JPH10163797A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the airtight ability of vibration space in SAW to be secure and to easily form vibration space with uniform height and width by providing a comb-line electrode in a recessed part area formed in a piezoelectric substrate and fitting the piezoelectric substrate on an insulating substrate by means of making the recessed part area face the surface of the insulating substrate. SOLUTION: An SAW element 1 is generated by forming the recessed part area 10 and a peripheral frame area 10a on one main face of the piezoelectric substrate and providing a pair of comb-line IDT electrodes 5 formed so that they are engaged each other in the recessed part 10. The recessed part area 10-side where the IDT electrodes 5 are provided is set to be phase down constitution facing the insulating substrate 7. A connection body 3 is electrically conducted by conductive adhesion and is connected to a conductor pattern 4. The SAW element 1 is placed and fixed on the insulating substrate 7. Then, insulating resin 6 is applied to and molded into the lower part of the outer face of the SAW element 1 for fixing the SAW element 1 and making the airtight ability of vibration space where the IDT electrodes 5 exist to be secure.

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 for a resonator and a frequency band filter incorporated in a mobile radio device such as a mobile phone and a mobile phone.

[0002]

2. Description of the Related Art Conventional surface acoustic waves (Surface Acoustic W)
ave, hereinafter abbreviated as SAW) FIGS. 5 and 6 are sectional views of the devices S ₁ and S ₂ . In FIG. 5, reference numeral 11 denotes a SAW element;
Is a pad of an input / output electrode, 13 is a pad of a conductive pattern formed on the surface of the package and connected to an external drive circuit, a resonance circuit, a ground circuit, etc., and 14 is a comb tooth formed on a piezoelectric substrate for a SAW element. Electrode IDT (Inter Digital Tr
An electrode 15 to 17 is a package made of an insulating material such as ceramic or resin, and 18 is a lid made of ceramic, metal (Al, Cu) or the like. 19 is pad 1
It is a wire connecting 2 and 13. In the configuration shown in the figure, the SAW element 11 is placed and fixed inside the packages 15 to 17 with an adhesive, the pads 12 and 13 are electrically connected by wires 19 such as Al and Au, and the lid 18 is soldered. The package 17 was adhered from above the package 17 with an adhesive or the like to maintain airtightness.

In FIG. 6, reference numeral 21 denotes a SAW element; 22, an input / output electrode pad; and 23, a bump (an approximately semi-spherical, approximately semi-elliptical spherical, or substantially cylindrical convex) for electrically connecting the pad 22 to the pad 24. 24) is a conductive pattern pad formed on the surface of the substrate 27 and connected to an external drive circuit, resonance circuit, ground circuit, etc. 25 is a comb tooth formed on a piezoelectric substrate for a SAW element IDT (Inter)
Digital Transducer) electrodes 26, an insulating resin molded over the entire SAW device as a protective film, and 27 a substrate made of an insulating material such as ceramic or resin. The configuration shown in the figure is a face-down configuration in which the functional surface on which the IDT electrode 25 is provided faces the substrate 27, and the insulating resin 26 enters the vibration space of the SAW where the functional surface exists.

The connecting body 23 shown in FIG. 6 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 22 by an electrolytic plating method or an electrolytic plating method. And
The piezoelectric substrate provided with the connection body 23 is connected to the connection body 23 and the pad 2.
4 and are connected by applying a conductive adhesive or by a reflow melting method of solder, and fixed on the substrate 27.

As another conventional example, a SAW element 21 made of a piezoelectric substrate or a substrate having the same configuration as that shown in FIG. 6 is used to prevent the insulating resin 26 from entering the vibration space (the space where the IDT electrode 25 exists). 27, a dam is provided on the vibration space side of the connecting body 23 (Japanese Patent Laid-Open No. 5-55).
No. 303). Further, as another conventional example, an annular member made of silicone resin or the like is provided on the functional surface of the piezoelectric substrate so as to surround the SAW propagation path with the same configuration as that of FIG.
7 is mounted in a face-down configuration so as to prevent the insulating resin 26 from entering the vibration space (see Japanese Patent Laid-Open No. 5-90885).

