JP2005191716A - Piezo-resonator, filter, and composite substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezo-resonator whose parts count is small and cost is low, and which reduces influence of dust and is low in height, a filter, and a composite substrate. <P>SOLUTION: The piezo-resonator element is obtained by forming an interdigital transducer (IDT) consisting of a pair of interdigital electrodes on the principal plane of a piezoelectric substrate, and utilizes an SH surface wave is arranged above a base substrate in such a way as to form an excitation space between the base substrate and the IDT. A pair of side-face support members are provided so as to pinch and hold both side faces of the base substrate and the piezoelectric substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an end surface reflection type piezoelectric resonator element using a surface wave of an SH wave applied to a resonator or a filter, a piezoelectric resonator, a filter using the same, and a composite substrate.

  Conventionally, microcomputers and the like have been frequently used for communication devices and electronic devices, and a clock oscillation circuit or the like has been connected to such microcomputers.

  Here, in the oscillation circuit, two load capacitance components 15 (C1, C2) are connected between both ends of the piezoelectric resonance element 1 and the ground potential, as in the equivalent circuit shown in FIG. A feedback resistor 13 and an inverter 14 are connected between both ends of 1.

Generally, in order to obtain stable oscillation, it is necessary to increase the P / V value of the main vibration of the piezoelectric resonant element. The P / V value is represented by 20 × log (R _a / R ₀ ), where R _a is defined as an anti-resonance impedance and R ₀ is defined as a resonance impedance.

  2. Description of the Related Art Conventionally, in a surface-mount piezoelectric resonator to which a piezoelectric element thickness longitudinal third harmonic vibration or thickness shear fundamental wave vibration is applied, for example, in a resonator as shown in FIG. A piezoelectric vibrator that is physically and electrically connected to the base substrate on which the substrate is formed is covered with an outer case so as not to disturb the vibration operation, and the P / V value of the piezoelectric vibrator is kept large at 55 dB or more, How to achieve miniaturization and thinning has become important (see, for example, Patent Document 1).

  However, in the conventional surface mount type piezoelectric resonator as described above, a piezoelectric vibrator is formed by connecting and fixing a base substrate such as a dielectric having a load capacitance and a piezoelectric vibration element via a conductive paste. In addition, a lid for covering the piezoelectric vibrator is required, and in addition, a gap between the periphery of the piezoelectric vibrator and the lid is sufficient to cover the lid while avoiding spreading of the conductive paste. I had to secure it.

  However, in recent years, electronic devices have become thinner, and are used in, for example, mobile phones, HDDs, memory cards, and the like. Therefore, there is a demand for downsizing of piezoelectric resonant elements, particularly reduction in thickness. was there.

  In particular, in terms of product thickness, since the piezoelectric vibrator having the piezoelectric element connected and fixed on the base substrate is covered with the lid, the walls on the upper and lower surfaces of the lid are added to the thickness. It was difficult to turn over.

  Furthermore, in the case of a piezoelectric element to which a conventional thickness longitudinal third harmonic wave vibration or thickness shear fundamental wave vibration is applied, a lead-out electrode and a drive electrode are formed so as to face both main surfaces of the piezoelectric resonance element, and the electrodes intersect at the center. Since the drive electrodes are used, it is difficult to connect the electrodes at both ends of the piezoelectric resonant element and the electrode terminals of the base substrate, and the structure is complicated in order to increase electrical reliability.

  There is a strong demand for low-priced parts as the price of electronic equipment decreases. However, as described above, conventional piezoelectric resonators have a complicated structure, a large number of parts, and a large number of manufacturing steps. There was a limit to the cost increase.

  Therefore, in order to reduce the size of the piezoelectric vibration element that serves as an oscillator, an end surface reflection type surface wave resonator using a surface wave or a surface wave device with a lead in which the surface wave resonator is covered with an exterior resin, etc. The structure is proposed. In this structure, an IDT is formed on the surface of the piezoelectric substrate, and the piezoelectric substrate is covered with an exterior resin layer so that a cavity is formed on the surface of the excitation unit (see, for example, Patent Document 2).

  In addition, a structure in which a SAW element serving as an oscillator is hermetically sealed inside a package has been proposed. As an example, an electrode land is formed on the upper surface of a case substrate, and a SAW element is placed thereon via a solder bump. In addition, an electronic component in which a cap is placed on a case substrate and the both are joined together by soldering and hermetically sealed can be exemplified (see, for example, Patent Document 3).

