Surface acoustic wave device, packaging structure and preparation method

Abstract

This invention discloses a surface acoustic wave (SAW) device, a packaging structure including the device, and a fabrication method thereof. The device includes a piezoelectric substrate and an inductively coupled dielectric (IDT) electrode disposed on the surface of the piezoelectric substrate. The IDT electrode includes an electrode layer and a protective layer disposed on the electrode layer away from the surface of the piezoelectric substrate. The electrode layer contains at least 90 wt% aluminum. The protective layer comprises Ti and Al, with at least 50 wt% Ti. By providing the protective layer, the electrode layer is isolated from the external environment, eliminating the influence of moisture and impurities from the external environment on the electrode layer.

Description

Technical Field

[0001] This invention relates to the field of surface acoustic wave (SAW) technology, and more specifically, to a SAW device, packaging structure, and fabrication method. Background Technology

[0002] Surface Acoustic Wave (SAW) devices typically consist of a piezoelectric substrate and metal electrodes deposited on its surface. Because the structure of these metal electrodes resembles interlaced fingers, they are figuratively called IDT (Interdigital Transducer) electrodes. In SAW devices, the excitation and reception of SAW waves are accomplished on the piezoelectric substrate using the direct and inverse piezoelectric effects; the IDT is a crucial component in realizing this sound-to-electric conversion process. IDT devices are relatively sensitive; changes in external ambient temperature and moisture ingress due to poor device packaging can negatively impact the overall performance of SAW devices.

[0003] Therefore, for harsh high-temperature conditions, current solutions for device temperature compensation mostly focus on two main aspects: using piezoelectric single-crystal tangents with low operating frequency temperature coupling coefficient (TCF) and placing temperature compensation plates on the IDT electrodes. To improve the reliability of SAW devices in high-humidity environments, existing technologies mainly focus on improving the packaging methods of SAW devices.

[0004] In high-humidity environments, the above technical solutions only address the packaging method of SAW devices and do not solve the problem of the traditional aluminum metal electrodes of the IDT being corroded by moisture after moisture intrusion, leading to the overall failure of the SAW device.

[0005] Therefore, it is necessary to improve related technologies to solve the above problems and further improve the reliability of SAW devices under high temperature and high humidity conditions. Summary of the Invention

[0006] To address the above problems, this invention provides a surface acoustic wave device, a packaging structure containing the device, and a method for fabricating the same.

[0007] The present invention provides a surface acoustic wave device, comprising: a piezoelectric substrate; and an IDT electrode disposed on the surface of the piezoelectric substrate. The IDT electrode includes an electrode layer and a protective layer disposed on the electrode layer away from the surface of the piezoelectric substrate. The electrode layer contains more than 90 wt% aluminum. The protective layer includes Ti and Al, and the protective layer contains more than 50 wt% Ti.

[0008] According to one embodiment of the present invention, the surface acoustic wave device further includes: a buffer layer disposed between the electrode layer and the piezoelectric substrate, the buffer layer comprising Ti or Cr, wherein the content of Ti or Cr in the buffer layer is above 90 wt%.

[0009] According to another embodiment of the present invention, an insulating layer is provided on the side and side of the IDT electrode away from the piezoelectric substrate, the insulating layer comprising silicon oxide or silicon nitride.

[0010] According to another embodiment of the present invention, the thickness of the buffer layer is 1-200 nm.

[0011] According to another embodiment of the present invention, the corrosion potential of the protective layer is higher than that of the electrode layer.

[0012] According to another embodiment of the present invention, the protective layer includes at least one of α-Ti and TiAl.

[0013] According to another embodiment of the present invention, the Al component content in the protective layer is distributed in a gradient, with the Al element content on the side away from the piezoelectric substrate being lower than the Al element content on the side closer to the piezoelectric substrate.

[0014] According to another embodiment of the present invention, when the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set as λ, the thickness of the electrode layer is 5-15%λ, and the thickness of the protective layer is 1-200nm.

[0015] According to another embodiment of the present invention, the projected area of ​​the protective layer on the piezoelectric substrate is smaller than the projected area of ​​the electrode layer on the piezoelectric substrate.

[0016] According to another embodiment of the present invention, the projected area of ​​the electrode layer on the piezoelectric substrate is smaller than the projected area of ​​the buffer layer on the piezoelectric substrate.

