JP2000174580A - Manufacture of surface acoustic wave element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacture method for a surface acoustic wave element by which a characteristic deterioration caused by an excessive adhesive adhering a cap and an insulation substrate that reaches an upper face of a piezoelectric film is prevented and a small sized surface acoustic wave element can be supplied. SOLUTION: The manufacture method includes a process where an insulation substrate 11 formed with interdigital electrodes 12 and a piezoelectric film 15 in contact with the interdigital electrodes 12 is prepared, a process where a cap 16 to seal the interdigital electrodes 12 formed on the insulation substrate 11 and the piezoelectric film 15 is prepared, a process where a prescribed amount of an adhesive 17 is applied to an adhesion plane of the cap 16 to the insulation substrate 11, and a process where the cap 16 is adhered to the insulation substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a surface acoustic wave device in which a comb-shaped electrode and a piezoelectric film are formed on an insulating substrate, and the comb-shaped electrode and the piezoelectric film are hermetically sealed with a cap.

[0002]

2. Description of the Related Art A conventional method for manufacturing a surface acoustic wave device will be described. FIG. 3 is a cross-sectional view of a surface acoustic wave device obtained through a conventional method of manufacturing a surface acoustic wave device. In manufacturing the conventional surface acoustic wave element 110, first, a comb-shaped electrode 112 made of Al and an external connection pad 11 are formed on an insulating substrate 111 made of glass or the like by photolithography.
Third, an extraction electrode 114 for connecting the comb-shaped electrode 112 and the external connection pad 113 is formed. Next, a piezoelectric film 115 made of ZnO is formed by sputtering so as to cover a portion of the insulating substrate 111 where the comb-shaped electrode 112 is formed. further,
An adhesive 117 made of epoxy resin or the like is applied to the periphery of the piezoelectric film 115 formed so as to cover the comb electrodes 112 by screen printing. After that, the cap 116 made of alumina or the like and the insulating substrate 111 are adhered via the adhesive 117, and the comb-shaped electrode 112 and the piezoelectric film 115 are hermetically sealed.

The surface acoustic wave device thus formed
In 110, a through hole 118 is formed in the portion of the external connection pad 113 so as to penetrate the insulating substrate 111 above and below, and a conductor is applied in the through hole 118.
In this way, the terminal electrodes 119 formed on the lower surface of the insulating substrate 111 and the external connection pads 113 on the upper surface of the insulating substrate 111 are connected by the through holes 118, and the surface acoustic wave element 110 Surface mounted on location.

[0004]

In the conventional method of manufacturing a surface acoustic wave device, an adhesive used for bonding a cap and an insulating substrate is applied to the insulating substrate by screen printing. However, when the adhesive is applied by screen printing in the current technology, unevenness due to places cannot be avoided, for example, the applied amount is partially large.

When the cap and the insulating substrate are bonded together, if the cap is pressed against a place where the amount of the adhesive applied is large, excess adhesive will protrude to the inner surface and the outer surface of the cap. At this time, when the adhesive is applied by screen printing, a part of the adhesive may be applied in a considerably large amount, so that the adhesive which has protruded to the inner surface side of the cap has a thickness of about 20 μm formed on the insulating substrate. There is a possibility of reaching not only the side surface but also the upper surface of the piezoelectric film. Here, if the adhesive reaches the side surface of the piezoelectric film, the characteristics of the surface acoustic wave element are not so affected. However, if the adhesive reaches the upper surface of the piezoelectric film, the characteristics of the surface acoustic wave element deteriorate. Specifically, when a surface acoustic wave element is used as a filter, the frequency characteristics thereof are deviated from desired ones, and the characteristics are deteriorated such that the loss in the band is increased.

In order not to cause such characteristic deterioration,
In a conventional method of manufacturing a surface acoustic wave element, when applying an adhesive to an insulating substrate, the adhesive is applied by screen printing at a predetermined interval from the piezoelectric film. However, in such a conventional method of manufacturing a surface acoustic wave device, a dead space is required around the periphery of the piezoelectric film due to an adhesive, and there is a problem that the surface acoustic wave device cannot be downsized.

The method of manufacturing a surface acoustic wave device according to the present invention has been made in view of the above-mentioned problems, and solves these problems, so that the adhesive does not reach the upper surface of the piezoelectric film.
It is another object of the present invention to provide a method for manufacturing a surface acoustic wave device that can reduce the size of the surface acoustic wave device.

[0008]

In order to achieve the above object, a method of manufacturing a surface acoustic wave device according to the present invention comprises the steps of: providing a comb-shaped electrode and an insulating substrate having a piezoelectric film in contact with the comb-shaped electrode; A step of preparing a cap for sealing the comb-shaped electrode and the piezoelectric film portion formed on an insulating substrate, and a step of transferring a predetermined amount of adhesive to an adhesive surface of the cap with the insulating substrate, Bonding the cap to the insulating substrate.

An adhesive layer previously formed to a predetermined thickness has
When the cap is pressed with a predetermined pressure, an adhesive having a desired thickness can be transferred to the cap. That is, since the amount of the adhesive transferred to the cap can be finely controlled, there is no possibility that the protruding adhesive reaches the upper surface of the piezoelectric film. Therefore,
There is no need to provide a dead space around the periphery of the piezoelectric film,
The size of the surface acoustic wave element can be reduced.

In a method of manufacturing a surface acoustic wave device according to a second aspect of the present invention, the piezoelectric film is formed on the comb-shaped electrodes formed on the insulating substrate. As a result, the adhesive does not adhere to the comb-shaped electrode even if a slight manufacturing error occurs.

