JP2005217670A - Surface acoustic wave device and communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide highly reliable surface acoustic wave device and communication device, e.g. a frequency band filter or a demultiplexer employing a surface acoustic wave element being incorporated in a mobile wireless apparatus such as a portable telephone, in which heat dissipation is enhanced while sustaining airtightness of the device. <P>SOLUTION: On the upper surface of a supporting substrate 2, a surface acoustic wave element 1 provided with an excitation electrode on one major surface of a piezoelectric substrate is mounted while facing the one major surface of a piezoelectric substrate, and the other major surface of the piezoelectric substrate is covered with a protective member 4. One or more through hole 5 is made to penetrate between the one and the other major surfaces of the piezoelectric substrate, and at least one opening of the through hole 5 is covered with a good heat conductor 6 having thermal conductivity higher than that of the piezoelectric substrate. Since no outer air intrudes from the through hole 5, the excitation electrode does not corrode and sufficient heat dissipation is attained by the good heat conductor 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface acoustic wave device and a communication device that can be applied to a frequency band filter, a duplexer, and the like built in a mobile wireless device such as a mobile phone and a vehicle-mounted sensor.

  In recent years, electronic components used in mobile communication devices such as mobile phones include active components made of semiconductor elements, chip capacitors, chip resistors, chip inductors, and surface acoustic waves (hereinafter abbreviated as SAW). There are filters and duplexers that use filters.

FIG. 12 shows a basic configuration of the SAW resonator constituting the SAW filter. In the figure, 11 is an IDT (Inter Digital Transducer) electrode of an excitation electrode formed by a method such as sputtering on a piezoelectric substrate made of LiTaO ₃ single crystal or the like, and in the figure, 12 is a SAW on the IDT electrode 11 side. It is a reflector that resonates and resonates efficiently. In the figure, the electrode fingers of the IDT electrode 11 and the reflector 12 are actually simplified because they are several tens to several hundreds, and the same applies to other drawings.

10 and 11 show a conventional SAW filter. FIG. 10 is a sectional view taken along line BB ′ in FIG. It comprises a SAW element 101 in which at least a pair of IDT electrodes, a reflector and the like are formed on a piezoelectric substrate such as a LiTaO ₃ single crystal, and a base 102 on which it is hermetically sealed and mounted. The SAW element 101 is bonded and fixed to the upper surface of the base 102 with the electrode formation surface facing the base side via a gold bump 103 and the like. After the SAW element 101 and the electrode on the upper surface of the base 102 are electrically connected, the protective member 104 Airtightly sealed.

  The active components, chip capacitors, and chip resistors have been reduced in size and height in response to downsizing and thinning of mobile communication devices. However, a duplexer using a SAW filter or SAW filter (hereinafter referred to as a duplexer). , SAW duplexers) and power amplifiers occupy most of the volume of mobile communication devices, and there is an increasing demand for miniaturization and low profile. Therefore, so-called flip-chip mounting is generally used for recent SAW filters or SAW duplexers in which the surface of the piezoelectric substrate on which the electrodes are formed is mounted so as to face the substrate. The SAW filter or SAW duplexer on which the flip chip mounting is performed maintains the airtightness of the surface on which the electrodes are formed by applying and curing a resin in order to improve reliability.

  Here, FIG. 13 shows a block circuit diagram of a high-frequency circuit of a cellular phone. The high-frequency signal to be transmitted is removed from the unnecessary signal by the SAW filter 20, amplified by the power amplifier 21, and then radiated from the antenna 13 through the isolator 22 and the SAW duplexer 14. The high frequency signal received by the antenna 13 passes through the SAW branching filter 14 and is amplified by the low noise amplifier 15. After the unnecessary signal is removed by the SAW filter 16, the signal is re-amplified by the amplifier 17 and reduced by the mixer 18. Converted to a frequency signal.