[0006]

However, in the conventional example shown in FIG. 5, since the wire 19 is used, the volume of the SAW device is reduced by the distance between the horizontal direction where the wire 19 exists and the height direction. This is disadvantageous in reducing the size, weight, and thickness. In addition, since the wires are connected one by one by the wire bonding apparatus, the manufacturing process becomes complicated and the manufacturing cost increases. Furthermore, the presence of the wire 19 adds an unnecessary inductance component, changes the frequency characteristic of the SAW device, and causes a problem that it takes time to consider it in design.

In the conventional example shown in FIG. 6, the insulating resin 26 enters the vibration space (the space where the IDT electrode 25 is present) and is in contact with the functional surface. It is difficult to obtain the desired properties of Even if a dam is provided so that the insulating resin 26 does not enter the vibration space or an annular member is provided on the functional surface so as to surround the SAW propagation path, it is possible to completely prevent the insulating resin 26 from entering. It was not enough. When the annular member is provided, it is difficult to accurately form a vibration space with a uniform height and width because the annular member is formed by applying a silicone resin or the like.

Accordingly, the present invention has been completed in view of the above circumstances, and an object of the present invention is to completely prevent the insulating resin from entering the vibration space of the SAW, and to make the vibration space uniform in height and width. An object of the present invention is to form the SAW device accurately, so that the SAW device is not deteriorated in characteristics, is thin, small, and lightweight, and can be manufactured at low cost.

[0009]

A surface acoustic wave device according to the present invention comprises a concave region on one principal surface of a piezoelectric substrate and a frame region on the periphery thereof, and at least a pair of comb-like electrodes in the concave region. The recessed region side faces an insulating substrate having a conductive pattern and a lead pattern extending to the outside in connection with the conductive pattern, and the frame region is brought into contact with or adhered to the insulating substrate to form a piezoelectric substrate. And the input / output electrode of the comb-shaped electrode and the conductive pattern are electrically connected via a connector.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIGS. 1 to 4 are cross-sectional views of four embodiments of the SAW device S.

In FIG. 1, 1 is a SAW element, 2 is an input / output electrode pad, 3 is an electrical connection such as a bump, 4 is a conductive pattern, 5 is an IDT electrode, and 6 is an insulating resin as an adhesive. Reference numeral 7 denotes an insulating substrate made of ceramic, resin, or the like, and reference numeral 8 denotes a lead pattern provided on the insulating substrate 7 connected to an external drive circuit, a resonance circuit, a ground circuit, and the like. The SAW element 1 has a concave region 10 and a peripheral frame region 10a formed on one main surface of a piezoelectric substrate, and at least a pair of IDT electrodes of a comb-shaped electrode formed so as to mesh with each other in the concave region 10. 5 is provided. The IDT electrode 5 is used to obtain desired characteristics.
A plurality of pairs of comb-shaped electrodes may be connected and connected in a series connection, parallel connection, cascade connection, or the like.

The concave region 10 can be easily formed by a photolithography method, an etching method, a mechanical grinding method or a laser processing method, and 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. I do.
The depth of the concave region 10 is set to 10 to 150 μm,
This is preferable because the depth can be easily adjusted to match the height of the bump and the thickness of the conductive adhesive used for connection. The connection body 3 is formed by forming a wire of a metal 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, or the like.
It is obtained by forming it on the input / output electrode pad 2 by a transfer method, an electroless plating method, an electrolytic plating method, or the like.

Then, the connection body 3 is electrically connected to the conductive pattern 4 by a conductive adhesive, solder, or the like in a face-down configuration in which the concave region 10 provided with the IDT electrode 5 faces the insulating substrate 7. Connect, SAW element 1
Is placed and fixed on the insulating substrate 7. At this time, the connection body 3
May be connected only by contacting and pressing the conductive pattern 4.

Thereafter, in order to secure the SAW element 1 and to ensure the hermeticity of the vibration space in which the IDT electrode 5 is present, an insulating resin 6 is applied and molded to the lower portion of the outer surface of the SAW element 1 and is cured. Complete. At this time, it is not always necessary to mold the insulating resin 6, but it is preferable to mold the SAW element 1 in order to secure the SAW element 1 and to ensure the airtightness of the vibration space. As the material of the insulating resin 6, thermosetting epoxy resin, silicone resin, phenol resin, polyimide resin, low melting point glass (glass frit), thermoplastic polyphenylene sulfide, and the like are preferable. Epoxy resins are preferred in terms of hygroscopicity, electrical insulation, mechanical strength, chemical resistance, heat resistance, and the like.