Further, there has been proposed an end surface reflection type surface wave filter in which an IDT is formed on the surface of a piezoelectric substrate, and a resin coating layer made of a flexible resin is provided on the piezoelectric substrate so as to directly cover the IDT (for example, , See Patent Document 4)
See Japanese Utility Model Publication No. 62-70453 JP-A-8-195644 JP-A-8-191181 JP 2003-133888 A

  However, the surface acoustic wave element described in Patent Document 2 covers the entire end surface reflection type surface acoustic wave resonator with resin, so that the cost can be reduced. However, the outer packaging resin is porous on the wax by applying wax to the piezoelectric substrate. Since the outer resin is absorbed by the heat treatment and the outer resin is absorbed, and the outer resin is cured, there is a problem that the outer resin portion is inevitably thick and there is a limit to the reduction in size and height.

  In addition, the electronic component described in Patent Document 3 has a problem that it is large in size because a container is necessary, although it has high reliability against dust adhesion because the SAW element is mounted in a package and hermetically sealed. .

  Furthermore, since the electronic component of Patent Document 4 covers the surface of the IDT with a flexible resin, it has a remarkable effect on reducing the height, but the P / V is reduced by covering the surface of the IDT with a resin. When used in this state, there is a problem that dust adheres to the resin on the IDT and vibration is not normally performed, so that the P / V value becomes small. For example, a resonator does not transmit. However, it cannot be used as it is, and must be accommodated in a package.

  Accordingly, an object of the present invention is to provide a piezoelectric resonator, a filter, and a composite substrate that have a small number of parts, are low in cost, and are reduced in the influence of dust and reduced in height.

  The piezoelectric resonator of the present invention includes a piezoelectric resonator element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) including a pair of comb electrodes on one main surface of a piezoelectric substrate. A pair of side surface support members are provided above the base substrate and the IDT so as to form an excitation space and sandwich both side surfaces of the base substrate and the piezoelectric substrate. It is a feature.

  Another piezoelectric resonator of the present invention is based on a piezoelectric resonant element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) comprising a pair of comb electrodes on one main surface of a piezoelectric substrate. A pair of side surface support members are arranged above the substrate so as to form an excitation space between the base substrate and the IDT, and sandwich the piezoelectric substrate from both sides on the base substrate. It is characterized by being provided.

  It is preferable that a reinforcing substrate having substantially the same shape as the piezoelectric substrate is provided on the other main surface facing the one main surface of the piezoelectric substrate via an adhesive layer.

  Still another piezoelectric resonator of the present invention includes a piezoelectric resonator element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) including a pair of comb electrodes on one main surface of a piezoelectric substrate, A reflecting bank member disposed on a side surface of the piezoelectric resonant element in parallel to the side surface and at a predetermined distance is provided on a main surface of the reinforcing substrate, and the reinforcing substrate is disposed above the base substrate and the base substrate. The IDT is disposed so as to be opposed to each other and an excitation space is formed therebetween, and a pair of side surface support members are provided so as to sandwich the reflection member from the side surfaces.

  The comb electrode includes a plurality of electrode fingers, a connecting portion for electrically connecting the plurality of electrode fingers, an external connecting portion, and a bridge for electrically connecting the external connecting portion and the connecting portion. It is preferable that the external connection portion and the surface electrode provided on the side surface of the base substrate are electrically connected.

  It is preferable that the base substrate includes an electrode for forming a capacitor.

  The side support member is preferably made of an organic polymer.

The Young's modulus of the side support member is preferably 1 × 10 ¹⁰ Pa or less.

  The height of the excitation space is preferably 5 to 100 μm.

  The piezoelectric substrate is preferably made of a lead titanate-based or lead niobate-based material.

  The filter of the present invention is characterized in that another IDT is formed on the surface of the base substrate in the piezoelectric resonator so as to face the IDT provided on one main surface of the piezoelectric substrate.

  The composite substrate of the present invention is characterized in that an IC chip is mounted on the surface of the base substrate of the piezoelectric resonator described above.

  It is preferable that an electronic component is further mounted on the surface and / or inside of the base substrate.

  The piezoelectric resonator of the present invention includes a piezoelectric resonator element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) including a pair of comb electrodes on one main surface of a piezoelectric substrate. A pair of side surface support members are provided above the base substrate and the IDT so as to form an excitation space and sandwich both side surfaces of the base substrate and the piezoelectric substrate. Due to its characteristics, it has a very simple structure in which a piezoelectric resonant element using SH wave type surface waves is bonded to a base substrate so that a minute space can be formed between them. In addition, the influence of dust can be reduced, the height can be reduced, and excellent resonance characteristics can be obtained.

  Further, another piezoelectric resonator of the present invention is a piezoelectric resonator element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) including a pair of comb electrodes on one main surface of a piezoelectric substrate. And a pair of side supports so as to form an excitation space between the base substrate and the IDT above the base substrate, and sandwich the piezoelectric substrate from both sides on the base substrate. A member is provided, and the same effect as the above-described piezoelectric resonator can be obtained.