In addition, in order to reduce the size of the mobile phone, it is necessary to reduce the interval between components, and the interval between the SAW filter or SAW duplexer and the power amplifier is also very small. The power amplifier itself is a component that generates heat, and the surrounding SAW filter or SAW duplexer also becomes hot due to heat from the power amplifier or heat generated by the input signal. For this reason, the SAW filter or the SAW duplexer is accelerated in its characteristic deterioration, and a mobile phone failure occurs in a short time, so there is a problem in reliability. Therefore, as shown in FIG. 11, a countermeasure has been taken in which through holes 105 are formed in the piezoelectric substrate to dissipate heat generated in the electrodes (see Patent Document 1).
JP 2003-87093 A

  However, in the conventional SAW filter or SAW duplexer, the through hole is formed around the SAW resonator, but the surface on which the IDT electrode of the piezoelectric substrate is formed and the surface on which the IDT electrode is not formed. No electrode is formed on the upper part of the through hole. In this case, outside air (especially moisture) may enter the space where the IDT electrode is formed through the through hole, and the IDT electrode may be corroded to cause a failure. Moreover, since the electrode is not formed in the upper part of the through hole as described above, heat dissipation is poor.

  Therefore, the present invention has been proposed in view of the above circumstances, and its purpose is to achieve a surface acoustic wave that has excellent heat dissipation and high reliability while maintaining the airtightness of the SAW filter or SAW duplexer. It is to provide a device and a communication device.

  In the surface acoustic wave device of the present invention, 1) a surface acoustic wave element in which an excitation electrode is provided on one main surface of a piezoelectric substrate is placed on the upper surface of a support base so that the one main surface of the piezoelectric substrate faces. And a surface acoustic wave device in which the other main surface of the piezoelectric substrate is covered with a protective member, and includes one or more through holes penetrating between the one main surface and the other main surface of the piezoelectric substrate. And at least one opening of the through hole is covered with a good thermal conductor having a higher thermal conductivity than the piezoelectric substrate.

  2) In the surface acoustic wave device according to 1), the good thermal conductor covers the other main surface of the piezoelectric substrate over the entire surface.

  3) In the surface acoustic wave device according to 1) or 2), the good thermal conductor covers a side surface of the piezoelectric substrate.

  4) In the surface acoustic wave device according to any one of 1) to 3), a good thermal conductor having a thermal conductivity higher than that of the piezoelectric substrate is provided inside the through hole.

  The communication device of the present invention is characterized in that 5) the surface acoustic wave device according to any one of 1) to 4) is used as a filter means.

  According to the surface acoustic wave device of the present invention, the surface acoustic wave element in which the excitation electrode is provided on one main surface of the piezoelectric substrate is placed on the upper surface of the support base so that the one main surface of the piezoelectric substrate faces the surface. In addition, in the surface acoustic wave device in which the other main surface of the piezoelectric substrate is covered with a protective member, one or more through-holes penetrating between the one main surface and the other main surface of the piezoelectric substrate are provided, Since at least one opening of the through-hole is covered with a good heat conductor having a thermal conductivity higher than that of the piezoelectric substrate, the good heat conductor can prevent entry of outside air as much as possible, so that airtightness is good. It becomes. Further, heat is dissipated by the good heat conductor and the through hole, and heat can be transmitted to the support base, so that sufficient heat dissipation is obtained.

  Further, since the good heat conductor covers the entire surface of the other main surface of the piezoelectric substrate, it becomes difficult for outside air to enter, thereby improving airtightness. In addition, heat can be efficiently radiated by the good heat conductor and the through hole, and heat can be transferred to the support base, so that sufficient heat dissipation can be obtained.

  In addition, since the good heat conductor covers the side surface of the piezoelectric substrate, the area of heat conduction becomes wider, so that more sufficient heat dissipation can be obtained.

  Further, by providing a good thermal conductor having a thermal conductivity larger than that of the piezoelectric substrate inside the through hole, it is possible to obtain further sufficient heat dissipation and airtightness.

  Furthermore, since the communication device of the present invention uses the surface acoustic wave device as a filter means, a high-quality communication device can be provided.

