Surface acoustic wave sensor and its packaging structure

Abstract

The application provides a surface acoustic wave sensor and a packaging structure thereof, and based on a POI piezoelectric substrate and a multifunctional reflection grating layout, temperature, pressure and acceleration sensitive units are highly integrated in a single chip. In order to realize decoupling of multiple sensing quantities, two reference gratings located on both sides of a uniform interdigital transducer, and a group of acceleration measurement reflection gratings, temperature measurement reflection gratings and pressure measurement reflection gratings are designed. The two reference gratings are used for differential time delay measurement of the sensitive quantity, the temperature measurement reflection grating is arranged close to the reference grating, effectively ensures that the temperature measurement is not affected by other sensing quantities, and effectively suppresses environmental noise interference. Efficient separation and synchronous detection of temperature, pressure and acceleration multi-parameter signals are realized, and the electromagnetic coupling problem of the traditional multi-interdigital transducer structure is avoided. The surface acoustic wave sensor packaging structure adopts an SMD packaging structure, the overall structure of the device is compact, and the installation difficulty and system maintenance cost under a complex environment are greatly reduced.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and in particular relates to a surface acoustic wave sensor and its packaging structure. Background Technology

[0002] Surface acoustic wave (SAW) sensors are passive wireless sensors based on the piezoelectric effect and the propagation characteristics of sound waves. They work by exciting and receiving surface acoustic waves through interdigital transducers (IDTs) on a piezoelectric substrate, utilizing the modulation of sound wave propagation characteristics by external physical quantities (such as temperature, pressure, and acceleration) to achieve sensing. Compared to traditional wired sensors, SAW sensors offer significant advantages such as small size, high sensitivity, resistance to electromagnetic interference, and no need for external power supply, and have been widely used in aerospace, industrial monitoring, and medical equipment.

[0003] However, existing SAW sensors are mostly limited to single-parameter detection and lack integrated design. For example, when monitoring temperature, they cannot simultaneously monitor other parameters such as pressure and strain. This single-parameter detection mode necessitates the deployment of multiple independent sensors to cover multiple parameters such as temperature, pressure, and acceleration in complex applications (such as aircraft condition monitoring and engine health diagnostics). This not only significantly increases system complexity and wiring costs but also reduces overall reliability due to space contention and signal interference between sensors.

[0004] In recent years, although some research has attempted to integrate multi-parameter detection functions into a single SAW sensor, significant drawbacks remain. A few sensors capable of multi-parameter detection employ a stacked design of multiple interdigital transducers (IDTs) and reflective gratings, using discrete reflective gratings for differential measurement; however, these designs have limitations in integration and signal separation efficiency. Such structures not only increase signal transmission loss but also cause cross-interference due to multi-physics coupling. Furthermore, an excessive number of reflective gratings makes device miniaturization difficult, hindering applications in confined spaces. In addition, increasing the number of reflective gratings exacerbates process complexity, impacting device yield and consistency.

[0005] In summary, existing SAW sensors have significant shortcomings in terms of multi-parameter integration, miniaturization, and anti-interference capabilities. Developing a novel integrated SAW sensor with a compact structure capable of simultaneously and accurately detecting temperature, pressure, and acceleration is a key requirement for overcoming the bottleneck of real-time monitoring of multiple physical quantities under complex working conditions. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a surface acoustic wave sensor and its packaging structure to solve the problems of limited functionality, large size and low anti-interference capability of surface acoustic wave sensors in the prior art.

[0007] To achieve the above and other related objectives, the present invention provides a surface acoustic wave (SAW) sensor, comprising: a piezoelectric substrate, a uniform interdigital SAW transducer, a temperature measurement reflective grating, a pressure measurement reflective grating, an acceleration measurement reflective grating, and two reference gratings disposed on the piezoelectric substrate, and bonded to a substrate under the piezoelectric substrate; wherein,

[0008] The uniform interdigital transducer is used to excite and receive surface acoustic waves.

[0009] The piezoelectric substrate is a POI piezoelectric substrate composed of a high-resistivity substrate layer, an insulating layer and a piezoelectric single crystal layer;

[0010] The two reference grids are respectively disposed on both sides near the uniform interdigital transducer;

[0011] The pressure measurement reflective grating and the acceleration measurement reflective grating are respectively disposed on two sides away from the uniform interdigital transducer;

[0012] The temperature measurement reflective grid is disposed between the reference grid and the pressure measurement reflective grid, which are located on the same side of the uniform interdigital transducer as the pressure measurement reflective grid.

