JP7711966B2 - Acoustic wave device and method for manufacturing same - Google Patents

Description

This disclosure relates to an acoustic wave device and a manufacturing method thereof. More specifically, it relates to a surface acoustic wave device using SH waves and an FBAR using BAW, for example, a duplexer or multiplexer.

In high-frequency communication systems for mobile communication terminals, such as smartphones, high-frequency filters are used to remove unnecessary signals outside the frequency band used for communication.

High frequency filters and the like use acoustic wave devices that have surface acoustic wave (SAW) elements. A SAW element is an element in which an IDT (Interdigital Transducer) with a pair of comb-shaped electrodes is formed on a piezoelectric substrate.

For example, a surface acoustic wave device is manufactured as follows. First, a multilayer film substrate is created by bonding a piezoelectric substrate that propagates acoustic waves to a support substrate that has a smaller thermal expansion coefficient than the piezoelectric substrate. Next, multiple IDT electrodes are formed on the multilayer film substrate using photolithography technology, and then the substrate is cut to a specified size by dicing to create a surface acoustic wave device. In this manufacturing method, by using a multilayer film substrate, changes in size of the piezoelectric substrate when the temperature changes are suppressed by the support substrate, stabilizing the frequency characteristics of the acoustic wave device.

Patent document 1 discloses an example of technology related to acoustic wave devices.

Patent Publication No. 2019-54354

The main problem that this disclosure aims to solve is explained below.

In acoustic wave devices such as bandpass filters and duplexers, device chips such as SAW filters are flip-chip bonded to wiring substrates.

A hollow region is formed in which the resonators that make up the SAW filter can mechanically vibrate, and is then sealed with synthetic resin, metal, or the like. To prevent the sealing portion from peeling off from the wiring board, it is desirable for there to be strong adhesion between the sealing portion and the wiring board. It is also desirable for there to be strong adhesion between the sealing portion and the wiring board to prevent moisture from penetrating into the sealed hollow region.

In addition, the metal pattern through which electrical signals in the desired frequency band pass can be subject to interference from external electromagnetic waves. Therefore, a structure with a high shielding effect is desirable.

In addition, there is a demand for acoustic wave devices to be made smaller. If the pads on the wiring board are surrounded by a metal pattern to improve the shielding effect, the wiring board will end up becoming larger. Furthermore, if there are too many metal patterns on the outer periphery of the wiring board, the adhesion between the sealing part and the wiring board will decrease, which may lead to peeling between the wiring board and the sealing part.

The present disclosure has been made in consideration of the above problems, and aims to provide an acoustic wave device that is small, has a stronger shielding effect for signal lines and a stronger ground electrode, and has excellent adhesion between the sealing portion and the wiring board.

The acoustic wave device according to the present disclosure comprises:
A wiring board having a mounting surface;
a ground electrode, an antenna pad, a transmission pad, a reception pad, an antenna metal ring surrounding the antenna pad, a transmission metal ring surrounding the transmission pad, and a reception metal ring surrounding the reception pad, which are formed on the mounting surface;
a device chip mounted on the wiring substrate;
the antenna metal ring, the transmitting metal ring, and the receiving metal ring are connected to the ground electrode,
The acoustic wave device is such that the average distance from the outer periphery of the wiring board to the ground electrode is longer than the average distance from the outer periphery of the wiring board to the antenna metal ring, the transmitting metal ring, and the receiving metal ring.

In one aspect of the present disclosure, the mounting surface includes an inductor pad and an inductor metal ring surrounding the inductor pad.

a sealing portion that seals the device chip together with the wiring substrate,
In one aspect of the present disclosure, the sealing portion is joined to an insulating region between the antenna pad and the antenna metal ring.

a sealing portion that seals the device chip together with the wiring substrate,
In one embodiment of the present disclosure, the sealing portion is bonded to an insulating region between the transmitting pad and the transmitting metal ring, and to an insulating region between the receiving pad and the receiving metal ring.

It is one aspect of the present invention that the shortest distance from the outer edge of the wiring board to the transmitting metal ring is shorter than the shortest distance from the outer edge of the corner of the wiring board to the transmitting metal ring.

