JPH1174755A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely prevent intrusion of an insulating resin, etc., into a vibration space of a SAW(surface acoustic wave), to eliminate deterioration of characteristics, to make a surface acoustic wave device thinner, in smaller size and lighter weight. SOLUTION: A piezoelectric substrate 1 bottom of which an exciting electrode 9 to generate the surface acoustic wave is mounted on an insulated substrate 7 with a conductor pattern 4 to be connected with the exciting electrode 9 and the piezoelectric substrate 1 is joined with the insulated substrate 7 with a frame body 6 consisting of photocuring resin. Furthermore, a protective film 11 with high moisture proofness is attached to at least an outer circumferential surface 6a of the frame body 6, the intrusion of the insulated resin into the vibration space in which the exciting electrode 9 is provided is prevented by the surface acoustic wave S1 and the surface acoustic wave device is made thinner and in smaller size.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonator built in a mobile radio device such as a mobile phone and a mobile phone.
And a surface acoustic wave device used for a frequency band filter.

[0002]

2. Description of the Related Art Conventional typical surface acoustic waves (Surface Ac
oustic Wave (hereinafter also referred to as SAW) FIGS. 5 and 6 are schematic sectional views of devices J1 and J2.

In FIG. 5, reference numeral 11 denotes a piezoelectric substrate, 12 denotes input / output electrode pads, 13 denotes an electrode pattern pad connected to an external drive circuit, resonance circuit, ground circuit, etc. formed on the surface of the package, and 14 denotes a pad. Piezoelectric substrate 1 for SAW element
IDT (Inter Digital) of a comb-shaped electrode formed on
Transducer) electrodes 19 are wires connecting the pads 12 and 13. These members constitute a SAW element. Further, 15 to 17 are package members made of an insulating material such as ceramic or resin, and 18 is a ceramic member.
A lid made of metal (Kovar, Al, Cu) or the like,
A package is constituted by these members, and the SAW element is accommodated in the package.

As described above, the conventional surface acoustic wave device J1
Is to mount and fix the piezoelectric substrate 11 in a region surrounded by the package members 15 to 17 with an adhesive, electrically connect the pads 12 and 13 with wires 19 such as Al and Au, and further connect the lid 18 with solder. , Package material 1 with adhesive, etc.
7 was adhered from above to maintain airtightness.

In FIG. 6, reference numeral 21 denotes a piezoelectric substrate;
Is an input / output electrode pad, 23 is a pad 22 and a pad 24
A connection body such as a bump for electrically connecting
An electrode pattern pad 25 formed on the surface of the substrate and connected to an external drive circuit, resonance circuit, ground circuit, etc., is a comb-shaped electrode IDT (In
The reference numeral 26 denotes a protective member made of an insulating material molded over the entire SAW element.

As described above, another conventional surface acoustic wave device J
2 is a functional surface on which the IDT electrode 25 is provided
The protection member 26 made of an insulating resin has entered the vibration space of the SAW in which the functional surface exists.

Here, the connecting member 23 in FIG.
A metal wire such as u or Al is formed into a bump by a ball bonding method, or a bump made of Au, solder, or the like is formed by a vapor deposition method, a printing method, a transfer method, an electroless plating method, an electrolytic plating method, or the like. , Formed on the pad 22. Then, the piezoelectric substrate 21 provided with the connection body 23
Are fixed between the connecting body 23 and the pad 24, connected by applying a conductive adhesive or by a solder reflow melting method, and fixed on the base 27.

As another conventional example, a damper is provided on the piezoelectric substrate 21 or the connecting body 23 of the base 27 on the vibration space side so as to prevent the insulating resin 26 from entering the vibration space side with the same structure as that of FIG. (Other conventional examples: see, for example, JP-A-5-55303).

As another conventional example, a SAW element is flip-chip mounted face down in a package 17 shown in FIG. 5, and the outer periphery of the SAW element is fixedly arranged with an insulating resin. There are also proposals that do not enter the vibration space (other conventional examples: for example,
See JP-A-5-291864).

Further, as another conventional example, the SAW element is flip-chip mounted face-down inside the package 17 shown in FIG. 5, and the back surface of the SAW element is bonded and fixed to the lid 18 with an insulating resin. There has also been proposed a resin in which the conductive resin is prevented from entering the vibration space (another conventional example: see, for example, JP-A-6-61778).

[0011]

However, since the wire 19 is used in the conventional example shown in FIG.
The volume of the entire surface acoustic wave device is increased by the distance between the horizontal direction and the height direction in which 9 exists, which is disadvantageous in reducing the size, weight, and thickness.