[0013] The substrate exposes at least the piezoelectric substrate beneath the acceleration measurement reflective grating to form a cantilever beam;

[0014] A pressure measuring cavity is formed in the piezoelectric substrate between the temperature measuring reflective grating and the pressure measuring reflective grating, penetrating the high-resistivity substrate layer and the insulating layer.

[0015] Optionally, the material of the piezoelectric single crystal layer in the piezoelectric substrate is lithium niobate, lithium tantalate, quartz, lead zirconate titanate, or aluminum nitride; the insulating layer is a silicon dioxide layer, a silicon nitride layer, or an aluminum oxide layer; and the high-resistivity substrate layer is a high-resistivity silicon layer, a high-resistivity silicon carbide layer, or a high-resistivity gallium arsenide layer.

[0016] Optionally, the high-resistivity substrate layer is a high-resistivity silicon layer, the substrate is a glass substrate, and the high-resistivity substrate layer and the substrate are pre-formed with an alumina transition layer at the bonding interface and bonded based on a low-temperature anodic bonding process.

[0017] Optionally, a mass block is fixed under the piezoelectric substrate below the acceleration measurement reflective grating.

[0018] Furthermore, the cantilever beam extends at least to the reference gate near its side, and the cantilever beam is provided with a micropore slit sensitization structure in the acceleration sensitive region. The micropore slit sensitization structure is a plurality of micropores and / or microslits extending inward from the lower surface of the high-resistivity substrate towards the piezoelectric single crystal layer and extending to a depth not exceeding the thickness of the high-resistivity substrate.

[0019] Optionally, the metal electrode of the uniform interdigital transducer is an aluminum thin film electrode with a linewidth of 0.5μm to 1.0μm, a spacing of 0.5μm to 1.0μm, 20 to 50 pairs of interdigital fingers, a length of 50μm to 200μm, and is kept consistent along the direction of surface acoustic wave propagation. It excites surface acoustic waves to both sides and operates in the frequency range of 10MHz to 10GHz.

[0020] The present invention also provides a surface acoustic wave (SAW) sensor packaging structure, the packaging structure comprising: a SAW sensor as described in any one of the above claims, a cover plate, and a housing base; wherein,

[0021] The surface acoustic wave sensor is housed in the accommodating base;

[0022] The cover plate is fastened onto the receiving base to form an SMD packaging structure;

[0023] An antenna is fixed below the accommodating base.

[0024] Optionally, the cover plate is a glass cover plate, and the receiving base is a ceramic base.

[0025] Optionally, the packaging structure further includes solder bonding leads that are electrically connected to the uniform interdigital transducer.

[0026] Furthermore, the welding bonding lead is a gold wire, a silicon-aluminum wire, or a platinum wire.

[0027] Optionally, the encapsulation structure further includes a vent hole, which is disposed on the cover plate or the bottom wall of the receiving base; when the vent hole is disposed on the cover plate, the vent hole penetrates the cover plate and is located above the pressure measuring chamber; when the vent hole is disposed on the bottom wall of the receiving base, the vent hole penetrates the bottom wall of the receiving base and the substrate of the surface acoustic wave sensor to communicate with the pressure measuring chamber.

[0028] Furthermore, when the vent is located on the cover plate, the pressure measuring chamber forms a sealed space and is vented with inert gas; when the vent is located on the bottom wall of the accommodating base, a sealed space is formed between the cover plate and the piezoelectric substrate and is vented with inert gas.

[0029] Optionally, the encapsulation structure further includes an overload damping block, which is disposed on the inner wall of the cover plate and / or the inner side of the bottom wall of the accommodating base and corresponds to the acceleration measurement reflection grating area of ​​the surface acoustic wave sensor.

[0030] Furthermore, the overload damping block is made of silicone rubber.