It is one aspect of the present invention that the shortest distance from the outer edge of the wiring board to the receiving metal ring is shorter than the shortest distance from the outer edge of the corner of the wiring board to the receiving metal ring.

In one aspect of the present invention, the thickness of the antenna metal ring is 10 μm to 35 μm.

In one embodiment of the present invention, the thickness of the transmitting metal ring and the receiving metal ring is 10 μm to 35 μm.

In one aspect of the present invention, the device chip includes a piezoelectric substrate made of lithium tantalate, lithium niobate, or quartz crystal.

In one aspect of the present invention, the device chip is made of sapphire, silicon, alumina, spinel, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, or glass.

A module including the above-described acoustic wave device is one aspect of the present invention.

The present disclosure provides an acoustic wave device with excellent characteristics, including better heat dissipation, excellent adhesion between the sealing portion and the wiring substrate, and reduced coupling between a metal pattern through which an electrical signal of a desired frequency band passes and a metal pattern through which an electrical signal of the desired frequency band does not pass.

FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to a first embodiment. FIG. 2 is a schematic diagram of a mounting surface of a wiring board 3 of the acoustic wave device 1 according to the first embodiment. FIG. 3 is a diagram illustrating an example of an acoustic wave element 50 of the acoustic wave device according to the first embodiment. FIG. 4 is a vertical cross-sectional view of a module to which the acoustic wave device 1 according to the first embodiment is applied.

The embodiment will be described with reference to the attached drawings. In each drawing, the same or corresponding parts are given the same reference numerals. Duplicate explanations of the parts will be appropriately simplified or omitted.

Embodiment 1.
FIG. 1 is a cross-sectional view of an acoustic wave device 1 according to a first embodiment.

As shown in FIG. 1, the acoustic wave device 1 includes a wiring substrate 3, an external connection terminal 31, a device chip 5, bumps 15, and a sealing portion 17.

For example, the wiring board 3 is a multi-layer board made of resin. For example, the wiring board 3 is a low temperature co-fired ceramics (LTCC) multi-layer board made of multiple dielectric layers.

Multiple external connection terminals 31 are formed on the main surface opposite the mounting surface of the wiring board 3.

On the mounting surface of the wiring board 3, a ground electrode 20, a transmitting pad 22, a receiving pad 23, a transmitting metal ring 25 surrounding the transmitting pad 22, and a receiving metal ring 26 surrounding the receiving pad 23 are formed.

The bumps 15 are formed on the upper surface of each of the electrode pads 9. For example, the bumps 15 are gold bumps. For example, the height of the bumps 15 is 10 μm to 50 μm.

A gap 16 is formed between the wiring substrate 3 and the device chip 5.

The device chip 5 is mounted on the wiring substrate 3 by flip-chip bonding via the bumps 15. The device chip 5 is electrically connected to multiple pads via multiple bumps 15.

The device chip 5 is a substrate on which the acoustic wave elements 50 are formed. For example, a transmission filter and a reception filter including a plurality of acoustic wave elements 50 are formed on the main surface of the device chip 5.

The transmit filter is formed so that electrical signals in the desired frequency band can pass through. For example, the transmit filter is a ladder-type filter consisting of multiple series resonators and multiple parallel resonators.

The receiving filter is formed so that electrical signals in the desired frequency band can pass through. For example, the receiving filter is a ladder filter.

The device chip 5 includes a piezoelectric substrate 11 and a support substrate 13. The piezoelectric substrate 11 is, for example, a substrate formed of a piezoelectric single crystal such as lithium tantalate, lithium niobate, or quartz. In another example, the piezoelectric substrate 11 is a substrate formed of a piezoelectric ceramic.

The thickness of the piezoelectric substrate 11 can be, for example, 0.3 μm to 5 μm.

The support substrate 13 can be made of, for example, sapphire, silicon, alumina, spinel, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, glass, etc. The smaller the thermal expansion coefficient of the support substrate 13, the better. This is because the temperature characteristics of the acoustic wave device 1 are improved.

The thickness of the support substrate 13 can be, for example, 50 μm to 200 μm.

