JPH0951247A - Surface acoustic wave device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the size and the profile of a surface acoustic wave device in air-tight sealing small and thin and to reduce the cost by providing a hollow part to a vibration function face on which interdigital converter electrodes are arranged. SOLUTION: A recessed part 5 is provided to a position corresponding to a function face including a surface acoustic wave element consisting of interdigital converter electrodes 2 and their lead electrodes 3 provided onto a piezoelectric substrate 1 and their peripheral parts with an area larger than the vibration function face. Furthermore, the cap 4 provided with notches 6 at positions corresponding to the lead electrodes 3 is overlapped with the substrate 1 and adhered by a sealing agent 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 in which a hollow space in a free space that does not prevent excitation is formed on a functional surface on the electrode side where surface acoustic waves are excited, and a method for manufacturing the same.

[0002]

2. Description of the Related Art For example, a surface acoustic wave resonator, a surface acoustic wave filter, etc. are sealed by welding using a package of ceramic or the like in order to secure a free space on a functional surface of an exciting electrode and to hermetically seal the surface. It has stopped. FIG. 3 is a sectional view of a conventional surface acoustic wave device housed in a surface mount type package. In the figure, 31 is a ceramic package, 3
Reference numeral 2 is a surface acoustic wave element, 33 is a package electrode, 34 is a cap, 35 is a bonding wire, and 36 is a hollow portion.

[0003]

However, since the above-mentioned ceramic package and the like are expensive, they account for a large proportion of the cost as parts. Further, in the case of the surface mount package as shown in FIG. 3, one surface acoustic wave element is stored in one package, and therefore there is a limit to the size reduction due to the size of the package 31. Regarding the height, a hollow portion 36 is required so that the bonding wire 35 and the cap 34 do not come into contact with each other, and the thickness of the package 31 is
There were also restrictions on thinning. On the other hand, when a chip-shaped surface acoustic wave element is mounted on the same substrate as other IC circuits and simultaneously resin-sealed, the resin directly touches the electrode surface where it is excited, so that the desired electric power as a surface acoustic wave device is obtained. There was a problem that the physical characteristics could not be obtained.

An object of the present invention is to provide a hollow portion on an electrode surface of a surface acoustic wave element or the like on which surface waves are excited and to hermetically seal it without using an expensive package which is a problem of the prior art. Thus, it is to provide a surface acoustic wave device that can be made small and thin and a method for manufacturing the same.

[0005]

A surface acoustic wave device according to the present invention is a surface acoustic wave element having a comb-shaped transducer electrode and its extraction electrode disposed on a piezoelectric substrate, the comb-shaped transducer electrode and its surface. An insulating cap having a recessed portion provided in a position corresponding to the functional surface, which is larger than the area of the vibration functional surface including the peripheral portion, and a notch provided in the portion corresponding to the extraction electrode, and the surface acoustic wave element. And a sealing agent that overlaps and joins the electrode disposition surface of the cap and the recess disposition surface of the cap so as to face each other, and the cap is made of glass such as quartz, or The material is the same as the material of the piezoelectric substrate of the surface acoustic wave element, and the sealing agent is low melting point glass or an insulating adhesive.