[0031] As described above, the surface acoustic wave sensor and its packaging structure of the present invention, based on a POI piezoelectric substrate and a multifunctional reflective grating layout, highly integrates temperature, pressure, and acceleration sensing units onto a single chip. The design not only considers the structural optimization of individual sensors in existing technologies but also addresses issues such as cross-coupling between multiple sensors. To achieve decoupling of multiple sensing quantities, two sets of reference reflective gratings are designed: two reference gratings located on both sides of the uniform interdigital transducer, and a set of acceleration measurement reflective gratings, temperature measurement reflective gratings, and pressure measurement reflective gratings. The two reference gratings are used for differential time delay measurement of the sensing quantities. The temperature measurement reflective grating is positioned close to the reference gratings to effectively ensure that temperature measurement is not affected by other sensing quantities and to effectively suppress environmental noise interference. The acceleration and pressure measurement reflective gratings are positioned on both sides of the uniform interdigital transducer, enabling the measurement of pressure and acceleration while effectively avoiding cross-sensitivity effects between pressure and acceleration. The response signal of the temperature measurement reflective grating not only provides an independent temperature measurement value but also serves as a reference parameter for pressure measurement. Dynamic compensation is performed on force and acceleration signals. For example, the time delay change of the pressure measurement reflector includes the thermal expansion effect of the piezoelectric single crystal layer caused by temperature. By subtracting the linear contribution of the temperature component, the net deformation caused by pressure can be accurately extracted. The sensitivity of the acceleration measurement reflector is affected by temperature drift. The change in the elastic modulus of the cantilever beam is corrected in real time using the temperature signal to ensure the temperature stability of acceleration measurement. This achieves efficient separation and synchronous detection of multiple parameter signals such as temperature, pressure and acceleration, avoiding the electromagnetic coupling problem of traditional multi-interdigital transducer structures. The surface acoustic wave sensor adopts an SMD packaging structure, and the overall structure of the device is compact, which greatly reduces the installation difficulty and system maintenance cost in complex environments. Attached Figure Description

[0032] Figures 1 to 3 The diagram shows four examples of the surface acoustic wave sensor of the present invention.

[0033] Figure 4 The diagram shown illustrates the working principle of the surface acoustic wave sensor of this invention.

[0034] Figures 5 to 7 The diagram shows three examples of the surface acoustic wave sensor packaging structure of the present invention.

[0035] Component designation explanation

[0036] 10 Surface Acoustic Wave Sensor

[0037] 11 Piezoelectric substrate

[0038] 110 High-resistivity substrate layer

[0039] 111 Insulation layer

[0040] 112 Piezoelectric Single Crystal Layer

[0041] 113 Cantilever Beam

[0042] 12 Uniform interdigitated transducers

[0043] 13 Reference Grid

[0044] 130 First Reference Grid

[0045] 131 Second Reference Grid

[0046] 14 Temperature measurement reflector grid

[0047] 15 Pressure Measurement Reflector

[0048] 150 pressure measuring chamber

[0049] 16 Accelerometer Reflector

[0050] 160 mass blocks

[0051] 161 Microporous slit sensitizing structure

[0052] 17 Substrate

[0053] 18. Surface Acoustic Wave Sensor Packaging Structure

[0054] 19 Cover plate

[0055] 20. Receiving base

[0056] 21 Welding and binding leads

[0057] 22 ventilation holes

[0058] 23 Overload damping block

[0059] 24 antennas Detailed Implementation

[0060] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0061] Please see Figures 1 to 7 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0062] Example 1

[0063] like Figures 1 to 3 As shown, this embodiment provides a surface acoustic wave (SAW) sensor 10, which includes: a piezoelectric substrate 11, a uniform interdigital transducer 12, a temperature measurement reflection grating 14, a pressure measurement reflection grating 15, an acceleration measurement reflection grating 16, and two reference gratings 13 disposed on the piezoelectric substrate 11, and a substrate 17 bonded to the piezoelectric substrate 11; wherein, the uniform interdigital transducer 12 is used to excite and receive surface acoustic waves; the piezoelectric substrate 11 is a POI piezoelectric substrate composed of a high-resistivity substrate layer 110, an insulating layer 111, and a piezoelectric single crystal layer 112; the two reference gratings 13 are respectively disposed near the uniform interdigital transducer 12. Both sides; the pressure measurement reflective grating 15 and the acceleration measurement reflective grating 16 are respectively disposed on both sides away from the uniform interdigital transducer 12; the temperature measurement reflective grating 14 is disposed between the reference grating 13 and the pressure measurement reflective grating 15, which are located on the same side of the uniform interdigital transducer 12 as the pressure measurement reflective grating 15; the substrate 17 exposes at least the piezoelectric substrate 11 below the acceleration measurement reflective grating 16 to form a cantilever beam 113; a pressure measuring cavity 150 is formed in the piezoelectric substrate 11 between the temperature measurement reflective grating 14 and the pressure measurement reflective grating 15, penetrating the high-resistivity substrate layer 110 and the insulating layer 111.