The sealing portion 17 is formed to cover the device chip 5. The device chip 5 is hermetically sealed by the wiring substrate 3 and the sealing portion 17. For example, the sealing portion 17 is formed of an insulating material such as a synthetic resin. For example, the sealing portion 17 is formed of a metal.

When the sealing portion 17 is formed of a synthetic resin, the synthetic resin is an epoxy resin, a polyimide, or the like. Preferably, the sealing portion 17 is formed of an epoxy resin using a low-temperature curing process.

As shown in FIG. 1, the sealing portion 17 is bonded to the insulating region 17Tx between the transmitting pad 22 and the transmitting metal ring 25. The sealing portion 17 is also bonded to the insulating region 17Rx between the receiving pad 23 and the receiving metal ring 26. This improves the adhesion between the wiring board 3 and the sealing portion 17.

Figure 2 is a schematic diagram of the mounting surface of the wiring board 3 of the acoustic wave device 1 according to the first embodiment. As shown in Figure 2, the mounting surface of the wiring board 3 includes a ground electrode 20, an antenna pad 21, a transmission pad 22, a reception pad 23, an antenna metal ring 24 surrounding the antenna pad 21, a transmission metal ring 25 surrounding the transmission pad 22, a reception metal ring 26 surrounding the reception pad 23, an inductor pad 27, and an inductor metal ring 28 surrounding the inductor pad 27.

As shown in FIG. 2, the antenna metal ring 24, the transmit metal ring 25, the receive metal ring 26, and the inductor metal ring 28 surround the antenna pad 21, the transmit pad 22, the receive pad 23, and the inductor pad 27, respectively. This enhances the shielding effect for electrical signals passing through the antenna pad 21, the transmit pad 22, and the receive pad 23.

The thickness of the ground electrode 20, the antenna pad 21, the transmission pad 22, the reception pad 23, the antenna metal ring 24 surrounding the antenna pad 21, the transmission metal ring 25 surrounding the transmission pad 22, the reception metal ring 26 surrounding the reception pad 23, the inductor pad 27, and the inductor metal ring 28 surrounding the inductor pad 27 is, for example, 10 μm to 35 μm. A thickness of 15 μm to 30 μm is more preferable. The thickness of the acoustic wave device 1 prototyped by the inventors was 15 μm. In particular, in acoustic wave devices for high-frequency applications such as the 5 GHz and sub-6 GHz bands, each pad having such a thickness is subject to electrical interference from the lateral direction (perpendicular to the thickness direction). Therefore, it is desirable to surround each pad with each metal ring.

Furthermore, as shown in FIG. 2, the antenna metal ring 24, the transmission metal ring 25, the reception metal ring 26, and the inductor metal ring 28 are connected to the ground electrode 20. This further enhances the shielding effect for electrical signals passing through the antenna pad 21, the transmission pad 22, and the reception pad 23.

The ground electrode 20, the antenna pad 21, the transmission pad 22, the reception pad 23, the antenna metal ring 24 surrounding the antenna pad 21, the transmission metal ring 25 surrounding the transmission pad 22, the reception metal ring 26 surrounding the reception pad 23, the inductor pad 27 and the inductor metal ring 28 surrounding the inductor pad 27 are formed, for example, from copper or an alloy containing copper.

As shown in FIG. 2, the distance A and the average distance from the exterior of the wiring board 3 to the ground electrode 20 are longer than the distance B and the average distance from the exterior of the wiring board 3 to the antenna metal ring 24. The distance A and the average distance from the exterior of the wiring board 3 to the ground electrode 20 are longer than the distance C and the average distance from the exterior of the wiring board 3 to the transmitting metal ring 25. The distance A and the average distance from the exterior of the wiring board 3 to the ground electrode 20 are longer than the distance D and the average distance from the exterior of the wiring board 3 to the receiving metal ring 26.

In the acoustic wave device 1 prototyped by the inventors, the average distance from the outer periphery of the wiring board 3 to the ground electrode 20 was approximately 75 μm. The average distance from the outer periphery of the wiring board 3 to the antenna metal ring 24 was 15 μm. The average distance from the outer periphery of the wiring board 3 to the transmitting metal ring 25 was 15 μm. The average distance from the outer periphery of the wiring board 3 to the receiving metal ring 26 was 15 μm.