Further, since the wires are connected one by one by the wire bonding apparatus, the manufacturing process becomes complicated.

Further, unnecessary inductance components are added due to the presence of the wires 19, and the frequency characteristics of the SAW device change, which must be taken into account in the design.

In the conventional example shown in FIG.
Enters the vibration space and is in contact with the functional surface.
Since the propagation of W is obstructed, it is difficult to obtain desired characteristics as a surface acoustic wave device.

Further, as in other conventional examples, even if a dam member is provided so that the insulating resin 26 does not enter the vibration space, or if an annular member is provided on the functional surface so as to surround the SAW propagation path, It was insufficient to completely prevent the insulating resin 26 from entering. When such an annular member is provided, since the annular member is formed by applying a silicone resin or the like, the annular member is formed on the chip side in advance, so that the height is uniformly formed during the formation. It was difficult.

Further, as in another conventional example, in the case of a surface acoustic wave device in which a piezoelectric substrate is flip-chip mounted face down on an insulating substrate and the peripheral portion of the piezoelectric substrate is hermetically sealed with a silicon-based insulating resin, Because the gelation of the insulating resin is due to thermal curing, the inert gas or air layer filling the vibration space causes thermal expansion, and voids are generated in the insulating resin, and the environment resistance, especially There was a problem with moisture resistance. Also, in the case of a surface acoustic wave device having a structure in which the applied portion of the insulating resin is only the outer peripheral portion of the SAW element and does not include the bump connector, the stress relaxation between the insulating substrate and the piezoelectric material is insufficient, and a long time is required for bump bonding. There was a problem with reliability.

Further, as in another conventional example, the sealing member is attached to the package substrate so that the bump and the package terminal are in contact with each other and the space formed by the sealing member and the package substrate is sealed. In the case of a surface acoustic wave device, since the structure is sealed with a lid, it is necessary to ensure the height of the lid, which is disadvantageous in reducing the thickness of the surface acoustic wave device.

Therefore, the present invention has been completed in view of the above-mentioned conventional problems, and it is possible to completely prevent the insulating resin from entering the vibration space of the SAW with a simple configuration, and to make the vibration space a uniform height. Now, it can be formed precisely in width, so that SA
It is an object of the present invention to provide a surface acoustic wave device that does not deteriorate the characteristics of a W device, is extremely thin, can be reduced in size and weight, and can be manufactured at low cost.

[0019]

An elastic wave device according to the present invention comprises:
A piezoelectric substrate provided with an excitation electrode for generating a surface acoustic wave on the lower surface is placed on an insulating substrate having a conductor pattern connected to the excitation electrode, in a state where a vibration space for the excitation electrode is formed, and The piezoelectric substrate and the insulating substrate are hermetically sealed with an adhesive made of a photocurable resin.

Specifically, for example, a piezoelectric substrate provided with an excitation electrode for generating a surface acoustic wave is placed on an insulating substrate having a conductor pattern connected to the excitation electrode, and the piezoelectric substrate and the insulating substrate are connected to each other. Is hermetically sealed with a frame-shaped adhesive made of a photocurable resin.

Further, a protective film having high moisture resistance may be applied to at least the outer peripheral surface of the frame-shaped adhesive.

The vibration space of the excitation electrode formed by the adhesive may be filled with an inert gas. Here, the inert gas includes not only a rare gas such as an argon gas but also a nitrogen gas and the like.

[0023]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a surface acoustic wave device S
1 is a partially omitted plan view, and a frame-like body (adhesive material) to be described later interposed between a piezoelectric substrate 1 and an insulating substrate 7 for simplicity;
6 is a plan view of the upper half of FIG. 6, and FIG.
FIG. 1 is a cross-sectional view taken along the line A. In FIG. 1, a piezoelectric substrate 1 and an IDT electrode 5 serving as an excitation electrode are included in the omitted SAW element.
Etc. are illustrated.

In FIG. 2, 1 is a piezoelectric substrate, 2 is an input / output electrode pad connected to an excitation electrode described later, 3 is a connection body such as a bump, 4 is a pad (conductive pattern) of an electrode lead pattern 8 described later, 5 is an IDT electrode which is an excitation electrode,
Reference numeral 6 denotes a frame (adhesive) made of a photocurable insulating resin;
Reference numeral 1 denotes a moisture-resistant protective film provided on at least the outer peripheral surface of the frame 6. Reference numeral 7 denotes an insulating substrate made of ceramics, resin, or the like, and reference numeral 8 denotes an electrode lead pattern provided on the insulating substrate 7 connected to an external drive circuit, a resonance circuit, a ground circuit, and the like. Reference numeral 9 denotes a vibration space of the IDT electrode 5.

