JP2015080131A - Acoustic wave filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic wave filter device which can be made compact in size, and which can more effectively radiate heat generated in an IDT electrode.SOLUTION: In an acoustic wave filter device 1, a plurality of IDT electrodes 3 and 4 are formed on a piezoelectric substrate 2, and a filter circuit is configured of the plurality of IDT electrodes 3 and 4, and a support member 5 is disposed to surround the plurality of IDT electrodes 3 and 4, and a cover member 6 is disposed on the upper face of the support member 5, and an electrode 31 is disposed to receive the heat of the IDT electrodes 3 and 4 which generate heat during operation among a plurality of electrode lands 31 disposed on the piezoelectric substrate 2, and a via hole electrode 24 is connected to the electrode land 31, and the via hole electrode 24 is electrically connected to an external connection terminal 8 for connection to the outside by a wiring electrode 10 disposed on the cover member 6.

Description

  The present invention relates to an elastic wave filter device used for, for example, a bandpass filter, and more particularly to an elastic wave filter device in which a plurality of IDT electrodes are provided on a piezoelectric substrate.

  Conventionally, along with miniaturization of mobile phones and the like, there is a demand for further miniaturization of surface mountable electronic components. Patent Document 1 below discloses an elastic wave device that can be reduced in size.

  In the elastic wave device described in Patent Document 1, a plurality of IDT electrodes are provided on a piezoelectric substrate. A hollow portion for sealing a portion where a plurality of IDT electrodes are provided is configured. In order to form the hollow portion, a support layer is formed on the piezoelectric substrate so as to surround a region where the IDT electrode is provided. A cover member is provided on the support layer.

  A columnar external connection electrode penetrating the support layer and the cover member is provided. An electrode pad is provided on the piezoelectric substrate so as to be electrically connected to the IDT electrode. The lower end of the external connection electrode is joined to the upper surface of the electrode pad. An external connection terminal made of a metal bump is joined to the upper end of the external connection electrode.

  In the elastic wave device described in Patent Document 1, surface mounting can be performed from the side of the external connection terminal made of a metal bump. Therefore, the size can be reduced. Further, it is described that heat dissipation can be enhanced by utilizing the heat dissipation of the columnar external connection electrode.

WO2009 / 057699

  However, in the acoustic wave device described in Patent Document 1, in order to further improve heat dissipation, a columnar external connection electrode is disposed in the vicinity of the heat generating portion together with a heat dissipation electrode pad, and the external connection electrode An external connection terminal made of a metal bump or the like to be joined to the upper end had to be joined. Therefore, a space for newly providing columnar external connection electrodes and external connection terminals is required, and it is difficult to promote downsizing.

  An object of the present invention is to provide an elastic wave filter device that can be miniaturized and can dissipate heat generated in an IDT electrode more effectively.

  An acoustic wave filter device according to the present invention includes a piezoelectric substrate, a plurality of IDT electrodes formed on the piezoelectric substrate and electrically connected to form a filter circuit, and the piezoelectric substrate. A support member provided so as to surround the plurality of IDT electrodes; a cover member provided on an upper surface of the support member and forming a hollow portion facing the IDT electrode; and the plurality of the plurality of IDT electrodes on the piezoelectric substrate. A plurality of electrode lands electrically connected to the IDT electrode, and the heat generating portion configured to receive heat of the IDT electrode constituting the heat generating portion that generates heat during operation among the plurality of electrode lands. A via-hole electrode provided so as to be electrically connected to the electrode land that is electrically connected to the IDT electrode and to penetrate the support member and the cover member; A plurality of external connection terminals provided on the cover member and electrically connected to the outside; provided on the cover member; and the via-hole electrode and the at least one external connection terminal. Wiring electrodes that are electrically connected.

  On the specific situation with the elastic wave filter apparatus which concerns on this invention, the electrode pad electrically connected to the IDT electrode which comprises the said heat-emitting part is a ground electrode.

  In another specific aspect of the elastic wave filter device according to the present invention, the plurality of IDT electrodes constitute a plurality of resonators, and the plurality of resonators include a series arm resonator and a parallel arm resonator. A ladder filter is configured by the series arm resonator and the parallel arm resonator.

