JP5127969B2 - Surface acoustic wave device, filter device, and communication device - Google Patents

Description

  The present invention relates to a small surface acoustic wave device used for a communication device such as a cellular phone, and more specifically, an elastic material capable of easily and satisfactorily sealing an electrode for generating a surface acoustic wave at a wafer level. The present invention relates to a surface wave device, a filter device using the surface wave device, and a communication device.

  2. Description of the Related Art Conventionally, a surface acoustic wave device in which electrodes are sealed on a piezoelectric substrate by providing an electrode that generates surface acoustic waves on a piezoelectric substrate and a member that forms an accommodation space for accommodating the electrode is widely known. It has been. Such a surface acoustic wave device secures a space in which the electrode vibrates due to the piezoelectric effect and seals the electrode on the piezoelectric substrate. Therefore, the entire surface acoustic wave device is accommodated in a package and sealed. It can be made smaller than what it does.

  As a method for forming such an accommodation space, for example, a plurality of regions where electrodes are formed are formed on a wafer, and an accommodation space as described above is formed for each region in a wafer state, so that a wafer stage is formed. After sealing at (wafer level), what is cut out from the wafer for each sealed region to obtain a plurality of surface acoustic wave devices is disclosed (for example, Patent Document 1, Patent Document 2, Non-Patent Document 2) (See Patent Document 1). Such a surface acoustic wave device sealed at the wafer level may be referred to as a wafer level package (WLP) type surface acoustic wave device.

JP-A-6-318625 Japanese Patent Laid-Open No. 2002-300000

"Wafer-Level-Package for Bulk Acoustic Wave Filter" (Iwae MMT-S 2004 Digest) "Wafer-Level-Package for Bulk Acoustic Wave Filter"

  On the other hand, as a surface acoustic wave device, in order to increase the Q value, it is desired to confine propagating surface acoustic waves and suppress the loss of surface acoustic waves.

  Further, a surface acoustic wave device has been proposed in which reflector electrodes provided at both ends of the surface acoustic wave propagation direction of the electrode are arranged so as to confine the surface acoustic wave. However, when these reflector electrodes are included, there is a problem that the accommodation space becomes larger and the surface acoustic wave device becomes larger, or the production of the hollow structure becomes difficult as the accommodation space becomes larger. It was.

  The present invention has been completed in view of the above circumstances, and an object of the present invention is to provide a small surface acoustic wave device having a high Q value that can be easily and satisfactorily sealed at a wafer level, and a filter device using the same. It is to provide a communication device.

The surface acoustic wave device of the present invention includes 1) a piezoelectric substrate that propagates a surface acoustic wave, and a pair of bus bar electrodes that are formed on the piezoelectric substrate and extend in the propagation direction of the surface acoustic wave and are opposed to each other. A surface acoustic wave device including: an IDT electrode; and a sealing member that is disposed on the piezoelectric substrate and forms a housing space for housing the IDT electrode between the piezoelectric substrate and the piezoelectric substrate. Then, when a virtual center line passing through the center of the IDT electrode is defined on the piezoelectric substrate, the outline of the arrangement surface that is the surface of the sealing member on the piezoelectric substrate side is the center line. On both sides of the substrate, the distance from the center line to the contour line constituting the arrangement surface decreases as the distance from the IDT electrode along the center line decreases. Part is the pair Being present sandwiched between trajectory on a region by a pair of imaginary lines extend along the bus bar electrode on the propagation direction.

  Further, the filter device of the present invention has an input terminal, an output terminal, and a ground terminal, on the input / output line connecting the input terminal and the output terminal, or between the input / output line and the ground terminal, The surface acoustic wave device described above is provided.

  Moreover, the communication apparatus of this invention is provided with at least one of a receiving circuit and a transmission circuit which has said filter apparatus.

  According to the surface acoustic wave device of the present invention, with the above-described configuration, the reflecting portion whose distance from the center line to the outline forming the arrangement surface becomes shorter as the distance from the IDT electrode is leaked to the outside of the IDT electrode. Since the surface acoustic wave to be reflected can be reflected to the IDT electrode side and the surface acoustic wave can be confined, a high Q value can be provided.