[0017] According to another embodiment of the present invention, a groove structure is provided in the piezoelectric substrate, the groove structure accommodating the IDT electrode, and when the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set as λ, the depth of the groove structure is greater than or equal to 5-15%λ.

[0018] According to another embodiment of the present invention, the piezoelectric substrate comprises a piezoelectric thin film, a substrate, and an oxide layer located between the piezoelectric thin film and the substrate. The piezoelectric thin film is a single-crystal thin film, and the volume wave velocity propagating on the substrate is higher than the surface acoustic wave velocity propagating on the piezoelectric thin film. The oxide layer is a polycrystalline thin film, and the volume wave velocity propagating on the oxide layer is lower than the surface acoustic wave velocity propagating on the piezoelectric thin film. The oxide layer has a frequency temperature coefficient greater than zero.

[0019] According to another embodiment of the present invention, the thickness of the oxide layer is 30 nm or more.

[0020] The present invention also provides a packaging structure including the above-mentioned surface acoustic wave device, comprising the surface acoustic wave device, a circuit board, a first packaging layer and a second packaging layer; the surface acoustic wave device is disposed on the surface of the circuit board, the first packaging layer is disposed on the surface of the surface acoustic wave device, and the second packaging layer is disposed on the side of the first packaging layer away from the surface acoustic wave device; the first packaging layer comprises thermosetting acrylic resin, and the second packaging layer comprises epoxy resin.

[0021] According to one embodiment of the present invention, the second encapsulation layer further includes a thermally conductive filler, wherein the thermally conductive filler accounts for 30-70 wt% of the second encapsulation layer.

[0022] According to another embodiment of the present invention, the thermally conductive filler includes one or more of metal oxides, metal nitrides, thermally conductive polymers, and non-metallic compounds.

[0023] According to another embodiment of the present invention, the thermally conductive filler is Al2O3.

[0024] According to another embodiment of the present invention, a third encapsulation layer is disposed on the side of the second encapsulation layer away from the surface acoustic wave device or between the first encapsulation layer and the second encapsulation layer, the third encapsulation layer comprising SiO2.

[0025] According to another embodiment of the present invention, the thickness of the second encapsulation layer is greater than the thickness of the first encapsulation layer.

[0026] According to another embodiment of the present invention, the thickness relationship of the first encapsulation layer, the second encapsulation layer and the third encapsulation layer is as follows: thickness of the second encapsulation layer > thickness of the first encapsulation layer > thickness of the third encapsulation layer.

[0027] According to another embodiment of the present invention, the thickness relationship of the first encapsulation layer, the second encapsulation layer and the third encapsulation layer is: the thickness of the second encapsulation layer > the sum of the thicknesses of the first encapsulation layer and the third encapsulation layer.

[0028] The present invention further provides a method for manufacturing the above-mentioned surface acoustic wave device, comprising: providing a piezoelectric substrate; forming an electrode layer on the surface of the piezoelectric substrate; and forming a protective layer on the electrode layer.

[0029] According to another embodiment of the present invention, after forming the protective layer, a heat treatment step is further included, the heat treatment step comprising: a first heat treatment, treating at 600-650°C for 15-30 minutes to form a titanium-aluminum intermetallic compound between the electrode layer and the protective layer; and a second heat treatment, treating at 200-300°C for 1-5 hours.

[0030] According to another embodiment of the present invention, a buffer layer is formed on the piezoelectric substrate before the electrode layer is formed.

[0031] According to another embodiment of the present invention, the protective layer formed on the electrode layer is formed by using a titanium- and aluminum-containing alloy target and a sputtering method.

[0032] The present invention provides a protective layer on the outside of the electrode layer, which can protect the electrode layer from corrosion under high temperature and high humidity, and improve the reliability of SAW devices under high temperature and high humidity. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a surface acoustic wave device according to an embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a surface acoustic wave device according to another embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a surface acoustic wave device according to another embodiment of the present invention.

[0036] Figure 4A , Figure 4B , Figure 4C , Figure 4D , Figure 4E , Figure 4F This is a schematic diagram of a surface acoustic wave device according to another embodiment of the present invention.

[0037] Figure 5A , Figure 5B and Figure 5C This is a schematic diagram of a surface acoustic wave device according to another embodiment of the present invention.