  An embodiment of a surface acoustic wave device of the present invention will be described in detail with reference to the drawings schematically shown. 1 and 2 are cross-sectional views showing the configuration of a basic SAW filter of the present invention. 2 is a top view of the SAW filter shown in FIG. 1, and FIG. 1 is a cross-sectional view taken along the line A-A 'shown in FIG.

  The SAW filter of the present invention includes a SAW element 1, a support base 2 on which the SAW element 1 is mounted, and a bump (connecting conductor) that is a gold bump or a solder bump that connects electrode terminals formed on the SAW element 1 and the support base 2. 3 and a protective member 4 made of an epoxy resin or the like for hermetically sealing. That is, the surface acoustic wave element 1 provided with an IDT electrode on one main surface of the piezoelectric substrate is placed on the upper surface of the support base 2 with the one main surface of the piezoelectric substrate facing the other surface of the piezoelectric substrate. In the configuration in which the main surface is covered with a protective member, one or more through holes 5 penetrating between the one main surface and the other main surface of the piezoelectric substrate are provided, and at least one opening of the through hole 5 is provided. It is covered with a good thermal conductor 6 having a higher thermal conductivity than the piezoelectric substrate.

The SAW element 1 has an IDT electrode, a reflector, an input / output electrode, a ground electrode, and the like as excitation electrodes on a piezoelectric substrate such as a lithium tantalate (LiTaO ₃ ) single crystal or lithium niobate (LiNbO ₃ ) single crystal. Is formed. The support base 2 is made of alumina, a low-temperature co-fired ceramic, a resin such as BT resin (bismaleimide / triazine), or the like. The high-frequency signal input / output electrode and the ground electrode are formed by a thick film printing method. The protective member 4 for hermetically sealing is hermetically sealed by applying and curing a resin. Reference numeral 7 in the figure denotes a terminal electrode for taking out a signal, which is formed on the lower surface of the support base 2.

  A feature of the present invention is that a through-hole 5 is formed on the piezoelectric substrate 1 and a good thermal conductor 6 made of a conductor pattern is formed in at least one opening of the through-hole on the surface on which the electrode is formed. It is. Here, the good heat conductor 6 only needs to be made of a material having a higher thermal conductivity than the piezoelectric substrate. For example, a metal material, ceramics, a composite material of a metal material and ceramics, or the like can be used. A metal material is preferred from the viewpoints of high thermal conductivity and easy fabrication on a piezoelectric substrate. For example, if the piezoelectric substrate is made of a lithium tantalate single crystal or a lithium niobate single crystal (thermal conductivity: several W / m · K), the single crystal can be easily manufactured and the thermal conductivity is piezoelectric. An IDT electrode material described later, which is sufficiently higher than the substrate, is preferable.

  Thus, since the good heat conductor 6 which covers the through hole 5 formed in the piezoelectric substrate is formed, the heat generated from the SAW resonator is transferred from the good heat conductor 6 to the through hole 5 and the support base 2. It is transmitted to and dissipated. Further, since the opening of the through hole 5 is covered, there is no gap for the outside air to enter from the through hole 5 into the space 25 where the IDT electrode is formed. As a result, the airtightness is excellent and the IDT electrode is corroded as much as possible. Is prevented.

  Moreover, as shown in FIG. 3, it is good also as a structure which covers the opening part of the through-hole 5 of the surface by which the IDT electrode of the piezoelectric substrate is not formed with the good heat conductor 6. FIG. Other configurations are the same as those in FIG. Even with such a configuration, the heat generated from the SAW resonator is transmitted to the through hole 5 and the good thermal conductor 6, and sufficient heat dissipation is obtained. Similarly, as shown in FIG. 4, the openings on both main surface sides of the piezoelectric substrate of the through hole 5 may be covered with the good heat conductor 6. Other configurations are the same as those in FIG. Even with such a configuration, heat transfer is promoted, and in particular, the good thermal conductor 6 (on the lower side in the figure) provided on the side where the IDT electrode of the piezoelectric substrate is formed → the through hole 5 → the piezoelectric substrate. By sequentially transferring heat to the good thermal conductor 6 (upper side in the drawing) provided on the side where the IDT electrode is not formed (the back side of the piezoelectric substrate), the heat radiation effect can be further enhanced. Furthermore, airtightness can be improved by covering the through-hole 6 from both sides.

