JP2000353934A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact and inexpensive and highly reliable surface acoustic wave device by reducing the number of parts, and reducing manufacturing man-hours. SOLUTION: In this surface acoustic wave device, a surface acoustic wave element 20 is bonded on a base member 10 with anisotropic conductive adhesive 30, and a plurality lead of electrodes of the surface acoustic wave element 20 are electrically connected with the plurality of lead electrodes on the base member 10 with anisotropic conductive adhesive 30, and a space necessary for the propagation of the surface acoustic wave is formed so as to be closed between the surface acoustic wave element 20 and the base member 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface acoustic wave device, and more particularly to a packaging structure of a surface acoustic wave device.

[0002]

2. Description of the Related Art A surface acoustic wave device of this kind is generally
The surface acoustic wave element is bonded and fixed on the base member with an adhesive (die bonding agent) and electrically connected by wire bonding, or the surface acoustic wave element and the base member are electrically and mechanically connected by bump bonding to provide elasticity. The cap member is joined to the base member by seam welding to cover the surface acoustic wave element, by heating and melting of a joining material such as solder or Au-Sn alloy, etc., so that the surface acoustic wave element is in a package comprising the base member and the cap member. Hermetically sealed. However, such a structure has problems that the number of parts is large, the structure is complicated, the manufacturing cost is increased, and the whole is increased in size. For this reason, a surface acoustic wave device having a structure in which a surface acoustic wave element is sealed without using a cap member has been proposed (JP-A-4-293310,
JP-A-9-74329).

Japanese Patent Application Laid-Open No. 4-293310 discloses that an input / output electrode of a surface acoustic wave element and an electrode of a base member corresponding to the input / output electrode are connected by a solder bump, and a ground side pattern provided on a peripheral portion of the surface acoustic wave element. A surface acoustic wave device having a structure in which a ground surface of a base member is connected with a solder sealing frame, and the surface acoustic wave propagation surface of the surface acoustic wave element is sealed using the surface acoustic wave element itself as a part of a package is disclosed. Have been. According to this structure, the number of parts can be reduced, and the number of steps required for assembly can be reduced. Japanese Patent Application Laid-Open No. 9-74329 discloses a method in which a plurality of electrodes of a surface acoustic wave element and the corresponding electrodes of a base member are bump-connected to each other, and a portion of the surface acoustic wave element other than the surface acoustic wave propagation portion is sealed with a sealing resin. There is disclosed a surface acoustic wave device having a structure in which the surface acoustic wave element is sealed by covering the surface acoustic wave element. It is described that this structure can provide a highly reliable surface acoustic wave device that can be miniaturized.

[0004]

However, in the surface acoustic wave device having the structure disclosed in Japanese Patent Application Laid-Open No. 4-293310, it is possible to reduce the size of the surface acoustic wave device by reducing the number of cap members. It is necessary to form a ground side pattern for solder sealing and form input / output electrodes inside the ground side pattern, that is, connect the ground side pattern and the input / output electrodes connected to the solder bumps to the surface acoustic wave element. Since it cannot be arranged on the periphery, there is a limit in reducing the size of the surface acoustic wave device. Further, since the surface acoustic wave element and the base member are connected and fixed by the solder bumps and the solder sealing frame, when a thermal stress or the like is applied, the stress due to a difference in thermal expansion between the surface acoustic wave element and the base member. There is a problem that a connection failure is likely to occur at the bump connection portion.

In the surface acoustic wave device having the structure of Japanese Patent Application Laid-Open No. 9-74329, a sealing resin is used in place of the cap member, and it is difficult to reduce the number of parts and reduce the size of the liquid resin. However, there is a problem that it is difficult to perform proper sealing and sealing work is difficult, and complete sealing cannot be performed, or the sealing resin enters the surface acoustic wave propagation surface, resulting in poor characteristics. In addition, there is a problem that man-hours such as bump formation and bump connection are required, and the manufacturing cost is increased.