Further, in the method of manufacturing a surface acoustic wave device according to a third aspect of the present invention, a short-circuit electrode is formed so as to be in contact with the piezoelectric film. Thereby, the characteristics of the surface acoustic wave element are improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a surface acoustic wave device according to an embodiment of the present invention will be described below. FIG. 1 is a plan view of the surface acoustic wave element obtained through the method of manufacturing a surface acoustic wave element according to the present invention with the cap removed, and FIG.
FIG. 2 shows a cross-sectional view taken along the line. In the manufacture of the surface acoustic wave device 10 of the present invention, first, on an insulating substrate 11 made of glass or the like, a comb-shaped electrode 12 and an external connection pad 13 made of Al by photolithography, Lead electrode 14 for connecting pad 13 for external connection
To form Next, a piezoelectric film 15 made of ZnO is formed by sputtering so as to cover a portion of the insulating substrate 11 where the comb-shaped electrode 12 is formed.

Here, a cap 16 made of alumina or the like having a concave portion for forming a space around the comb-shaped electrode 12 of the surface acoustic wave element 10 and the piezoelectric film 15 on one surface is prepared. Then, the adhesive surface of the cap 16 is pressed against an adhesive layer made of an epoxy resin or the like having a predetermined thickness with a predetermined pressure, and the adhesive 17 is transferred to the cap. After that, the cap 16 and the insulating substrate 11 are bonded by thermosetting or the like, and the comb-shaped electrode 12 and the piezoelectric film 15 are hermetically sealed.

The surface acoustic wave device thus formed
In 10, a through hole 18 is formed in the portion of the external connection pad 13 so as to penetrate the insulating substrate 11 above and below, and a conductor is applied in the through hole 18. Thus, the terminal electrode 19 formed on the lower surface of the insulating substrate 11 and the insulating substrate
The external connection pads 13 on the upper surface 11 are connected by through holes 18, and the surface acoustic wave element 10 is surface-mounted at a predetermined position on a circuit board (not shown).

In the method of manufacturing a surface acoustic wave device as described above, an adhesive for bonding the cap and the insulating substrate is applied to the cap by transfer. By applying the adhesive by transfer, it is possible to apply the adhesive to the cap with a constant thickness, so that the amount of the adhesive, such as occurs when applying the adhesive by conventional screen printing, is partially increased. Will not be enormous. Therefore, the protruding adhesive only reaches the side surface of the piezoelectric film and does not reach the upper surface of the piezoelectric film, so that deterioration of the characteristics of the surface acoustic wave element can be prevented. At the same time,
In consideration of preventing the protruding adhesive from reaching the upper surface of the piezoelectric film, there is no need to provide a dead space around the periphery of the piezoelectric film, so that the surface acoustic wave element can be downsized.

In this embodiment, the manufacturing method for manufacturing a single surface acoustic wave device has been described. However, a plurality of comb-shaped electrodes or piezoelectric films are formed on a large insulating substrate, and the cap is bonded. After that, a manufacturing method in which individual surface acoustic wave elements are separated by dicing may be used. Also,
The present invention can be applied to a device using a sapphire substrate as an insulating substrate and a surface acoustic wave device having a short-circuit electrode formed on a piezoelectric film. Further, in the present embodiment, the description has been made using a surface acoustic wave element in which a comb-shaped electrode is formed on an insulating substrate and a piezoelectric film is formed on the comb-shaped electrode. The present invention can also be applied to a surface acoustic wave device having a comb electrode formed thereon. Furthermore, not only a filter but also a duplexer can be manufactured by using the method for manufacturing a surface acoustic wave element of the present invention.

[0017]

As described above, according to the present invention, in a surface acoustic wave device in which a cap is placed on a comb-shaped electrode portion covered with a piezoelectric film, an adhesive is transferred to the cap, and the cap and the insulating substrate are bonded. A method of manufacturing a surface acoustic wave device is described. Thus, the amount of the adhesive applied to the cap can be controlled, and the adhesive does not reach the upper surface of the piezoelectric film. Therefore, deterioration of the characteristics of the surface acoustic wave element is eliminated, and a dead space is eliminated, so that it is possible to provide a surface acoustic wave element that can be downsized.

[Brief description of the drawings]

FIG. 1 is a plan view of a surface acoustic wave device obtained by a method of manufacturing a surface acoustic wave device according to the present invention, from which a cap is removed.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 is a cross-sectional view of a surface acoustic wave device obtained by a conventional method for manufacturing a surface acoustic wave device.

[Explanation of symbols]

 10 Surface acoustic wave element 11 Insulating substrate 12 Comb electrode 13 External connection pad 14 Leader electrode 15 Piezoelectric film 16 Cap 17 Adhesive 18 Through hole 19 Terminal electrode

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Claims (3)

[Claims] A step of preparing an insulating substrate on which a comb-shaped electrode and a piezoelectric film in contact with the comb-shaped electrode are formed; and a cap for sealing the comb-shaped electrode and the piezoelectric film portion formed on the insulating substrate. An elastic surface, comprising: transferring a predetermined amount of an adhesive to a surface of the cap to be bonded to the insulating substrate; and bonding the cap to the insulating substrate. Method of manufacturing wave element. 2. The piezoelectric film is formed on the comb-shaped electrode formed on the insulating substrate.
A manufacturing method of the surface acoustic wave device according to the above. 3. The method for manufacturing a surface acoustic wave device according to claim 1, wherein a short-circuit electrode is formed so as to be in contact with said piezoelectric film.