  In the surface acoustic wave device shown in FIG. 5, the entire surface of the back surface (back surface) of the piezoelectric substrate on which the IDT electrodes of the piezoelectric substrate are not formed is covered with the good thermal conductor 6. Other configurations are the same as those in FIG. According to such a configuration, the area of the good heat conductor 6 that can be used for heat dissipation can be further increased, and as a result, even better heat dissipation can be obtained. Further, for the same reason as in the case of the surface acoustic wave device shown in FIG.

  In addition, as shown in FIG. 6, the good thermal conductor 6 may be extended to the side surface of the piezoelectric substrate or the support base 2. Other configurations are the same as those in FIG. According to such a configuration, the formation area of the good heat conductor 6 that can be used for heat dissipation can be further increased, and as a result, even better heat dissipation can be obtained. Further, the airtightness can be improved for the same reason as in the surface acoustic wave device of FIGS.

  Further, as shown in FIG. 7, a connection conductor made of gold or solder is provided between the good thermal conductor 6 provided on the through hole 6 on the surface of the piezoelectric substrate on which the IDT electrode is formed and the support base 2. Bumps 3 are formed. The presence of the bumps 3 makes it more difficult for outside air to enter and further improves airtightness. Other configurations are the same as those in FIG.

  Moreover, as shown in FIG. 8, the inside of the through-hole 5 is filled with the electrically conductive paste 8 which comprises a good heat conductor. This configuration also improves the heat conductivity, so that even better heat dissipation can be obtained. Since other configurations are the same as those in FIG. The conductive paste 8 may be the same material as the good heat conductor 6 or a different material.

  Moreover, as shown in FIG. 9, the electroconductive thin film 9 which comprises a good heat conductor is formed inside the through-hole 5 (inner wall surface). This configuration also improves the heat conductivity, so that good heat dissipation is obtained. Other configurations are the same as those in FIG.

  Further, by using the above-described surface acoustic wave device as the filter means of the communication device such as the cellular phone as shown in FIG. 13, the SAW filter 20, the SAW duplexer 14, and the SAW filter 16 in FIG. For example, a communication device with excellent quality can be provided.

In the SAW resonator of the surface acoustic wave device of the present invention, the IDT electrode is Al or an Al alloy such as Al—Cu, Al—Ti, Al—Mg, or Al—Cu—Mg, or Al in the lower layer / upper layer. -Cu alloy / Cu / Al-Cu alloy, Ti / Al-Cu alloy, Ti / Al-Cu alloy / Ti, Ti / Al-Cu-Mg alloy / Ti, Ti / Al-Cu-Mg It is preferable to be made of a laminated film such as a titanium alloy / Ti / Al—Cu—Mg alloy. The IDT electrode is formed by a thin film forming method such as an evaporation method, a sputtering method, or a CVD method. The number of electrode fingers of the IDT electrode is about 50 to 300, the line width of the electrode fingers is about 0.1 to 10.0 μm, the distance between the electrode fingers is about 0.1 to 10.0 μm, and the opening width (intersection width) of the electrode fingers is 10 to About 200 μm and the IDT electrode thickness of about 0.1 to 0.5 μm are suitable for obtaining desired characteristics as a SAW resonator or SAW filter. As the piezoelectric substrate, 36 ° ± 10 ° Y cut-X propagation LiTaO ₃ single crystal, 64 ° ± 10 ° Y cut-X propagation LiNbO ₃ single crystal, 45 ° ± 10 ° X cut-Z propagation Li ₂ A B ₄ O ₇ single crystal or the like is preferable because it has a large electromechanical coupling coefficient and a small group delay time temperature coefficient, and a 36 ° ± 10 ° Y cut-X propagation LiTaO ₃ single crystal having a large electromechanical coupling coefficient is particularly preferable. . Further, the cut angle in the crystal Y-axis direction may be in the range of 36 ° ± 10 °, and in that case, sufficient piezoelectric characteristics can be obtained. The thickness of the piezoelectric substrate is preferably about 0.1 to 0.5 mm. This is because the piezoelectric substrate becomes brittle when the thickness is less than 0.1 mm, and the material cost increases when the thickness exceeds 0.5 mm. Further, there is no problem even if a piezoelectric substrate subjected to reduction treatment is used in order to prevent electrode destruction due to the pyroelectric effect of the piezoelectric substrate. In order to prevent electrode destruction due to the pyroelectric effect of the piezoelectric substrate, there is no problem even if a piezoelectric substrate added with Fe element is used. In the case of the SAW duplexer, the reception SAW element and the transmission SAW element may be formed on the main surface of one piezoelectric substrate, or may be formed on separate piezoelectric substrates, Furthermore, it may be individually mounted on each substrate.