  In particular, when a reinforcing substrate having substantially the same shape as the piezoelectric substrate is provided on the other main surface facing the one main surface of the piezoelectric substrate via an adhesive layer, unnecessary vibration caused by bulk waves is reduced. It becomes easy.

  Still another piezoelectric resonator according to the present invention is a piezoelectric resonator element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) including a pair of comb electrodes on one main surface of a piezoelectric substrate. And a reflecting bank member disposed on a side surface of the piezoelectric resonant element in parallel with the side surface and at a predetermined distance, is provided on a main surface of the reinforcing substrate, and the reinforcing substrate is disposed above the base substrate and on the base The substrate and the IDT face each other and are arranged so as to form an excitation space therebetween, and a pair of side surface support members are provided so as to sandwich the reflection member from the side surface. The same effect as the above piezoelectric resonator can be obtained.

  The comb electrode includes a plurality of electrode fingers, a connecting portion for electrically connecting the plurality of electrode fingers, an external connecting portion, and a bridge for electrically connecting the external connecting portion and the connecting portion. When the external connection portion and the surface electrode provided on the side surface of the base substrate are electrically connected, for example, it is easy to configure a ladder type filter.

  When the base substrate includes an electrode for forming a capacitor, it is possible to form two capacitors by applying a dielectric ceramic to the base substrate of the piezoelectric resonator, and a resonator having a built-in load capacitor. Can be obtained. Furthermore, by providing a plurality of independent comb electrodes on one surface of the piezoelectric substrate and changing the number of each comb electrode and adjusting the capacitance ratio, a band pass filter having a damping characteristic as a filter, a transversal type, etc. A piezoelectric resonator having the following functions can be obtained.

  In the case where the side support member is made of an organic polymer, the dimensional system is further improved, and it is easy to prevent the entry of dust into the internal excitation space portion at low cost.

When the Young's modulus of the side support member is 1 × 10 ¹⁰ Pa or less, it is possible to damp the bulk wave and reduce the P / V value of the bulk wave.

  When the height of the excitation space is 5 to 100 μm, the piezoelectric resonant element can be remarkably lowered.

  When the piezoelectric substrate is made of a lead titanate-based or lead niobate-based material, since these materials have a large electrical opportunity coupling coefficient, it is easy to excite SH type surface waves and obtain a larger P / V value. It becomes easy.

  The filter of the present invention is characterized in that another IDT is formed on the surface of the base substrate in the piezoelectric resonator so as to face the IDT provided on one main surface of the piezoelectric substrate. With this configuration, it is possible to efficiently use the space and greatly contribute to the downsizing of the filter.

  The composite substrate of the present invention is characterized in that an IC chip is mounted on the surface of the base substrate of the piezoelectric resonator. With this configuration, it is possible to realize a composite substrate on which a plurality of electronic components having a high integration density and a low profile are mounted.

  In particular, when an electronic component is further mounted on the surface and / or inside of the base substrate, it is easy to obtain a substrate with a higher degree of integration.

  The present invention will be described with reference to the drawings. 1A and 1B show an embodiment of a piezoelectric resonant element according to the present invention. FIG. 1A is a perspective view, and FIG. 1B is a cross section taken along line XX ′ in FIG. 1 and FIG. 1C show a case where a reinforcing substrate is bonded to the piezoelectric substrate of FIG. 1B, and FIG. 2 is an assembly explanatory diagram of the structure of FIG. 2 is displayed in a state in which FIG. 1 is turned upside down so that the IDT formed on the surface of the piezoelectric resonator 1 can be easily seen.

  1 and 2, the piezoelectric resonator according to the present invention includes a piezoelectric resonator element 1, a base substrate 2, and a side support member 9, and sandwiches both side surfaces of the piezoelectric substrate 1b and the base substrate 2. Thus, it is important that the side surface support member 9 is provided.

  The piezoelectric resonant element 1 has a pair of comb electrodes (hereinafter referred to as IDT) 3 formed on one main surface 1c of a piezoelectric substrate 1a. Each IDT 3 has a plurality of electrode fingers 3a and 3b on a side surface 1d of the piezoelectric substrate. The electrode fingers 3a and 3b of the pair of IDTs 3 are alternately arranged so as to be parallel, that is, parallel to the polarization axis direction, and the electrode fingers 3a and 3b of the pair of comb-teeth electrodes are piezoelectric substrate 1a. It overlaps near the center of.

  The electrode fingers 3a and 3b are electrically connected to the connection electrodes 7a and 7b via the connecting portions 6a and 6b, respectively. The connection electrodes 7a and 7b can be provided with conductive bumps 8 for connection to an external circuit.

  Since the piezoelectric resonator 1 is configured in this way, it is easy to make it small and thin.

