JP2000004139A - Structure and method for sealing surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the structure and method for sealing a surface acoustic wave device which can easily and surely form an air gap and reduce the pack age cost. SOLUTION: The sealing structure for a surface acoustic wave device which forms an air gap 14 by forming a join member 16 surrounding a function surface 11a of a piezoelectric substrate 11 and mounting it facedown on a base substrate 13 with the function surface 11a under is equipped with a sheet 20 which is adhered and fixed to the base substrate 13 and a sealing material 19 which seals the piezoelectric substrate 11 covered with the sheet 20.

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 sealing structure and a sealing method thereof.

[0002]

2. Description of the Related Art In recent years, portable telephones and PHS (Person)
al Handyphone System) has become remarkably widespread, and personalization of electronic devices has been progressing. Accordingly, high-frequency analog components required for wireless communication have become very important. Among them, a surface acoustic wave (or Rayleigh wave, hereinafter referred to as SAW: Surface Acou)
Stick Wave) devices are smaller,
It is very effective in terms of cost reduction and is used for resonators and filters.

[0003] A general SAW device requires a transducer for converting an electric signal into an elastic wave or vice versa, and a piezoelectric material is used as a material therefor. When an electric field is applied to the piezoelectric body, distortion, that is, deformation occurs, and conversely, when a stress is applied, the electrical displacement changes, that is, a so-called piezoelectric effect occurs. Utilizing it to convert electric and elastic waves. As the piezoelectric single crystal material, quartz, lithium niobate (LiNbO ₃ ), lithium tantalate (LiT
aO ₃ ) is widely used.

For example, FIG. 15 is a configuration diagram of a conventional SAW transversal filter, FIG. 15A is a plan view of the filter, and FIG. 15B is a side view of the filter. FIG. 16 is a sectional view showing a sealing structure of the surface acoustic wave device. As shown in these figures, SA
The W transversal type filter is composed of a piezoelectric substrate 1 having a piezoelectric effect and an IDT (Interdigital T).
(transducer: interdigital transducer)
2 is comprised.

Therefore, when the input signal 6 is applied to the IDT 2, a periodic distortion is generated in the vicinity of the surface of the piezoelectric substrate 1 due to the piezoelectric effect in accordance with the applied electric field distribution in the IDT 2 part,
Excite the AW. Further, the SAW propagates on the surface of the piezoelectric substrate 1 and is converted into an electric signal again by the IDT 2 to become an output signal 7. Further, the wavelength λ of the SAW is a frequency f0 (= v / 2d, v: surface wave velocity) corresponding to the electrode period 2d of the IDT 2, and the SAW excited from each electrode is added to the same phase, so that the sensitivity between transmission and reception is reduced. Will be the highest.

[0006] The mounting method of such a SAW device is as follows.
As shown in FIG. 16, a mounting method similar to that of a general LSI, such as electrical connection using connection by wire bonding, can be applied. However, SAW devices
Since the SAW propagates on the surface of the piezoelectric substrate 1, the air gap 4 is indispensable on the surface of the piezoelectric substrate 1.
A package in which a sealing lid 5 is mounted on a base substrate 3 having a cavity and sealed to form an air gap 4 in a SAW propagation portion on the surface of the piezoelectric substrate 1 is a package of the most common SAW device at present. Structure (for example,
Design of communication filter circuit and its application, see Sogo Denshi Publisher).

[0007]

However, in the above-described conventional mounting method of a SAW device, a general LW device is used.
SI package (eg, transfer mold)
In comparison with the above, there is a problem that it is difficult to reduce the package size and the package cost becomes extremely high due to a structural problem for securing the air gap.

The present invention eliminates the above-mentioned problems, and provides a sealing structure and a sealing method for a surface acoustic wave device capable of easily and reliably forming an air gap and reducing the package cost. The purpose is to provide.

[0009]

According to the present invention, in order to achieve the above object, [1] a joining member is formed so as to surround a functional surface of a piezoelectric substrate in a sealing structure of a surface acoustic wave device; In a surface acoustic wave device sealing structure in which an air gap is formed by mounting the piezoelectric substrate face down on a base substrate with the functional surface of the piezoelectric substrate facing down, the piezoelectric substrate is wrapped and closely fixed to the base substrate. A sheet and a sealing material for sealing the piezoelectric substrate covered by the sheet are provided.