  In still another specific aspect of the elastic wave filter device according to the present invention, the IDT electrode constituting the heat generating portion is an IDT electrode constituting the parallel arm resonator, and the wiring electrode is the via hole. The electrode land is electrically connected to the ground potential of the parallel arm resonator via the electrode.

  In another specific aspect of the acoustic wave filter device according to the present invention, an external connection terminal electrically connected to the wiring electrode has a larger planar shape than the remaining external connection terminals.

  In still another specific aspect of the acoustic wave filter device according to the present invention, the wiring electrode and an external connection terminal cascaded to the wiring electrode are combined with a conductive film connected to the via-hole electrode.

  According to the elastic wave device of the present invention, the via-hole electrode and at least one external connection terminal among the plurality of external connection terminals are electrically connected by the wiring electrode provided on the cover member. Therefore, heat can be dissipated to the external connection terminals using the wiring electrodes. Therefore, since it is not necessary to newly provide an external connection terminal and a heat dissipation electrode pad in order to improve heat dissipation, it is possible to effectively dissipate heat generated in the IDT electrode while proceeding with downsizing.

It is sectional drawing of the elastic wave apparatus which concerns on the 1st Embodiment of this invention, and is sectional drawing equivalent to the part in alignment with the AA of FIG. It is a typical top view except the external connection terminal of the elastic wave apparatus of the 1st Embodiment of this invention. It is a schematic plan view showing an electrode formation position on a piezoelectric substrate in the elastic wave device according to the first embodiment of the present invention. It is a typical top view of the elastic wave device concerning a 2nd embodiment of the present invention. It is a typical top view which shows the electrode structure on the piezoelectric substrate of the elastic wave apparatus which concerns on the 3rd Embodiment of this invention. It is a typical top view except an external connection terminal of an elastic wave device concerning a 3rd embodiment. In the elastic wave apparatus of a comparative example, it is a figure which shows the attenuation amount frequency characteristic in 25 degreeC, the attenuation amount frequency characteristic in 55 degreeC, and the attenuation amount frequency characteristic when 800 mW electric power is supplied in 55 degreeC. In the elastic wave apparatus of embodiment, it is a figure which shows the attenuation amount frequency characteristic in 25 degreeC, the attenuation amount frequency characteristic in 55 degreeC, and the attenuation amount frequency characteristic when 800 mW electric power is supplied in 55 degreeC.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1 is a cross-sectional view of the acoustic wave device according to the first embodiment of the present invention, and is a cross-sectional view corresponding to a portion along line AA in FIG. FIG. 2 is a schematic plan view excluding external connection terminals of the acoustic wave device of the present embodiment, and FIG. 3 is a schematic plan view showing electrode formation positions on the piezoelectric substrate.

As shown in FIG. 1, the acoustic wave device 1 has a piezoelectric substrate 2. In the present embodiment, the piezoelectric substrate 2 is made of a piezoelectric single crystal such as LiTaO ₃ or LiNbO ₃ . Piezoelectric ceramics may be used instead of the piezoelectric single crystal.

  A plurality of IDT electrodes 3 and 4 are formed on the piezoelectric substrate 2. In FIG. 1, the cross-sectional shape of a plurality of electrode fingers of the IDT electrodes 3 and 4 is shown. However, more IDT electrodes are formed on the piezoelectric substrate 2.

  FIG. 3 is a plan view schematically showing electrode formation positions on the piezoelectric substrate 2. The elastic wave device 1 of the present embodiment constitutes a duplexer of a mobile phone. On the piezoelectric substrate 2, a transmission circuit and a reception circuit for configuring a duplexer are configured. More specifically, an acoustic wave resonator unit 11 and first and second longitudinally coupled resonator type acoustic wave filter units 12 and 13 constituting a receiving circuit are provided on the piezoelectric substrate 2. Yes. In FIG. 3, the part in which these parts are comprised shall be shown schematically.