  In the piezoelectric resonant element 1, side support members 9 are provided on both side surfaces 1 d of the piezoelectric substrate 1 a formed adjacent to the outermost electrode finger of the IDT, and side support members 9 are also disposed on both side surfaces of the base substrate 2. The insulating adhesive resin completely seals the driving portion of the interdigital transducer (IDT) 3 composed of comb electrodes.

  The piezoelectric resonant element 1 is arranged such that an IDT 3 provided on one main surface 1 c of the piezoelectric substrate 1 a faces the surface of the base substrate 2, and an excitation space A is provided between the IDT 3 and the base substrate 2. It is important that it is formed. The excitation space A is a space that is excited by the IDT 3 and does not suppress the SH type surface wave, and can prevent an extreme frequency shift, spurious generation, and a decrease in P / V value.

  The height H of the excitation space A, that is, the distance between the IDT 3 and the base substrate 2 is not particularly limited, but is 5 to 100 μm, particularly 5 to 30 μm, and further 5 to 20 μm from the viewpoint of reducing the height. It is preferable that In this way, by setting the excitation space A to the minimum necessary height H, the piezoelectric resonator can be made thinner.

  Adhesive layers are provided between the piezoelectric resonant element 1 and the side surface support member 9 and between the base substrate 2 and the side surface support member 9, and these are adhered to each other by an adhesive. The side support member 9 itself may have an adhesive function. That is, the piezoelectric substrate 1a can be disposed above the base substrate 2 while forming the excitation space A, and both side surfaces thereof can be fixed with an adhesive.

The piezoelectric resonator of the present invention, as shown in FIG. 2 connection electrodes _{P IN, P GND,} and provided _{P OUT,} electrode _{C IN} and between _{P GND} connected to the electrode _{P IN,} and the electrode _{P OUT} Capacitors are formed between the formed electrodes C _OUT and P _GND based on the dielectric constant of the base substrate. By disposing the capacitor forming electrodes and using the dielectric ceramic on the base substrate, two capacitors (capacitors) can be formed, and a piezoelectric resonator suitable for a resonator with a built-in load capacitor is obtained. I can do things.

The side supporting member 9 preferably has a Young's modulus of 1 × 10 ¹⁰ Pa or less. In the vibration generated in the IDT, it is possible to effectively prevent the occurrence of spurious due to the large deviation between the phase of the traveling surface wave and the phase of the vibration reflected by the outermost electrode finger. That is, vibration reflection is likely to occur at the outermost electrode finger of the IDT, so that it is possible to prevent the spurious from being superimposed on the main vibration and to increase the P / V value.

  The side support member 9 is preferably an organic polymer. By configuring the side support member 9 with an organic polymer such as an organic resin, the dimensional system is further enhanced, and it is easy to prevent dust from entering the internal excitation space at low cost.

  As the organic polymer, at least one of an epoxy resin, a silicon resin, an acrylic resin, and a urethane resin is preferable because adhesion and sealing properties can be further improved. Among these, an epoxy resin is particularly desirable in terms of good reflow heat resistance.

The piezoelectric resonator element 1, PT (lead titanate), PZT (lead zirconate titanate) or a piezoelectric ceramic material ₃ such as sodium niobate NaNbO, lithium tantalate, lithium niobate single crystal materials such Yontanasan lithium of it is preferable for these are formed from, electrical opportunity coupling coefficient large, to be a piezoelectric ceramic mainly composed of lead titanate PbTiO ₃ and lead zirconate titanate PbZrTiO ₃ and sodium niobate NaNbO ₃ The lead titanate PbTiO ₃ and sodium niobate having a large electromechanical coupling coefficient and a relative dielectric constant of 300 or less are preferable in that a larger P / V value can be obtained. It is desirable to use a piezoelectric ceramic mainly composed of NaNbO ₃ .

  The piezoelectric substrate 1a is polarized such that the direction of the arrow is the polarization axis direction.

For example, the capacitance of the vibrating electrode portion of a piezoelectric resonator of a ceramic resonator that has been conventionally used is remarkably large with a comb-tooth electrode of 60 pF or more, compared to about 15 pF or less. For this reason, the two load capacitors that make up the feedback circuit must also be approximately equal to or greater than the capacitance of the vibrating electrode part to satisfy the oscillation conditions. There was a problem that led to an increase in size of the substrate. Accordingly, suitable piezoelectric material in resonator applications, the dielectric constant of the piezoelectric element has a small value of about 300 or less, is desired piezoelectric ceramic mainly composed of lead titanate PbTiO ₃ and sodium niobate NaNbO _3.

  The base substrate 2 may be any material as long as it has insulating properties. For example, the base substrate 2 is excellent in heat resistance such as a dielectric material containing barium titanate, ceramics such as an alumina substrate, polyimide, or liquid crystal polymer. It is desirable to be composed of a resin material or the like.

  The material of the electrode fingers of the comb electrode is not particularly limited, but it is preferable that the main component is a low-resistance metal such as Al, Cr, Ag, Au, Pt, or Ni.