[2] In a sealing structure of a surface acoustic wave device, bonding in which a functional surface of a piezoelectric substrate is directed upward and a connection pad formed around the functional surface side and a connection portion of a base substrate are connected. A sheet that covers the bonding wires and is tightly fixed to the base substrate so as to form an air gap between the wires and the functional surface; and a seal that seals the piezoelectric substrate covered by the sheet. A stop member is provided.

[3] In the sealing structure of the surface acoustic wave device, bonding in which the function surface of the piezoelectric substrate is directed upward and connection pads formed around the function surface side and connection portions of the base substrate are connected. A wire, a frame formed so as to surround the bonding wire, and a sheet that wraps the frame so as to form an air gap between the functional surface and is tightly fixed to the base substrate; And a sealing material for sealing the piezoelectric substrate covered by.

[4] In the sealing structure of the surface acoustic wave device, bonding in which the functional surface of the piezoelectric substrate is directed upward and connection pads formed around the functional surface side are connected to connection portions of the base substrate. A sheet enclosing the column and tightly fixed to the base substrate so as to form an air gap between the wire, the column formed at at least four corners of the connection region by the bonding wire, and the functional surface; And a sealing material for sealing the piezoelectric substrate covered by the sheet.

[5] In the sealing structure for a surface acoustic wave device according to the above [1], [2], [3] or [4],
A conductive portion formed on the outer surface of the sheet and a ground pattern to which the conductive portion is connected are provided. [6] In the method for sealing a surface acoustic wave device, a bonding member is formed so as to surround a functional surface of a piezoelectric substrate, and the functional surface of the piezoelectric substrate is face-down mounted on a base substrate with an air gap. In the method for encapsulating a surface acoustic wave device, a step of covering a sheet on the piezoelectric substrate and temporarily fixing the sheet to the base substrate, and heating the sheet to wrap the piezoelectric substrate and the base substrate And a step of sealing the piezoelectric substrate covered by the sheet with a sealing material.

[7] In the method of sealing a surface acoustic wave device, the functional surface of the piezoelectric substrate is directed upward, and a bonding wire is formed between a connection pad formed around the functional surface and a connection portion of the base substrate with a bonding wire. A wire bonding step for connecting, a step of covering a sheet on the bonding wire so as to form an air gap between the functional surface and a step of temporarily fixing the sheet to the base substrate, and heating the sheet to bond the bonding wire. A step of covering and closely fixing the piezoelectric substrate to the base substrate and a step of sealing the piezoelectric substrate covered by the sheet with a sealing material are performed.

[8] In the method of sealing a surface acoustic wave device, the bonding surface is formed between a connection pad formed around the function surface side and a connection portion of the base substrate with a bonding wire with the function surface of the piezoelectric substrate facing upward. A wire bonding step of connecting, a step of forming a frame surrounding the bonding wire region, and a step of covering a sheet on the frame so as to form an air gap between the functional surface and temporarily fixing the sheet to the base substrate. And a step of heating the sheet to wrap the frame and tightly fixing the sheet to the base substrate, and a step of sealing the piezoelectric substrate covered by the sheet with a sealing material. is there.

[0016]

[9] In the method for sealing a surface acoustic wave device, a wire for connecting a connection pad formed around the functional surface side and a connection portion of a base substrate with a bonding wire with the functional surface of the piezoelectric substrate facing upward. A bonding step, a step of forming pillars in at least four corners of a connection region by the bonding wires, and a step of covering the pillars with a sheet so as to form an air gap between the functional surfaces and temporarily fixing the sheet to the base substrate. Heating the sheet to form an air gap between the functional surface, and wrapping the pillars, and closely fixing the pillars to the base substrate; and a piezoelectric substrate covered by the sheet. With a sealing material.

[10] The above [6], [7], [8] or

[9] The method for sealing a surface acoustic wave device according to the above,
The outer surface of the sheet is subjected to a conductive treatment and is connected to a ground pattern of a base substrate.

[0018]

Embodiments of the present invention will be described below in detail. FIG. 1 is a sectional view showing a sealing structure of a surface acoustic wave device according to a first embodiment of the present invention, and FIG.
3 is a plan view showing a sealing structure of the surface acoustic wave device.

As shown in these figures, the piezoelectric substrate 11
The piezoelectric substrate 11 and the base substrate 13 are connected by the joining member 16 so that the functional surface 11 a of the piezoelectric substrate 11 faces the base substrate 13. This is performed by using a commonly used bump connection technique, and a material such as solder or Au is often used for the bonding member 16. Next, the connected piezoelectric substrate 11 is
Then, sealing is performed so as to cover with an air gap 9, and an air gap 14 is formed.