  Moreover, since the sealing member has a reflection part, the area of the arrangement surface can be increased, so that the roof portion of the sealing member can be reliably supported. For this reason, it can suppress that a roof part deform | transforms by self-loading. Thereby, since the accommodation space can be reliably maintained, it becomes possible to stably and continuously express good characteristics.

  In addition, as described above, even if no reflector electrode is provided, the Q value can be increased depending on the shape of the sealing member, so that a small surface acoustic wave device can be obtained. Further, it is not necessary to enlarge the accommodation space so as to seal the plurality of reflector electrodes. For this reason, the problem that it becomes difficult to manufacture the sealing member due to the increase in the size of the accommodation space does not occur, so the surface acoustic wave device can be easily provided at the wafer level, and the productivity becomes high.

  In addition, according to the filter device of the present invention, a small product with a high Q value and high productivity can be provided by the above configuration.

  Furthermore, according to the communication apparatus of the present invention, the above configuration can provide a small, high Q value, high productivity device.

(A) is a schematic perspective view showing an example of an embodiment of the surface acoustic wave device of the present invention, (b) is a cross-sectional view taken along line AA ′ in (a), and (c) is It is BB 'sectional view taken on the line of (a). It is the top view of the see-through state which expanded the principal part of the surface acoustic wave apparatus shown to Fig.1 (a). (A)-(c) is a top view of the typical see-through state which shows the other example of embodiment of the surface acoustic wave apparatus of this invention, respectively. (A)-(d) is sectional drawing for every process which shows an example of the manufacturing method of the surface acoustic wave apparatus of this invention, respectively. (A)-(b) is an equivalent circuit diagram which respectively shows an example of embodiment of the filter apparatus of this invention. It is a block diagram which shows an example of embodiment of the communication apparatus of this invention.

  The surface acoustic wave device of the present invention will be described in detail with reference to the drawings.

  1A to 1C are schematic plan views showing an example of an embodiment of a surface acoustic wave device according to the present invention, and a cross-sectional view taken along line AA ′ in FIG. 6A is a cross-sectional view taken along line BB ′ in FIG.

  In FIG. 1, 1 is a piezoelectric substrate, 2 is an IDT electrode, 3 is an accommodating space for accommodating the IDT electrode 2, 4 is a sealing member, 4a is an arrangement surface of the sealing member 4 in contact with the piezoelectric substrate 1, and 4A is an arrangement surface. A reflection part which is a part of the outline of the installation surface 4a, 7 is a protective member, 8 is a conductive pattern for connecting the IDT electrode 2 to an external circuit, and 9 is for extracting an electrical signal from the conductive pattern 8 to the outside of the apparatus. The external connection electrodes 10 and 10 are reflector electrodes disposed adjacent to both ends of the IDT electrode 2 in the propagation direction. In FIG. 1A, in order to facilitate understanding of the configuration of the surface acoustic wave device, a part of the members located on the upper surface is omitted and the arrangement surface 4a is hatched.

  The same applies to the following drawings, but the same portions are denoted by the same reference numerals, and redundant description is omitted. Further, the number and interval of the electrode fingers of the IDT electrode 2 in the figure are schematically shown and are not limited to those shown in the figure.

In FIG. 1, a surface acoustic wave device of the present invention includes a piezoelectric substrate 1, an IDT electrode 2 that is an electrode for generating surface acoustic waves formed on the piezoelectric substrate 1, and an IDT electrode formed on the piezoelectric substrate 1. 2 and a conductive pattern 8 that connects an external circuit and the piezoelectric substrate 1, and a sealing member 4 that forms an accommodating space 3 that accommodates the IDT electrode 2, and a structure that covers these structures. The protective member 7 is connected to the conductive pattern 8, and the external connection electrode 9 is exposed on the upper surface of the protective member 7. The external connection terminal 9 includes an input terminal 9 _in for inputting a signal, an output terminal 9 _out for outputting a signal, and a ground terminal 9 _ground for grounding.