  The cross section of the porcelain provided in parallel with the outermost electrode finger of the comb electrode is processed by a slicer processing machine or a wire saw. Here, the electrode width in the outermost electrode finger of the comb electrode is set to a width of about λ / 8. As a result, the outermost electrode fingers are formed adjacent to the porcelain cross section to enable end surface reflection of SH type surface waves.

  3A and 3B show another piezoelectric resonator according to the present invention, in which FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view taken along line Y-Y ′ in FIG. Parts common to FIGS. 1 and 2 are given the same reference numerals, and description of the common parts is omitted.

  According to FIG. 3, the piezoelectric resonator is disposed above the base substrate 2 so as to form an excitation space A between the base substrate 2 and the IDT 3, and a pair of side support members on the base substrate 2. 9 is provided to sandwich the piezoelectric substrate 1a from both side surfaces. The side support member 9 is provided so as to sandwich the piezoelectric substrate 1a bonded to the support substrate 1b from both sides together with the support substrate 1b, and the side support member 9 is provided on the base substrate 2.

  Thus, by bonding the piezoelectric substrate 1a and the reinforcing substrate 1b, the strength of the piezoelectric resonant element 1 can be improved, and the side support members 9 can be easily disposed and fixed, thereby further improving the sealing performance. Can be achieved.

The reinforcing substrate 1b is made of ceramics having higher strength and toughness than piezoelectric ceramics, such as alumina (a porcelain containing Al ₂ O ₃ as a main component), zirconia (a porcelain containing ZrO ₂ as a main component), magnesia (based on MgO as a main component). ), Aluminum nitride, silicon nitride, silicon carbide and the like are desirable. Of these, alumina is preferable because of its high strength and low cost, zirconia is preferable because of its high toughness, and aluminum nitride and silicon carbide are preferable because of its high thermal conductivity and excellent heat dissipation.

  Other explanations are omitted.

  FIG. 4 shows still another piezoelectric resonator element of the present invention and a piezoelectric resonator using the same, FIG. 4 (a) is a perspective view of the piezoelectric resonator element, and FIG. 4 (b) is FIG. It is sectional drawing of the piezoelectric resonator using the piezoelectric resonant element of a). In addition, the same code | symbol was provided to the common part with FIG. 1 and 2, and description of the common part was abbreviate | omitted.

  In another piezoelectric resonator of the present invention, the piezoelectric resonator element 1 is bonded to the reinforcing substrate 1b. The reinforcing substrate 1b has a main surface having an area larger than the area of the one main surface 1c of the piezoelectric substrate 1a, and the main surface is opposite to the main surface 1c of the piezoelectric substrate 1a. It is joined via.

  The side surface support member 9 is in contact with the side surface of the piezoelectric substrate 1a and is bonded to the reinforcing substrate 1b and the base substrate 2 via an adhesive (not shown). The side support member 9 itself may function as an adhesive.

  Furthermore, according to FIG. 4, it is preferable that the reflecting bank member 14 is provided outside the piezoelectric substrate 1a in parallel with the side surface 1d of the piezoelectric substrate 1a and at a certain distance. Specifically, after bonding the piezoelectric substrate 1a to the reinforcing substrate 1b, the groove end space is processed from one end surface to the other end surface of the piezoelectric resonance element by a slicer processing machine, a laser processing machine, etc. The groove 16 and the reflection bank member 14 can be formed. Thus, between the piezoelectric substrate 1a and the reflecting bank member 14, the reflecting groove for reflecting the SH type surface wave so that the side surface 14d of the reflecting bank member 14 is parallel to the side surface 1d of the piezoelectric substrate 1a. 16 is preferably formed.

  When the reflection bank member 14 and the reflection groove 16 are formed, the side surface support member for sealing does not easily enter the upper surface of the IDT, and SH wave end surface reflection is improved.

  When the reflecting bank member 14 is provided, the surface wave composed of SH waves vibrates also in the depth direction of the piezoelectric substrate, so that the end surface reflection is effective against the vibration generated in the depth direction, and spurious is generated. It is desirable that the depth of the reflection groove 16 is larger than the height of the piezoelectric substrate 1a from the viewpoint of suppressing the level. For example, in the above processing, it is desirable to process so that the reflection groove space 16 extends not only to the piezoelectric substrate 1a but also to a part of the reinforcing substrate 1b.

  As described above, even when the groove is formed in parallel with the outermost electrode finger of the IDT 3 to the end face of the porcelain, if the piezoelectric resonator element 1 is bonded to the reinforcing substrate 1b, the reinforcing substrate 1b causes the piezoelectric resonator element 1 to Strength can be improved and it becomes easy to prevent destruction.

