WO2018198508A1 - Surface acoustic wave device, high frequency front-end circuit using surface acoustic wave device, and communication device using surface acoustic wave device - Google Patents

Abstract

A surface acoustic wave device (20) relating to the present invention is provided with: a package substrate (60); a surface acoustic wave chip (210) that is provided with a chip substrate (211), i.e., a lithium niobate substrate; a surface acoustic wave chip (220) that is provided with a chip substrate (221), i.e., a lithium tantalate substrate; a bump (41) bonded to the surface acoustic wave chip (210); and a bump (42) bonded to the surface acoustic wave chip (220). The surface acoustic wave chip (210) is mounted on the package substrate (60) using the bump (41), and the surface acoustic wave chip (220) is mounted on the package substrate (60) using the bump (42). At this time, the material of the bump (41) has a Young's modulus that is lower than that of the material of the bump (42).

Description

Elastic wave device, and high-frequency front-end circuit and communication device using the same

The present invention relates to an elastic wave device, a high-frequency front-end circuit using the same, and a communication device.

Patent Document 1 discloses an acoustic wave duplexer in which a filter chip including a lithium tantalate substrate and a filter chip including a lithium niobate substrate are flip-chip mounted on the same wiring substrate. .

JP 2011-199810 A

When a thermal load is applied to an acoustic wave device such as an acoustic wave duplexer described in Patent Document 1 due to a change in ambient temperature environment, the acoustic wave chip that is a filter chip and the package substrate that is a wiring board expand. As a result, stress is generated. The generated stress is applied to each acoustic wave chip via a bump connecting the acoustic wave chip and the package substrate.

At this time, the lithium niobate substrate provided in one acoustic wave chip is inferior in bending strength to the lithium tantalate substrate provided in the other acoustic wave chip, and therefore is resistant to cracks caused by stress (crack Resistance) is very weak. Then, for example, when all the bumps have the same Young's modulus, each bump can only relieve the same level of stress, so the elastic wave chip on the lithium niobate substrate side, which is relatively inferior in crack resistance, There is a risk of cracking occurring earlier than the acoustic wave chip on the lithium tantalate substrate side. When a crack occurs in one of the acoustic wave chips mounted on the package substrate, an abnormality occurs in a part of the acoustic wave device including the package substrate, so that the acoustic wave device fails.

Therefore, the object of the present invention is to reduce the stress applied to the elastic wave chip on the lithium niobate substrate side, which is relatively inferior in crack resistance, through the bumps compared to the elastic wave chip on the lithium tantalate substrate side, which is relatively superior in crack resistance. It is to reduce the failure rate of the elastic wave device.

To achieve the above object, an acoustic wave device according to an aspect of the present invention includes a package substrate, and a first acoustic wave chip that is mounted on the package substrate and includes a first substrate that is a lithium niobate substrate. A second acoustic wave chip that is mounted on the package substrate and has a second substrate that is a lithium tantalate substrate; a first bump that electrically connects the first acoustic wave chip and the package substrate; An elastic wave device including a second bump for electrically connecting a second elastic wave chip and a package substrate, wherein the first bump is joined to the first elastic wave chip, and the second bump is The elastic wave device is bonded to the second elastic wave chip, and the material of the first bump has a lower Young's modulus than the material of the second bump.

In this configuration, the first bump on the first acoustic wave chip side including the crack-resistant inferior lithium niobate substrate includes the lithium tantalate substrate superior in crack resistance on the second acoustic wave chip side. The degree of freedom of deformation is higher than that of the second bump. Therefore, the first bump can relieve more stress than the second bump. Accordingly, since the stress applied to the first elastic wave chip that is inferior in crack resistance is more likely to be reduced than in the second elastic wave chip that is superior in crack resistance, an elastic wave device including a package substrate on which both elastic wave chips are mounted. The failure rate is also reduced.

Further, the height of the first bump is preferably higher than the height of the second bump.
According to this configuration, the distance between the first acoustic wave chip and the package substrate is likely to increase more than the distance between the second acoustic wave chip and the package substrate. The greater the distance between the acoustic wave chip and the package substrate, the smaller the influence that the acoustic wave chip receives from the expansion of the package substrate. Therefore, the stress applied to the first acoustic wave chip is more likely to be reduced than the stress applied to the second acoustic wave chip, and the failure rate of the acoustic wave device is further reduced.

In addition, when the acoustic wave device is viewed in plan from the first and second acoustic wave chips, the area of the joint surface between the first bump and the first acoustic wave chip is the second bump and the second The area is preferably larger than the area of the joint surface with the acoustic wave chip.

According to this configuration, the stress applied to the first acoustic wave chip at the joint surface between the first bump and the first acoustic wave chip is the first stress at the joint surface between the second bump and the second acoustic wave chip. 2 is widely dispersed compared to the stress applied to the elastic wave chip 2. Therefore, the stress applied to the first acoustic wave chip is more likely to be reduced than that of the second acoustic wave chip, so that the acoustic wave device is further less likely to fail.

Furthermore, it is preferable that the material of the first bump includes solder.
Solder has a relatively low Young's modulus compared to other metals used as bump materials. Furthermore, since the melting point is relatively low, the bump including solder can be welded to the package substrate only by applying heat. That is, since it is not necessary to apply a mechanical load at the time of welding unlike a bump made of a metal other than solder, the bump height after being welded to the package substrate is likely to be higher than that of the bump. Accordingly, the height of the first bump is easily formed, and the stress applied to the first acoustic wave chip is more likely to be reduced compared to the stress applied to the second acoustic wave device. The failure rate is easier to reduce.

On the other hand, the material of the second bump may have a higher thermal conductivity than the material of the first bump.
Since the lithium tantalate substrate is weaker to the thermal load than the lithium niobate substrate, when applied, a part of the lithium tantalate substrate is inferior in resistance to electric power (power resistance) that changes to the thermal load. Therefore, in the elastic wave device to which electric power is applied, when electric power or a thermal load is applied to both the first and second elastic wave chips, the second elastic wave chip is destroyed earlier than the first elastic wave chip. This may cause the acoustic wave device to break down. However, according to this configuration, since the second bump can dissipate more heat than the first bump, the heat load applied to the second elastic wave chip, which is inferior in power resistance, can be increased with the advantage in power resistance. It is easier to reduce than the thermal load applied to the elastic wave chip 1. Accordingly, the failure rate of the acoustic wave device including the package substrate on which both acoustic wave chips are mounted is further reduced.