What is important at this time is to prevent the sealing material 19 from flowing into the functional surface 11a. For this purpose, before sealing with the sealing material 19, the piezoelectric substrate 11 is completely wrapped in the sheet 20, heated and adhered to the base substrate 13. Thereby, the sealing material 19 does not enter between the piezoelectric substrate 11 and the base substrate 13, and the air gap 14 is reliably secured. In consideration of productivity, when the sheet 20 is temporarily fixed to the base substrate 13 before heating, there is no need to worry about movement of the sheet 20 before the heating step. Use or use the outer periphery of the sheet 20 and the base substrate 1
It is better to heat-press three surfaces. That is, they are temporarily fixed.

Here, the material used for the sheet 20 is preferably a resin material which softens and shrinks when heat is applied, and the heating temperature is preferably such that the sheet 20 does not liquefy. For example, vinyl resin has a heat deformation temperature of about 50 ° C.
At least at a heating temperature of 60 to 70 ° C., it can be sufficiently adhered and fixed to the base substrate 13. In addition, those having a certain degree of tackiness at the beginning may be generally commercially available adhesive sheets. For example, in the case of a sheet-like adhesive in which an acrylic resin is impregnated into a nonwoven fabric made of polyester, the curing temperature is around 100 ° C., and the adhesive can be sufficiently fixed to the base substrate 13.

Furthermore, since the structure has a nonwoven fabric,
The adhesive itself of the sheet 20 does not enter between the piezoelectric substrate 11 and the base substrate 13. In FIG. 2,
17 is an input / output terminal, and 18 is a connection pad. As described above, according to the first embodiment, since the air gap can be formed easily and surely, the package cost can be extremely reduced, and further, the bump connection technique is used. Since a face-down mounting is also used, it is easy to reduce the package size.

Next, a second embodiment of the present invention will be described. FIG. 4 is a sectional view showing a sealing structure of a surface acoustic wave device according to a second embodiment of the present invention, and FIG. 5 is an enlarged view of a portion B in FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Also in this example,
As in the first embodiment, the sheet 31 is arranged. However, the outer surface of the sheet 31, that is, one surface of the sheet 31 located on the opposite side to the piezoelectric substrate 11 is subjected to a conductive process, and a conductive portion is formed. 32, and after heating, is grounded to the ground pattern 34 of the base substrate 33 or the sealing material 3
5, the surface of the sealing material 35 is subjected to a conductive process to form a conductive portion 36, and the ground pattern 3 of the base substrate 33 is formed.
Connect to ground.

The conductive treatment applied here is performed by spraying a conductive paint or performing electroless plating.
The conductive portion 32 of the sheet pull can be easily formed.
In addition, the conductive treatment 36 for the sealing material 35 can be performed by a vapor deposition method, a sputtering method, or the like, and can be performed without a thermal problem. Thus, according to the second embodiment, the sheet 31
The conductive portion 32 is formed on the outer surface of the sheet 31 together with the sealing by the ground pattern 34 of the base substrate 33.
To ground.

Next, a third embodiment of the present invention will be described. FIG. 6 is a sectional view showing a sealing structure of a surface acoustic wave device according to a third embodiment of the present invention, FIG. 7 is an enlarged view of a portion C in FIG.
FIG. 8 is a sectional view showing a sealing step of a sheet portion of a surface acoustic wave device according to a third embodiment of the present invention. As shown in these figures, the air gap 40 can be formed using the sheet 46 in a structure in which electrical connection with the piezoelectric substrate 41 is performed by W / B (Wire Bonding) using bonding wires 42. 6 and 7, 44
Is a connection pad (first bonding portion) formed around the functional surface side of the piezoelectric substrate 41, and 45 is a base substrate 43
, A conductive portion, 47 and 50 are ground patterns, and 49 is a sealing material.

Hereinafter, a method of forming the sheet portion of the surface acoustic wave device will be described with reference to FIG. (1) First, as shown in FIG.
The convex sheet 46 'is positioned above the functional surface 41a. (2) Next, as shown in FIG.
In order to form an air gap on the functional surface 41a of the piezoelectric substrate 41, a bonding wire 4
Along with 2, the piezoelectric substrate 41 is covered with a convex sheet 46 'and temporarily fixed.