  Here, the IDT electrode 2 is a combination of a bus bar electrode 2a and a comb-like electrode composed of a plurality of electrode fingers 2b commonly connected thereto. Specifically, the pair of comb-like electrodes of the IDT electrode 2 are combined so that the electrode fingers 2b are alternately arranged, and the electrode fingers 2b are opposed to the adjacent electrode fingers 2b. A portion (hereinafter referred to as an opposing portion) that performs (crosses). Further, reflections disposed adjacent to the IDT electrode 2 on both sides of the repetition direction of the electrode finger 2b, which is the main propagation direction (hereinafter, simply referred to as the propagation direction) of the surface acoustic wave excited from the IDT electrode 2. Instrument electrode 10 may be provided. Note that a plurality of these IDT electrodes 2 and reflector electrodes 10 are arranged according to required characteristics, or further include a connection line or the like for connecting them to each other.

  The sealing member 4 is a cap-shaped member, and forms an accommodation space 3 for sealing the IDT electrode 2 between the sealing member 4 and the piezoelectric substrate 1. The sealing member 4 is arranged on the piezoelectric substrate 1 so as to surround the IDT electrode 2. It has the arrangement | positioning surface 4a provided. The shape of the arrangement surface 4a will be described in detail with reference to FIG. 1 (a) and FIG. FIG. 2 is an enlarged view of the main part around the reflecting portion 4A in FIG.

First, a virtual center line is defined for the IDT electrode 2 in order to describe the shape of the arrangement surface 4a. The center line coincides with the repetition direction of the electrode finger 2 b, which is the main propagation direction of the surface acoustic wave excited from the IDT electrode 2, and passes through the center of the IDT electrode 2 on the piezoelectric substrate 1. In FIG. 1, for example, the line AA ′. Here, the center of the IDT electrode 2 is
This indicates a portion that becomes the center when the facing portion of the electrode finger 2b is viewed in a direction orthogonal to the propagation direction.

  On the both sides of the center line, the disposition surface 4a has a shorter distance from the center line to the outline of the disposition surface 4a in the direction perpendicular to the propagation direction as the distance from the IDT electrode 2 increases along the center line. It has a location (reflecting part 4A). Here, the outline of the arrangement surface 4a forms the outer shape of the arrangement surface 4a, and is indicated by 4e in FIG.

  Further, at least a part of the reflecting portion 4A is arranged so as to exist on a locus when the IDT electrode 2 is moved along the center line. In FIG. 1A and FIG. 2, the locus outline 15 on the piezoelectric substrate 1 is indicated by a broken line. The trajectory is an area sandwiched between two trajectory outlines. In FIG. 1A and FIG. 2, the distance between the IDT electrode 2 and the outer surface of the IDT electrode 2 facing the sandwiching space 3 in the outer surface of the arrangement surface 4 a is the IDT electrode. It is designed to shorten in a linear function as the distance from 2 increases. Since the reflection part 4A is provided on both sides of the center line, when the surface acoustic wave leaked from the IDT electrode 2 reaches the reflection part 4A located on one side of the center line, the reflection part 4A located on the other side is formed. Therefore, it can be reliably reflected to the IDT electrode 2 side, and a surface acoustic wave can be confined.

  In addition, it is preferable to arrange | position the reflection part 4A and the IDT electrode 2 close.

  Since the arrangement surface 4a has such a shape, the surface acoustic wave device of the present invention shown in FIG. 1 has an increased area of the arrangement surface 4a. For this reason, the housing space 3 is crushed due to deformation of the roof portion of the sealing member 4 facing the piezoelectric substrate 1 across the housing space 3, or when the protective member 7 is covered with the protective member 7, It is possible to prevent the accommodating space 3 from being crushed due to the influence of the self-load or the pressure generated during condensation. Further, by adopting a structure in which the surface acoustic wave leaked to the arrangement surface 4a itself is reflected to the IDT electrode 2, the surface acoustic wave confinement efficiency can be increased. Accordingly, it is possible to stably provide a surface acoustic wave device having a small propagation loss and a high Q value. Further, since the surface acoustic wave can be confined by the reflecting portion of the surface acoustic wave arrangement surface 4a without providing the reflector electrode 10, the area for forming the accommodation space 3 can be minimized. Thereby, a small surface acoustic wave device having a high Q value can be provided.

  Moreover, as shown in FIG. 1, it is preferable that the reflection part 4A is continuously formed from the center line to the locus outline of the locus. With this configuration, the reflective portion 4A can be disposed so as to surround the end portion of the IDT electrode 2 in the propagation direction, so that the surface acoustic wave can be confined more efficiently.

