JP2000022488A - Surface acoustic wave movement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make improved performance of the surface acoustic wave movement single body compatible with a requirement of cost reduction. SOLUTION: In the transversal surface acoustic wave device consisting of interdigital type electrodes 111, 112 formed on a piezoelectric substrate 110 opposite to each other and of lead electrodes 115, 116, 117, 118 connecting electrically to the interdigital type electrodes, an air gap of 5 microns or over is formed between the interdigital type electrodes formed opposite to each other, a surface acoustic wave vibrating region is surrounded by a simple or a composite film made of a metal or an insulating material whose thickness is 300 microns or below to form an enclosed structure, and thick film processing is applied to the lead electrodes. Thus, an investment for assembly installation for a composite component (surface acoustic wave chip + ceramic face mount chip carrier) that has been conventionally a fixed concept is not required and the ceramic face mount chip carrier sharing most that of the material cost in the product cost is saved, therefore the industrial value of this invention is very high.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a surface acoustic wave movement,
More specifically, it can be applied to all surface acoustic wave filters and surface acoustic wave oscillators, but it is particularly applicable to mobile telephone devices in the field of mobile communications and optical communications in the field of optical communications where miniaturization and high functionality are required. This is related to the structure of surface mount type surface acoustic wave filters for the purpose of miniaturizing and enhancing the function of surface acoustic wave devices as the heart of module components used in various communication equipment of a device. An object of the present invention is to provide a packageless surface acoustic wave filter and a packageless surface acoustic wave vibrator each having a single device.

[0002]

2. Description of the Related Art Surface acoustic wave filters have established themselves as indispensable electromechanical functional components in fields requiring ultra-miniaturization and high functionality such as mobile telephone devices. The method of manufacturing a surface acoustic wave filter is as follows: a surface acoustic wave chip manufactured by the same photolithography technology as an LSI is housed in a ceramic surface mount chip carrier with a seal ring, and is a composite part consisting of a surface acoustic wave chip and a ceramic package. It is implemented in various communication devices. Specifically, a method in which a surface acoustic wave chip is die-bonded in a ceramic surface mount chip carrier, and then a wire bonding is performed between an extraction electrode pad formed on the surface acoustic wave chip and a bonding pad formed in the chip carrier. Although there is a problem in partly confirming the reliability of the mounting state, there is a method of forming bumps on the extraction electrode pad formed on the surface acoustic wave chip and performing free chip bonding. Thereafter, in order to maintain high reliability of the surface acoustic wave filter, a metal cap is placed on a seal ring and hermetically sealed by seam welding or the like to achieve high reliability.

[0003]

Problems to be Solved by the Invention It is difficult for the surface acoustic wave filter realized by the conventional technology to respond to the rapid demand for miniaturization, weight reduction, high performance, and low cost of mobile communication equipment. The situation is coming down. The main focus of the development so far is
The performance and function of the surface acoustic wave alone were improved. In response to demands for cost reduction, downsizing of surface acoustic wave chips has been the main focus of development by each company. He has responded to user requests by selecting a chip carrier to match the developed surface acoustic wave chip. In parallel with this, in terms of production technology, the introduction of automated equipment has been actively studied and implemented as a measure to reduce assembly and inspection costs. However, following the conventional technology has reached its limits in terms of both development technology and production technology. If the surface acoustic wave device is comprehensively considered as a composite component composed of a conventional surface acoustic wave chip and a ceramic surface mount chip carrier, there are technical advantages, but cost disadvantages are increasing. Therefore, some manufacturers take a challenging approach, in which bumps are formed on the extraction electrode pads formed on the surface acoustic wave chip, and then they are free-chip bonded directly to the equipment board and potted with resin from above. Unfortunately, since there is no resin that does not completely transmit moisture, unfortunately the reliability is poor because the aluminum thin film for surface acoustic wave excitation formed on the piezoelectric substrate cannot withstand severe external use environment . Therefore, the performance improvement of the surface acoustic wave alone,
We considered a means to simultaneously solve the cost reduction request.

[0004]

[Means for Solving the Problem] Surface acoustic wave filters are
A surface acoustic wave region surrounding the interdigital electrode (IDT) in an operating frequency range of 0 MHz to 1 GHz (area where a gap is provided)
Has an extremely small area of 0.004 square mm to 3 square mm. The thickness of a simple or composite film made of metal or insulating material is a few to several tens of microns because diamond thin film and β-C ₃ N ₄ nitride have extremely strong film itself. The strength is enough. As means for solving the conventional problem, the present invention employs the following configuration.