Furthermore, it is preferable that the material of the second bump includes gold.
Gold has a relatively high thermal conductivity as compared with other metals used as bump materials, and also has high corrosion resistance, which is resistance to corrosion due to oxidation. If the gold is included in the material of the second bump, not only the thermal load applied to the second acoustic wave chip is likely to decrease, but also the corrosion resistance of the joint between the second acoustic wave chip and the second bump is reduced. It can be secured. Therefore, the failure rate of the acoustic wave device including the package substrate on which the acoustic wave chip is mounted is further reduced.

The above-described elastic wave device may be a composite filter device including a transmission-side filter chip, and the transmission-side filter chip may be an elastic wave device that is a first elastic wave chip.

The lithium niobate substrate provided in the first acoustic wave chip is superior in power durability as compared with the lithium tantalate substrate provided in the second acoustic wave chip. According to this configuration, the required transmission-side filter chip having high power durability is the first acoustic wave chip including the lithium niobate substrate having relatively high power durability. By setting it as such an elastic wave apparatus, the elastic wave apparatus concerning this invention can ensure the electric power durability sufficient to function as a composite filter apparatus provided with a transmission side filter chip.

In addition, the above-described elastic wave device may be a composite filter device including a reception-side filter chip, and the reception-side filter chip may be an elastic wave device that is a second elastic wave chip.

The lithium tantalate substrate provided in the second acoustic wave chip is a substrate obtained at a lower cost than the lithium niobate substrate provided in the first acoustic wave chip. Therefore, the second acoustic wave chip is used as the reception filter chip that is not required to have much power durability compared to the transmission filter chip, so that the acoustic wave device according to the present invention can be obtained at lower cost. become.

A high-frequency front end circuit according to an aspect of the present invention includes the elastic wave device described above and an amplifier circuit that amplifies a high-frequency signal.

A communication apparatus according to an aspect of the present invention includes the above-described high-frequency front-end circuit and an RF signal processing circuit that processes a high-frequency signal.

According to the present invention, the stress applied to the acoustic wave chip on the lithium niobate substrate side can be reduced more easily through the bump than the acoustic wave chip on the lithium tantalate substrate side, thereby reducing the failure rate of the acoustic wave device. it can. In addition, a high-frequency front-end circuit using an elastic wave device and a communication device can be obtained.

FIG. 1 is a schematic cross-sectional view showing the structure of the acoustic wave device according to the first embodiment. FIG. 2 is a schematic cross-sectional view showing the structure of the acoustic wave device according to Modification 1 of the first embodiment. FIG. 3A is a diagram illustrating a structure of the acoustic wave device according to the second modification of the first embodiment, and is a plan view illustrating a main part of the acoustic wave device. FIG. 3B is a diagram illustrating the structure of the acoustic wave device according to the second modification of the first embodiment, and is a schematic cross-sectional view taken along the line A1-A1 in FIG. 3A. FIG. 4 is a schematic cross-sectional view showing the structure of an acoustic wave device according to Modification 3 of the first embodiment. FIG. 5 is a circuit diagram of a composite filter device (duplexer) that is an elastic wave device according to the second embodiment. FIG. 6 is a plan view showing a main part of a composite filter device (multiplexer) which is an elastic wave device according to the third embodiment. FIG. 7 is a circuit diagram of a composite filter device (multiplexer) which is an elastic wave device according to the third embodiment. FIG. 8 is a cross-sectional view illustrating a structure of an acoustic wave chip included in a composite filter device (multiplexer) that is an acoustic wave device according to a modification of the third embodiment. FIG. 9 is a circuit diagram of the high-frequency front-end circuit and the communication device according to the embodiment of the present invention.

<Elastic wave device>
[First Embodiment]
FIG. 1 shows an example of a surface acoustic wave device having a CSP (Chip Size Package) structure including a plurality of surface acoustic wave chips, as an example of the surface acoustic wave device according to one aspect of the first embodiment of the present invention. This will be described with reference to FIG.

(1. Basic structure)
FIG. 1 is a schematic cross-sectional view showing the structure of an acoustic wave device 20 according to the first embodiment of the present invention. The elastic wave device 20 includes a package substrate 60, elastic wave chips 210 and 220, and bumps 41 and 42. The elastic wave chip 210 is mounted on the package substrate 60 using the bump 41 and the elastic wave chip 220 is mounted on the package substrate 60 using the bump 42 and is electrically connected thereto. At this time, the bump 41 is bonded to the elastic wave chip 210, and the bump 42 is bonded to the elastic wave chip 220. As the package substrate 60, for example, a ceramic substrate, a resin substrate, a printed substrate, or the like is used. The acoustic wave chip 210 is a lithium niobate substrate (hereinafter referred to as an LN substrate) and is a first substrate 211 of the present invention, and an IDT (Inter Digital Transducer) electrode 212 provided on the chip substrate 211. And. The acoustic wave chip 220 includes a chip substrate 221 that is a lithium tantalate substrate (hereinafter referred to as an LT substrate) and is a second substrate of the present invention, and an IDT electrode 222 provided on the chip substrate 221. ing. The acoustic wave chips 210 and 220 are sealed so as to provide the gaps 213 and 223 by a protective layer 80 formed using, for example, a resin material.

At this time, the material of the bump 41 has a lower Young's modulus than the material of the bump 42. For example, when gold having a Young's modulus of 78 GPa is used as the material of the bump 41, silver having a Young's modulus of 82.7 may be used as the material of the bump. As another example, the material of the bumps 41 and 42 is a combination of gold and copper, silver and copper, solder and copper, solder and silver, etc. It can be lower than the Young's modulus of the material.

According to this configuration, the failure rate of the acoustic wave device 20 is lower than when the bumps 41 and 42 are made of the same material. The reason for this will be described below.