Then, the manufacturing method thereof includes a step of forming a large number of surface acoustic wave elements having interdigital transducer electrodes and lead electrodes thereof on a wafer-shaped piezoelectric substrate, A recess is provided at a position corresponding to each cap of a large number of surface acoustic wave elements, and a recess is provided at a position corresponding to the function surface, which is larger than the area of the vibration function surface including the interdigital transducer electrode and its periphery, and corresponds to the extraction electrode. A step of forming a hole for a notch in a portion to be formed, an electrode disposition surface of a wafer-shaped piezoelectric substrate on which the large number of surface acoustic wave elements are formed, or a wafer-shaped substrate on which the large number of caps are formed. A step of adhering a sealing agent to one of the recessed surfaces by printing or the like, and the electrode-disposed surface of the wafer-shaped piezoelectric substrate and the recessed surface of the wafer-shaped substrate are opposed to each other, and A step of aligning a surface acoustic wave element and a large number of caps, superposing them in close contact with each other, and heat-bonding them together, and dicing to cut two heat-bonded wafers at the same time into individual chip-shaped surface acoustic wave devices Further, the wafer-shaped substrate is a glass substrate such as quartz or a substrate made of the same material as the piezoelectric substrate of the surface acoustic wave element, and the sealing agent is a low melting point glass or an insulating material. It is characterized by being an adhesive.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1A is an exploded perspective view showing the whole embodiment of the present invention, and FIG. 1B is a sectional view showing the embodiment of the present invention. In the figure, 1 is a piezoelectric substrate, 2 is a interdigital transducer electrode, 3 is an extraction electrode, 4 is a cap, and a recess 5 and a notch 6 are provided. 7 is an adhesive (sealing agent) for hermetically sealing. The recess 5 of the cap 4 is
The area is equal to the area of the vibration function surface including the peripheral portion of the interdigital transducer electrode 2 provided on the piezoelectric substrate 1, and is provided at a position corresponding to the function surface. The notch 6 is the extraction electrode 3
The part is exposed and the bonding wire is attached. Such a cap 4 is placed on the piezoelectric substrate 1 as shown by the arrow in FIG.
By sealing with the sealing agent 7 as described above, the concave portion 5 of the cap 4 becomes an airtight hollow portion.

FIG. 2 is a plan view of a wafer 21 having a large number of caps 4 according to the present invention. A wafer 21 made of a cap material is provided with a large number of concave portions 5 and lead electrode connecting holes 22. Reference numeral 23 is a dicing line (cutting line), which is bonded to a wafer-shaped piezoelectric substrate on which a large number of surface acoustic wave elements are formed and then divided into chips by this dicing line. In the embodiment shown in FIG. 1A, a cap 4 is made of a material that is relatively easy to make holes and recesses, such as quartz, and is sealed with a sealing agent such as low melting point glass in a wafer state. As shown in FIG. 1 (b), a hollow portion is formed in the portion of the interdigital transducer electrode 2 where the surface wave is excited, and it is hermetically sealed.

The holes 22 in the cap 4 and the recesses 5 are processed by etching or the like, and when a CO ₂ laser or the like is used, the caps 4 can be processed at one time and processed in a relatively short time. Further, the thickness of the cap can be made thin by using quartz or the like, and is set to be thin so as to maintain mechanical strength after drilling, recessing, and bonding.

For sealing, a low melting point glass or the like is adhered to the bonding surface of the piezoelectric substrate 1 or the surface of the cap 4 which does not come into contact with the interdigital transducer electrode 2, and they are superposed.
Heat and join at around 0 ° C. By sealing in this way, the functional surface including the periphery of the interdigital transducer electrode 2 to be excited is kept hollow and airtight. As the sealing agent,
If an insulating adhesive is used in place of the low melting point glass, it can be processed at a lower temperature. Further, electrical connection to the outside or the like is performed by wire bonding to the extraction electrode 3 exposed in the cutout portion 6.

Quartz or the like is used as the material of the wafer 21 in which a large number of caps shown in FIG. 2 are manufactured by batch processing, and a large number of holes 22 and concave portions 5 are provided by laser processing or etching in a wafer shape. A sealing agent such as low melting point glass is attached to one of the surfaces of the wafer on which the electrodes of the surface acoustic wave element are arranged by screen printing or the like, and the both are superposed and heated to bond them. When the wafers are stacked, the quartz is transparent, so alignment is easy. When the bonded product is cut by the dicing line 23, the surface acoustic wave element side wafer on which the electrodes are arranged and the cap material side wafer can be cut at the same time to be separated into chips.