[0038] Figure 6 The curves show the reliability comparison of the surface acoustic wave filter in Example 1.

[0039] Figure 7 The curves show the reliability comparison of the surface acoustic wave filter in Example 2.

[0040] Figure 8 The curves show the reliability comparison of the surface acoustic wave filter in Comparative Example 1.

[0041] The reference numerals in the attached figures are explained as follows:

[0042] 1-Piezoelectric substrate; 11-Piezoelectric thin film; 12-Substrate; 13-Oxide layer; 2-IDT electrode; 21-Electrode layer; 22-Protective layer; 23-Buffer layer; 3-Insulating layer; 41-First encapsulation layer; 42-Second encapsulation layer; 43-Third encapsulation layer; 5-Circuit board; 6-Solder joint; 10-Surface acoustic wave device Detailed Implementation

[0043] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that the invention will be thorough and complete, and the concept of the exemplary embodiments will be fully conveyed to those skilled in the art. In the drawings, for clarity, the thickness of regions and layers is exaggerated. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed descriptions will be omitted.

[0044] It should be noted that the terms "upper" and "lower" used in this invention are only relative concepts or are used in reference to the normal use of the product, and should not be considered as restrictive.

[0045] like Figure 1 As shown, the surface acoustic wave (SAW) device 10 includes a piezoelectric substrate 1 and an IDT electrode 2. The IDT electrode 2 is disposed on the surface of the piezoelectric substrate 1, and includes an electrode layer 21 and a protective layer 22 disposed on the electrode layer 21 away from the surface of the piezoelectric substrate 1. The aluminum content in the electrode layer 21 is above 90 wt%. The protective layer 22 includes Ti and Al, and the Ti content in the protective layer 22 is above 50 wt%. By providing the protective layer, the electrode layer is isolated from the outside environment, eliminating the influence of moisture and impurity ions in the external environment on the electrode layer.

[0046] In an optional embodiment, the corrosion potential of the protective layer 22 is higher than that of the electrode layer 21. By providing a protective layer 22 with a higher corrosion potential on the electrode layer 21, the corrosion resistance of the device is improved, thereby enhancing the reliability of the SAW device.

[0047] In an optional embodiment, the protective layer 21 includes at least one of α-Ti and TiAl.

[0048] In an optional embodiment, the Al component content in the protective layer 21 is distributed in a gradient, with the Al element content on the side away from the piezoelectric substrate 1 being lower than the Al element content on the side closer to the piezoelectric substrate 1.

[0049] In an optional embodiment, when the wavelength of the elastic wave determined by the electrode period of the IDT electrode 2 is set to λ, the thickness of the electrode layer 1 is 5-15%λ, and the thickness of the protective layer 22 is 1-200nm.

[0050] In an optional embodiment, the projected area of ​​the protective layer 22 on the piezoelectric substrate 1 is smaller than the projected area of ​​the electrode layer 21 on the piezoelectric substrate 1.

[0051] In an optional embodiment, the projected area of ​​the electrode layer 21 on the piezoelectric substrate 1 is smaller than the projected area of ​​the buffer layer 23 on the piezoelectric substrate 1.

[0052] In an optional embodiment, a groove structure is provided in the piezoelectric substrate 1, the groove structure accommodating the IDT electrode 2, and when the wavelength of the elastic wave determined by the electrode period of the IDT electrode 2 is set as λ, the depth of the groove structure is greater than or equal to 5-15%λ.

[0053] Furthermore, such as Figure 2 As shown, a buffer layer 23 is disposed between the electrode layer 21 and the piezoelectric substrate 1. The buffer layer 23 comprises titanium (Ti) or chromium (Cr). By providing the buffer layer 23, the interfacial bonding strength between the electrode layer 21 and the piezoelectric substrate 1 is improved. This avoids the problem of the IDT electrode 2, which is a vibration clamp, easily detaching from the piezoelectric substrate 1 during 5G high-frequency applications, thus preventing device failure. In addition, the buffer layer 23 can effectively prevent Al migration during the operation of SAW devices, enhance the anti-electromigration ability of the Al metal electrode, and extend the average lifetime of the thin film. In an optional embodiment, the Ti or Cr content in the buffer layer 23 is above 90 wt%.