When a thermal load is applied to the acoustic wave device 20 due to, for example, a change in ambient temperature environment, each substrate ( chip substrates 211, 221 and package substrate 60) included in the acoustic wave device expands. Then, stress is generated between the acoustic wave chips 210 and 220 having the chip substrates 211 and 221 and the package substrate 60. The generated stress is applied to the acoustic wave chips 210 and 220 via the bumps 41 and 42 that connect the acoustic wave chips 210 and 220 and the package substrate 60.

On the other hand, the LN substrate constituting the chip substrate 211 is significantly inferior in resistance to cracks (crack resistance) caused by stress compared to the LT substrate constituting the chip substrate 221. Therefore, when stress is applied to both of the acoustic wave chips 210 and 220, the acoustic wave chip 210 including the chip substrate 211 is more likely to crack early. When a crack occurs in the acoustic wave chip 210 mounted on the package substrate 60, an abnormality occurs in a part of the acoustic wave device 20, and the acoustic wave device 20 fails. That is, if the crack resistance of the acoustic wave chip 210 including the LN substrate remains significantly inferior to that of the acoustic wave chip 220 including the LT substrate, the failure rate of the acoustic wave device 20 itself remains high.

Here, when the material of the bump 41 has a Young's modulus lower than that of the material of the bump 42, the bump 41 has a higher degree of freedom of deformation than the bump 42, so that more stress can be relieved. That is, when a stress is generated between the elastic wave chips 210 and 220 and the package substrate 60, the stress applied to the elastic wave chip 210 via the bump 41 is greater than the stress applied to the elastic wave chip 220 via the bump 42. It tends to decrease. Therefore, since the stress applied to the crack-resistant inferior elastic wave chip 210 is likely to be less than the stress applied to the crack-resistant dominant acoustic wave chip 220, the failure rate of the acoustic wave device 20 including both acoustic wave chips is also reduced. .

In addition, the use of bumps made of a material having a low Young's modulus for the elastic wave chip 210 provided with the LN substrate makes it possible to achieve both maintenance of electrical characteristics and control of TCF (Temperature Coefficients of Frequency: frequency temperature characteristics). Suitable for

TCF is the amount of frequency fluctuation caused by the expansion and contraction of the chip substrate due to temperature change. In general, when a bump having a relatively low Young's modulus is used for mounting an elastic wave chip, the expansion and contraction of the chip substrate due to a temperature change before and after the current flows cannot be suppressed, and the TCF increases. In such an elastic wave device having an elastic wave chip with a high TCF, the frequency greatly varies with a temperature change, so that the loss increases.

In order to control the TCF that causes the increase in loss, for example, the chip substrate on which the IDT electrode is provided may be covered with a silicon oxide film. The LN substrate and the LT substrate used for the chip substrate have a negative temperature coefficient that decreases in frequency as the temperature rises, whereas the silicon oxide film has a positive temperature coefficient that increases in frequency as the temperature increases. If the chip substrate is covered with this silicon oxide film, an action to lower the frequency and an action to increase the frequency can occur at the same time. Therefore, even if the chip substrate expands and contracts, the frequency does not vary so much. However, when the silicon oxide film is formed on the LT substrate, the TCF of the acoustic wave chip including the LT substrate can be controlled, but the electrical characteristics of the acoustic wave chip may be greatly deteriorated. Therefore, this control method cannot be used for an acoustic wave chip including an LT substrate.

However, the electrical characteristics of the LN substrate are less likely to deteriorate than the LT substrate. Therefore, even if a material having a low Young's modulus that may increase TCF is used for the bump on the acoustic wave chip side provided with the LN substrate, the electrical characteristics are not greatly deteriorated by forming the silicon oxide film. The TCF can be suppressed. Therefore, the low Young's modulus is not a problem in the bump on the acoustic wave chip side provided with the LN substrate.

It should be noted that LN substrates that are usually used in acoustic wave devices are often cut with a Y-axis rotation angle in the range of −4 ° to 0 ° or + 115 ° to + 135 °. Among these, according to experiments by the inventors, it has been found that an LN substrate cut with a Y-axis rotation angle in the range of + 115 ° to + 135 ° is most susceptible to cracking. Therefore, when the LN substrate used for the chip substrate 211 is an LN substrate with a Y-axis rotation angle of + 115 ° to + 135 °, the effect of the present invention is remarkably obtained.

Further, when the ceramic substrate is used as the package substrate 60, the effect of the present invention is remarkably obtained. Since the ceramic substrate has a higher Young's modulus than other package substrate materials such as a resin substrate, when the ceramic substrate is used as the package substrate 60, more stress is generated than when the resin substrate is used. , 220. In the acoustic wave device 20 using such a ceramic substrate as the package substrate 60, cracks are likely to occur as compared with an acoustic wave device using a resin substrate or the like, so that the configuration of the present invention functions more effectively.

(2. Modification)
Hereinafter, the elastic wave device concerning the modification of this embodiment is each demonstrated. In addition, below, description is abbreviate | omitted about the location provided with the same structure as the said embodiment in each modification, and only the location provided with a different structure is described.

FIG. 2 is a schematic cross-sectional view showing the structure of the acoustic wave device 20 according to Modification 1 of the first embodiment. As shown in this modification, the height of the bump 41 on the elastic wave chip 210 side including the LN substrate is preferably higher than the height of the bump 42 on the elastic wave chip 220 side including the LT substrate.

According to this configuration, the distance between the acoustic wave chip 210 and the package substrate 60 tends to be larger than the distance between the acoustic wave chip 220 and the package substrate 60. The greater the distance between the elastic wave chip and the package substrate, the smaller the influence of the elastic wave chip on the expansion of the package substrate. Therefore, the stress applied to the first elastic wave chip is more likely to decrease than the second elastic wave chip. . Therefore, the failure rate of the acoustic wave device 20 including both acoustic wave chips is further reduced.

3A and 3B are diagrams showing the structure of the acoustic wave device according to the second modification of the first embodiment. FIG. 3A is a plan view showing a main part of the acoustic wave device, and FIG. 3B is a schematic cross-sectional view taken along the line A1-A1 in FIG. 3A. In FIG. 3A, illustration of the protective layer 80 shown in FIG. 3B is omitted.