(3) Next, as shown in FIG. 8C, the convex sheet 46 'is heated and brought into close contact with the base substrate 43 to form the sheet 46. Although not shown, the piezoelectric substrate is then sealed with a sealing material. Here, when the piezoelectric substrate 41 is wrapped by the sheet 46, the bonding wires 42
A convex sheet 46 'which does not come into contact with the bonding wire 42 so as not to be crushed is used.
After the outer periphery of the base substrate 43 and the surface of the base substrate 43 are thermocompression-bonded, heating is performed. Then, since the convex sheet 46 'which is softened by heating contracts as a whole, the bonding wire 42 does not collapse. However, when there is no such fear, the sheet need not be a convex sheet.

As for the shielding property of the piezoelectric substrate 41, it is of course possible to adopt the same configuration as in the second embodiment. As described above, according to the third embodiment, since the air gap can be easily and reliably formed, the package cost can be extremely reduced.

Further, in the conventional sealing structure, a gap is provided so as to prevent the wire bonding portion and the sealing lid from coming into contact with each other. However, in the structure of the present invention, this is not necessary. It is easy to reduce the package size. Next, a fourth embodiment of the present invention will be described. FIG. 9 is a sectional view showing a sealing structure of a surface acoustic wave device according to a fourth embodiment of the present invention, FIG. 10 is an enlarged view of a portion D in FIG.
FIG. 1 is a plan view showing a sealing structure of the surface acoustic wave device.

As shown in these figures, 50 is an air gap, 51 is a piezoelectric substrate, 51a is a functional surface, 51b is an outer portion of the piezoelectric substrate, 52 is a bonding wire, 53 is a base substrate, and 54 is a piezoelectric substrate. Connection pads (1st bonding portion) formed around the functional surface side of the body substrate 51, 55
Denotes a connection portion (2nd bonding portion) of the base substrate 53,
Reference numeral 56 denotes a frame disposed so as to surround the second bonding portion 55, 57 denotes a sheet, and 58 denotes an outer surface of the sheet 57, that is, a conductive portion formed on one surface of the sheet 57 located on the opposite side to the piezoelectric substrate 51. After heating by the conductive portion 58, the ground portion is grounded to the ground pattern 59 of the base substrate 53, or after being sealed with the sealing material 60, the conductive portion 61 having the surface of the sealing material 60 subjected to a conductive process is used to ground. The pattern 59 is grounded.

As described above, the functional surface 51 of the piezoelectric substrate 51
A frame 56 is provided so as to surround the second bonding portion 55 in order to form the air gap 50 in the area a. The frame 56 including the piezoelectric substrate 51 is sealed with a sheet 57 before sealing with the sealing material 60. The sheet 57 is enclosed and heated so that the sheet 57 is in close contact with the frame 56. Finally, the piezoelectric substrate 51 is sealed with the sealing material 60.

Therefore, the height of the frame 56 is preferably about the height from the base substrate 53 to the highest position of the loop of the bonding wire 52. As described above, according to the fourth embodiment, since the load of the seat can be received by the frame, the wire hiding does not collapse. Further, as for the shielding property of the piezoelectric substrate, it is naturally possible to configure the same as in the second embodiment, and further, a bump connection technique such as a bonding material is used for the potential connection between the piezoelectric substrate and the base substrate. Needless to say, it is applicable to the existing structure.

Next, a fifth embodiment of the present invention will be described. 12 is a cross-sectional view showing a sealing structure of a surface acoustic wave device according to a fifth embodiment of the present invention, FIG. 13 is an enlarged view of a portion E in FIG. 12, and FIG. 14 shows a sealing structure of the surface acoustic wave device. It is a top view. As shown in these figures, 70 is an air gap, 71 is a piezoelectric substrate, 71a is a functional surface, 71b
Is the outer portion of the piezoelectric substrate, 72 is a bonding wire, 7
3 is a base substrate, 74 is a connection pad (1st bonding part) formed around the functional surface side of the piezoelectric substrate 71,
Reference numeral 75 denotes a connection portion (2nd bonding portion) of the base substrate 73.

Further, reference numeral 76 designates at least the bonding area of the piezoelectric substrate 71 instead of the frame shown in the fourth embodiment.
Columns 77 formed at the corners, 77 is a sheet, and 78 is a conductive portion formed on the outer surface of the sheet 77, that is, on one surface of the sheet 77 located on the side opposite to the piezoelectric substrate 71. After heating by the conductive portion 78, the ground pattern is grounded to the ground pattern 79 of the base substrate 73, or after sealing with the sealing material 80, the conductive portion 81 having the surface of the sealing material 80 subjected to a conductive treatment is used to form the ground pattern. Ground to 79.