  Similarly, series arm resonators S1 to S4 and parallel arm resonators P1 to P4 are configured to configure a transmission filter. A ladder type filter is configured by the series arm resonators S1 to S4 and the parallel arm resonators P1 to P4. As for the series arm resonators S1 to S4 and the parallel arm resonators P1 to P4, the portions provided with the series arm resonators S1 to S4 are schematically shown by a figure surrounded by a shape such as a rectangle. The series arm resonators S1 to S4 and the parallel arm resonators P1 to P4 have IDT electrodes and reflectors arranged on both sides of the surface acoustic wave propagation direction of the IDT electrodes.

  A plurality of electrode lands (not shown) are provided on the piezoelectric substrate 2, and via hole electrodes described later are connected to the upper surfaces of the electrode lands. In FIG. 3, the position of the via hole electrode is schematically shown, and the planar shape of the via hole electrode is indicated by a circular symbol. In FIG. 3, a via hole electrode 21 constituting an antenna terminal is disposed in the vicinity of the parallel arm resonator P1. Further, a via hole electrode 22 for constituting a transmission terminal is disposed near the series arm resonator S4. Further, a via hole electrode 23 connected to the ground potential is provided at a corner near the parallel arm resonator P4. A via-hole electrode 24 is also provided in the vicinity of the parallel arm resonators P1 and P2. The via hole electrode 24 is connected to a ground potential as will be described later.

  Returning to FIG. 1, the IDT electrodes 3 and 4 provided on the piezoelectric substrate 2 are made of an appropriate metal such as Al, Cu, Au, Pt, or W, or an appropriate alloy such as Ag—Pd. The IDT electrodes 3 and 4 may be formed of a laminated metal film formed by laminating a plurality of metal layers. The IDT electrodes 3 and 4 are electrically connected by connection wiring (not shown). It is electrically connected like other IDT electrodes on the piezoelectric substrate 2. Thereby, the above-described transmission circuit and reception circuit are configured.

  In the acoustic wave device 1, hollow portions A and B shown in FIG. 1 are formed in order to seal the portion where the IDT electrode is formed. The hollow portions A and B are portions where the IDT electrodes 3 and 4 face. In order to form the hollow portions A and B, a support layer 5 as a support material is provided so as to surround a region where the IDT electrodes 3 and 4 are provided. The support layer 5 is made of an appropriate insulating material. As such an insulating material, synthetic resin, insulating ceramics, or the like can be used.

  A cover member 6 is provided so as to close an opening opened above the support layer 5. The cover member 6 can be formed of synthetic resin or insulating ceramics. The hollow portions A and B are formed by providing the support layer 5 and the cover member 6.

  In the acoustic wave device 1, a protective material 7 is formed so as to cover the cover member 6. The protective material 7 is made of an appropriate insulating material. The protective material 7 can be formed using a synthetic resin or an appropriate insulating ceramic. The protective material 7 may be formed of the same material as the cover member 6. The cover member 6 and the protective material 7 and the piezoelectric substrate 2 constitute a package having hollow portions A and B.

  External connection terminals 8 and 9 are provided on the cover member 6. The external connection terminals 8 and 9 are made of metal bumps such as solder bumps and Au bumps. Therefore, the acoustic wave device 1 can be surface-mounted on the circuit board from the side where the external connection terminals 8 and 9 are provided. Further, since the planar shape of the acoustic wave device 1 is the same as the planar shape of the piezoelectric substrate 2, it is possible to reduce the size. In addition, in the acoustic wave device 1, it is possible to improve heat dissipation using the via hole electrode 24. This will be described more specifically.

  As shown in FIG. 1, electrode lands 31 are formed on the piezoelectric substrate 2. In FIG. 3, illustration of electrode lands provided on the piezoelectric substrate 2 is omitted. Actually, a large number of electrode lands including the electrode lands 31 are provided on the piezoelectric substrate 2. The lower ends of the via hole electrodes 21 to 28 shown in FIG. 3 are joined to the electrode lands, respectively.