As shown in FIG. 3A, when the elastic wave device 20 is viewed in plan from the elastic wave chips 210 and 220 side, the area of the bonding surface between the bump 41 and the elastic wave chip 210 is equal to the bump 42 and the elastic wave chip 220. It is preferable that the area is larger than the area of the joint surface. At this time, as shown in FIG. 3B, the diameter of the bump 41 is larger than that of the bump 42.

According to this configuration, the stress applied to the elastic wave chip 210 at the bonding surface between the bump 41 and the elastic wave chip 210 is more widely dispersed than the stress applied to the elastic wave chip 220 at the bonding surface between the bump 42 and the elastic wave chip 220. Is done. Therefore, since the stress applied to the elastic wave chip 210 is more likely to be reduced than that of the elastic wave chip 220, the failure rate of the elastic wave device 20 including the elastic wave chips 210 and 220 is further reduced.

FIG. 4 is a schematic cross-sectional view showing the structure of the acoustic wave device 20 according to Modification 3 of the first embodiment. In the present modification, the height of the bump 41 is higher than that of the bump 42. At the same time, the diameter of the bump 41 is larger than the diameter of the bump 42. That is, when the elastic wave device 20 is viewed in plan, the area of the bonding surface between the bump 41 and the elastic wave chip 210 is larger than the area of the bonding surface between the bump 42 and the elastic wave chip 220.

According to this configuration, the magnitude of stress applied to the elastic wave chip 210 is likely to be smaller than that of the elastic wave chip 210 shown in the first and second modifications. Therefore, the failure rate of the acoustic wave device 20 is greatly reduced.

In the elastic wave device according to the present embodiment as shown in FIGS. 1 to 4 and the elastic wave device according to the modification of the present embodiment, the material of the bump 42 is more preferably the material of the bump 41. It is better to have a higher thermal conductivity.

The LT substrate that constitutes the chip substrate 221 is weaker to the thermal load than the LN substrate that constitutes the chip substrate 211. Therefore, the resistance to electric power that partially changes to the thermal load when applied (power resistance) Also inferior. Therefore, in the elastic wave device to which electric power is applied, when electric power or a thermal load is applied to both of the elastic wave chips 210 and 220, the elastic wave chip 220 is broken earlier than the elastic wave chip 210, causing the elastic wave device 20 to fail. There is a fear. However, according to this configuration, since the bump 42 can dissipate more heat than the bump 41, the heat load applied to the inferior elastic wave chip 220 with power durability is the heat applied to the elastic wave chip 210 with superior power durability. It can be reduced from the load. Therefore, the failure rate of the acoustic wave device 20 including the package substrate 60 on which both acoustic wave chips are mounted is further reduced.

When the material of the bump 41 has a lower Young's modulus than the material of the bump 42 and the material of the bump 42 has a higher thermal conductivity than the material of the bump 41, a combination of the materials of the bumps 41 and 42 is, for example, gold and Examples include silver, gold and copper, solder and copper, and solder and silver. Of these, the most preferable is the case where the material of the bump 41 is made of solder and the material of the bump 42 is made of gold.

First, compare the Young's modulus of both materials. The Young's modulus of the solder is about 30 to 50 GPa, although it varies depending on the composition, and the Young's modulus of gold is 79 GPa. Thus, since the Young's modulus of the bump 41 on the elastic wave chip 210 side is lower than the Young's modulus of the bump 42 on the elastic wave chip 220 side, the stress applied to the elastic wave chip 210 is changed to the stress applied to the elastic wave chip 220. Easy to decrease.

Next, compare the thermal conductivity of both materials. The thermal conductivity of the solder is approximately 45 to 65 W / m · K, although it varies depending on the composition, and the thermal conductivity of gold is approximately 315 W / m · K. As described above, the thermal conductivity of the bumps 42 on the elastic wave chip 220 side is higher than the thermal conductivity of the bumps 41 on the elastic wave chip 210 side. It is easier to reduce than the heat load applied to the.

Furthermore, since solder has a relatively low melting point compared to other metals such as gold, solder bumps can be welded to the package substrate only by applying heat. That is, since it is not necessary to apply a mechanical load at the time of welding unlike a bump made of a metal other than solder, the bump height after being welded to the package substrate is likely to be higher than that of the bump. Therefore, when the material of the bump 41 is solder, the height of the bump 41 is likely to be formed higher, and the influence of the elastic wave chip from the expansion of the package substrate 60 tends to be small. Therefore, the stress applied to the elastic wave chip 210 can be easily reduced, and the failure rate of the elastic wave device 20 can be further reduced.

Also, gold has higher corrosion resistance than other metals such as solder. If the elastic wave chip 220 is mounted using the gold bump, the corrosion resistance of the joint between the elastic wave chip 220 and the bump 42 can be ensured. Then, the acoustic wave device including the package substrate 60 on which the acoustic wave chip 220 is mounted is further less likely to fail.

In the above description, the bump 41 is made of solder and the bump 42 is made of gold. However, the bump 41 is made of a material containing solder and other conductive material, and the bump 42 is made of gold and other conductive material. The above-mentioned effect can be sufficiently obtained even when it is made of a material containing. In addition, even when the material of at least one of the bumps 41 and 42 is solder or gold, the effect of the present invention can be sufficiently obtained. That is, the material of the bump 41 may include solder, and the material of the bump 42 may be a material having a higher Young's modulus than the solder among materials other than gold. In addition, the material of the bump 41 may be a material having a Young's modulus lower than that of the material other than the solder, and the material of the bump 42 may include gold.

[Second Embodiment]
Next, for a surface acoustic wave device according to a second embodiment of the present invention, referring to FIG. 5 as an example of a composite filter device configured using a surface acoustic wave device including two surface acoustic wave chips. I will explain. The elastic wave device according to the present embodiment is an embodiment when the elastic wave device 20 according to the first embodiment is a composite filter device that functions as a duplexer having a transmission / reception separation function. Therefore, hereinafter, the acoustic wave device according to the present embodiment is referred to as a composite filter device.