  In addition, as shown in FIG. 1, the reflector electrode 10 is provided so as to be adjacent to both ends of the propagation direction of the IDT electrode 2, and at least a part of the reflecting portion 4 </ b> A is provided on the arrangement surface 4 a of the sealing member 4. It is preferable to arrange on the reflector electrode 10. The surface acoustic wave leaked from the IDT electrode 2 can be reflected to the IDT electrode 2 by the reflector electrode 10 in addition to the reflecting portion 4A of the sealing member 4 and confined to the surface acoustic wave, so that the surface acoustic wave can be more reliably generated. And a surface acoustic wave device having a high Q value can be provided. In particular, when the reflecting portion 4A of the arrangement surface 4a is disposed on the reflector electrode 10, even if the reflector electrode 10 is provided, an increase in the size of the accommodation space 3 can be suppressed. Can be expensive. Further, both ends of the IDT electrode 2 in the main propagation direction of the surface acoustic wave are portions where the leakage of the surface acoustic wave is the largest. However, by arranging the reflecting portion 4A and the reflector electrode 10 here, the elastic surface is effectively elastic. Surface waves can be confined. When the arrangement surface 4 a is provided on the reflector electrode 10, the sealing member 4 is formed of an insulating material so that the reflector electrode 2 and the arrangement surface 4 a of the sealing member 4 are not electrically short-circuited. To do.

  Moreover, the protective member 7 is formed so that the structure containing such a sealing member 4 may be covered. Part of the IDT electrode 2 and the conductive pattern 8 is sealed by the sealing member 4, and a part of the conductive pattern 8 is led out to the outside of the sealing member 4. The conductive pattern 8 has an external connection electrode 9 connected to the end of the sealing member 4 on the side not connected to the IDT electrode 2. The external connection electrode 9 is led out to the outside through the protective member 7. That is, the external connection electrode 9 is formed directly on the conductive pattern 8, and the protective member 7 is formed so that the upper surface of the external connection electrode 9 is exposed. With such a structure, the piezoelectric substrate 1, the LTCC substrate (Low Temperature Cofire Ceramic), and the HTCC substrate (High Temperature Cofire Ceramic) are formed in order to form the accommodating space 3 and connect to an external circuit board or the like. Since there is no need to attach an interposer such as an organic multilayer substrate, connection to an external circuit is possible without an interposer. As a result, the number of parts can be reduced, the profile can be reduced, and the size can be reduced.

  In addition, since the protective member 7 mechanically protects the sealing member 4, a good sealing state is maintained even if mechanical impact or stress occurs when the surface acoustic wave device is mounted on a circuit board or the like. The

  Thus, according to the surface acoustic wave device of the present invention, it is possible to provide a small and high Q value that can be easily and satisfactorily sealed at the wafer level.

  In the example shown in FIG. 1, the planar shape (outer shape) of the sealing member 4 is rectangular, but the planar shape is not particularly limited as long as the IDT electrode 2 can be sealed. For example, the shape of the reflecting portion 4A may be reflected.

  In addition, in the arrangement surface 4a, the shape of the reflecting portion 4A may be a curved shape such as an arc shape in addition to the linear shape as shown in FIG. 1, and if the leaked surface acoustic wave can be reflected efficiently, the shape There is no limit. For example, the shape of the reflecting portion 4A may be different on both sides of the center line. Here, when the smaller one of the angles formed by the locus outline 15 and the reflecting portion 4A is the angle of the reflecting portion 4A, the resonance is caused by the electrical characteristics of the surface acoustic wave device as the angle of the reflecting portion 4A decreases. The signal suppression degree near the resonance frequency other than the frequency is good. On the other hand, taking a small angle increases the areas of the reflector electrode 10 and the reflecting portion 4A, and therefore it is preferable to set the angle appropriately.

  In addition, the position where the reflecting portion 4A is provided on the arrangement surface 4a is not limited to both ends in the propagation direction of the IDT electrode 2, and may be provided only at one end in the propagation direction of the IDT electrode 2, for example. You may provide in the direction perpendicular | vertical to a propagation direction.