The groove adjacent to the outermost electrode finger may be filled with an organic polymer having a Young's modulus of 1 × 10 ¹⁰ Pa or less. As the organic polymer, an epoxy resin, a silicon resin, an acrylic resin, or a urethane resin is used.

  The piezoelectric resonator of the present invention configured as described above has a base substrate that maintains a space that is excited by the vibration IDT and does not suppress the SH type surface wave on the surface of the piezoelectric resonator element 1 on which the IDT is formed. A piezoelectric resonator capable of being reduced in height can be obtained by adopting a structure in which it is fixedly sealed with 2 and a bonding resin. Furthermore, by forming a reflection end face 1d having a porcelain cross section adjacent to the outermost electrode finger of the IDI, it is possible to reflect the end face of the SH type surface wave, suppress spurious generation, and increase the P / V value. can do. Furthermore, by using the wafer of the piezoelectric resonator element 1 formed with a plurality of IDTs and the wafer constituting the base substrate 2 and bonding them together in the wafer state, a large number of pieces can be obtained, resulting in excellent productivity and low cost. Can be achieved.

  In the filter of the present invention, it is preferable that two load capacitors are formed by applying a dielectric material to the base substrate 2 to form a laminated structure, and a piezoelectric resonator incorporating the load capacitor is obtained. A piezoelectric resonator having a filter characteristic can be obtained by forming an electrode and making an electrical connection. Then, by changing the number of comb electrodes and adjusting the capacitance ratio, a bandpass filter having a damping characteristic as a filter and a piezoelectric resonator having a transversal type function can be obtained.

  For example, in the case of a ladder filter, the center frequency of the filter is determined by combining the resonance frequency of the piezoelectric resonance element arranged in series with the anti-resonance frequency arranged in parallel, and the guaranteed attenuation amount is arranged in a series row. A desired attenuation can be obtained by increasing the capacitance arranged in parallel to the capacitance. That is, the amount of attenuation can be increased by increasing the number of IDTs of the resonators arranged in parallel to the IDTs of the resonators arranged in series.

  The filter of the present invention is formed by electrically connecting a plurality of the above-described piezoelectric resonant elements. For example, a ladder type filter according to one embodiment is shown in FIG.

  According to FIG. 5, this filter includes a series resonator 201 and a parallel resonator 202, and the series resonator 201 forms a series resonator 201 by electrically arranging an input terminal 205 a and an output terminal 205 b in series. . The parallel resonator 202 connects the output side terminal 205b of the series resonator 201 to the output terminal 215b and grounds the ground side terminal 215g to the ground, and a filter circuit can be formed with such a circuit configuration. it can.

  Each of the series resonator 201 and the parallel resonator 202 can form a filter by forming an independent comb-tooth electrode through the reflection end face portion 206 to achieve electrical connection. For example, in the case of a ladder type filter, the center frequency of the filter is determined by combining the resonance frequency of the piezoelectric resonance element arranged in series with the anti-resonance frequency arranged in parallel, and the guaranteed attenuation amount is arranged in a series row. A desired attenuation amount as a filter can be obtained by making the capacitance larger than the capacitance arranged in parallel with the capacitance. That is, the amount of attenuation can be increased by increasing the number of resonator IDTs 203B arranged in parallel to the number of resonator IDTs 203a arranged in series.

  Furthermore, according to the present invention, as shown in FIG. 6, another IDT 33 is provided on the surface of the base substrate 2 in the piezoelectric resonator described above so as to face the IDT 3 provided on one main surface 1c of the piezoelectric substrate 1a. Is formed on the piezoelectric substrate 31 bonded to the base substrate 2. Specifically, a pair of piezoelectric resonance elements 1 are arranged to face each other, a pair of side support members 9 are sandwiched between a pair of reinforcement substrates 1b, and the reinforcement substrate 1b and the side support members 9 are bonded with an adhesive. can do.

  Such a filter can use space efficiently and can greatly contribute to the downsizing of the filter.

  In the composite substrate of the present invention, for example, as shown in FIG. 7, a cavity 302 is formed in a circuit motherboard 301, and the IDT formation surface of the piezoelectric resonance element 303 is opposed to the cavity bottom surface in the cavity 302. The piezoelectric resonator element 303 of the present invention is accommodated so as to provide a space between the IDT formation surface and the cavity bottom surface, and an IC chip 304 is disposed on the cavity so as to cover the cavity 302.

The piezoelectric resonant element 303 and the IC chip 304 are bonded using an adhesive, and the adhesive used for the piezoelectric resonator 303 is preferably made of a synthetic resin having a Young's modulus of 1 × 10 ¹⁰ Pa or less. Further, the IC chip 304 can also serve as a lid for sealing the cavity 302, and it is preferable to bond the cavity 302 with an adhesive or a brazing material so as to seal the cavity 302.