FIG. 5 is a circuit diagram of the composite filter device 20 according to the second embodiment of the present invention. The acoustic wave device 20 includes a transmission filter 21 and a reception filter 22. One end of the transmission filter 21 is connected to the transmission input / output terminal 25, and the other end is connected to the antenna input / output terminal 29. One end of the reception filter 22 is connected to the reception input / output terminal 26, and the other end is connected to the antenna input / output terminal 29.

As shown in the figure, the transmission filter 21 preferably has the acoustic wave chip 210 shown in the first embodiment as a transmission filter chip. That is, the transmission filter 21 may include a chip substrate 211 that is an LN substrate.

In a communication device or the like having a filter function, the transmission-side filter processes a transmission signal amplified by a power amplifier or the like. Therefore, it is required to be able to withstand a large amount of power as compared with a reception-side filter that processes a weak reception signal input from the outside of the communication apparatus. Therefore, if the acoustic wave chip 210 provided with the LN substrate having higher power resistance than the LT substrate is used as the transmission-side filter chip, the composite filter device 20 uses a transmission-side filter that secures sufficient power resistance. Can be provided.

In addition, in the composite filter device 20, the reception-side filter 22 may include the acoustic wave chip 220 shown in the first embodiment as a reception-side filter chip. That is, it is preferable that the reception-side filter 22 includes a chip substrate 221 that is an LT substrate.

The LT substrate can be obtained at a lower cost than the LN substrate. Therefore, the composite filter device 20 can be obtained at a lower cost by using the acoustic wave chip 220 including the LN substrate as the reception-side filter chip that does not require so high power durability as compared with the transmission-side filter.

In the present embodiment, the acoustic wave chip 210 having an LN substrate on the transmission side filter chip and the acoustic wave chip 220 having an LT substrate on the reception side filter chip are used. However, the acoustic wave chip 220 and the reception side are used as the transmission side filter chip. An elastic wave chip 210 may be used as the side filter chip. Also in this case, the effect of the present invention that the failure rate of the composite filter device 20 is reduced can be obtained.

[Third Embodiment]
With reference to FIGS. 6 and 7, an example of a composite filter device configured by using a surface acoustic wave device including three or more surface acoustic wave chips for a surface acoustic wave device according to a third embodiment of the present invention will be described. To explain. The elastic wave device in the present embodiment is a composite filter device that functions as a multiplexer having a function of separating a plurality of electrical signals. Therefore, hereinafter, the acoustic wave device according to the present embodiment is referred to as a composite filter device.

(1. Basic structure)
FIG. 6 is a plan view of the main part of the composite filter device 30 according to the present embodiment viewed in plan. The composite filter device 30 includes a package substrate 70, elastic wave chips 310, 320, 330, and 340, and bumps 51, 52, 53, and 54. The elastic wave chip 310 is mounted on the package substrate 70 using the bumps 51, and the elastic wave chip 320 is mounted on the package substrate 70 using the bumps 52, and is electrically connected. The elastic wave chip 330 is mounted on the package substrate 60 using the bumps 53, and the elastic wave chip 340 is mounted on the package substrate 60 using the bumps 54. That is, the bump 51 is bonded to the elastic wave chip 310, the bump 52 is bonded to the elastic wave chip 320, the bump 53 is bonded to the elastic wave chip 330, and the bump 54 is bonded to the elastic wave chip 340. As the package substrate 70, for example, a ceramic substrate, a resin substrate, a printed substrate, or the like is used. The acoustic wave chips 310, 320, 330, and 340 are all sealed with a protective layer formed using, for example, a resin material, but the illustration of the protective layer is omitted in this drawing.

The acoustic wave chip 310 is provided with a chip substrate 311 which is an LN substrate and is the first substrate of the present invention, like the acoustic wave chip 210 shown in the first embodiment. The acoustic wave chip 320 includes a chip substrate 321 that is an LT substrate and is the second substrate of the present invention, like the acoustic wave chip 220 shown in the first embodiment. Each of the chip substrates 311 and 321 is provided with an IDT electrode (not shown).

Like these acoustic wave chips 310 and 320, the acoustic wave chips 330 and 340 also include an acoustic wave chip including chip substrates 331 and 341 and IDT electrodes (not shown) formed on the chip substrates 331 and 341, respectively. It is. The chip substrate 331 is an LN substrate such as the chip substrate 311, and the chip substrate 341 is an LT substrate such as the chip substrate 321.

At this time, the material of the bumps 51 and 53 has a lower Young's modulus than the material of the bumps 52 and 54. According to this configuration, the bumps 51 and 53 on the acoustic wave chip 310 and 330 side including the inferior LN substrate with crack resistance are the bumps 52 and 54 on the acoustic wave chip 320 and 340 side including the LT substrate superior in crack resistance. More stress can be relieved. As a result, the stress applied to the elastic wave chips 310 and 330 is more likely to be smaller than the stress applied to the elastic wave chips 320 and 340, so that the bumps 51 to 54 are all made of a material having the same Young's modulus. A composite filter device 30 with a low failure rate can be obtained.

Note that the bump 51 and the bump 53 need not be made of the same material. The bumps 51 and 53 on the acoustic wave chips 310 and 330 provided with the LN substrate are each single, and it is sufficient that the Young's modulus is lower than the bumps 52 and 54 on the acoustic wave chips 320 and 340 provided with the LT substrate. For example, when the bumps 52 and 54 are copper bumps having a Young's modulus of 110 to 128 GPa, the bump 51 may be a gold bump having a Young's modulus of 78 GPa, and the bump 53 may be a silver bump having a Young's modulus of 82.7 GPa. Similarly, the bumps 52 and 54 may not be made of the same material. For example, even if the bump 52 is a copper bump, the bump 54 is a silver bump, and the bumps 51 and 53 are gold bumps, the effects of the present invention can be obtained.

In addition, it is preferable that the material of the bumps 52 and 54 has a higher thermal conductivity than the material of the bumps 51 and 53. According to this structure, the bumps 52 and 54 on the elastic wave chip 320 and 340 side including the inferior LT substrate with power durability are the bumps 51 and 54 on the elastic wave chip 310 and 330 side including the LN substrate with superior power durability. More heat than 53 can be dissipated. Accordingly, the thermal load applied to the acoustic wave chips 520 and 540 having relatively low power durability is more easily reduced than the thermal load applied to the elastic wave chips 510 and 520 having relatively high power durability. The failure rate of the composite filter device 30 including the wave chip is also reduced.