  As described above, according to the surface acoustic wave device of the present invention, the surface acoustic wave device 1 in which the IDT electrode is provided on the one main surface of the piezoelectric substrate on the upper surface of the support base 2 is used. One or more penetrations that pass between the one main surface and the other main surface of the piezoelectric substrate in a configuration in which the surfaces are placed facing each other and the other main surface of the piezoelectric substrate is covered with a protective member Since the hole 5 is provided and at least one opening of the through-hole 5 is covered with the good heat conductor 6 having a higher thermal conductivity than the piezoelectric substrate, the good heat conductor 6 prevents the entry of outside air as much as possible. And airtightness is improved. Further, since heat can be conducted to the support base 2 by the through holes 6, sufficient heat dissipation can be obtained.

  Moreover, since the good heat conductor 6 covers the other main surface of the piezoelectric substrate over the entire surface, it becomes difficult for outside air to enter, thereby improving airtightness. Further, heat is dissipated by the good heat conductor 6 and the through-hole 5, and the heat conduction to the support base 2 is better, so that sufficient heat dissipation is obtained.

  In addition, since the good heat conductor 6 also covers the side surface of the piezoelectric substrate, the area of heat conduction is widened, so that further sufficient heat dissipation can be obtained.

  Further, by providing a good heat conductor having a higher thermal conductivity than the piezoelectric substrate also inside the through hole 5, sufficient heat dissipation and airtightness can be obtained.

  Furthermore, since the surface acoustic wave device can be used as a filter means in the communication device of the present invention, it is possible to provide a high-quality communication device.

  In addition, this invention is not limited to said embodiment, A various change does not interfere in the range which does not deviate from the summary of this invention.

  Examples in which the present invention is further embodied will be described below.

<Example 1>
The surface acoustic wave device shown in FIG. 1 was produced as follows. In this example, a case where LTCC: Low Temperature Co-fired Ceramics (low temperature co-fired ceramics) is used as a package will be described. First, the support base 2 will be described. A large number were taken from the ceramic parent substrate, and an electrode pattern was printed on the ceramic parent substrate, fired, and then individually cut to form an input / output electrode and a ground electrode of the substrate by a printing method.

Next, the SAW element 1 will be described. On a 38.7 ° Y-cut LiTaO ₃ single crystal piezoelectric substrate, the base electrode is Ti as shown in FIG. 2, and the base electrode is Al (99 mass%)-Cu (1 mass%)-Mg (1 mass%). A fine electrode pattern made of an alloy was formed. At this time, the SAW filter was a 2.5-stage T-type ladder. The electrode period of the SAW filter at this time was about 2.2 to 2.3 μm. For pattern production, photolithography was performed using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the piezoelectric substrate was scrubbed to remove impurities. Next, the base electrode Ti was formed. A sputtering apparatus was used to form the base electrode Ti, and the base electrode film thickness at this time was about 0.09 μm. Next, Al—Cu—Mg, which is a fine electrode, was formed. A sputtering apparatus was used for film formation of the electrode, and the film thickness of the base electrode at this time was about 0.34 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the ladder type surface acoustic wave filter was formed.