[0005] 1. In a transversal surface acoustic wave device including an interdigital electrode formed on a piezoelectric substrate to face and an extraction electrode electrically connected to the interdigital electrode, a surface acoustic wave vibration region The crossed finger electrodes facing each other are held with an organic solvent such as a photoresist so that a gap of 5 μm or more can be formed,
The whole surface acoustic wave chip is covered with a film made of metal or insulating material from above, and then a hole is made in a part of the film formed to hold the surface acoustic wave vibration region, and the organic solvent such as photoresist is removed. Then, the hole made in a part of the film is closed again with a film of metal or insulating material, and a closed structure that completely shuts off the interdigital electrodes from the outside atmosphere and maintains high reliability is formed. Provided is a surface acoustic wave movement in which the thickness of a film formed in a surface acoustic wave vibration region is 300 microns or less, and the extraction electrode is subjected to a thick film treatment such as plating.

[0006] 2. In a resonator-type surface acoustic wave device composed of interdigital electrodes formed on a piezoelectric substrate, a reflective electrode, and an extraction electrode electrically connected to the interdigital electrodes, a surface acoustic wave vibration region The interdigital electrode and the reflective electrode are covered with an organic solvent of photoresist so that a gap of 5 μm or more can be formed, and the surface acoustic wave chip is made of a film made of metal or insulating material from above. Then, a hole is made in a part of the film formed so as to hold the surface acoustic wave vibration region, an organic solvent such as a photoresist is removed, and a hole made again in a part of the film is made of a metal or insulating material film. To form a hermetically sealed structure that can keep high reliability by completely intercepting the interdigitated electrode portion and the reflective electrode from the external atmosphere. The thickness of the film formed in the surface acoustic wave vibration region is 300. Below micron And to provide a surface acoustic wave movement comprising a thick film process such as plating is applied to the extraction electrode.

[0007] 3. 3. A surface acoustic wave movement characterized in that the surface corresponding to the thick film processing portion applied to the extraction electrode on the front surface of the surface acoustic wave movement according to claim 1 is mirror-finished. thing.

[0008] 4. The surface acoustic wave movement according to claim 1 or 2, wherein each corner is chamfered to provide a surface acoustic wave movement.

[0009] 5. 3. A surface acoustic wave movement according to claim 1, wherein a surface of the surface acoustic wave movement other than an extraction electrode portion subjected to a thick film treatment is covered with a conductive material. .

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of the basic structure of the surface acoustic wave movement. As apparent from this figure, the piezoelectric substrate (for example, quartz, lithium tantalate, lithium niobate, lithium tetraoxide, langasite, Bi ₁₂ GaO ₂₀ ,
Interdigital electrodes 111 and 112 of a transversal surface acoustic wave filter are formed on piezoelectric ceramics, a piezoelectric material having a diamond thin film formed on its surface, an organic piezoelectric material, and a non-piezoelectric material having a piezoelectric thin film formed on its surface. A gap 113 is provided between the interdigital electrodes 111 and 112 facing each other. The interdigital electrode 11
1 and 112 have lead electrodes 119, 120, 121,
122 are provided, and these lead electrodes 119,
Reference numerals 120, 121, and 122 are pattern-connected to the bonding pad portions 115, 116, 117, and 118, respectively. The bonding pad portions 115, 11
6, 117 and 118 have pads 122 and 12 respectively.
3, 125, 126 are provided.

In the present invention, the surface acoustic wave vibration region 114 formed by the interdigital electrodes 111 and 112 and the gap 113 and the interdigital electrodes 111 and 11 are formed.
2 bonding pad portion (lead electrode) 1 pattern-connected to lead electrodes 119, 120, 121, 122
15, 116, 117 and 118 are covered with an organic solvent such as a photoresist.

The thickness of the photoresist is chosen between 5 and 10 microns. For 5 microns or less, the surface acoustic wave vibration region 11
Since the metal or insulating film formed on the substrate 4 is in mechanical contact with the interdigital electrodes 111 and 112 due to external stress, it is necessary to select 5 μm or more.