  As shown in FIG. 1, the lower end of the via hole electrode 24 is joined to the electrode land 31. As shown in FIG. 3, the electrode land 31 is provided near the parallel arm resonators P1 and P2. In the elastic wave device 1 of the present embodiment, the parallel arm resonator P1 constituting the transmission filter emits the largest amount of heat at the time of bonding. The via-hole electrode 21 is disposed closer to the IDT electrode of the parallel arm resonator P1 than other IDT electrodes. The electrode land 31 is electrically connected to the end of the parallel arm resonator P1 on the side connected to the ground potential. Therefore, the heat generated in the parallel arm resonator P <b> 1 is transmitted to the electrode land 31.

  On the other hand, the via-hole electrode 24 penetrates the support layer 5, penetrates the cover member 6, and reaches the upper surface of the cover member 6. The via hole electrode 24 is electrically connected to the wiring electrode 10. The wiring electrode 10 extends in a band shape on the upper surface of the cover member 6. The wiring electrode 10 is electrically connected to the external connection terminal 8. The via-hole electrode 24 and the wiring electrode 10 can be formed of an appropriate metal or alloy in the same manner as the IDT electrodes 3 and 4 described above.

  As described above, the heat generated in the parallel arm resonator P <b> 1 is transmitted to the via hole electrode 24, and the heat is transmitted to the external connection terminal 8 through the wiring electrode 10. Therefore, the heat generated in the IDT electrode having the highest temperature is quickly dissipated from the external connection terminal 8 to the outside. Therefore, in the elastic wave device 1 of this embodiment, heat dissipation can be improved.

  As described above, in the acoustic wave device described in Patent Document 1, it has been described that heat dissipation is enhanced by a columnar external connection electrode, that is, a via-hole electrode. However, in Patent Document 1, an external connection terminal is directly bonded onto the columnar external connection electrode. Therefore, in order to improve the heat dissipation, when the columnar external connection electrode is provided, the external connection terminal for heat dissipation must be newly provided. Therefore, downsizing has been difficult.

  On the other hand, in the acoustic wave device 1 of the present embodiment, the wiring electrode 10 is provided on the upper surface of the cover member 6 so as to electrically connect the via hole electrode 24 and the external connection terminal 8.

  On the other hand, the electrode land 31 and the external connection terminal 8 have been conventionally used as essential components for connecting the IDT electrode to the ground potential. However, in order to improve heat dissipation, in the present embodiment, both are joined by the wiring electrode 10. Therefore, it is possible to improve heat dissipation without increasing new external connection terminals and electrode lands. Thereby, not only can heat dissipation be improved, but also miniaturization can be promoted.

  In order to improve heat dissipation, it is preferable that the via-hole electrode 24 is disposed in the vicinity of the IDT electrode that has the highest temperature among the IDT electrodes that constitute the heat generating portion that generates heat during operation, that is, the heat that generates heat most strongly. . In the present embodiment, in the duplexer, the via hole electrode 24 is arranged close to the parallel arm resonator P1 that generates the highest amount of heat in the transmission filter that operates at a higher temperature than the reception filter in the duplexer. . More specifically, the via-hole electrode 24 is disposed so as to be closer to the IDT electrode of the parallel arm resonator P1 having the highest temperature than the other IDT electrodes. Therefore, in this embodiment, it is possible to further improve heat dissipation.

  As described above, it is preferable to arrange the via hole electrode connected to the wiring electrode so that the IDT electrode that is the highest temperature during operation is closer to the other IDT electrodes.

  In the present invention, as described above, heat dissipation can be improved by appropriately providing a wiring electrode connected to the upper end of the via-hole electrode. That is, the wiring electrodes 41 to 44 shown in FIG. 2 are provided so as to be electrically connected to the via hole electrode connected to the IDT electrode and the external connection terminal, similarly to the wiring electrode 10 described above. Thus, by providing the wiring electrodes 41 to 44 that electrically connect the via-hole electrodes and the external connection terminals above the cover member 6, the heat dissipation can be improved without increasing the number of external connection terminals. it can. In other words, by connecting the external connection terminal, which is an indispensable configuration for connection with the outside, and the via-hole electrode by using the wiring electrodes 41 to 44, heat dissipation can be achieved without hindering downsizing. Can be effectively increased.