As described above, in the fifth embodiment, the columns 76 formed at least at the four corners of the bonding region of the piezoelectric substrate 71 are arranged instead of the frame 56 shown in the fourth embodiment. In order to form the air gap 70 on the functional surface 71a of the piezoelectric substrate 71, the second bonding portion 75
Is provided so as to surround the column 76, and before sealing with the sealing material 80, the column 76 including the piezoelectric substrate 71 is covered with a sheet 77, and heated to make the sheet 77 adhere to the column 76, Finally, the piezoelectric substrate 71 is sealed with a sealing material 80. This pillar 7
The height of the connecting wire 7 is
The height is preferably about the height of the maximum position of the second loop.

Further, although the columns 76 are arranged at the four corners surrounding the wire bonding portion, they can be arranged at any positions. In other words, an optimal arrangement can be performed according to the connection position of the bonding wires and the outer size of the piezoelectric substrate. In addition, the shielding property of the piezoelectric substrate 71 can be the same as that of the second embodiment. Further, it is needless to say that the electrical connection between the piezoelectric substrate 71 and the base substrate 73 can be applied to a structure using a bump connection technique such as a bonding material.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0038]

As described above, according to the present invention, the following effects can be obtained. (1) According to the first or sixth aspect of the present invention, the air gap can be easily and reliably formed, and the package cost can be significantly reduced.

Further, since a face-down mounting using a bump connection technique is also used, it is easy to reduce the package size. (2) According to the second or seventh aspect of the invention, the air gap can be easily and reliably formed, so that the package cost can be extremely reduced.

Further, in the conventional sealing structure, a gap is provided so as to prevent the wire bonding portion and the sealing lid from contacting with each other. However, in the structure of the present invention, this is not necessary, and the height is reduced. It is easy to reduce the package size. (3) According to the third or eighth aspect of the present invention, since the load of the seat can be received by the frame, the wire hiding does not collapse.

(4) According to the fourth or ninth aspect of the invention, the frame in (3) is replaced with a pillar, so that the material required for the frame can be reduced. (5) According to the fifth or tenth aspect of the present invention, it is possible to form a conductive portion on the outer surface of the seal together with the seal using the sheet, and connect the ground to the ground pattern of the base substrate.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sealing structure of a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is a plan view showing a sealing structure of the surface acoustic wave device according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a sealing structure of a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 5 is an enlarged view of a portion B in FIG. 4;

FIG. 6 is a sectional view showing a sealing structure of a surface acoustic wave device according to a third embodiment of the present invention.

FIG. 7 is an enlarged view of a portion C in FIG. 6;

FIG. 8 is a sectional view of a sheet portion of a surface acoustic wave device according to a third embodiment of the present invention in a sealing step.

FIG. 9 is a sectional view showing a sealing structure of a surface acoustic wave device according to a fourth embodiment of the present invention.

FIG. 10 is an enlarged view of a portion D in FIG. 9;

FIG. 11 is a plan view showing a sealing structure of a surface acoustic wave device according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view showing a sealing structure of a surface acoustic wave device according to a fifth embodiment of the present invention.

FIG. 13 is an enlarged view of a portion E in FIG. 12;

FIG. 14 is a plan view showing a sealing structure of a surface acoustic wave device according to a fifth embodiment of the present invention.

FIG. 15 is a configuration diagram of a conventional SAW transversal type filter.

FIG. 16 is a sectional view showing a sealing structure of a conventional surface acoustic wave device.

[Explanation of symbols]

11, 41, 51, 71 Piezoelectric substrate 11a, 41a, 51a, 71a Functional surface 13, 33, 53, 73 Base substrate 14, 40, 50, 70 Air gap 16 Joining member 19, 35, 49, 60, 80 Sealing Stoppers 20, 31, 46, 57, 77 Sheets 32, 36, 47, 50, 58, 61, 78, 81
Conductive portions 34, 48, 59, 79 Ground patterns 42, 52, 72 Bonding wires 44, 54, 74 Connection pads (1st bonding portion) 45, 55, 75 Connection portion of base substrate (2nd bonding portion) 46 ' Sheets 51b, 71b External part of piezoelectric substrate 56 Frame 76 Column

Claims (10)