As described above, in the acoustic wave device S1, the piezoelectric substrate 1 provided with the IDT electrode 9 for generating a surface acoustic wave on the lower surface is placed on the insulating substrate 7 having the conductor pattern 4 connected to the IDT electrode. At the same time, the outer peripheral portion of the lower surface of the piezoelectric substrate 1 and the upper surface of the insulating substrate 7 are joined by a frame member 6 made of a photocurable resin. A membrane 11 has been applied.

The SAW element is provided on the piezoelectric substrate 1,
The IDT electrode 5 is composed of at least a pair of IDT electrodes 5 of a comb-like electrode formed so as to mesh with each other. In order to obtain desired characteristics, the IDT electrode 5 is formed by connecting a plurality of pairs of comb-like electrodes in series connection. , May be connected by a parallel connection method.

The insulating substrate 7 is manufactured, for example, by laminating one ceramic substrate or a ceramic substrate and one or more frame-shaped ceramic substrates.
Is formed by electrolytic plating or electroless plating.

The IDT electrode 5 is formed by a thin film forming method such as a vapor deposition method, a sputtering method or a CVD method.

The connection body 3 is formed by forming a metal wire such as Au, Al or the like into a bump by a ball bonding method, or forming a bump made of Au, solder or the like by a vapor deposition method, a printing method, a transfer method, It is obtained by forming on the pad 2 by an electrolytic plating method or an electrolytic plating method.

The frame 6 is obtained by applying a dispenser on the conductive pattern 4 of the insulating substrate 7 or by applying an insulating photocurable resin by a printing method.

The main body (functional surface) of the piezoelectric substrate 1 on which the IDT electrode 5 is provided faces the upper surface of the insulating substrate 7 in a face-down configuration, and the connecting body 3 is electrically connected to the conductive pattern 4 by a conductive adhesive. And electrically connected to each other, and the piezoelectric substrate 1
Is placed and fixed on the insulating substrate 7.

After that, the frame 6 does not enter the functional surface on which the IDT electrode 5 is formed, and the frame 6 is secured to secure the piezoelectric substrate 1 and airtight the vibration space 9 where the IDT electrode 5 is present. The structure 6 is configured such that the shape body 6 surrounds the entire outer periphery of the piezoelectric substrate 1.

Then, the photo-curable resin is cured by irradiating ultraviolet light from the side or passing through a lamp furnace, and the surface acoustic wave device
Complete 1 Here, at least the outer peripheral surface 6 of the frame 6
a is covered with a protective film having better moisture resistance than the photo-curable resin constituting the main body of the frame-shaped body 6, the vibration space 9
It is good because the inside can be made more airtight.

For example, the main body of the frame 6 is made of an acrylic photocurable resin, and the protective film 11 is made of a urethane photocurable resin or an epoxy resin. In particular, when urethane is used, not only adhesion due to hydrogen bonding of the resin itself, such as acrylic, but also adhesion to the base increases. The protective film 11 may contain a predetermined amount of metal particles. The main body of the frame 6 is made of an acrylic photocurable resin, and the protective film 1 is made of a resin.
1 may be covered with a solder material. In this case, the airtightness is increased as compared with the resin sealing, and the moisture resistance is also improved. In the case where the protective film 11 is made of an epoxy resin, the epoxy resin is heat-curable and involves a heat process. Therefore, the epoxy resin is heat-cured by heating at 150 ° C. for 30 seconds to such an extent that the IDT electrode is not affected. Thus, no sharp temperature gradient is applied to the piezoelectric substrate 1.

Next, another embodiment of the present invention will be described with reference to FIG. In the same manner as described above, after the photocurable resin has a structure including the connecting body 3 and surrounding the entire outer peripheral portion of the piezoelectric substrate 1, the photocurable resin is applied with a dispenser or the like so as to cover the entire back surface of the piezoelectric substrate 1. The protective member 10 serving as a lid may be formed by irradiating ultraviolet light or passing through a lamp furnace from above to form the cover member, thereby completing the surface acoustic wave device S2.

Here, as the main material of the frame 6 and the protective member 10, acrylic oligomers such as polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, and oligo acrylate are used.

In particular, a thixotropic agent is added as an additive or the viscosity is adjusted to be higher by the amount of the filler so that the photocurable insulating material does not spread more than necessary by coating with a dispenser or printing. Are preferred, and S
It is preferable that the impurity ion concentration is reduced as much as possible so that the electrode corrosion of the AW element does not occur.