As shown in FIG. 2, the shortest distance from the exterior of the wiring board 3 to the transmitting metal ring 25 is shorter than the shortest distance E from the exterior of a corner of the wiring board 3 to the transmitting metal ring 25. In the acoustic wave device 1 prototyped by the inventors, the shortest distance from the exterior of the wiring board 3 to the transmitting metal ring 25 was 15 μm, and the shortest distance E was 75 μm.

The shortest distance from the exterior of the wiring board 3 to the receiving metal ring 26 is shorter than the shortest distance F from the exterior of a corner of the wiring board 3 to the receiving metal ring 26. In the acoustic wave device 1 prototyped by the inventors, the shortest distance from the exterior of the wiring board 3 to the receiving metal ring 26 was 15 μm, and the shortest distance F was 75 μm.

The corners of the transmitting pads 22 and the receiving pads 23 are less susceptible to electrical interference. On the other hand, the corners of the wiring board 3 are prone to becoming the starting point for peeling between the wiring board 3 and the sealing part 17. Therefore, by making the area of the resin part that has good adhesion to the sealing part large at the corners of the wiring board 3, it is possible to enjoy great benefits while accepting minor disadvantages.

Next, an example of an acoustic wave element formed on a piezoelectric substrate 11 will be described with reference to FIG. 3. FIG. 3 is a diagram showing an example of an acoustic wave element 50 of an acoustic wave device according to the first embodiment.

As shown in FIG. 3, an IDT (Interdigital Transducer) 51 and a pair of reflectors 52 are formed on the main surface of the piezoelectric substrate 11. The IDT electrode 51 and the pair of reflectors 52 are arranged so as to excite elastic waves (mainly SH waves).

For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an alloy of aluminum and copper. For example, the IDT electrode 51 and the pair of reflectors 52 are formed of an appropriate metal such as aluminum, molybdenum, iridium, tungsten, cobalt, nickel, ruthenium, chromium, strontium, titanium, palladium, silver, or an alloy of these metals.

For example, the IDT electrode 51 and the pair of reflectors 52 are formed from a laminated metal film in which multiple metal layers are stacked. For example, the thickness of the IDT electrode 51 and the pair of reflectors 52 is 150 nm to 450 nm.

The IDT electrode 51 has a pair of comb electrodes 51a. The pair of comb electrodes 51a face each other. The comb electrode 51a has a plurality of electrode fingers 51b and a bus bar 51c.

The multiple electrode fingers 51b are arranged with their longitudinal directions aligned. The bus bar 51c connects the multiple electrode fingers 51b.

One of the pair of reflectors 52 is adjacent to one side of the IDT electrode 51. The other of the pair of reflectors 52 is adjacent to the other side of the IDT electrode 51.

According to the first embodiment described above, it is possible to provide an acoustic wave device that is small, has a stronger shielding effect for the signal lines and the ground electrode, and has excellent adhesion between the sealing portion and the wiring board.

Embodiment 2.
4 is a vertical cross-sectional view of a module to which the acoustic wave device 1 according to the first embodiment is applied. Note that the same reference numerals are used to designate the same or corresponding parts as those in the first embodiment, and the description of these parts is omitted.

In FIG. 4, the module 100 includes a wiring board 130, a plurality of external connection terminals 131, an integrated circuit component IC, an acoustic wave device 1, an inductor 111, and a sealing portion 117.

The multiple external connection terminals 31 are formed on the underside of the wiring board 130. The multiple external connection terminals 131 are mounted on the motherboard of a pre-set mobile communication terminal.

For example, the integrated circuit component IC is mounted inside the wiring board 130. The integrated circuit component IC includes a switching circuit and a low-noise amplifier.

The acoustic wave device 1 is mounted on the main surface of the wiring board 130.

The inductor 111 is mounted on the main surface of the wiring board 130. The inductor 111 is mounted for impedance matching. For example, the inductor 111 is an integrated passive device (IPD).