[Claims] 1. A surface acoustic wave device in which a bonding member is formed so as to surround a functional surface of a piezoelectric substrate, and the functional surface of the piezoelectric substrate is face-down mounted on a base substrate to form an air gap. The sealing structure includes: (a) a sheet that encloses the piezoelectric substrate and is tightly fixed to the base substrate; and (b) a sealing material that seals the piezoelectric substrate covered by the sheet. A sealing structure for a surface acoustic wave device. 2. A bonding wire which connects between a connection pad formed around the functional surface side with the functional surface of the piezoelectric substrate facing upward and a connecting portion of the base substrate, and (b) the functional surface. And (c) a sealing material that seals the piezoelectric substrate covered by the sheet while covering the bonding wires so as to form an air gap therebetween. A sealing structure for a surface acoustic wave device, comprising: 3. A bonding wire for connecting between a connection pad formed around the functional surface side of the piezoelectric substrate with the functional surface thereof facing upward and a connecting portion of the base substrate, and (b) the bonding wire. (C) a frame formed so as to surround
A sheet enclosing the frame and tightly fixed to the base substrate so as to form an air gap with the functional surface; and (d) sealing for sealing the piezoelectric substrate covered by the sheet. A sealing structure for a surface acoustic wave device, comprising a material. 4. A bonding wire for connecting between a connection pad formed around the functional surface side of the piezoelectric substrate with the functional surface of the piezoelectric substrate facing upward and a connecting portion of the base substrate, and (b) the bonding wire. And (c) a sheet enclosing the columns and tightly fixed to the base substrate so as to form an air gap between the functional surfaces, d) A sealing structure for a surface acoustic wave device, comprising a sealing material for sealing the piezoelectric substrate covered by the sheet. 5. The surface acoustic wave device sealing structure according to claim 1, wherein the conductive portion formed on the outer surface of the sheet and a ground pattern to which the conductive portion is connected. A sealing structure for a surface acoustic wave device, comprising: 6. A surface acoustic wave device in which a joining member is formed so as to surround a functional surface of a piezoelectric substrate, and the functional surface of the piezoelectric substrate is face-down mounted face down on a base substrate to form an air gap. In the sealing method, (a) a step of covering the piezoelectric substrate with a sheet and temporarily fixing the sheet to the base substrate; and (b) heating the sheet to wrap the piezoelectric substrate and adhere to the base substrate. A method for sealing a surface acoustic wave device, comprising: a step of fixing; and (c) a step of sealing a piezoelectric substrate covered by the sheet with a sealing material. 7. A wire bonding step of connecting a connection pad formed around the functional surface side of the piezoelectric substrate with the functional surface of the piezoelectric substrate upward and a connecting portion of the base substrate by a bonding wire; A) covering the bonding wire with a sheet so as to form an air gap with the functional surface, and temporarily fixing the sheet to the base substrate; and (c) heating the sheet to cover the bonding wire. A method of sealing a surface acoustic wave device, comprising the steps of: adhering and fixing to a base substrate; and (d) sealing a piezoelectric substrate covered by the sheet with a sealing material. 8. A wire bonding step of connecting a connection pad formed around the function surface side of the piezoelectric substrate with the function surface of the piezoelectric substrate upward and a connection portion of the base substrate by a bonding wire; (C) forming a frame surrounding the bonding wire region; and (c) covering a sheet on the frame so as to form an air gap between the functional surface and temporarily fixing the sheet to the base substrate. d)
A step of heating the sheet to wrap the frame and closely fixing the frame to the base substrate; and (e) sealing the piezoelectric substrate covered by the sheet with a sealing material. Method for sealing a surface acoustic wave device. 9. A wire bonding step of connecting a connection pad formed around the function surface side of the piezoelectric substrate with the function surface of the piezoelectric substrate upward and a connection portion of the base substrate with a bonding wire; Forming a pillar in at least four corners of a connection region by the bonding wire;
(C) a step of covering the pillar with a sheet so as to form an air gap with the functional surface and temporarily fixing the sheet to the base substrate; and (d) heating the sheet to form a gap between the functional surface and the functional surface. Enclosing the column and closely fixing the column to the base substrate so as to form an air gap, and (e) sealing the piezoelectric substrate covered by the sheet with a sealing material. A method for sealing a surface acoustic wave device. 10. The method for sealing a surface acoustic wave device according to claim 6, wherein the outer surface of the sheet is subjected to a conductive treatment and is connected to a ground pattern of a base substrate. Method for sealing a surface acoustic wave device.