Therefore, an object of the present invention is to reduce the number of parts and the number of manufacturing steps, thereby reducing the size,
It is an object of the present invention to provide an inexpensive and highly reliable surface acoustic wave device.

[0007]

In order to achieve the above object, a surface acoustic wave device according to the present invention comprises a surface acoustic wave element having a plurality of extraction electrodes formed on a peripheral edge thereof, and a position corresponding to each extraction electrode. The base member on which the extraction electrode is formed and the peripheral portion of the surface acoustic wave element on which the extraction electrode is formed are annularly provided, and are hermetically sealed between the surface acoustic wave propagation surface of the surface acoustic wave element and the base member. The surface acoustic wave device and the base member are joined so as to form a space, and an anisotropic conductive adhesive for electrically connecting each extraction electrode and each extraction electrode is provided.

As the anisotropic conductive adhesive, there is used a resin adhesive in which conductive particles such as spherical metal particles or a spherical resin having a surface plated with metal are mixed with a resin adhesive.

As the resin adhesive, an epoxy-based resin,
Acrylic, urethane, and silicone resin adhesives can be used. In order to obtain high airtightness and sufficient bonding strength, it is desirable to use a high-density epoxy resin adhesive.

According to this structure, the anisotropic conductive adhesive has a function of mechanically joining the surface acoustic wave element and the base member and electrically connecting the respective electrodes. Further, the surface acoustic wave element itself functions as a part of the packaging member, and forms a hermetically sealed packaging structure together with the base member and the anisotropic conductive adhesive. The thickness of the anisotropic conductive adhesive forms a space necessary for propagation of the surface acoustic wave.

Further, since there is no metal bump bonding portion and the stress due to mechanical or thermal stress is reduced by the conductive adhesive itself, bonding failure and connection failure due to the stress can be prevented.

Therefore, the number of the cap members can be reduced and all the electrodes can be arranged on the peripheral portion of the element, so that the whole surface acoustic wave device can be reduced in size, and the electrical connection by bumps as in the conventional example can be achieved. It is unnecessary, and it can be manufactured by a simple process of applying an adhesive and hardening, so that the manufacturing cost can be reduced and the reliability is high. The surface acoustic wave device according to the present invention includes general devices using surface acoustic waves such as surface acoustic wave resonators, surface acoustic wave filters, and surface acoustic wave delay lines. Thus, one or more arbitrary number of interdigital transducers (IDTs) are provided on the piezoelectric substrate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a surface acoustic wave device according to a first embodiment of the present invention will be described with reference to FIGS. 1 is a perspective view of a surface acoustic wave device, FIG. 2 is a sectional view taken along line XX of FIG. 1, FIG. 3 is a sectional view taken along line YY, FIG. 4 is a perspective view of a base member, and FIG. FIG. 6 is a perspective view showing a state in which an anisotropic conductive adhesive is applied on a base member. In the surface acoustic wave device according to the present embodiment, the surface acoustic wave element 20 is bonded and joined to the base member 10 with an anisotropic conductive adhesive 30 provided in an annular shape over the entire periphery thereof. The plurality of extraction electrodes 25a to 25 of the surface acoustic wave element 20
25c and the plurality of input / output and ground extraction electrodes 12a to 12c on the base member 10 are connected to the anisotropic conductive adhesive 30.
Are electrically connected to each other, and a space necessary for the propagation of the surface acoustic wave is formed between the surface acoustic wave element 20 and the base member 10 in a sealed state. More specifically,
As shown in FIGS. 2 and 3, each of the electrodes 25 a to 25 c of the surface acoustic wave element 20 and each of the corresponding electrodes 12 a to 12 c of the base member 10 are electrically conductive particles 31 in the anisotropic conductive adhesive 30. Are electrically connected to each other.