[0054] In an optional implementation, the thickness of the buffer layer is 1-200 nm.

[0055] Furthermore, such as Figure 3 The piezoelectric substrate 1 shown is a composite substrate, including a piezoelectric thin film 11, a substrate 12, and an oxide layer 13 located between the piezoelectric thin film 11 and the substrate 12. The piezoelectric thin film 11 is a single-crystal thin film, and the volume wave velocity propagating on the substrate 12 is higher than the surface acoustic wave velocity propagating on the piezoelectric thin film 11. The oxide layer 13 is disposed between the substrate 12 and the piezoelectric thin film 11. The oxide layer 13 is a polycrystalline thin film, and the volume wave velocity propagating on the oxide layer 13 is lower than the surface acoustic wave velocity propagating on the piezoelectric thin film. The oxide layer 13 has a frequency temperature coefficient greater than zero. Therefore, warping is less likely to occur, insertion loss is reduced, temperature stability is improved, and device reliability is enhanced.

[0056] In an optional embodiment, the thickness of oxide layer 13 is 30 nm or more.

[0057] Furthermore, such as Figures 4A to 4D As shown, insulating layers 3 are disposed on the side of the IDT electrode 2 away from the piezoelectric substrate 1 and on its side surface. The method of disposing the insulating layer 3 is not limited to... Figures 4A to 4D As shown, it can be any suitable method. The insulating layer 3 is composed of silicon oxide (SiO2) or silicon nitride. By providing the insulating layer 3, the frequency drift problem of SAW devices under temperature variations is solved.

[0058] Furthermore, such as Figure 4E and 4F As shown, an insulating layer 3 is provided on the plane of the piezoelectric substrate 1 where the IDT electrode 2 is not located. The method of providing the insulating layer 3 is not limited to... Figure 4E and Figure 4F As shown, it can be any appropriate method.

[0059] like Figure 5A As shown, the encapsulation structure of the surface acoustic wave (SAW) device includes a SAW device 10, a circuit board 5, a first encapsulation layer 41, and a second encapsulation layer 42. The SAW device 10 is fixed to the surface of the circuit board 5 by solder points 6, and the SAW device 10 and the circuit board 5 form a hollow structure. The first encapsulation layer 41 is disposed on the surface of the SAW device 10, and the second encapsulation layer 42 is disposed on the side of the first encapsulation layer 41 away from the SAW device 10. The first encapsulation layer 41 includes thermosetting acrylic resin (TSA), and the second encapsulation layer 42 includes epoxy resin. By setting a multi-layer encapsulation structure, the heat resistance and moisture resistance of the SAW device are improved, as well as its reliable sealing performance. This better prevents water vapor, dust, etc., from entering the internal space of the encapsulation, thereby better avoiding the generation of bulging cracks when the internal space expands. Therefore, it can improve the connection reliability between circuit components such as SAW acoustic devices and the circuit board, thereby ensuring the stability and reliability of the communication device.

[0060] Furthermore, such as Figure 5B As shown, a third encapsulation layer 43 is disposed on the side of the second encapsulation layer 42 away from the surface acoustic wave device 1 or between the first encapsulation layer 41 and the second encapsulation layer 42. The third encapsulation layer 43 comprises SiO2. Figure 5C As shown, the third encapsulation layer 43 can also be disposed on the other side of the second encapsulation layer 42 away from the first encapsulation layer 41.

[0061] In an optional embodiment, the second encapsulation layer 42 further includes a thermally conductive filler, which accounts for 30-70 wt% of the second encapsulation layer. By adding the thermally conductive filler, the encapsulation resin is guaranteed to have excellent heat dissipation and improved thermal cycling resistance, which can meet the requirements of high thermal conductivity performance for high-frequency, high-power surface acoustic wave devices.

[0062] In optional embodiments, the thermally conductive filler includes one or more of metal oxides, metal nitrides, thermally conductive polymers, and non-metallic compounds.

[0063] In an optional embodiment, the thermally conductive filler is Al2O3.

[0064] In an optional embodiment, the thickness of the second encapsulation layer 42 is greater than the thickness of the first encapsulation layer 41.

[0065] In an optional implementation, the thicknesses of the first encapsulation layer 41, the second encapsulation layer 42, and the third encapsulation layer 43 are related as follows: the thickness of the second encapsulation layer > the thickness of the first encapsulation layer > the thickness of the third encapsulation layer.