  Further, at least a part of the arrangement surface 4a may be arranged on the bus bar electrode 2a. Since the mass of the sealing member 4 is added to the bus bar electrode 2a portion, a difference in the propagation speed of the surface acoustic wave can be provided between the electrode finger 2b portion and the bus bar electrode 2a portion due to the mass effect. Waves can be prevented from leaking to the bus bar electrode 2a side. For this reason, the surface acoustic wave confinement efficiency can be further increased, and a surface acoustic wave device having a high Q value can be realized.

  In FIG. 1, an example in which the arrangement surface 4 a is integrated is described. However, as shown in FIG. 3A, the arrangement surface 4 a is a frame-shaped ring for forming the accommodation space 3. It is good also as what has the auxiliary | assistant part 4c which comprises 4 A of reflection parts by the part 4b and the ring part 4b separately. When the auxiliary portion 4c is provided, the outline of the ring portion 4b on the side in contact with the accommodation space 3 may be rectangular or have an angle with respect to the locus outline 15 as shown in FIG. It may be a thing.

  FIG. 1 illustrates an example in which a plurality of sets of IDT electrodes 2 are provided on the piezoelectric substrate 1, and an example in which one accommodating space 3 is formed in the sealing member 4. As shown in b), a plurality of accommodating spaces 3 may be formed in one sealing member 4. Furthermore, in the example shown in FIG. 3B, a plurality of storage spaces 3 are formed in one sealing member 4, but a single storage space 3 may be used. In this case, in order to support the roof portion of the sealing member 4, it is preferable to provide a column 4 d between the plurality of IDT electrodes 2.

  Next, each part of the surface acoustic wave device of the present invention will be described.

The material of the piezoelectric substrate 1 is lithium tantalate (LiTaO ₃ , LiTaO _x ; x <3), lithium niobate (LiNbO ₃ , LiNbO _y ; y <3), lithium tetraborate (Li ₂ B ₇ O ₄ , Li ₂ B ₇ O _z ; z <4), zinc oxide (ZnO), langasite, quartz, and other piezoelectric dielectric materials can be selected.

  Moreover, as a material of the IDT electrode 2 that generates surface acoustic waves, aluminum (Al), aluminum / copper alloy (Al—Cu), aluminum / copper / magnesium alloy (Al—Cu—Mg), or the like is preferable. Further, titanium (Ti) or chromium (Cr) may be used as the underlayer.

  Further, considering that the material of the sealing member 4 has good adhesion to the piezoelectric substrate 1, polyimide resin, epoxy resin, phenol resin, siloxane resin, acrylic resin, polymethylmethacrylate (PMMA) resin, polycarbonate ( PC) resin, benzocyclobutene (BCB) resin, and the like. In particular, an epoxy resin having a thermal expansion coefficient close to that of the piezoelectric substrate 1 is preferably used.

  Further, the thickness of the portion that continues from the arrangement surface 4a of the sealing member 4 to the roof portion is about several hundred microns that can be formed from a thickness of about 5 μm that functions as a continuous film. Considering the mechanical strength as 4 and the thickness of the IDT electrode 2, 10 μm to 100 μm is a preferable range.

  Furthermore, the sealing member 4 may be formed of a single material or may be formed of a plurality of materials, but a single material is preferable in consideration of airtightness.

In addition, as the protective member 7, it is preferable to use an epoxy resin having a thermal expansion coefficient equivalent to that of the piezoelectric substrate 1. This prevents thermal stress due to reflow from being applied to the piezoelectric substrate 1 and the external connection electrode 9 when mounted on the circuit board. For this reason, it is possible to suppress the occurrence of breakage of the piezoelectric substrate and the connection failure between the external connection electrode 9 and the pattern on the circuit board, and to achieve high reliability. In order to make the thermal expansion coefficient of the protective member 7 equal to that of the piezoelectric substrate 1, it is preferable to adjust the material for forming the protective member 7 by adding a filler such as SiO ₂ . Basically, the sealing member 4 blocks moisture intrusion into the accommodation space 3, but the protective member 7 is silica gel, zeolite, polyacrylate based so as to more reliably block moisture penetration. A hygroscopic agent may be added. Furthermore, it is preferable to select a material having heat resistance at 250 ° C. or higher for the protective member 7. This is because an electrode terminal such as a bump electrode is provided at an exposed portion of the external connection electrode 9 from the sealing member 4 and is electrically connected to the electrode on the circuit board side on which the surface acoustic wave device is mounted via the electrode terminal. The surface acoustic wave device can be stably fixed to the mounting substrate by using such a material.