Since the lead pattern 8 provided on the insulating substrate 7 of FIG. 1 and connected to the conductive pattern 4 is provided so as to extend on the back surface of the insulating substrate 7, the SAW device can be mounted on another circuit board. Although surface mounting is possible, such a configuration is not always necessary, and the lead pattern 8 may be provided only on the upper surface of the insulating substrate 7.

FIG. 2 shows an insulating resin 6 molded over the entire SAW element 1. The insulating resin 6 protects the piezoelectric substrate and prevents damage to the piezoelectric substrate.
It is suitable for preventing deterioration of characteristics due to adhesion of dirt.

FIG. 3 shows a simple structure in which the insulating resin 6 is applied to the frame region 10a around the concave region 10 of the piezoelectric substrate and the SAW element 1 is bonded and fixed on the insulating substrate 7. A secure fixing and an airtight structure can be obtained.

FIG. 4 shows the structure of FIG. 1 in which ceramic, metal (Al, Cu,
A cover 9 made of a material such as stainless steel or brass) or resin is provided on the insulating substrate 7 via an adhesive 6a such as solder. With such a configuration, the protection of the SAW element 1 and the hermetic structure are further ensured.

In FIG. 1 to FIG. 4, deterioration of the IDT electrode 5 due to oxidation is suppressed by enclosing and sealing air of low humidity (room temperature (20 to 30 ° C.) and a relative humidity of 50% or less) in the vibration space. It is preferable. The same effect can be obtained by enclosing and sealing an inert gas such as nitrogen gas or argon gas instead of low-humidity air.

In the present invention, the IDT electrode 5 is made of Al or an Al alloy (Al-Cu system, Al-Ti system, etc.), and Al is particularly preferable because of its 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.
About 0, the width of the electrode fingers is about 0.1 to 10.0 μm, the interval between the electrode fingers is about 0.1 to 10.0 μm, the cross width of the electrode fingers is about 10 to 80 μm, and the thickness of the IDT electrode 5 is about 0. Two
The thickness of about 0.4 μm is preferable for obtaining desired characteristics as a resonator or a filter. Also, I
At both ends of the SAW propagation path of the DT electrode 5, reflectors for reflecting the SAW and efficiently resonating may be provided. Further, if a piezoelectric material such as ZnO or AlO is formed between the electrode fingers, This is preferable because the resonance efficiency of the SAW is improved.

As the piezoelectric substrate for the SAW element 1, 36
LiTaO ₃ crystal of ° Y cut-X propagation, LiNbO ₃ crystal of 64 ° Y cut-X propagation, LiB ₄ O ₇ crystal of 45 ° X cut-Z propagation, quartz, etc. are particularly preferred.
The LiTaO ₃ crystal propagated by ° Y cut-X has a wide pass band width, and the LiB ₄ O ₇ crystal propagated by 45 ° X cut-Z has a large electromechanical coupling coefficient and a small group delay time temperature coefficient. The thickness of the piezoelectric substrate is 0.3-0.5
mm is good. If it is less than 0.3 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost increases.

Thus, according to the present invention, it is possible to completely prevent the insulating resin from entering the vibration space of the SAW, and to form the vibration space accurately with a uniform height and width. In addition, it has the effect of being thinner, smaller and lighter, and capable of being manufactured at low cost.

It should be noted that the present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The SAW device S shown in FIG. 1 was constructed as follows. A 36 ° Y-cut X-propagation LiTaO ₃ crystal is used as the piezoelectric substrate material for the SAW element 1, the size is 1.1 mm × 1.5 mm × 0.4 mm, and the center of one main surface of the piezoelectric substrate is Polishing is performed to form the recessed region 10 and its peripheral frame region 10a, and the depth of the recessed region 10 is set to 45 degrees.
μm. In the recess region 10, a pair of comb-shaped electrodes, ie, an IDT electrode 5 and an input / output electrode pad 2 which are configured to mesh with each other, were formed by a vapor deposition method. The IDT electrode 5 and the pad 2 of the input / output electrode are made of Al, and the logarithm of the IDT electrode 5 is about 100.
The thickness of the input / output electrode pad 2 was about 0.4 μm.