[0066] In an optional implementation, the thicknesses of the first encapsulation layer 41, the second encapsulation layer 42, and the third encapsulation layer 43 are related as follows: the thickness of the second encapsulation layer is greater than the sum of the thicknesses of the first and third encapsulation layers.

[0067] The manufacturing method of the above-mentioned surface acoustic wave device includes: providing a piezoelectric substrate; forming an electrode layer on the surface of the piezoelectric substrate; and forming a protective layer on the electrode layer.

[0068] In an optional embodiment, after forming the protective layer, a heat treatment step is further included, which includes: a first heat treatment at 600-650°C for 15-30 minutes to form a titanium-aluminum intermetallic compound between the electrode layer and the protective layer; and a second heat treatment at 200-300°C for 1-5 hours.

[0069] In an alternative embodiment, a buffer layer is formed on the piezoelectric substrate before the electrode layer is formed.

[0070] In an optional embodiment, the protective layer on the electrode layer is formed by using a titanium- and aluminum alloy target and sputtering method.

[0071] The concept of the present invention will be explained in further detail below with reference to specific embodiments.

[0072] Example 1

[0073] Surface acoustic wave devices include a piezoelectric substrate, a buffer layer, an IDT electrode, a protective layer, and an insulating layer.

[0074] The piezoelectric substrate consists of a piezoelectric thin film, an oxide layer, and a substrate stacked sequentially. The oxide layer is a polycrystalline thin film with a thickness of 50 nm.

[0075] The buffer layer is made of titanium alloy with a titanium content of 90 wt%. The thickness of the buffer layer is 100 nm.

[0076] The electrode layer is an Al alloy with an Al content of 95 wt% and a thickness of 300 nm.

[0077] The protective layer is a TiAl alloy with a gradient distribution of Al content, where the Al content on the side furthest from the piezoelectric substrate is lower than that on the side closer to the piezoelectric substrate. The thickness of the protective layer is 100 nm.

[0078] The insulating layer is silicon nitride. Example 2

[0079] Except for the protective layer thickness of 50nm, the other parameters are the same as in Example 1.

[0080] Comparative Example 1

[0081] Except for the absence of a protective layer, the other parameters are the same as in Example 1.

[0082] The surface acoustic wave (SAW) filters of Examples 1-2 and Comparative Example 1 were subjected to reliability tests under the same conditions. Then, the SAW filters of the above examples and comparative examples were subjected to high-temperature and high-humidity corrosion treatment before the aforementioned reliability tests were performed. The high-temperature and high-humidity corrosion treatment involved placing the filters at 130°C and 85% humidity for 96 hours.

[0083] The reliability of the same surface acoustic wave filter before and after testing was compared, and the test curves are shown in the figure. Figure 6-8 As shown in the figure, the test results of Examples 1-2 are better than those of Comparative Example 1, which indicates that the surface acoustic wave filter of the present invention has better reliability under high temperature and high humidity conditions because it includes a protective layer.

[0084] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A surface acoustic wave device, characterized in that, include: Piezoelectric substrate; An IDT electrode is disposed on the surface of the piezoelectric substrate. The IDT electrode includes an electrode layer and a protective layer disposed on the electrode layer away from the surface of the piezoelectric substrate. The electrode layer contains more than 90 wt% aluminum. The protective layer includes Ti and Al, with more than 50 wt% Ti. The Al content in the protective layer exhibits a gradient distribution, with a lower Al content on the side away from the piezoelectric substrate than on the side closer to the piezoelectric substrate. The corrosion potential of the protective layer is higher than that of the electrode layer. The protective layer includes at least one of α-Ti and TiAl. A buffer layer is disposed between the electrode layer and the piezoelectric substrate, the buffer layer comprising Ti or Cr, wherein the content of Ti or Cr in the buffer layer is above 90 wt%. Wherein, when the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set as λ, the thickness of the electrode layer is 5-15%λ, and the thickness of the protective layer is 1-200nm.

2. The surface acoustic wave device according to claim 1, characterized in that, An insulating layer is provided on the side and side of the IDT electrode away from the piezoelectric substrate, the insulating layer comprising silicon oxide or silicon nitride.

3. The surface acoustic wave device according to claim 1, characterized in that, The thickness of the buffer layer is 1-200 nm.