The material of the conductive pattern 8 is preferably aluminum (Al), aluminum / copper alloy (Al—Cu), aluminum / copper / magnesium alloy (Al—Cu—Mg), or the like. Further, titanium (Ti) or chromium (Cr) may be used as the underlayer. In addition, the same material as that of the conductive pattern 8 can be used for a connection line for connecting the surface acoustic wave resonators 2 to each other.

  The external connection electrode 9 is made of gold (Au), copper (Cu), nickel (Ni) or the like, and preferably has a diameter of 50 to 100 microns (μm) and a height of about 20 to 400 microns (μm). is there. In order to form the external connection electrode 9 on the surface acoustic wave resonator 2, a laminated film of titanium, Cu, or the like may be formed as a base layer.

  As the material of the reflector electrode 10, the same material as that of the IDT electrode 2 can be used.

  Next, the manufacturing method of the surface acoustic wave device of the present invention will be described with reference to FIG.

  An example of a method for manufacturing a surface acoustic wave device according to the present invention includes a step A of forming a frame 5 surrounding the IDT electrode 2 on the piezoelectric substrate 1 on which the IDT electrode 2 and the conductive pattern 8 are formed, and a lid 6. Is formed on the frame body 5, the sealing member 4 is formed by the frame body 5 and the lid body 6, and the housing space 3 is formed between the piezoelectric substrate 1 and the external connection on the conductive pattern 8. A process C for forming the electrode 9 and a process D for covering the sealing member 4 and the input / output electrode 9 with the protective member 7 are provided. 4A to 4D show the respective stages of steps A to D in the manufacturing process of the surface acoustic wave device.

First, as shown in FIG. 4A, an IDT electrode 2, a conductive pattern 8, and a reflector electrode 10 are formed on a piezoelectric substrate 1 by sputtering, vapor deposition or CVD (Chemical Vapor).
The film is formed by a thin film forming method such as a deposition method, and is patterned by a photolithography method using a reduction projection exposure machine (stepper) and a RIE (Reactive Ion Etching) apparatus to obtain a desired shape.

Next, a frame 5 is formed on the piezoelectric substrate 1 so as to surround the IDT electrode 2. Here, the frame 5 is
A liquid material may be formed by a spin coating method, or a film material may be formed by using a film sticking apparatus and then patterned.

  Next, as shown in FIG. 4B, the lid body 6 is formed on the frame body 5. The lid 6 is preferably placed on the frame 5 while pressurizing a film-like material using a film sticking apparatus. This is because the storage space 3 can be easily formed by using a film-like material for the lid 6. The frame body 5 and the lid body 6 are preferably formed by a photolithography method using a photosensitive material in consideration of processing into a desired shape. Next, the frame body 5 and the lid body 6 are heated and cured, whereby the frame body 5 and the lid body 6 can be integrated to form the sealing member 4.

  Further, if the lid 6 is formed under an inert gas atmosphere, the accommodation space 3 can be filled with an inert gas such as nitrogen or argon, and oxidation of the IDT electrode 2 and the like in the accommodation space 3 can be prevented. Can be reliable.

  Next, as shown in FIG. 4C, the external connection electrode 9 is formed on the conductive pattern 8. Specifically, electroless and electric field plating processes, screen printing, and the like are preferable.

  Next, as shown in FIG. 4D, these structures are covered with the protective member 7 so that the external connection electrodes 9 are exposed on the upper surface of the protective member 7. The protective member 7 can be formed of resin using a printing machine or a vacuum printing machine. In the configuration of the product of the present invention, since there is a large step of about several hundred microns on the surface of the substrate (structure) on which the resin is printed, air bubbles easily enter the protective member 7 during printing. Therefore, a method of printing while removing bubbles by a vacuum printing method is preferable.