Next, another embodiment of the present invention will be described with reference to FIG. As in the case of the surface acoustic wave device S3, the vibration space 9 of the excitation electrode 5 may be secured by forming a concave portion 7a described later in the insulating substrate 7. That is, the conductor pattern 4 formed on the step 7b of the insulating substrate 7
Is electrically connected to the input / output electrode pads 2 formed on the piezoelectric substrate 1, and a lower portion of the excitation electrode 5 is secured to secure a vibration space of the excitation electrode 5 electrically connected to the input / output electrode pads 2. The concave portion 7a of the insulating substrate 7 may be formed at the same time. In such a case, the adhesive 6 may hermetically seal the space between the back surface (upper surface) 1a of the piezoelectric substrate 1 and the peripheral portion 7c of the insulating substrate 7, or may form a seal with the step portion 7d of the insulating substrate 7. The space between the piezoelectric substrate 1 and the lower surface may be hermetically sealed.

In the same manner as described above, the photocurable resin is
Then, a photo-curable resin is applied by a dispenser or the like so as to cover the entire back surface of the piezoelectric substrate 1 and is cured from above by irradiating ultraviolet rays or passing through a lamp furnace. Forming a protective member 10 serving as a body,
The surface acoustic wave device S2 may be completed.

Here, as the main material of the frame 6 and the protective member 10, acrylic oligomers such as polyester acrylate, polyurethane acrylate, epoxy acrylate, polyether acrylate, and oligo acrylate are used.

In particular, a thixotropic agent is added as an additive or the viscosity is adjusted to be higher by the amount of the filler so that the photocurable insulating material is not unnecessarily spread by dispenser coating or printing. Are preferred, and S
It is preferable that the impurity ion concentration is reduced as much as possible so that the electrode corrosion of the AW element does not occur.

In FIGS. 1 to 4, low-humidity air may be sealed in the vibrating space 9 to seal it. This is preferable because deterioration of the IDT electrode 5 due to oxidation or the like can be suppressed. Further, if an inert gas such as nitrogen gas or argon gas or the like is sealed and sealed instead of air, more preferable effects can be obtained.

In the present invention, the IDT electrode 5 is made of Al or an Al alloy (Al-Cu system, Al-Ti system, etc.). In particular, Al is preferable because of high excitation efficiency and low material cost. The IDT electrode 5 has a comb-like shape formed so as to mesh with each other. However, the IDT electrode 5 can be applied to a slit-type electrode such as a reflector in which a plurality of electrode fingers are arranged in parallel. It may be a type.

The logarithm of the IDT electrode 5 is 50 to 20.
0, the width of the electrode fingers is 0.1 to 10.0 μm, the interval between the electrode fingers is 0.1 to 10.0 μm, and the intersection width of the electrode fingers is 10 to 80.
It is preferable to set the thickness of the IDT electrode 5 to 0.2 to 0.4 μm in order to obtain desired characteristics as a resonator or a filter. Further, reflectors for reflecting the SAW and efficiently resonating the SAW may be provided at both ends of the SAW propagation path of the IDT electrode 5.
It is preferable to form a film of a piezoelectric material such as O or AlO because the SAW resonance efficiency is improved.

As the piezoelectric substrate 1, a 36 ° Y-cut-X
Propagating LiTaO ₃ single crystal, 64 ° Y cut-X propagating LiNbO ₃ single crystal, 45 ° X cut-Z propagating LiB
₄ O ₇ single crystal is preferable because it has a large electromechanical coupling coefficient and a small group delay time temperature coefficient. The thickness of the piezoelectric substrate is preferably about 0.3 to 0.5 mm. If the thickness is less than 0.3 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost increases.

Thus, the present invention provides a vibration space 9 for a SAW.
It is possible to completely prevent the insulating resin from entering the semiconductor device. Also,
Since the SAW element is not damaged due to the pyroelectricity of the piezoelectric substrate 1, the characteristic deterioration can be prevented as much as possible. Further, since the vibration space 9 can be accurately formed with a uniform height and width, the thickness and the size can be reduced. Further, since a heating step is not performed at the time of manufacturing, defects such as voids do not occur in the sealing insulating material, and thus long-term reliability can be secured.

It should be noted that the present invention is not limited to the above-described embodiment, and the connecting body 3 does not need to be included in the frame-shaped body 6 as in the above-described example. May be surrounded by a frame body 6 to join the piezoelectric substrate 1 and the insulating substrate 7. Also, for example, a frame-shaped dam member may be provided on the upper surface of the insulating substrate 7 in the vibration space 9. By forming a concave portion or the like, entry of the photocurable resin for forming the frame-shaped body 6 may be prevented as much as possible, and various changes may be made without departing from the scope of the present invention. Absent.

