the substrate 4 after the mask 9 is removed. A thick film 8 of conductive paint is formed at a position corresponding to the electrode of the surface acoustic wave element. The surface acoustic wave device with the IDT electrode surface facing down is placed on the substrate 4 (see FIG. 4).
(E)). This is heated in an oven or the like to evaporate and fix the solvent of the conductive paint, and then the surface acoustic wave element and the substrate 4
Highly viscous resin is placed on top of it to seal it airtightly (Fig. 4
(F)).

In the present embodiment, the entire acoustic wave element is covered with resin, but if a resin that can maintain the mechanical strength and airtightness of the joint between the acoustic wave element and the substrate is used, only the peripheral portion of the element will be covered with resin. It can also be sealed.

[0010]

By implementing the present invention, the following advantages are obtained because the package used in the prior art is not used. (1) Since the package, which occupies a large proportion of the device cost, is not used, the cost can be significantly reduced. (2) The size and thickness can be reduced as compared with the case where the package is used.

[Brief description of drawings]

FIG. 1 is a perspective view and a sectional view showing a configuration example of the present invention.

FIG. 2 is a perspective view of a surface acoustic wave device.

FIG. 3 is an explanatory view showing a manufacturing process of the present invention.

FIG. 4 is an explanatory view showing a manufacturing process of the present invention.

FIG. 5 is a sectional view illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 IDT electrode 3 Terminal electrode part 4 Substrate 5 Wiring conductor 6 Hollow part 7 Resin 8 Conductive paint (Ag-Pb) 9 Mask 10 Hole 11 Squeegee 12 Package 13 Electrode 14 Cap 15 Wire

Claims (2)

[Claims] 1. A surface acoustic wave device having a crossed finger electrode and a terminal electrode portion thereof provided on a piezoelectric substrate, and an area larger than the area of the piezoelectric substrate and provided at a portion corresponding to the crossed finger electrode portion. A substrate having a hollow portion having a depth that does not make surface contact when the crossed finger electrode is excited, and a wiring conductor continuously arranged from a portion corresponding to the terminal electrode portion to a peripheral edge portion; A conductive coating material interposed between a terminal electrode portion of a surface acoustic wave element mounted on the substrate so that surfaces provided with electrodes face each other and a portion of a wiring conductor of the substrate corresponding to the terminal electrode portion, A surface acoustic wave device comprising a surface acoustic wave element mounted on the substrate and a resin that covers a peripheral portion of the surface acoustic wave element and hermetically seals the surface acoustic wave element. 2. A surface contact having a larger area than that of the piezoelectric substrate of the surface acoustic wave element to be mounted, and a portion of the surface acoustic wave element corresponding to a crossing finger electrode portion when the crossing finger electrode is excited. From the top of the substrate provided with the hollow portion having a depth which does not exist and the wiring conductors continuously arranged from the portion corresponding to the terminal electrode portion of the surface acoustic wave element to the peripheral portion, the terminal electrode portion of the surface acoustic wave element is provided. A mask having a hole provided in the portion of the wiring conductor corresponding to the above is placed, a creamy conductive paint is extended from above the mask with a squeegee to fill the hole with the conductive paint, and then the mask is removed. The surface acoustic wave pendulum is placed on the substrate after the crossing finger electrode portion is made to correspond to the hollow portion and the terminal electrode portion is made to correspond to the portion coated with the conductive paint, and then heated. Dissolution of conductive paint Method for producing a fixed evaporated, the surface acoustic wave pendulum surface acoustic wave device in the peripheral portions thereof so as to hermetically seal covered with a resin.