[0064] A uniform interdigital transducer is a surface acoustic wave (SAW) device based on the piezoelectric effect. Its main function is to convert electrical signals into acoustic signals through electroacoustic conversion. In its working principle, the uniform interdigital transducer consists of two sets of cross-arranged metal combs. Each set of combs consists of multiple electrode strips of equal width and spacing, which are alternately arranged and connected to the input and output ports. When a high-frequency electrical signal is applied to the input port, the electric field generates a piezoelectric effect between the electrodes, thereby exciting SAW waves on the surface of the piezoelectric substrate. These sound waves propagate along the surface at a specific frequency. Simultaneously, when the sound waves reach the output port, the SAW waves convert acoustic energy into electrical signals through the inverse piezoelectric effect, thus realizing signal transmission and processing. In this embodiment, the uniform interdigital transducer 12 is used to excite and receive SAW waves, i.e., it is a transceiver integrated device.

[0065] like Figure 4As shown, in practical applications, a reader typically transmits a point-frequency pulse signal, which is received by a signal transmission device, such as an antenna, and then converted into a surface acoustic wave (SAW) by the uniform interdigital transducer 12. The SAW propagates outward along the piezoelectric single-crystal layer 112 in the piezoelectric substrate 11 towards both sides of the uniform interdigital transducer 12. It is partially reflected sequentially by the first reference grating 130 on the left side of the uniform interdigital transducer 12, the temperature measurement reflection grating 14, and the pressure measurement reflection grating 15, and simultaneously partially reflected by the second reference grating 131 on the right side of the uniform interdigital transducer 12 and the acceleration measurement reflection grating 16. The reflected SAW is then converted back into an electrical signal by the uniform interdigital transducer 12 and transmitted back to the reader via the antenna. By analyzing the time delay difference and frequency characteristics of each reflection grating, the signal components corresponding to temperature, pressure, and acceleration are separated. That is, the SAW sensor structure of this embodiment achieves independent detection of temperature, pressure, and acceleration through a delayed linear structure. Specifically:

[0066] 1. The principle of independent temperature detection is as follows: When the detected temperature changes, the temperature change will cause a change in the propagation velocity ν(T) of the surface acoustic wave, thereby changing the propagation time delay τ of the surface acoustic wave. The formula for the temperature measurement principle is:

[0067]

[0068] Δτ T =Δτ 温度栅 -Δτ 参考栅2

[0069]

[0070] Where TCD is the temperature coefficient of the piezoelectric single crystal layer 112, in ppm / ℃; ΔT is the temperature change; τ0 is the reference propagation delay of the surface acoustic wave between the uniform interdigital transducer 12 and the temperature measurement reflector grating 14, the delay being calculated from the echo phase obtained by the reader; Δτ is the change in delay time, for example, Δτ 温度栅 Δτ is the change in time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the temperature measurement reflector grating 14. 参考栅 2 represents the change in time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the first reference grating 130, Δτ. T v is the change in time delay of the surface acoustic wave between the temperature measurement reflector grating 14 and the first reference grating 130; l is the distance between the uniform interdigital transducer 12 and the temperature measurement reflector grating 14; v s Let be the propagation speed of surface acoustic waves.

[0071] 2. The independent pressure detection principle is as follows: When the detected pressure changes, the pressure acts on the sensitive area of ​​the sensor, causing a change in stress in the piezoelectric single crystal layer 112, which in turn affects the surface acoustic wave propagation delay τ. The pressure measurement principle formula is:

[0072]

[0073] Δτ P =Δτ 压力栅 -Δτ 温度栅

[0074] Where PCD is the pressure sensitivity coefficient of the piezoelectric single crystal layer 112, in ppm / Pa; ΔP is the pressure change; τ0 is the propagation delay of the surface acoustic wave between the uniform interdigital transducer 12 and the pressure measurement reflector grating 15; Δτ 压力栅 Δτ is the change in time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the pressure measurement reflector grating 15. 温度栅 Δτ is the change in time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the temperature measurement reflector grating 14. P The change in time of the surface acoustic wave between the pressure measuring reflector 15 and the temperature measuring reflector 14 is the amount of time delay.