The present invention is directed to a 70 M
Hz digital IF filter. Aperture length 8
A 5 μm heat-resistant AZ-based photoresist is applied to a surface acoustic wave vibration region of λ (about 0.4 mm) and length of 5.7 mm, and SiO ₂ is sputtered to a thickness of 2 μm on the entire surface acoustic wave chip. A window for removing a heat-resistant AZ-based photoresist is formed in a part of the surface acoustic wave vibration region 114 by photolithography (wet etching), the resist is removed in an acetone solution, and the residual organic solvent is completely removed by plasma ashing. Remove. Thereafter, a titanium thin film is again sputtered over the entire surface acoustic wave chip by 2 μm, and the window for removing the photoresist is closed with the titanium thin film. In order to enhance the mechanical film strength of the surface acoustic wave vibration region 114, masking is performed on portions other than the surface acoustic wave vibration region 114, and a hard Ni
r is plated for 50-60 microns. In this experiment, if the total film thickness in the surface acoustic wave vibration region 114 was 50 microns or more, the mechanical strength was sufficient. The masking applied to areas other than the surface acoustic wave vibration region 114 is removed, windows are opened in the pads 123, 124, 125, and 126, and solder plating is performed to realize the surface acoustic wave movement.

FIG. 2 is a cross-sectional side view of the surface acoustic wave movement of the present invention mounted on an equipment board 208. In FIG.
02, a surface acoustic wave oscillation region is secured by surrounding the composite film 203, and the pad portions 20 on the extraction electrodes 204 and 205 are provided.
6 and 207 are subjected to solder plating, and the pad portions 206 and 2
07 is mounted on the equipment board 208 by soldering.

In addition, by making the portions corresponding to the pad portions 206 and 207 of the back surface 209 of the surface acoustic wave movement 209 in FIG. 2 of the present invention into a mirror surface state, the mounting state of soldering can be directly inspected from the upper surface, and the reliability is improved. It is very convenient in terms of points.

Further, in the surface acoustic wave movement of the present invention, each corner is chamfered by barrel polishing or the like.
A surface acoustic wave chip component without chipping can be provided. Also,
In the case of ferroelectric materials such as lithium tantalate and lithium niobate, the interdigital electrodes cause electrostatic breakdown due to the strong current collection effect. Since there is a concern about electrostatic breakdown of the interdigital electrodes, the entire chip is covered with a conductive film except for the solder-plated pad part of the surface acoustic wave movement. It can be prevented before it happens.
Note that a diamond thin film or β-C ₃ N ₄ can also be applied as a film for forming the surface acoustic wave vibration region. Although the present invention has been described with respect to a surface acoustic wave filter, it is needless to mention that the present invention can be applied to a surface acoustic wave oscillator.

As described above, the surface acoustic wave movement of the present invention can be manufactured for a piezoelectric substrate, a piezoelectric substrate having a diamond thin film formed on its surface, and a non-piezoelectric substrate having a piezoelectric thin film formed on its surface.

As described above, the present invention can be applied to all surface acoustic wave filters and surface acoustic wave vibrators. In particular, the present invention is applicable to module parts in various communication fields where ultra-miniaturization and high functionality are required. An object of the present invention is to provide a package-less surface acoustic wave filter and a package-less surface acoustic wave vibrator using a surface acoustic wave chip itself as a single device for the purpose of miniaturization and high performance of a surface acoustic wave device as a heart. The total film thickness formed in the surface acoustic wave vibration region of the surface acoustic wave movement of the present invention is 300 microns or less as a practical value in consideration of ensuring high reliability in the used frequency region and considering the combination of materials. .

In the surface acoustic wave movement of the present invention, when a translucent material is used as the substrate, the back surface of the surface acoustic wave movement is mirror-finished so that the surface acoustic wave movement can be directly transferred to the equipment board from the upper surface. The mounting state at the time of soldering can be inspected, which is extremely advantageous in terms of reliability.

Further, in the surface acoustic wave movement of the present invention, each corner is chamfered by barrel polishing or the like.
A surface acoustic wave chip component having no chip can be provided. Also,
In the surface acoustic wave movement using ferroelectric materials lithium tantalate and lithium niobate, antistatic measures were taken by covering the entire chip with a conductive film except for the solder-plated pads. It can be provided as a surface acoustic wave device.

[0022]

According to the surface acoustic wave movement of the present invention,
Composite parts (surface acoustic wave chip +
The industrial value is extremely high because the investment in assembly equipment, which is regarded as a ceramic surface mount chip carrier, is not required, and the ceramic surface mount chip carrier, which accounts for most of the material cost of the product price, can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a structure of a surface acoustic wave movement.

FIG. 2 is a sectional view from the side when the surface acoustic wave movement is mounted.