  Note that the IC chip 304 may be a bare chip or an IC encapsulated inside a package.

  In addition, it is desirable that the circuit mother board 301 has a built-in capacitor. For example, as shown in FIG. 6, a circuit mother board 301 includes a dielectric layer 305, and a pair of electrodes 306a and 306b are provided so as to sandwich the dielectric layer 305 and to face each other. Capacitors 307a and 307b are formed. In this case, two capacitors are formed, and these capacitors 307 a and 307 b are electrically connected to the piezoelectric resonance element 303.

  Thus, by mounting the IC chip 304 for a microcomputer or the like so as to seal the piezoelectric resonator 303 in the cavity 302, a so-called low-profile composite substrate can be provided, This can contribute to downsizing of electronic devices.

  Furthermore, another electronic component 308, for example, a capacitor, a resistor, a filter, or the like can be mounted on the composite substrate, whereby a circuit board mounted with high density can be obtained.

  As described above, the composite substrate of the present invention is mounted with the microcomputer IC chip and the piezoelectric resonator (the comb electrodes on the piezoelectric substrate facing each other in the direction of the mother substrate) adjacent to each other on the circuit mother board. And by molding with sealing resin, it can be set as a still lower composite substrate, and other electronic components can also be mounted.

  The piezoelectric resonator shown in FIG. 3 was produced.

  A piezoelectric ceramic wafer made of a PT-based material (L = 21 mm, W = 40 mm, t = 0.15 mm) is polarized in the L direction, and an Au electrode is deposited on the main surface of the mirrored porcelain, and then a photolithography process is performed. A plurality of IDTs composed of comb-teeth electrodes and lead electrodes electrically connected to the IDTs were formed. The IDT is disposed in a region corresponding to the central portion of each piezoelectric resonant element. At this time, the electrode finger of the IDT composed of comb-teeth electrodes and the polarization axis direction were set in parallel. This was bonded to an alumina wafer (L = 21 mm, W = 40 mm, t = 0.1 mm) as a reinforcing substrate with an epoxy adhesive.

  Next, in order to form a cross-sectional portion for reflecting the SH type surface wave, dicing processing is performed so that the reflective groove and the reflective bank portion are formed so that the porcelain cross-section is in contact with the outermost electrode finger of the IDI. It was. At this time, the number of IDT tolerance electrodes was 15.5 pairs, and the electrode crossing length was 660 μm. Furthermore, the width of the electrode finger of the IDT was 15 μm, the distance between the electrode finger was 15 μm, and the metallization ratio (IDT electrode width / no electrode width between electrodes) was set to 1. The position of the groove for reflecting the SH type surface wave was such that the electrode width of the outermost electrode finger of the IDT electrode was λ / 8 (about 7.5 μm).

  Thereafter, conductive bumps were printed on a part of the lead electrode portion that was electrically connected to the IDT.

Next, an Ag electrode serving as a terminal electrode is printed on both main surfaces of a wafer of a base substrate (L = 21 mm, W = 40 mm, t = 0.1 mm) mainly composed of a BaTiO ₃ based dielectric material, and then baked. A substrate with a built-in load capacitance of 10 to 50 pF was prepared. Thereafter, an epoxy resin was printed on the base substrate, and bonded and fixed so as to face the surface on which the IDT of the strip-shaped piezoelectric ceramic wafer was formed and the surface on which the load capacitance was formed. At this time, the height of the excitation space was set to 50 μm.

  Thereafter, an insulating organic resin was applied to the space between the strip-shaped piezoelectric resonance elements. Then, it processed with the dicing machine in the shape of each piezoelectric resonator (L = 2mm, W = 2mm, t = 0.4mm). Thereafter, an external terminal was formed by Ag sputtering, and electrical conduction between the IDT and the external terminal was performed.

  At this time, as shown in FIG. 7, the spurious characteristics did not occur in the main frequency band, and the P / V value was as large as 70 dB as shown in FIG. At this time, the capacitance of only the piezoelectric resonator is 16 pF, which is substantially equivalent to 15 pF of the resonator element used in the related art, and also in the oscillation characteristics within the range of 15 to 30 pF of the load capacity used conventionally. Stable oscillation was shown.

  Further, the thickness of the obtained piezoelectric resonator was 0.5 mm, the thickness covered by the conventional exterior resin was 1.4 mm, and the thickness of the piezoelectric resonator loaded in the package was 1 mm. Also, the capacity decreased by 68% compared to the conventional package type.