Next, a protective film was formed on a predetermined region of the electrode pattern. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD (Chemical Vapor Deposition) apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, using a sputtering apparatus, a laminated electrode made of Cr, Ni, Au was formed. The electrode film thickness at this time was about 1.0 μm. Thereafter, the photoresist and the laminated electrode at unnecessary portions were simultaneously removed by a lift-off method to complete a pad for connecting a flip chip bump.

  Next, the piezoelectric substrate was processed by a laser processing apparatus from the surface facing the IDT electrode of the piezoelectric substrate to form through holes in a desired shape.

  Next, the piezoelectric substrate was diced along dicing lines and divided into chips.

Next, an electrode pattern made of solder was printed on the ceramic parent substrate. Thereafter, each chip was temporarily bonded on a ceramic parent substrate with a flip chip mounting apparatus with the electrode formation surface on the bottom surface. Thereafter, baking was performed in an N ₂ atmosphere to melt the solder, thereby bonding the chip and the ceramic parent substrate.

Next, a resin was applied to the ceramic parent substrate to which the chip was bonded, and baked in an N ₂ atmosphere to seal the chip.

  Next, the ceramic parent substrate was diced along dicing lines and divided into individual sides to complete a SAW filter. A substrate having a laminated structure of 2.0 × 1.6 mm was used.

<Example 2>
First, the piezoelectric substrate was scrubbed to remove impurities. Next, the base electrode Ti was formed. A sputtering apparatus was used to form the base electrode Ti, and the base electrode film thickness at this time was about 0.09 microns. Next, the same Al—Cu—Mg film as in Example 1 which is a fine electrode was formed. A sputtering apparatus was used for film formation of the electrode, and the film thickness of the base electrode at this time was about 0.34 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the ladder type surface acoustic wave filter was formed.

Next, a protective film was formed on a predetermined region of the electrode pattern. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, using a sputtering apparatus, a laminated electrode made of Cr, Ni, Au was formed. The electrode film thickness at this time was about 1.0 micron. Thereafter, the photoresist and the laminated electrode at unnecessary portions were simultaneously removed by a lift-off method to complete a pad for connecting a flip chip bump.

  Next, the piezoelectric substrate was processed by a laser processing apparatus from the surface facing the IDT electrode of the piezoelectric substrate to form through holes in a desired shape.

  Next, an electrode Al—Cu was formed on the surface facing the IDT electrode. A sputtering apparatus was used to form the electrode Al—Cu, and the electrode film thickness at this time was about 0.6 μm. Next, dicing was performed, but the subsequent contents are the same as in Example 1 above, and will be omitted.

<Example 3>
Since the process until the piezoelectric substrate is diced and divided for each chip is the same as in Examples 1 and 2, description thereof is omitted.

An electrode pattern made of solder was printed on a ceramic parent substrate. Thereafter, each chip was temporarily bonded on a ceramic parent substrate with a flip chip mounting apparatus with the electrode formation surface on the bottom surface. Thereafter, baking was performed in an N ₂ atmosphere to melt the solder, thereby bonding the chip and the ceramic parent substrate.

  Next, an electrode Al—Cu was formed on each of the chip and the ceramic parent substrate. A sputtering apparatus was used to form the electrode Al—Cu, and the film thickness of the base electrode at this time was about 1.0 μm. Next, a resin is applied, but the subsequent contents are the same as in Example 1 and will be omitted.

<Example 4>
In each of the above examples, after forming the through hole, a process of printing the conductive paste was added. Since other contents are the same as those in Examples 1 to 3, they are omitted.

<Example 5>
In each of the above examples, after forming the through hole, a process of forming a conductive thin film in the through hole was added. Since other contents are the same as those in Examples 1 to 3, they are omitted.

<Example 6>
The surface acoustic wave device produced in each example was mounted on a printed wiring board in a mobile phone.