The base member 10 is formed in a plate shape by laminating a plurality of ceramics such as alumina, and has input / output extraction electrodes 12a, 1a on an upper surface serving as a mounting surface of the surface acoustic wave element.
2b and an extraction electrode 12c for grounding are formed. Terminal electrodes 14a, 14
b and a ground terminal electrode 14c. Upper surface electrodes 12a to 12c and lower surface terminal electrodes 14a to 1
Reference numeral 4c is connected via a via hole 16 and an internal electrode (not shown). The base member 10 may be a single layer, and the material is not limited to alumina, but may be any material having high airtightness. However, in order to secure a surface acoustic wave propagation space, the surface roughness and flatness are 5 μm or less. Is desirable. Further, the electrodes on the upper surface and the lower surface may be connected via a through hole or an end surface electrode. The surface acoustic wave device is used by being mounted on a mounting board (circuit board) using the lower surface of the base member 10 as a mounting surface.

The surface acoustic wave element 20 includes a piezoelectric substrate 21 and has two IDTs on one main surface serving as a surface acoustic wave propagation surface.
An electrode pattern including an electrode 22, input / output lead electrodes 25a and 25b connected to each IDT electrode, a ground lead electrode 25c, and the like is formed. The electrode pattern is Al
Alternatively, it is made of an alloy containing Al and is formed by a known thin film forming method. Each extraction electrode 25a to 25c is an IDT
It is arranged on the periphery of the element outside the electrode 22. Piezoelectric substrate 2
1 includes lithium tantalate, lithium niobate,
A piezoelectric material such as quartz is used. Surface acoustic wave device 2
No. 0 is mounted with the surface acoustic wave propagation surface on which the IDT electrode 22 and the extraction electrodes 25 a to 25 c are formed facing the element mounting surface of the base member 10.

The anisotropic conductive adhesive 30 is formed by mixing and dispersing about 5% by weight of an epoxy resin adhesive with conductive particles 31 having a spherical epoxy resin surface plated with Au. Things. The conductive particles 31 are not limited to this, but may be made of other resin such as acrylic resin.
u, Ag, Pt or other metal-plated metal or spherical metal particles of Au, Ag, Pt or the like may be used.
Further, as the resin adhesive, other acrylic-based, urethane-based, and silicon-based resin adhesives may be used in addition to the epoxy-based resin adhesive. The conductive particles 3 are contained in these resin adhesives.
1 is mixed and dispersed in a weight ratio of 1% to 50% to form the anisotropic conductive adhesive 30.

Hereinafter, a method for manufacturing the surface acoustic wave device according to the present embodiment will be described. First, the base member 1 shown in FIG.
0 and the surface acoustic wave device 20 shown in FIG. 5 are prepared. Next, the base member 10 is aligned on a pallet (jig) provided with a large number of concave portions that are substantially fitted to the base member 10. The depth of the concave portion of the pallet is smaller than the thickness of the base member 10. For example, the thickness of the base member 10 is 0.5 m.
In the case of m, a pallet having a depth of 0.4 mm is used.

Next, this pallet is set on a stage of a screen printing machine and positioned, and as shown in FIG. 6, an anisotropic conductive adhesive 30 is screen-printed in a width of about 0.5 mm and applied. The conductive particles 31 have a particle diameter (diameter) of 10 μm ± 1 μm, and a coating thickness of 30 μm ± 1 μm.
It is set to about 10 μm.

Next, the surface acoustic wave element 20 is connected to the base member 1.
A chip mounter or the like is mounted on the anisotropic conductive adhesive 31 on the reference numeral 0. Next, using a pressing jig, 10
The anisotropic conductive adhesive 30 is cured by heating at a temperature of 100 ° C. to 300 ° C. for about 1 minute to 30 minutes using a belt-type heating furnace while applying a pressure of about g to 200 g. After heating for a short time in a belt heating furnace, it may be completely cured in a batch heating furnace.