Also, since a large number of caps can be manufactured and processed in a batch form in a wafer form, they can be provided in a short manufacturing period and at low cost, which is a great effect. Further, the cap material may be, for example, transparent LiNbO ₃ (lithium niobate) or L used for a piezoelectric substrate material.
If the same material as iTaO ₃ (lithium tantalate) or the like is used, the thermal expansion coefficient can be made the same, so that cracks and the like can be prevented and reliability can be improved. Moreover, since hardness and the like are the same, cutting _and processing are facilitated.

[0013]

As described in detail above, by carrying out the present invention, it is possible to use a relatively inexpensive cap material, which is excellent in economic efficiency. In addition, the surface acoustic wave element can be directly covered with the cap, and the hollow portion can be hermetically sealed so that the size can be reduced, and it can be mounted on the same substrate as other semiconductor integrated circuits in combination and resin-sealed. It is even more effective for downsizing the device to be incorporated.

[Brief description of drawings]

FIG. 1 is an exploded perspective view and a sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of an embodiment of a cap structure used in the present invention.

FIG. 3 is a cross-sectional view of a conventional surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate 2 Interdigital transducer electrode 3 Extraction electrode 4 Cap 5 Recess 6 Cutout 7 Sealing agent 21 Wafer 22 Opening (hole) 23 Dicing line 31 Package 32 Surface acoustic wave element 33 Electrode 34 Package cap 35 Wire 36 Hollow Department

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shishio Tominaga 3-14-20 Higashi-Nakano, Nakano-ku, Tokyo Kokusai Electric Co., Ltd. Ta Denshi Co., Ltd.

Claims (7)

[Claims] 1. A surface acoustic wave device in which a comb-shaped transducer electrode and its extraction electrode are arranged on a piezoelectric substrate, and a function larger than an area of a vibration function surface including the comb-shaped transducer electrode and its peripheral portion. An insulating cap having a recess provided at a position corresponding to the surface and a notch provided at a portion corresponding to the extraction electrode, an electrode mounting surface of the surface acoustic wave element and a recess mounting surface of the cap A surface acoustic wave device comprising: a sealing agent that is superposed and bonded so as to face each other. 2. The surface acoustic wave device according to claim 1, wherein the cap is glass such as quartz. 3. The surface acoustic wave device according to claim 1, wherein the cap is made of the same material as the material of the piezoelectric substrate of the surface acoustic wave element. 4. The surface acoustic wave device according to claim 1, wherein the sealing agent is a low melting point glass. 5. The surface acoustic wave device according to claim 1, wherein the sealing agent is an insulating adhesive agent. 6. A step of incorporating a large number of surface acoustic wave elements having interdigital transducer electrodes and extraction electrodes thereof formed on a wafer-shaped piezoelectric substrate, and the plurality of surface acoustic waves on the wafer-shaped substrate. A recess is provided at a position corresponding to each of the caps of the element, which is larger than the area of the vibrating functional surface including the interdigital transducer electrode and its peripheral portion, and a position corresponding to the functional surface, and a cutout portion is provided at a portion corresponding to the extraction electrode. A step of forming holes for use, an electrode disposition surface of a wafer-shaped piezoelectric substrate on which the large number of surface acoustic wave elements are formed, or a recessed surface of a wafer-shaped substrate on which the large number of caps are formed. A step of adhering a sealing agent to one surface by printing or the like; and a plurality of surface acoustic wave devices by making the electrode arrangement surface of the wafer-shaped piezoelectric substrate and the recessed surface of the wafer-shaped substrate face each other. Many A step of aligning with the cap of the above and superposing them in close contact with each other and heating and bonding, and a dicing step of simultaneously cutting the two wafers that have been heated and bonded and separating them into individual chip-shaped surface acoustic wave devices. Method for manufacturing surface acoustic wave device. 7. The wafer-shaped substrate according to claim 6 is a substrate made of the same material as a glass substrate such as quartz or a piezoelectric substrate of a surface acoustic wave element, and the sealing agent according to claim 6 is low in 7. The method for manufacturing a surface acoustic wave device according to claim 6, wherein the surface acoustic wave device is a melting point glass or an insulating adhesive.