  In the first embodiment, the external connection terminals 8 and 9 made of the metal bumps shown in FIG. 1 are used. However, in order to improve heat dissipation, the external connection terminals having a larger plane area than the metal bumps. It is desirable to use.

  In the second embodiment shown in FIG. 4, external connection terminals 51 to 60 made of a conductive film are provided instead of metal bumps in order to improve heat dissipation.

  By forming the external connection terminals 51 to 60 used for surface mounting with a conductive film having a larger area than the metal bumps, heat dissipation can be further enhanced.

  In the second embodiment, the external connection terminal 60 has an elongated slip shape as shown in the drawing. The external connection terminal 60 is not only electrically connected to the via-hole electrode located below, but also serves as a wiring electrode that constitutes an electrical connection portion with the outside. In other words, the external connection terminal 60 serves as both the external connection terminal 8 and the wiring electrode 10 in the first embodiment. In this case, the wiring electrode and the external connection terminal of the present invention can be formed without assimilating the manufacturing process.

  In addition, since the external connection terminal 60 has a large plane area, the heat dissipation can be further enhanced. Therefore, it is preferable that the external connection terminal and the wiring electrode serve as the conductive film.

  5 and 6 are schematic plan views showing positions where the IDT electrodes provided on the piezoelectric substrate and positions where the via-hole electrodes 21 to 28 are provided according to the third embodiment. These are figures corresponding to FIG. 2 shown about 1st Embodiment, and in FIG. 6, a wiring electrode is shown with a dashed-dotted line.

  In the third embodiment, the electrode land connected to the ground potential is not provided in the vicinity of the parallel resonator constituting the transmission filter having a large heat generation amount, but on the signal wiring connected to the adjacent heat generating resonator. An electrode pad is provided, a via hole electrode 24 is formed thereon, and connected to a wiring electrode on the cover member. Even with this configuration, the heat generated in the acoustic wave device can be efficiently dissipated.

  It will be described based on a specific experimental example that the heat dissipation is improved by the above embodiment.

  Similar to the above embodiment, except that the wiring electrode 10 and the via hole electrode 24 are not provided, and the electrode land connected to the lower end of the via hole electrode 24 is connected to another ground potential. A comparative example having the same configuration as that of the first embodiment was prepared except that it was electrically connected on the substrate.

  FIG. 7 shows the attenuation frequency characteristics of the elastic wave device of the comparative example. The one-dot chain line in FIG. 7 shows the attenuation frequency characteristic of the transmission filter of the elastic wave device of the comparative example when the temperature is 25 ° C. The broken line shows the attenuation frequency characteristic of the transmission filter when the temperature is 55 ° C. and power is not input in the elastic wave device of the comparative example. The solid line shows the attenuation frequency characteristic at 55 ° C. when 800 mW of power is applied to the transmission filter.

  On the other hand, FIG. 8 shows attenuation frequency characteristics in the above embodiment. That is, the alternate long and short dash line in FIG. 8 indicates the attenuation frequency characteristic of the transmission filter in a state where power at 25 ° C. is not applied. The broken line shows the attenuation frequency characteristic at 55 ° C. with no transmission power. The solid line shows the attenuation frequency characteristic of the transmission filter when power of 800 mW is input from the transmission terminal at 55 ° C. The frequency change of the dashed-dotted line and broken line in FIG.7 and FIG.8 is a change by the temperature rise of 30 degreeC when not supplying electric power. On the other hand, the change of the attenuation frequency characteristic from the broken line to the solid line is a change caused by power supply of 800 mW.

  In FIG. 7, the amount of frequency change at the power input frequency within the pass band is −1.1 MHz when the frequency characteristic changes from the alternate long and short dash line to the broken line, and −1.5 MHz when the frequency characteristic changes from the broken line to the solid line. It was. Therefore, when the broken line and the solid line are compared, a frequency change corresponding to a case where a temperature rise of 40.9 ° C. occurs due to power application.