The sealing portion 117 seals multiple electronic components including the acoustic wave device 1.

According to the second embodiment described above, the module 100 includes the acoustic wave device 1. This makes it possible to provide a module that includes an acoustic wave device that is small, has a stronger shielding effect for the signal line and the ground electrode, and has excellent adhesion between the sealing portion and the wiring board.

While several aspects of at least one embodiment have been described, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the scope of this disclosure.

It should be understood that the embodiments of the methods and apparatus described herein are not limited in their application to the details of construction and arrangement of components set forth in the above description or illustrated in the accompanying drawings. The methods and apparatus may be implemented in other embodiments and practiced or carried out in various ways.

The specific implementation examples are provided here for illustrative purposes only and are not intended to be limiting.

The phraseology and terminology used in this disclosure are for purposes of description and should not be regarded as limiting. The use herein of "including," "comprising," "having," "including" and variations thereof means the inclusion of the items listed thereafter and equivalents thereof as well as additional items.

References to "or" may be construed as meaning that any term described using "or" refers to one, more than one, and all of those described terms.

All references to front, back, left, right, top, bottom, top, bottom, width, length, front and back are intended for convenience of description. Such references are not intended to limit the components of this disclosure to any one positional or spatial orientation. Accordingly, the above description and drawings are by way of example only.

REFERENCE SIGNS LIST 1 Acoustic wave device, 3 Wiring substrate, 5 Device chip 11 Piezoelectric substrate, 13 Support substrate, 17 Sealing portion, 50 Acoustic wave element 20 Ground electrode, 21 Antenna pad, 22 Transmitting pad 23 Receiving pad 24 Antenna metal ring, 25 Transmitting metal ring 26 Receiving metal ring 27 Inductor pad, 28 Inductor metal ring 100 Module, 111 Inductor, 117 Sealing portion 130 Wiring substrate

Claims (11)

A wiring board having a mounting surface;
a ground electrode, an antenna pad, a transmission pad, a reception pad, an antenna metal ring surrounding the antenna pad, a transmission metal ring surrounding the transmission pad, and a reception metal ring surrounding the reception pad, which are formed on the mounting surface;
a device chip mounted on the wiring substrate;
the antenna metal ring, the transmitting metal ring, and the receiving metal ring are connected to the ground electrode,
An acoustic wave device, wherein an average distance from an outer periphery of the wiring board to the ground electrode is longer than an average distance from the outer periphery of the wiring board to the antenna metal ring, the transmitting metal ring, and the receiving metal ring. The acoustic wave device of claim 1, wherein the mounting surface comprises an inductor pad and an inductor metal ring surrounding the inductor pad. a sealing portion that seals the device chip together with the wiring substrate,
The acoustic wave device according to claim 1 , wherein the sealing portion is bonded to an insulating region between the antenna pad and the antenna metal ring. a sealing portion that seals the device chip together with the wiring substrate,
The acoustic wave device according to claim 1 , wherein the sealing portion is bonded to an insulating region between the transmitting pad and the transmitting metal ring and an insulating region between the receiving pad and the receiving metal ring. The acoustic wave device of claim 1, wherein the shortest distance from the outer edge of the wiring board to the transmitting metal ring is shorter than the shortest distance from the outer edge of the wiring board to the transmitting metal ring. The acoustic wave device of claim 1, wherein the shortest distance from the outer edge of the wiring board to the receiving metal ring is shorter than the shortest distance from the outer edge of the wiring board to the receiving metal ring. The acoustic wave device of claim 1, wherein the thickness of the antenna metal ring is 10 μm to 35 μm. The acoustic wave device of claim 1, wherein the thickness of the transmitting metal ring and the receiving metal ring is 10 μm to 35 μm. The acoustic wave device of claim 1, wherein the device chip includes a piezoelectric substrate made of lithium tantalate, lithium niobate, or quartz. The acoustic wave device of claim 1, wherein the device chip includes a support substrate made of sapphire, silicon, alumina, spinel, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, silicon oxynitride, diamond, quartz, or glass. A module comprising an acoustic wave device according to claim 1 .