[Explanation of symbols]

110 Piezoelectric substrate 111,112 Interdigital electrode 113 Interdigital electrode gap 114 Surface acoustic wave oscillation area 115,116,117,118 Extraction electrode 119,120,121,122 Lead electrode 123,124,125,126,206 , 207
Pad 200 Piezoelectric substrate 201 Interdigital electrode 202 Void 203 Composite film 204, 205 Extraction electrode 206, 207 Pad part 208 Equipment board 209 Surface acoustic wave movement back

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[Procedure amendment]

[Submission date] July 17, 1998 (1998.7.1)
7)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006] 2. In a resonator-type surface acoustic wave device composed of interdigital electrodes formed on a piezoelectric substrate, a reflective electrode, and an extraction electrode electrically connected to the interdigital electrodes, a surface acoustic wave vibration region The surface acoustic wave chip is covered with a film made of metal or insulating material from above, covering the interdigital electrode portion and the reflective electrode with an organic solvent such as photoresist so that a gap of 5 μm or more can be formed. Then, a hole is made in a part of the film formed so as to hold the surface acoustic wave vibration region, an organic solvent such as a photoresist is removed, and a hole made again in a part of the film is made of a metal or insulating material film. To form a hermetically sealed structure that can keep high reliability by completely intercepting the interdigitated electrode portion and the reflective electrode from the external atmosphere. The thickness of the film formed in the surface acoustic wave vibration region is 300. Below micron And to provide a surface acoustic wave movement comprising a thick film process such as plating is applied to the extraction electrode.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

FIG. 1 is a plan view of the basic structure of the surface acoustic wave movement. As is clear from this figure, the piezoelectric substrate (for example, quartz, lithium tantalate, lithium niobate, lithium tetraoxide, langasite, Bi ₁₂ GeO ₂₀ ,
Interdigital electrodes 111 and 112 of a transversal surface acoustic wave filter are formed on piezoelectric ceramics, a piezoelectric material having a diamond thin film formed on its surface, an organic piezoelectric material, and a non-piezoelectric material having a piezoelectric thin film formed on its surface. A gap 113 is provided between the interdigital electrodes 111 and 112 facing each other. The interdigital electrode 11
1 and 112 have lead electrodes 119, 120, 121,
122 are provided, and these lead electrodes 119,
Reference numerals 120, 121, and 122 are pattern-connected to the bonding pad portions 115, 116, 117, and 118, respectively. The bonding pad portions 115, 11
6, 117 and 118 have pads 123 and 12 respectively .
4 , 125, 126 are provided.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

Further, in the surface acoustic wave movement of the present invention, each corner is chamfered by barrel polishing or the like.
A surface acoustic wave chip component without chipping can be provided . Also,
In the surface acoustic wave movement using ferroelectric materials lithium tantalate and lithium niobate, antistatic measures were taken by covering the entire chip with a conductive film except for the solder-plated pads. It can be provided as a surface acoustic wave device.

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H03H 9/17 H03H 9/17 E

Claims (7)

[Claims] 1. A transversal surface acoustic wave device comprising an interdigital electrode formed facing a piezoelectric substrate and an extraction electrode portion electrically connected to the interdigital electrode. A sealed structure surrounding a surface acoustic wave vibration region with a single or composite film made of a metal or an insulating material having a thickness of 300 μm or less by providing a gap of 5 μm or more between the interdigital electrode portions formed opposite to each other, A surface acoustic wave movement in which the extraction electrode portion is subjected to a thick film treatment. 2. A resonator-type surface acoustic wave device comprising an interdigital electrode formed on a piezoelectric substrate, a reflective electrode, and an extraction electrode portion electrically connected to the interdigital electrode. A hermetically sealed structure surrounding a surface acoustic wave vibration region with a simple or composite film made of a metal or an insulating material having a thickness of 300 μm or less and having a gap of 5 μm or more between the interdigital electrode portion and the reflection electrode portion, and being drawn out A surface acoustic wave movement with a thick film treatment applied to the electrodes. 3. The surface acoustic wave movement according to claim 1, wherein the piezoelectric substrate is a non-piezoelectric substrate having a surface on which a piezoelectric thin film is formed. 4. The surface acoustic wave movement according to claim 1, wherein the piezoelectric substrate has a surface on which a diamond thin film is formed. 5. When the substrate material constituting the surface acoustic wave movement is a translucent material, the back surface corresponding to the thick film processing portion applied to the extraction electrode on the surface of the surface acoustic wave movement has a mirror surface state. 5. The method according to claim 1, wherein:
A surface acoustic wave movement according to any one of the above. 6. The surface acoustic wave movement according to claim 1, wherein each corner of the surface acoustic wave movement is chamfered. 7. The elastic surface according to claim 1, wherein a surface of the surface acoustic wave movement other than the extraction electrode portion subjected to the thick film treatment is covered with a conductive material. Wave movement.