  On the other hand, in the embodiment shown in FIG. 8, the change in frequency characteristic from the alternate long and short dash line to the broken line is the frequency change amount −1.1 MHz, and the change in frequency from the change to the filter characteristic from the broken line to the solid line Was about -1.1 MHz. Therefore, the amount of change in frequency when power is turned on corresponds to the amount of change in frequency when the temperature of 30 ° C. rises. Therefore, comparing FIG. 7 with FIG. 8, it can be seen that, according to the embodiment, compared with the comparative example, even when the temperature is increased by about 10 ° C., the same filter characteristics can be obtained. That is, it can be seen that frequency fluctuation due to heat can be effectively suppressed.

  In the present invention, the configuration of the filter circuit is not particularly limited as long as the plurality of IDT electrodes are configured to connect the filter circuit. That is, the present invention can be applied not only to the ladder type filter but also to various elastic wave filter devices.

  In the above embodiment, the electrode land close to the parallel arm resonator P1 is electrically connected to the via hole electrode 21, but the electrode land close to the other IDT electrode is not limited to the via hole electrode. Like the connection electrode 24 </ b> A shown in FIG. 6, the connection electrode may be electrically connected by an interlayer connection electrode other than the via hole electrode. The connection electrode 24A passes through the side surfaces of the support layer 5 and the cover member 6 described above, and electrically connects the electrode land 31A on the piezoelectric substrate 2 and the external connection terminal 9.

DESCRIPTION OF SYMBOLS 1 ... Elastic wave apparatus 2 ... Piezoelectric substrate 3, 4 ... IDT electrode 5 ... Support layer 6 ... Cover member 7 ... Protection material 8, 9 ... External connection terminal 10 ... Wiring electrode 11 ... Elastic wave resonator part 12, 13 ... No. DESCRIPTION OF SYMBOLS 1, 2nd longitudinally coupled resonator type | mold elastic wave filter part 21-28 ... Via-hole electrode 24A ... Connection electrode 31, 31A ... Electrode land 41-43 ... Wiring electrode 51-60 ... External connection terminal P1-P4 ... Parallel arm resonance Child S1-S4 ... Series arm resonator

Claims (6)

A piezoelectric substrate;
A plurality of IDT electrodes formed on the piezoelectric substrate and electrically connected to form a filter circuit;
A support member provided on the piezoelectric substrate so as to surround the plurality of IDT electrodes;
A cover member which is provided on the upper surface of the support member and forms a hollow portion facing the IDT electrode;
A plurality of electrode lands electrically connected to the plurality of IDT electrodes on the piezoelectric substrate;
Among the plurality of electrode lands, the electrode lands that are electrically connected to the IDT electrodes constituting the heat generating portion so as to receive heat of the IDT electrodes constituting the heat generating portion that generates heat during operation. A via-hole electrode provided so as to be electrically connected and to penetrate the support member and the cover member;
A plurality of external connection terminals provided on the cover member and electrically connected to the outside;
An elastic wave filter device comprising: the via hole electrode provided on the cover member; and a wiring electrode electrically connected to the at least one external connection terminal.   The acoustic wave filter device according to claim 1, wherein the electrode pad electrically connected to the IDT electrode constituting the heat generating portion is a ground electrode.   The plurality of IDT electrodes constitute a plurality of resonators, and the plurality of resonators include a series arm resonator and a parallel arm resonator, and a ladder is formed by the series arm resonator and the parallel arm resonator. The elastic wave filter apparatus of Claim 1 or 2 with which the type | mold filter is comprised.   The IDT electrode constituting the heat generating part is the IDT electrode constituting the parallel arm resonator, and the wiring electrode is electrically connected to the ground potential of the parallel arm resonator via the via-hole electrode. The acoustic wave filter device according to claim 3, wherein the acoustic wave filter device is connected to an electrode land.   The elastic wave filter apparatus as described in any one of Claims 1-4 with which the external connection terminal electrically connected to the said wiring electrode has a larger planar shape than the remaining external connection terminals.   The acoustic wave filter device according to any one of claims 1 to 5, wherein the wiring electrode and an external connection terminal cascaded to the wiring electrode are also used by a conductive film connected to the via-hole electrode.

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