If a combination of materials such as gold and silver, gold and copper, solder and copper, solder and silver is used for the bumps 51 and 53 and the bumps 52 and 54, the bumps 51 and 53 have a lower Young's modulus than the bumps 52 and 54. In addition, the bumps 52 and 54 have higher thermal conductivity than the bumps 51 and 53. However, it is most preferable that the material of the bumps 51 and 53 is made of solder and the bumps 52 and 54 are made of gold. Comparing solder and gold, it is solder that has a low Young's modulus, while gold has a high thermal conductivity. Furthermore, as described in the first embodiment, the bump made of solder has an advantage that the stress applied to the elastic wave chip can be more easily reduced because the bump is made of a high height. Has the advantage of high corrosion resistance. Therefore, when the bumps 51 to 54 are formed using these materials, the failure rate of the composite filter device 30 is further reduced.

It should be noted that the above effect can be sufficiently obtained when the bumps 51 and 53 are made of a material containing solder and other conductive material and the bumps 52 and 54 are made of a material containing gold and other conductive material. This is as described in the first embodiment. In addition, when the material of at least one of the bumps 51 and 53 includes solder, or when the material of at least one of the bumps 52 and 54 includes gold, the effect of the present invention is sufficiently obtained. It is done.

In this figure, the areas of the joint surfaces of the bumps 51, 52, 53, 54 and the acoustic wave chips 310, 320, 330, 340 are all the same. However, as in the first embodiment, the bonding surface between the elastic wave chips 310 and 330 including the LN substrate and the bumps 51 and 53 is the bonding surface between the elastic wave chips 320 and 340 including the LT substrate and the bumps 52 and 54. If it is larger, the failure rate of the composite filter device 30 can be further reduced. Further, the failure rate of the composite filter device 30 is further reduced by making the height of the bumps 51 and 53 on the elastic wave chips 310 and 330 side higher than the height of the bumps 52 and 54 on the elastic wave chips 320 and 340 side. it can.

FIG. 7 is a circuit diagram of the composite filter device 30. The composite filter device 30 includes transmission side filters 31 and 33 and reception side filters 32 and 34. One ends of the transmission side filters 31 and 33 are connected to the transmission side input / output terminals 35 and 37, and the other end is connected to the antenna input / output terminal 39. One ends of the reception side filters 32 and 34 are connected to the reception side input / output terminals 36 and 38, and the other end is connected to the antenna input / output terminal 39.

The transmission-side filter 31 and the reception-side filter 32 are filters that selectively pass high-frequency signals in the Band A communication band, for example. Moreover, the transmission side filter 33 and the reception side filter 34 are filters that selectively pass a high-frequency signal in the BandB communication band, for example.

At this time, the transmission side filter 31 corresponding to Band A may have the elastic wave chip 310 as a transmission side filter chip. Further, the transmission filter 33 corresponding to BandB may include the elastic wave chip 330 as a transmission filter chip. That is, it is preferable that the transmission- side filters 31 and 33 include chip substrates 311 and 331 that are LN substrates and bumps 51 and 53 having a relatively low Young's modulus.

A composite filter including a transmission-side filter that secures required power durability by providing a transmission-side filter chip that is required to have higher power resistance than a reception-side filter chip and having an LN substrate that is relatively superior in power resistance. A device 30 can be obtained.

On the other hand, the reception side filter 32 corresponding to Band A may have the elastic wave chip 320 as a reception side filter chip. Further, the reception-side filter 34 corresponding to BandB may include the elastic wave chip 340 as a reception-side filter chip. That is, it is preferable that the reception- side filters 32 and 34 include chip substrates 321 and 341 that are LT substrates and bumps 52 and 54 having relatively high Young's modulus.

As described above, in the composite filter device including the reception filter chip, the composite filter device 30 is obtained by using the elastic wave chip including the LN substrate for the reception filter chip that is not required to have much power durability. The cost can be reduced.

It should be noted that one of the acoustic wave chips 310 and 330 functioning as the transmission-side filter chip may be provided with an LT substrate. In a composite filter device including a plurality of transmission-side filter chips, at least one of the plurality of transmission-side filter chips includes an elastic wave chip having an LN substrate and is mounted by a bump having a relatively low Young's modulus. If so, the effects of the present invention can be obtained.

In the present embodiment, the multiplexer including the transmission side filter and the reception side filter is shown as the composite filter device. However, the composite filter device according to the embodiment of the present invention is not limited to this. That is, even if the filters constituting the multiplexer are multiplexers that are all transmission-side filters, multiplexers that are all reception-side filters, or multiplexers that include filters that selectively pass electric signals that do not distinguish between transmission and reception Good. However, more preferably, it is a multiplexer having at least one transmission side filter. This is because the power durability of the acoustic wave chip including the LN substrate in the present invention is more effective when used as a filter chip constituting the transmission filter.

(2. Modification)
A composite filter device according to a modification of the present embodiment will be described by taking, as an example, a multiplexer having an acoustic wave chip including a chip substrate other than an LN substrate and an LT substrate. The composite filter device 30 according to the modification of the third embodiment is the same as the composite filter device 30 according to the already described third embodiment, except for the differences regarding the acoustic wave chip. Therefore, only different points will be described below.

In the composite filter device 30 according to this modification, the chip substrate 331 included in the acoustic wave chip 330 is a laminate including a plurality of films including a piezoelectric thin film and a support substrate. The structure of the chip substrate 331 and the relationship between the chip substrate 331 and the IDT electrode will be described below with reference to FIG.