<Comparative example>
Further, as a comparative sample, the conventional surface acoustic wave device shown in FIGS. 10 and 11 was also manufactured in the same process as in the above examples.

<Evaluation>
With respect to Examples 1 to 6 and the comparative example described above, when a power durability test was performed at a temperature of 110 ° C. with an application time of 2 W of power of 180 hours, the loss was 0.5 dB in about several hours in the comparative example. Although the characteristic deterioration was severe as described above, in Examples 1 to 6, the loss was less than 0.5 dB, and no characteristic deterioration could be recognized.

In addition, for the purpose of evaluating heat dissipation, the temperature rise when signal power enters the surface acoustic wave device was obtained from thermal analysis by the finite element method. Model a models Example 1. That is, a through hole was formed in the piezoelectric substrate, and an electrode pattern covering the opening of the through hole was formed. Model b models the surface acoustic wave device of Example 2. In other words, in addition to the model a, the electrode is formed on the entire surface facing the IDT electrode. Model c models the surface acoustic wave device of Example 3. That is, in addition to the model b, an electrode is formed on the side surface of the piezoelectric substrate. Furthermore, a conventional model d having no electrode pattern of a good thermal conductor on the through hole and the through hole for comparison was also analyzed. As analysis conditions, the thermal conductivity (W / m · k) of each material is 4.1 for LiTaO ₃ single crystal substrate, 3.9 for LTCC substrate as a support base, 61 for solder connection material, 0.5 for epoxy resin, and through hole As a filling material, Ag of 150 and air of 2.6 × 10 ⁻² were used. As an analysis method, a signal power of 0.4 W is input to the surface acoustic wave device, and heat generated in the vicinity of the surface acoustic wave resonator is conducted inside the surface acoustic wave device, and is 25 ° C. from the surface of the surface acoustic wave device. The temperature in the heat generating part during the process of transferring to the atmosphere was analyzed.

  The maximum temperature in the heat generating part in the vicinity of the surface acoustic wave resonator was 81 ° C. for model a, 74 ° C. for model b, and 67 ° C. for model c having the same structure as the present invention. On the other hand, in the conventional model d, it was 86 ° C. From the above results, the heat generation was −5 ° C., −12 ° C., and −19 ° C., respectively, as compared with the conventional model, and a significant decrease in temperature was observed, confirming improvement in heat dissipation.

It is sectional drawing which shows an example of the surface acoustic wave apparatus of this invention. It is a top view which shows an example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing which shows the other example of the surface acoustic wave apparatus of this invention. It is sectional drawing of the conventional surface acoustic wave apparatus. It is sectional drawing of the conventional surface acoustic wave apparatus. It is a top view which shows an example of the electrode structure of a SAW resonator. It is a block diagram which shows the structure of a mobile telephone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101: Surface acoustic wave element 2,102: Support base | substrate 3,103: Bump (connection conductor)
4, 104: Protective member 5, 105: Through hole 6: Heat conductor 7, 107: Terminal electrode 8: Conductive paste 9: Conductive thin film

Claims (5)

A surface acoustic wave element having an excitation electrode provided on one main surface of the piezoelectric substrate is placed on the upper surface of the support base so that the one main surface of the piezoelectric substrate faces the other, and the other main surface of the piezoelectric substrate is protected. A surface acoustic wave device covered with a member, wherein one or more through holes penetrating between the one main surface and the other main surface of the piezoelectric substrate are provided, and at least one opening of the through hole The surface acoustic wave device is characterized in that it is covered with a good thermal conductor having a thermal conductivity higher than that of the piezoelectric substrate. The surface acoustic wave device according to claim 1, wherein the good heat conductor covers the other main surface of the piezoelectric substrate over the entire surface. 3. The surface acoustic wave device according to claim 1, wherein the good heat conductor covers a side surface of the piezoelectric substrate. 4. The surface acoustic wave device according to claim 1, wherein a good thermal conductor having a thermal conductivity larger than that of the piezoelectric substrate is provided inside the through hole. 5. A communication apparatus using the surface acoustic wave device according to claim 1 as filter means.

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