4. The surface acoustic wave device according to claim 1, characterized in that, The projected area of ​​the protective layer on the piezoelectric substrate is smaller than the projected area of ​​the electrode layer on the piezoelectric substrate.

5. The surface acoustic wave device according to claim 1, characterized in that, The projected area of ​​the electrode layer on the piezoelectric substrate is smaller than the projected area of ​​the buffer layer on the piezoelectric substrate.

6. The surface acoustic wave device according to claim 1, characterized in that, The piezoelectric substrate has a groove structure that accommodates the IDT electrode. When the wavelength of the elastic wave determined by the electrode period of the IDT electrode is set as λ, the depth of the groove structure is greater than or equal to 5-15%λ.

7. The surface acoustic wave device according to claim 1, characterized in that, The piezoelectric substrate comprises a piezoelectric thin film, a substrate, and an oxide layer located between the piezoelectric thin film and the substrate. The piezoelectric thin film is a single-crystal thin film, and the volume wave velocity propagating on the substrate is higher than the surface acoustic wave velocity propagating on the piezoelectric thin film. The oxide layer is a polycrystalline thin film, and the volume wave velocity propagating on the oxide layer is lower than the surface acoustic wave velocity propagating on the piezoelectric thin film. The oxide layer has a frequency temperature coefficient greater than zero.

8. The surface acoustic wave device according to claim 7, characterized in that, The thickness of the oxide layer is 30 nm or more.

9. A packaging structure comprising the surface acoustic wave device of claim 1, characterized in that, The device includes the surface acoustic wave (SAW) device, a circuit board, a first encapsulation layer, and a second encapsulation layer. The SAW device is disposed on the surface of the circuit board, the first encapsulation layer is disposed on the surface of the SAW device, and the second encapsulation layer is disposed on the side of the first encapsulation layer away from the SAW device. The first encapsulation layer comprises thermosetting acrylic resin, and the second encapsulation layer comprises epoxy resin.

10. The packaging structure according to claim 9, characterized in that, The second encapsulation layer further includes a thermally conductive filler, which accounts for 30-70 wt% of the second encapsulation layer.

11. The packaging structure according to claim 10, characterized in that, The thermally conductive filler includes one or more of the following: metal oxides, metal nitrides, thermally conductive polymers, and non-metallic compounds.

12. The packaging structure according to claim 10, characterized in that, The thermally conductive filler is Al2O3.

13. The packaging structure according to claim 9, characterized in that, A third encapsulation layer is disposed on the side of the second encapsulation layer away from the surface acoustic wave device or between the first encapsulation layer and the second encapsulation layer, the third encapsulation layer comprising SiO2.

14. The packaging structure according to claim 9, characterized in that, The thickness of the second encapsulation layer is greater than the thickness of the first encapsulation layer.

15. The packaging structure according to claim 13, characterized in that, The thickness relationship of the first encapsulation layer, the second encapsulation layer, and the third encapsulation layer is as follows: the thickness of the second encapsulation layer > the thickness of the first encapsulation layer > the thickness of the third encapsulation layer.

16. The packaging structure according to claim 13, characterized in that, The thickness relationship of the first encapsulation layer, the second encapsulation layer, and the third encapsulation layer is as follows: the thickness of the second encapsulation layer is greater than the sum of the thicknesses of the first encapsulation layer and the third encapsulation layer.

17. A method for manufacturing the surface acoustic wave device according to claim 1, characterized in that, include: Provide piezoelectric substrates; An electrode layer is formed on the surface of the piezoelectric substrate; as well as A protective layer is formed on the electrode layer.

18. The manufacturing method according to claim 17, characterized in that, After the protective layer is formed, a heat treatment step is further included, the heat treatment step including: The first heat treatment involves treating at 600-650°C for 15-30 minutes to form a titanium-aluminum intermetallic compound between the electrode layer and the protective layer; and The second heat treatment involves treating at 200-300℃ for 1-5 hours.

19. The manufacturing method according to claim 17, characterized in that, A buffer layer is formed on the piezoelectric substrate before the electrode layer is formed.

20. The manufacturing method according to claim 17, characterized in that, The protective layer is formed on the electrode layer by using an alloy target containing titanium and aluminum and forming it by sputtering.

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