FIG. 8 is a schematic cross-sectional view showing the structure of the acoustic wave chip 330. The acoustic wave chip 330 includes a chip substrate 331 and an IDT electrode 332 formed on the chip substrate 331. The chip substrate 331 includes a high sound speed support substrate 333, a low sound speed film 335 directly or indirectly stacked on the high sound speed support substrate 333, and a piezoelectric film 337 stacked on the low sound speed film 335. An IDT electrode 332 is formed on the piezoelectric film 337. The high sound velocity support substrate shown here refers to a support substrate in which the propagating bulk wave sound velocity is higher than the elastic wave propagating through the piezoelectric film 337. In the chip substrate 331, the high sound velocity support substrate 333 is a substrate made of silicon. Further, the low sound velocity film refers to a film made of a material having a propagating bulk wave sound velocity slower than an elastic wave propagating through the piezoelectric film 337. As such a material, for example, silicon oxide, glass, silicon oxynitride, tantalum oxide, a compound obtained by adding fluorine, carbon, or boron to silicon oxide can be used. In addition, the piezoelectric film 337 is made of, for example, a piezoelectric single crystal such as lithium tantalate or lithium niobate, or piezoelectric ceramics.

The material of the bump 53 to be bonded to the elastic wave chip 330 is not particularly limited. Like the elastic wave device 20 according to the first embodiment, various materials such as silver and copper can be used in addition to solder and gold. Can be used. That is, any material can be used as long as it is a material that can electrically connect the acoustic wave chip 530 and the package substrate 70.

Note that the composite filter device 30 according to the present modification includes the elastic wave chip 310 including the LN substrate, the elastic wave chip 320 including the LT substrate, and the elastic wave chip 330 including the laminate as described above. However, the present invention is not limited to the composite filter device 30 mixedly mounted on the same package substrate. For example, the acoustic wave chips 330 and 340 may include, as the chip substrates 331 and 341, substrates having piezoelectricity over the entire substrate, such as a quartz substrate and a sapphire substrate. Alternatively, as the chip substrate 341 included in the acoustic wave chip 340, a laminated body such as a piezoelectric thin film, a film having a sound velocity different from that of the piezoelectric thin film, and a supporting substrate can be used. As described above, as long as the chip substrates 331 and 341 included in the acoustic wave chips 330 and 340 are substrates having piezoelectricity at least in part, a substrate including any material can be used.

The elastic wave device and the composite filter device according to the embodiment of the present invention are not limited to the CSP structure elastic wave device shown in the present embodiment. For example, a module-structured acoustic wave device including a plurality of WLP (Wafer Level Package) surface acoustic wave chips on the same module package substrate can also be an elastic wave device according to the present invention. . Further, the number of mounted acoustic wave chips may be two or more, and is not limited to a specific number. Furthermore, as an elastic wave chip, a chip using any elastic wave such as an elastic boundary wave or a bulk wave can be used.

〔Production method〕
Hereinafter, a method of manufacturing an acoustic wave device or a composite filter device according to an embodiment of the present invention will be described.

A method for manufacturing an acoustic wave device (composite filter device) includes a step of forming an acoustic wave chip, a step of mounting the acoustic wave chip on a package substrate, and a step of sealing the mounted acoustic wave chip.

The step of forming the acoustic wave chip includes a step of forming a thin film on a wafer that is a material of the chip substrate, and a step of forming a circuit pattern such as an IDT electrode using the thin film. In the step of forming a thin film, a thin film such as a silicon oxide film or an aluminum film, which is a material for a circuit pattern such as an IDT electrode, is formed using a sputtering method, a vapor deposition method, an electrolytic plating method, or the like. In the step of forming the circuit pattern, the circuit pattern is formed through an exposure technique using a resist. By these steps, an acoustic wave chip including a chip substrate and an IDT electrode can be formed.

The process of mounting the acoustic wave chip includes various methods such as a conductive paste bonding method for mounting using a conductive paste together with bumps, a pressure welding method for applying heat load and load load to the bumps, and an ultrasonic bonding method. The flip chip mounting method can be used. At this time, when the bump used for mounting is a bump made of solder, it is preferable to use the reflow bonding method among the flip chip mounting methods. In this construction method, solder is applied to the bump forming portion at room temperature to form a bump made of solder, and then the bump is heated and cooled to perform mounting. In other words, mounting is possible only by applying heat without applying a mechanical load. Therefore, the bumps are easily formed higher than when using other mounting methods. Therefore, by using the reflow bonding method for the bumps made of solder, the stress applied to the elastic wave chip mounted using the bumps can be further reduced, and the elastic wave device (composite filter device) having a further reduced failure rate. ).

In this step, either the acoustic wave chip including the LN substrate or the acoustic wave chip including the LT substrate may be mounted on the package substrate first. However, in addition to these two types of acoustic wave chips, in a method for manufacturing a composite filter device having an acoustic wave chip including a substrate made of a laminate as shown in FIG. It is preferable to mount the wave chip last. That is, in the composite filter device 30 according to the modification of the third embodiment, after mounting the acoustic wave chips 310, 320, and 340 including the LN substrate or the LT substrate, the chip substrate 331 made of a stacked body. It is preferable to mount an acoustic wave chip 330 including

The LN substrate and the LT substrate included in the acoustic wave chips 310, 320, and 340 are inferior in crack resistance compared to the silicon substrate included in the acoustic wave chip 330 as a part of the chip substrate 311. Therefore, the acoustic wave chips 310, 320, and 340 are more likely to crack due to stress generated during mounting than the acoustic wave chip 330. That is, in the process of mounting the acoustic wave chip, there is a case where cracks are generated in any one of the acoustic wave chips 310, 320, and 330 inferior in crack resistance without being cracked in the elastic wave chip 330 superior in crack resistance. is there. At this time, if the acoustic wave chip 330 is first mounted, it is necessary to discard the composite filter device 30 as a defective product, including the acoustic wave chip 330 in which no crack is generated.

On the other hand, the elastic wave chip 330 includes a laminated body in which a plurality of films are stacked on a support substrate as the chip substrate 331. Compared with the manufacturing cost. When the relatively expensive elastic wave chip 330 is discarded as described above, the disposal loss increases. However, if the acoustic wave chips 310, 320, and 340 are mounted before the acoustic wave chip 330 is mounted, cracks due to stress at the time of mounting occur in the acoustic wave chips 310, 320, and 340, and the composite filter device 30 is Even when it is necessary to discard the elastic wave chip 330 before mounting, it is not necessary to discard it. That is, if such a manufacturing method is used, since the frequency of discarding relatively expensive elastic wave chips is reduced, the loss of disposal can be reduced.