The insulating substrate 7 has a size of 3.0.
A lead pattern 8 and a conductive pattern 4 made of Au were formed at predetermined positions on the surface of an alumina ceramic substrate of mm × 3.0 mm × 0.5 mm by electrolytic plating. Note that the lead pattern 8 was formed on the back surface (lower surface) of the surface (upper surface) facing the SAW element 1 and was connected to the conductive pattern 4 by through holes so as to be electrically conducted.

The connection body 3 was formed on the pad 2 of the input / output electrode so that the Au wire was formed into a bump (a substantially semi-elliptical spherical projection) by a ball bonding method. The diameter of the input / output electrodes of the bumps on the surface of the pad 2 is 75 μm, the height is 45 μm, and the SA between the SAW element 1 and the insulating substrate 7
A vibration space in which W can propagate was formed.

The connection between the connection body 3 and the conductive pattern 4 is A
A thermosetting epoxy resin-based conductive adhesive containing a g-Pd alloy was applied to the bumps, aligned with the conductive pattern 4, and heated and bonded at 100 ° C. Thereafter, in order to secure the airtightness of the vibration space, a thermosetting epoxy resin-based adhesive is used as the insulating resin 6 in the lower part of the outer surface of the SAW element 1 in an atmosphere at room temperature (about 25 ° C.) and a relative humidity of about 30%. Apply to
It was molded and cured by heating at 130 ° C. In this way, a SAW device in which the SAW element 1 is mounted in a face-down configuration is manufactured, and its height is about 0.9 mm and 1 mm.
It was below.

In the manufacture of the SAW device, the conventional wire bonding process is not required, and as a result, the size increase due to the wires extending in the horizontal direction and the height direction can be eliminated, and the reduction in size, weight, and thickness can be realized. Was. In addition, since the conventional SAW filter performs input and output of the drive signal by the wire, an inductance component of the wire occurs,
For this reason, the attenuation on the high frequency side deteriorated. However, by using the flip-chip mounting as in the present invention, a filter characteristic having a high attenuation on the high frequency side could be obtained.

[0030]

According to the present invention, a SAW is provided by providing a comb-shaped electrode in a concave region formed in a piezoelectric substrate, mounting the piezoelectric substrate on the insulating substrate with the concave region facing the surface of the insulating substrate. The vibration space is securely hermetically sealed, and the vibration space is accurately formed with a uniform height and width.Thus, it is possible to completely prevent insulative resin and dust from entering the vibration space, No input / output required, so SAW
Deterioration of device characteristics can be prevented. Further, the SAW device has an effect of being reduced in thickness, size, and weight, and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a surface acoustic wave device according to the present invention.

FIG. 2 is a sectional view of another embodiment of the surface acoustic wave device.

FIG. 3 is a sectional view of another embodiment of the surface acoustic wave device.

FIG. 4 is a sectional view of another embodiment of the surface acoustic wave device.

FIG. 5 is a sectional view of a conventional surface acoustic wave device.

FIG. 6 is a sectional view of another conventional surface acoustic wave device.

[Explanation of symbols]

 1: SAW element 2: input / output electrode pad 3: connector 4: conductive pattern 5: IDT electrode 6: insulating resin 7: insulating substrate 8: lead pattern 10: concave area 10a: frame area

Claims (1)

[Claims] 1. A concave region and a frame region are formed on one peripheral surface of a piezoelectric substrate, and at least a pair of comb-shaped electrodes are provided in the concave region, and the conductive pattern and the comb-like electrode extend to the outside. The concave region side faces the insulating substrate having a lead pattern, the frame region is abutted or adhered to the insulating substrate to attach the piezoelectric substrate to the insulating substrate, and the input / output electrodes of the comb-shaped electrode A surface acoustic wave device electrically connected to the conductive pattern via a connector.