  As described above, according to the method for manufacturing the surface acoustic wave device of the present invention shown in FIG. 4, since the above-described configuration can be used, the favorable state can be maintained in the accommodation space 3. A surface acoustic wave resonator including an electrode for generating a surface wave can be easily and satisfactorily sealed at the wafer level. In particular, since the sealing member 4 is formed by the frame body 5 and the lid body 6, the housing space 3 can be easily formed and the productivity can be increased. Further, since it is not necessary to use a sacrificial layer to form the accommodating space 3, the number of processes can be reduced, and an etchant and a sacrificial layer for removing the sacrificial layer remain in the accommodating space 3, and the IDT electrode 2 Therefore, productivity and reliability can be increased.

  In addition to the method for forming the housing space 3 described above, a layer called a sacrificial layer is formed in the housing space 3 forming portion, and a material for forming the sealing member 4 is formed on the sacrificial layer. A method of removing and forming the accommodation space 3 may be adopted.

  Next, an example in which a filter is formed using the variable resonance circuit of the present invention will be described.

  FIG. 5 is an equivalent circuit diagram showing a filter device according to an embodiment of the filter device of the present invention.

  When the surface acoustic wave device 100 of the present invention has a characteristic as a resonator, the filter device of the present invention has an input / output line connecting the input terminal In and the output terminal Out, as shown in FIG. The surface acoustic wave device 100 of the present invention may be connected between the ground terminal and the ground terminal. Further, as shown in FIG. 5B, a surface acoustic wave device 100 may be connected on the input / output line. Further, the surface acoustic wave device 100 may be connected both between the input / output line connecting the input terminal In and the output terminal Out and the ground terminal and on the input / output line. As the surface acoustic wave device having the characteristics as a resonator, for example, one of comb-like electrodes constituting the IDT electrode 2 is connected to the input terminal In and the other is connected to the output terminal Out. can give.

  In this way, a ladder type filter may be formed, or a balanced type filter such as an unbalanced input-balanced output may be formed.

For example, the surface acoustic wave device shown in FIG. 1 connects a plurality of sets of IDT electrodes 2 so as to form a balanced filter. That is, if the signal input terminal 9 _in is the input terminal In and the two output terminals 9 _out are the output terminals Out, the IDT electrode 2 is connected to each input / output line connecting the input terminal In and the output terminal Out as follows. Is connected. First, the IDT electrode 2 includes a first IDT electrode connected to the input terminal In, a second IDT electrode connected to the output terminal Out, and third and fourth IDT electrodes arranged on both sides of the second IDT electrode. . The input terminal In (9 _in ) is connected to one comb-like electrode of the first IDT electrode, and the other comb-like electrode is connected to one comb-like electrode of the third and fourth IDT electrodes. One of the comb-like electrodes of the second IDT electrode is connected to the output terminal Out (9 _out ). The other comb-like electrodes of the second to fourth IDT electrodes are connected to the ground terminal. By connecting in this way, the signal input from the input terminal In reaches the second IDT electrode from the first IDT electrode via the third and fourth IDT electrodes and is extracted from the output terminal Out. From the above, a filter device in which a plurality of IDT electrodes 2 are connected on the input / output line or between the input / output line and the ground terminal, and the surface acoustic wave device of the present invention including at least one of the plurality of IDT electrodes 2 is provided. The filter device using the surface acoustic wave device of the present invention can be obtained.

  Next, an example in which a communication device is formed using the filter device of the present invention will be described.

  FIG. 6 is a block diagram showing a communication apparatus according to an embodiment of the communication apparatus of the present invention.

  In FIG. 6, a transmission circuit Tx and a reception circuit Rx are connected to an antenna 140 via a duplexer 150. The high-frequency signal to be transmitted is removed from the unnecessary signal by the filter 210, amplified by the power amplifier 220, and then radiated from the antenna 140 through the isolator 230 and the duplexer 150. The high-frequency signal received by the antenna 140 is amplified by the low-noise amplifier 160 through the duplexer 150, the unnecessary signal is removed by the filter 170, re-amplified by the amplifier 180, and converted to a low-frequency signal by the mixer 190. Is done.

  In FIG. 6, if the filter device of the present invention is used for any one of the duplexer 150, the filter 170, and the filter 210, it can be made small and have a high Q value.

  In FIG. 6, the communication device having the transmission circuit Tx and the reception circuit Rx has been described. However, a communication device having either the transmission circuit Tx or the reception circuit Rx may be used.