The step of sealing the mounted acoustic wave chip is performed using a protective layer formed of a resin material or the like. At this time, a gap is formed between the acoustic wave chip and the package substrate so as to enable excitation of the IDT electrode provided on the acoustic wave chip and sealed.

<< High-frequency front-end circuit, communication device >>
A high-frequency front-end circuit and a communication device according to an embodiment of the present invention will be described with reference to FIG. As an example, a high frequency front-end circuit including the composite filter device according to the second embodiment and the composite filter device according to the third embodiment, and a communication device including the high-frequency front end circuit will be described. .

FIG. 9 is a circuit diagram of the high frequency front end circuit 10 including the composite filter device 20 and the composite filter device 30, and the communication device 1 including the high frequency front end circuit 10. As shown in FIG. 1, the communication device 1 includes a high frequency front end circuit 10, an RF signal processing circuit (RFIC) 3, and a baseband processing circuit (BBIC) 4. The high frequency front end circuit 10 is a circuit that transmits a high frequency signal transmitted and received by the antenna element 2. At this time, the RF signal processing circuit 3 performs signal processing on the high frequency signals input and output from the baseband signal processing circuit 4 and the high frequency front end circuit 10. The baseband signal processing circuit 4 performs signal processing so that the high-frequency signal can be used as, for example, an image signal or an audio signal.

The high-frequency front-end circuit 10 includes a composite filter device 20, a composite filter device 30, and amplifier circuits 11 to 16. The high-frequency front end circuit 10 is connected to the antenna element 2 via the switch unit 19. Among the amplifier circuits 11 to 16, the amplifier circuits 11, 13, and 14 amplify the high frequency transmission signal output from the RF signal processing circuit 3, and the antenna element 2 through the composite filter device 20 or the composite filter device 30. Is a transmission amplifier circuit that outputs to On the other hand, among the amplifier circuits 11 to 16, 12, 15, and 16 amplify a high frequency signal that has passed through the antenna element 2 and the composite filter device 20 or the composite filter device 30 and output the amplified signal to the RF signal processing circuit 3. A receiving amplifier circuit.

The composite filter device 20 is the composite filter device 20 according to the second embodiment, and includes a transmission side filter 21 and a reception side filter 22. The transmission side input / output terminal 25 and the reception side input / output terminal 26 function as terminals for inputting / outputting high frequency signals to / from the amplifier circuits 11, 12.

The composite filter device 30 is the composite filter device 30 according to the third embodiment, and includes transmission side filters 31 and 33 and reception side filters 32 and 34. The transmission-side filter 31 and the reception-side filter 32 are filters that selectively pass a high-frequency signal in the Band A communication band, for example. Moreover, the transmission side filter 33 and the reception side filter 34 are filters that selectively pass a high-frequency signal in the BandB communication band, for example. The transmission-side input / output terminals 35 and 37 function as via points for the high-frequency transmission signals output from the amplifier circuits 13 and 14, and the reception-side input / output terminals 36 and 38 via the high-frequency signals input to the amplification circuits 15 and 16. Acts as a point.

At this time, the filters 21 and 22 in the composite filter device 20 are, for example, the BandC communication band having a frequency band different from the high-frequency signal of the BandA and B communication bands that the filters 31 to 34 selectively pass. It is a filter which selectively passes the high frequency signal.

The switch unit 19 switches the connection between the antenna side terminal 9 and the antenna input / output terminal 29 in the composite filter device 20 and the connection between the antenna side terminal 9 and the antenna input / output terminal 39 in the composite filter device 30. Thereby, the communication apparatus 1 can function as a multiband-compatible communication apparatus that can process high-frequency signals of a plurality of bands having different frequency bands as communication bands.

Note that the configuration of the high-frequency front-end circuit and the configuration of the communication device according to the embodiment of the present invention are not limited to the configurations described above. The high-frequency front end circuit 10 only needs to include at least one composite filter device according to the present invention represented by the composite filter devices 20 and 30 and at least one amplifier circuit. Moreover, the communication apparatus 1 should just be equipped with the high frequency front end circuit concerning this invention represented by the high frequency front end circuit 10, and RF signal processing circuit.

20 elastic wave device, 41, 42 bump, 60 package substrate, 210, 220 elastic wave chip, 211, 221 chip substrate.

Claims (10)

1. A package substrate;
   A first acoustic wave chip mounted on the package substrate and having a first substrate that is a lithium niobate substrate;
   A second acoustic wave chip mounted on the package substrate and having a second substrate that is a lithium tantalate substrate;
   A first bump for electrically connecting the first acoustic wave chip and the package substrate;
   An elastic wave device comprising: a second bump for electrically connecting the second elastic wave chip and the package substrate;
   The first bump is joined to the first acoustic wave chip, the second bump is joined to the second acoustic wave chip,
   The material of the first bump has a lower Young's modulus than the material of the second bump.
   Elastic wave device.
2. 2. The elastic wave device according to claim 1, wherein a height of the first bump is higher than a height of the second bump.
3. When the acoustic wave device is viewed in plan from the first and second acoustic wave chips, the area of the joint surface between the first bump and the first acoustic wave chip is as follows. The elastic wave device according to claim 1, wherein the elastic wave device is larger than an area of a joint surface with the second elastic wave chip.
4. 4. The acoustic wave device according to claim 1, wherein the material of the first bump includes solder.
5. 5. The elastic wave device according to claim 1, wherein the material of the second bump has a higher thermal conductivity than the material of the first bump.
6. The elastic wave device according to any one of claims 1 to 5, wherein a material of the second bump includes gold.
7. The acoustic wave device is a composite filter device including a transmission filter chip,
   The acoustic wave device according to any one of claims 1 to 6, wherein the transmission-side filter chip is the first acoustic wave chip.
8. The acoustic wave device is a composite filter device including a reception side filter chip,
   The acoustic wave device according to any one of claims 1 to 7, wherein the reception-side filter chip is the second acoustic wave chip.
9. The elastic wave device according to any one of claims 1 to 8,
   A high-frequency front-end circuit comprising: an amplifier circuit that amplifies a high-frequency signal.
10. A high-frequency front-end circuit according to claim 9,
    An RF signal processing circuit that processes a high-frequency signal.

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