[0075] 3. The independent detection principle for acceleration is as follows: when the detected acceleration changes, the acceleration causes the cantilever beam 113 (e.g., Figure 1 The deformation of the piezoelectric single crystal layer 112 (as shown) causes a change in the stress distribution, thereby altering the surface acoustic wave propagation delay τ. The formula for the acceleration measurement principle is:

[0076]

[0077] Δτ a =Δτ 加速度栅 -Δτ 参考栅1

[0078] Where ACD is the acceleration sensitivity coefficient of the piezoelectric single crystal layer 112, and the unit is ppm / (m / s²). 2 ); ΔA is the change in acceleration; τ0 is the propagation delay of the surface acoustic wave between the uniform interdigital transducer 12 and the acceleration measurement reflector grating 16; Δτ 加速度栅 Δτ is the change in time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the acceleration measurement reflector 16. 参考栅 1 represents the change in the time delay of the surface acoustic wave between the uniform interdigital transducer 12 and the second reference grating 131, Δτ. a The change in time of the surface acoustic wave between the acceleration measurement reflection grating 16 and the second reference grating 131 is the amount of time delay.

[0079] This embodiment of the surface acoustic wave (SAW) sensor, based on a POI piezoelectric substrate and a multifunctional reflective grating layout, highly integrates temperature, pressure, and acceleration sensing units onto a single chip. The design not only considers the structural optimization of individual sensors in existing technologies but also addresses issues such as cross-coupling between multiple sensors. To achieve decoupling of multiple sensing quantities, two sets of reference reflective gratings are designed: two reference gratings located on either side of the uniform interdigital transducer, and one set each for acceleration, temperature, and pressure measurement. The two reference gratings are used for differential time-delay measurement of the sensing quantities. The temperature measurement reflective grating is positioned close to the reference gratings to effectively ensure that temperature measurement is not affected by other sensing quantities and to effectively suppress environmental noise interference. The acceleration and pressure measurement reflective gratings are positioned on either side of the uniform interdigital transducer, enabling the measurement of pressure and acceleration while effectively avoiding cross-sensitivity effects between these physical quantities. The response signal of the temperature measurement reflective grating not only provides an independent temperature measurement value but also serves as a reference parameter. The pressure and acceleration signals are dynamically compensated. For example, the time delay of the pressure measurement reflector includes the thermal expansion effect of the piezoelectric single crystal layer caused by temperature. By subtracting the linear contribution of the temperature component, the net deformation caused by pressure can be accurately extracted. The sensitivity of the acceleration measurement reflector is affected by temperature drift. The temperature signal is used to correct the change in the elastic modulus of the cantilever beam in real time to ensure the temperature stability of the acceleration measurement. This achieves efficient separation and synchronous detection of multiple parameters such as temperature, pressure and acceleration, avoiding the electromagnetic coupling problem of traditional multi-interdigital transducer structures. The overall structure of the sensor is compact, which greatly reduces the installation difficulty and system maintenance cost in complex environments. It is especially suitable for high-density monitoring scenarios with limited space.

[0080] like Figure 1 As shown, as an example, the material of the piezoelectric single crystal layer 112 in the piezoelectric substrate 11 can be lithium niobate, lithium tantalate, quartz, lead zirconate titanate, or aluminum nitride. The insulating layer 111 can be a silicon dioxide layer, a silicon nitride layer, or an aluminum oxide layer. The high-resistivity substrate layer 110 can be a high-resistivity silicon layer, a high-resistivity silicon carbide layer, or a high-resistivity gallium arsenide layer, but it is not limited to these. Other suitable materials as POI piezoelectric substrates can be used, and the specific selection depends on the actual needs.

[0081] As a preferred example, the high-resistivity substrate 110 is selected as a high-resistivity silicon layer, and the substrate 17 is a glass substrate. An alumina transition layer (not shown in the figure) is pre-formed at the bonding interface between the high-resistivity substrate 110 and the substrate 17, and they are bonded together using a low-temperature anodic bonding process. This bonding method can mitigate the difference in thermal expansion coefficients between the piezoelectric single-crystal layer 112 and the high-resistivity silicon substrate 110, avoiding bonding failure at high temperatures.

[0082] It should be noted that in this embodiment, the propagation direction of the surface acoustic wave is along the interdigital arrangement direction in the uniform interdigital transducer 12. Therefore, the corresponding reflective grating and reference grating are set on both sides of the interdigital arrangement direction of the uniform interdigital transducer 12. The specific structure of the reflective grating and reference grating is not overly restricted, as long as the surface acoustic wave signal can be reflected. For example, in this embodiment, the reflective grating and reference grating are metal strips, which can be formed simultaneously with the uniform interdigital transducer 12 to save on the manufacturing process.