The pressure-heating anisotropic conductive adhesive 30
Of the conductive particles 31 is about 70% in the thickness direction.
That is, the process is performed in a state where the conductive particles 31 are elastically deformed so as to be about 7 μm. Thereby, the height (thickness) between the surface acoustic wave element 20 and the base member 10 is about 7 μm.
Closed space is formed. That is, the presence of the conductive particles 31 forms a predetermined space between the IDT electrode of the surface acoustic wave element 20 and the base member 10, and obtains reliable electrical connection between the corresponding electrodes. I have. The height of the closed space can be set to a desired value by changing the particle size of the conductive particles 31 contained in the resin adhesive.

Next, a surface acoustic wave device according to a second embodiment of the present invention is shown in FIG. In the first embodiment, a base member having a flat element mounting surface is used. However, the surface acoustic wave device of the present embodiment employs a concave base member 10 having a thicker portion where the anisotropic conductive adhesive 30 is provided. Is used. Other configurations are the same as those of the first embodiment. With this configuration, the surface acoustic wave propagation space can be reliably ensured without being affected by the surface roughness or flatness (warpage) of the base member 10. In addition, it is possible to use conductive particles having a smaller particle size. In the above embodiment, a transversal type surface acoustic wave element has been described as an example.However, the present invention is not limited to this, and another surface acoustic wave element such as a resonator type surface acoustic wave element may be used. The electrode pattern of the base member is formed in a shape corresponding to the electrode pattern of the surface acoustic wave element used. Further, in the above-described embodiment, the base member has been described as having an outer shape having dimensions substantially equal to the outer shape of the surface acoustic wave element. May be a large-sized base member. In the surface acoustic wave device according to the above-described embodiment, the side surface and the upper surface of the surface acoustic wave element may be covered with an overcoat resin as necessary.

[0022]

As described above, according to the surface acoustic wave device according to the present invention, the extraction electrode of the surface acoustic wave element is arranged at the periphery of the element, and the anisotropic conductive adhesive is applied and cured. By joining and connecting the surface acoustic wave element and the base member and forming a closed surface acoustic wave propagation space by a simple method, the size can be reduced and the cost can be significantly reduced. it can.

Further, the stress applied to the joint and the connecting portion with the surface acoustic wave element and the base member due to thermal or mechanical stress is relieved by the anisotropic conductive adhesive itself, thereby preventing joining and connection failure due to the stress. be able to.

Therefore, according to the present invention, a small, inexpensive and highly reliable surface acoustic wave device can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a surface acoustic wave device according to a first embodiment.

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

FIG. 3 is a sectional view taken along line YY of FIG. 1;

FIG. 4 is a perspective view of a base member according to the first embodiment.

FIG. 5 is a perspective view of the surface acoustic wave device according to the first embodiment.

FIG. 6 is a perspective view showing a state in which an anisotropic conductive adhesive is applied on the base member of the first embodiment.

FIG. 7 is a sectional view of a surface acoustic wave device according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Base member 12a-12c Extraction electrode 20 Surface acoustic wave element 22 IDT electrode 25a-25c Extraction electrode 30 Anisotropic conductive adhesive 31 Conductive particles

Claims (3)

[Claims] 1. A surface acoustic wave element having a plurality of extraction electrodes formed on a peripheral portion, a base member having extraction electrodes formed at positions corresponding to the extraction electrodes, and each extraction electrode of the surface acoustic wave element. The surface acoustic wave element and the base member are joined together so as to form a closed space between the surface acoustic wave propagation surface of the surface acoustic wave element and the base member, and each extraction electrode And an anisotropic conductive adhesive for electrically connecting the extraction electrodes to each of the extraction electrodes. 2. The surface acoustic wave device according to claim 1, wherein the anisotropic conductive adhesive is a mixture of spherical metal particles or a spherical resin having a surface plated with metal mixed with a resin adhesive. Surface acoustic wave device. 3. The surface acoustic wave device according to claim 1, wherein the resin adhesive is a high-density epoxy adhesive.