The piezoelectric resonator shown in FIGS. 1A and 1B and FIG. 2 was produced. The base substrate is mainly composed of a BT-based dielectric, except that the final shape is L = 2 mm, W = 2 mm, t = 0.3 mm, and the height of the excitation space is 40 μm. The same operation as in Example 1 was performed. When a PZT piezoelectric ceramic was used, the P / V value was 72 dB, and the capacitance of the electrode portion of the resonator was 68 pF. Further, when a NaNbO ₃ piezoelectric ceramic was used, the P / V value was 61 dB, and the capacitance of the resonator electrode part was 10 pF, which showed a promising result as a resonator. Thus, according to the present invention, it was possible to obtain a significantly thin piezoelectric resonator while maintaining a high P / V value.

1 shows a piezoelectric resonator of the present invention, in which (a) is a perspective view, (b) is a cross-sectional view taken along line XX ′ in (a), and (c) is a reinforcement substrate on the piezoelectric substrate in (a). It is sectional drawing at the time of adhere | attaching. It is assembly explanatory drawing of the structure of FIG. FIG. 4 shows another piezoelectric resonator of the present invention, in which (a) is a perspective view and (b) is a cross-sectional view taken along Y-Y 'in (a). FIG. 5 shows still another piezoelectric resonator according to the present invention, in which (a) is a perspective view of the piezoelectric resonator element, and (b) is a cross-sectional view of the piezoelectric resonator using the piezoelectric resonator element of (a). It is a top view which shows the filter of this invention. It is a schematic sectional drawing which shows the other filter of this invention. It is a schematic sectional drawing which shows the composite substrate of this invention. It is an impedance characteristic figure of the piezoelectric resonator of this invention of an Example. It is an oscillation circuit diagram of a piezoelectric resonator. It is a schematic sectional drawing of the piezoelectric resonator using the conventional thickness longitudinal third harmonic vibration.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric resonance element 1a ... Piezoelectric substrate 1b ... Reinforcement substrate 1c ... One main surface of piezoelectric substrate 1d ... Side surface of piezoelectric substrate 1e ... Other main surface of piezoelectric substrate 2.・ Base substrate 3 ... IDT
3a, 3b ... electrode fingers 6a, 6b ... connecting portions 7a, 7b ... connecting electrodes 8 ... bumps 9 ... side support members 14 ... reflection dam members 14d ... reflection ridges Side 16 of member: Reflective groove

Claims (13)

A piezoelectric resonant element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) composed of a pair of comb electrodes on one main surface of a piezoelectric substrate is disposed above the base substrate and the base substrate. A piezoelectric resonator, characterized in that an excitation space is formed between the IDT and a pair of side support members so as to sandwich both side surfaces of the base substrate and the piezoelectric substrate. A piezoelectric resonant element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) composed of a pair of comb electrodes on one main surface of a piezoelectric substrate is disposed above the base substrate and the base substrate. A piezoelectric resonance characterized in that an excitation space is formed between the IDT and a pair of side support members provided on the base substrate so as to sandwich the piezoelectric substrate from both sides. Child. 3. The piezoelectric resonance according to claim 1, wherein a reinforcing substrate having substantially the same shape as the piezoelectric substrate is provided via an adhesive layer on the other main surface opposite to the one main surface of the piezoelectric substrate. Child. A piezoelectric resonance element using an SH wave type surface wave formed by forming an interdigital transducer (IDT) composed of a pair of comb electrodes on one main surface of a piezoelectric substrate, and a side surface of the piezoelectric resonance element parallel to the side surface. And a reflecting bank member disposed at a certain distance on the main surface of the reinforcing substrate, the reinforcing substrate is disposed above the base substrate, the base substrate and the IDT are opposed to each other, and A piezoelectric resonator comprising a pair of side surface support members disposed so as to form an excitation space and sandwiching the reflection member from the side surfaces. The comb electrode includes a plurality of electrode fingers, a connecting portion for electrically connecting the plurality of electrode fingers, an external connecting portion, and a bridge for electrically connecting the external connecting portion and the connecting portion. 5. The piezoelectric device according to claim 1, wherein the external connection portion is electrically connected to a surface electrode provided on a side surface of the base substrate. Resonator. The piezoelectric resonator according to claim 1, wherein the base substrate includes an electrode for forming a capacitor. The piezoelectric resonator according to claim 1, wherein the side support member is made of an organic polymer. The piezoelectric resonator according to claim 1, wherein a Young's modulus of the side support member is 1 × 10 ¹⁰ Pa or less. The piezoelectric resonator according to claim 1, wherein a height of the excitation space is 5 to 100 μm. The piezoelectric resonator according to claim 1, wherein the piezoelectric substrate is made of a lead titanate-based or lead niobate-based material. The other IDT is formed in the surface of the said base substrate in the piezoelectric resonator in any one of Claims 1-10 so that IDT provided in one main surface of the said piezoelectric substrate may be opposed. filter. An IC chip is mounted on the surface of the base substrate of the piezoelectric resonator according to claim 1. 13. The composite substrate according to claim 12, further comprising an electronic component mounted on the surface and / or inside of the base substrate.

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