  As described above, if a communication device including at least one of a reception circuit and a transmission circuit having the surface acoustic wave device having any one of the above-described configurations is configured, the surface acoustic wave used for the reception circuit or the transmission circuit of the communication device. Since the device can be reduced in size while having practical performance by being well sealed at the wafer level, the communication device can be reduced in size. For example, the communication device thus miniaturized is a portable communication terminal such as a mobile phone, a personal handyphone (PHS), an amateur radio portable transceiver, an IC card, an electronic information processing terminal such as a palmtop computer, or an in-vehicle communication device. It can be suitably used for a car navigation system and an ETC (Electronic Toll Collection System) vehicle-mounted terminal.

  Thus, according to the present invention, a small surface acoustic wave device capable of easily and satisfactorily sealing an electrode for generating a surface acoustic wave at the wafer level and a small filter device including the small surface acoustic wave device. And a communication device can be provided.

  It should be noted that the present invention is not limited to the examples of the embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

For example, in the example of the above-described embodiment, the sealing member 4 is covered with the protective member 7, but the protective member 7 may not be formed and the input / output electrode 9 may be exposed. Furthermore, in the present embodiment, the external connection electrode 9 is used to connect to an external circuit. However, a via hole that connects to the conductive pattern 8 is provided in the piezoelectric substrate 1 and the back surface of the piezoelectric substrate 1 is connected to an external circuit. May be. Alternatively, a hole may be formed in the protective member 7 on the conductive pattern 8 without forming the external connection electrode 9, and a method such as wire bonding may be used for connection with an external circuit. 4A, before forming the frame body 5, a protective film made of SiO ₂ that protects the IDT electrode 2 is formed on the entire surface of the piezoelectric substrate 1 except for the position where the external connection electrode 9 is formed. The frame 5 may be formed on the protective film. This is preferable because the frame 5 can be formed on a surface having no step.

1: Piezoelectric substrate 2: IDT electrode 2a: Bus bar electrode 2b: Electrode finger 3: Accommodating space 4: Sealing member 4A: Reflecting portion 4a: Installation surface 5: Frame body 6: Lid body 7: Protection member 8: Conductive pattern 9: External connection electrode 10: Reflector electrode 15: Trajectory outline

Claims (8)

A piezoelectric substrate that propagates surface acoustic waves;
An IDT electrode having a pair of bus bar electrodes formed on the piezoelectric substrate and extending in the propagation direction of the surface acoustic wave and arranged to face each other;
A surface acoustic wave device including a sealing member disposed on the piezoelectric substrate and forming a housing space for housing the IDT electrode between the piezoelectric substrate,
When a virtual center line passing through the center of the IDT electrode, which coincides with the propagation direction, is defined on the piezoelectric substrate,
The outline of the arrangement surface, which is the surface on the piezoelectric substrate side of the sealing member, is separated from the IDT electrode along the center line on both sides of the center line. Having a reflecting portion that shortens the distance to the contour line constituting
The surface acoustic wave device, wherein at least a part of the reflecting portion exists on a locus that is a region sandwiched between a pair of virtual lines obtained by extending the pair of bus bar electrodes along the propagation direction.   2. The surface acoustic wave device according to claim 1, wherein the sealing member includes a frame body disposed on the piezoelectric substrate and surrounding the IDT electrode, and a lid body disposed on the frame body. A reflector electrode formed on the piezoelectric substrate and disposed adjacent to both ends in the main propagation direction of the surface acoustic wave of the IDT electrode;
The surface acoustic wave device according to claim 1, wherein the sealing member is disposed at a position where at least a part of the reflecting portion is on the reflector electrode.   The surface acoustic wave device according to claim 1, wherein at least a part of the arrangement surface of the sealing member is disposed on the bus bar electrode. A protective film for protecting the IDT electrode;
The surface acoustic wave device according to claim 1, wherein the protective film is interposed between the piezoelectric substrate and the sealing member.   The surface acoustic wave device according to claim 1, wherein the reflection portion has a curved portion.   7. The device according to claim 1, further comprising: an input terminal, an output terminal, and a ground terminal, on an input / output line connecting the input terminal and the output terminal, or between the input / output line and the ground terminal. The filter apparatus provided with the surface acoustic wave apparatus of description. A communication device comprising at least one of a reception circuit and a transmission circuit, comprising the filter device according to claim 7.

Images