[0048]

Next, a specific embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, a 36 ° Y-cut X-propagating LiTaO 3 crystal was used as the piezoelectric substrate 1, and its chip size was 1.1 mm × 1.5 mm. In addition, 3.0 mm × 3.0 mm as a mounting board,
An alumina substrate having a thickness of 500 μm was used. Au and Ni having a total thickness of 1 μm were formed on the alumina substrate by electroless plating.

The connection body 3 was formed by forming a bump of an Au wire by a ball bonding method. The bump diameter was 70 μm and the height was 50 μm.

A modified acrylate-based ultraviolet curable resin was previously applied to the insulating substrate 7 at a position where the connector 3 was in contact with the dispenser. The line width of the applied resin is about 1
It was 00 μm.

The connection between the connection body 3 and the conductive pattern 4 is A
After transferring and applying a thermosetting epoxy-based conductive adhesive containing a g-Pd alloy to the connection body 3 and aligning the SAW element and the insulating substrate 7 face down in a nitrogen atmosphere,
The modified acrylate photocurable resin was cured by irradiating ultraviolet rays from the side surface at an illuminance of 80 mW / cm2 for 30 seconds to form the frame 6.

Further, a bisphenol-type epoxy resin was applied to the outer peripheral surface 6a of the photocurable resin with a dispenser, and was cured by heating at 150 ° C. for 30 seconds in an annealing furnace, a clean oven, or a hot plate.

In the above steps, the photocurable resin does not enter the inside of the vibration space 9, the vibration space 9 can be sufficiently secured, and only the outer peripheral portion of the SAW element chip including the connection body 3 is exposed to light. A surface acoustic wave device having a structure sealed with a curable insulating resin could be manufactured. The height of the surface acoustic wave device was about 1.0 mm.

As described above, the conventional wire bonding step is not required, the space in the horizontal direction of the wire and the size in the height direction of the wire can be reduced, and the size and thickness can be reduced.

[0055]

According to the surface acoustic wave device of the present invention, the space in which the excitation electrode is formed can be made air-tight by photo-curing the photo-curable resin at normal temperature, so No temperature gradient is applied, and problems such as open failure of the excitation electrode due to pyroelectricity of the piezoelectric substrate do not occur.

Further, the SA formed in the inner region of the adhesive material
Since the thermal expansion of the gas layer forming the vibrating space of the W element does not occur, it is possible to provide a surface acoustic wave device that does not generate voids in the sealing resin and has excellent long-term reliability and no deterioration in characteristics as in the related art.

Further, the photocurable resin of the adhesive can be relatively easily gelled, and the surface acoustic wave device can be manufactured in a short and simple process.

When the photo-curable resin is applied and cured, including the connection body such as bumps, the piezoelectric substrate can be more firmly bonded and fixed to the insulating substrate, and the SAW element and the insulating substrate can be formed. The stress due to the difference in linear expansion coefficient of the piezoelectric substrate can be dispersed and relaxed.

Further, according to the present invention, it is possible to provide a surface acoustic wave device capable of sufficiently reducing the thickness and size.

[Brief description of the drawings]

FIG. 1 is a partially omitted plan view illustrating an embodiment of a surface acoustic wave device according to the present invention.

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

FIG. 3 is a cross-sectional view illustrating an embodiment of another surface acoustic wave device according to the present invention.

FIG. 4 is a cross-sectional view illustrating an embodiment of another surface acoustic wave device according to the present invention.

FIG. 5 is a cross-sectional view illustrating a conventional surface acoustic wave device.

FIG. 6 is a cross-sectional view illustrating another conventional surface acoustic wave device.

[Explanation of symbols]

 1: piezoelectric substrate 2: input / output electrode pad 3: connection body (bump) 4: conductor pattern 5: IDT electrode (excitation electrode) 6: frame (adhesive) 7: insulating substrate 8: electrode lead pattern 9: vibration Space 10: Protection member S1, S2: Surface acoustic wave device

Claims (1)

[Claims] 1. A piezoelectric substrate having an excitation electrode for generating a surface acoustic wave on a lower surface thereof is mounted on an insulating substrate having a conductor pattern connected to the excitation electrode in a state in which a vibration space of the excitation electrode is formed. Wherein the piezoelectric substrate and the insulating substrate are hermetically sealed with an adhesive made of a photocurable resin.