[0083] As an example, for a surface acoustic wave (SAW) sensor operating in the frequency range of 10MHz to 10GHz, the parameters of the uniform interdigital transducer 12 are selected as follows: the metal electrode is an aluminum thin-film electrode with a linewidth of 0.5μm to 1.0μm, a spacing of 0.5μm to 1.0μm, 20 to 50 pairs of interdigitates, and a length of 50μm to 200μm, maintaining consistency along the SAW propagation direction and exciting SAW waves to both sides. For other operating frequencies, the parameters of the uniform interdigital transducer 12 are adjusted accordingly, specifically selected based on actual needs.

[0084] like Figure 2 As shown, in a preferred example, a mass block 160 is fixed under the piezoelectric substrate 11 below the acceleration measurement reflective grating 16, i.e., the mass block 160 is set at the end of the cantilever beam 113. The material of the mass block 160 can be, for example, glass. The mass block 160 can increase the vibration inertia of the cantilever beam and increase the bending deformation of the cantilever beam 113, thereby providing amplified inertial stress to be applied to the POI piezoelectric substrate to change the propagation delay of surface acoustic waves, improve the acceleration measurement sensitivity and measurement range, and at the same time ensure the stable response of high-frequency vibration signals.

[0085] like Figure 3 As shown, as another preferred example, the cantilever beam 113 extends at least to the reference grid 13 on its side, for example, Figure 3 The cantilever beam 113 extends beyond the reference grating 13 on its side. The cantilever beam 113 has a micro-perforation slit enhancement structure 161 in the acceleration-sensitive region (i.e., the region between the reference grating 13 on the right and the acceleration measurement reflection grating 16). The micro-perforation slit enhancement structure 161 consists of a plurality of micro-holes and / or micro-slits extending inward from the lower surface of the high-resistivity substrate 110 toward the piezoelectric single crystal layer 112, with an extension depth not exceeding the thickness of the high-resistivity substrate 110. Figure 3The extension depth of the micro-pore slit-enhancing structure 161 described herein is exactly the thickness of the high-resistivity substrate 110, and in practice, it may not exceed the thickness of the high-resistivity substrate 110. Furthermore, the shape and size of the micropores and / or slits in the micro-pore slit-enhancing structure 161 are not excessively restricted. Similarly, the micro-pore slit-enhancing structure 161 can increase the vibration inertia of the cantilever beam and increase the bending deformation of the cantilever beam 113, thereby providing amplified inertial stress to be applied to the POI piezoelectric substrate to change the propagation delay of surface acoustic waves, improve acceleration measurement sensitivity and measurement range, while ensuring the stable response of high-frequency vibration signals. Therefore, in order to obtain better acceleration measurement sensitivity, a larger measurement range, and ensure the stable response of high-frequency vibration signals, structures such as... Figure 3 The mass block 160 and the microporous slit sensitizing structure 161 in the above.

[0086] like Figure 2 and Figure 3 As shown, the pressure measuring cavity 150 formed in the piezoelectric substrate 11 between the temperature measuring reflective grating 14 and the pressure measuring reflective grating 15, penetrating the high-resistivity substrate layer 110 and the insulating layer 111, can be formed by back cavity etching. During the detection process, the pressure change in the pressure measuring cavity 150 causes deformation of the POI piezoelectric substrate, which changes the surface acoustic wave reflection characteristics and causes a surface acoustic wave time delay shift. This can achieve high-sensitivity capture of minute deformations and improve the accuracy of pressure measurement.

[0087] Example 2

[0088] This embodiment provides a surface acoustic wave sensor packaging structure, which encapsulates the surface acoustic wave sensor 10 disclosed in Embodiment 1. The beneficial effects of the surface acoustic wave sensor 10 in Embodiment 1 can be found in the description in Embodiment 1, and will not be described in detail in this embodiment.

[0089] like Figures 5 to 7 As shown, the surface acoustic wave sensor packaging structure 18 includes: a surface acoustic wave sensor 10 as described in Embodiment 1, a cover plate 19, and a housing base 20; wherein,

[0090] The surface acoustic wave sensor 10 is housed in the housing base 20;

[0091] The cover plate 19 is fastened onto the receiving base 20 to form an SMD packaging structure;

[0092] An antenna 24 is fixed below the accommodating base 20.

[0093] The surface acoustic wave sensor packaging structure 18 of this embodiment adopts an SMD packaging structure, which can be typically used for multi-parameter monitoring of pressure, temperature, and acceleration in aerospace vehicles, such as engine internal temperature monitoring, wing and tail temperature distribution monitoring, evaluation of aircraft surface thermal protection systems, health monitoring of internal aircraft equipment, and real-time monitoring during flight experiments. In practical applications, the surface acoustic wave sensor packaging structure 18 of this embodiment can be fixed to the surface of the object to be measured, ensuring that the housing base 20 is tightly fitted to the mounting surface to avoid external stress interference. Mechanical fixation is achieved through epoxy resin or high-temperature adhesives, while maintaining the antenna. The radiation direction of the 24 is unobstructed; during detection, the reader periodically transmits query pulses, and the echo signal of the surface acoustic wave sensor 10 is transmitted to the reader via a wireless channel; the signal processing unit extracts the time delay and frequency shift information of each reflection grating through Fast Fourier Transform (FFT), separates the temperature, pressure, and acceleration signals by combining the preset coding mapping relationship, and calls the temperature compensation algorithm to correct the cross-sensitivity error; before the first use, full-range calibration is performed under standard temperature and pressure environment to establish a time delay-physical quantity mapping database for each parameter, and online calibration is performed periodically through reference sources (such as constant temperature bath, standard pressure gauge) to correct the sensitivity drift caused by environmental aging.

[0094] As a specific application example, taking aircraft engine monitoring as an example, the surface acoustic wave sensor encapsulation structure 18 is installed outside the engine combustion chamber, and temperature, pressure, and acceleration vibration data are collected in real time via a wireless reader. A temperature measurement reflector monitors the heat distribution on the combustion chamber surface, a pressure measurement reflector detects pressure fluctuations in the fuel lines, and an acceleration measurement reflector captures high-frequency mechanical vibration signals. The reader fuses multi-parameter data and uses a temperature compensation algorithm to eliminate the influence of the thermal environment on pressure and acceleration measurements, ultimately outputting a high-precision operational health status assessment result.

[0095] The surface acoustic wave sensor packaging structure 18 in this embodiment adopts an SMD packaging structure, which makes the overall structure of the device compact and greatly reduces the installation difficulty and system maintenance cost in complex environments. It is especially suitable for high-density monitoring scenarios with limited space, such as aerospace, energy equipment and other technical fields with stringent requirements for monitoring extreme working conditions.

[0096] As an example, the cover plate 19 is selected as a glass cover plate and the receiving base 20 is selected as a ceramic base, which can improve the high temperature resistance of the packaging structure so that the packaging structure can withstand high alternating temperature differences.

[0097] As an example, the surface acoustic wave (SAW) sensor packaging structure 18 achieves electrical signal transmission of the SAW sensor 10 within the packaging structure through bonding leads 21; wherein, the bonding leads 21 are electrically connected to the uniform interdigital transducer 12 in the SAW sensor 10. The bonding leads 21 can be gold wire, silicon-aluminum wire, or platinum wire, but are not limited to these; other suitable bonding lead materials are also acceptable, selected according to actual needs. In this embodiment, the bonding leads 21 are preferably gold wire, and the uniform interdigital transducer 12 is bonded to the bonding leads 21 through gold bumps to ensure high-frequency signal integrity.

[0098] like Figure 5 and Figure 6 As shown, as an example, the surface acoustic wave sensor packaging structure 18 further includes a vent 22, which is disposed on the cover plate 19 or the bottom wall of the receiving base 20. When the vent 22 is disposed on the cover plate 19, the vent 22 penetrates the cover plate 19 and is located above the pressure measuring cavity 150. When the vent 22 is disposed on the bottom wall of the receiving base 20, the vent 22 penetrates the bottom wall of the receiving base 20 and the substrate 17 of the surface acoustic wave sensor 10 to communicate with the pressure measuring cavity 150. When the vent 22 is located on the cover plate 19, it is not connected to the pressure measuring chamber 150, but a sealed space is formed between the pressure measuring chamber 150 and the substrate 17. The external air pressure enters the packaging structure through the vent 22 and forms a pressure difference with the reference air pressure in the pressure measuring chamber 150 to measure the pressure. In this case, inert gas can be filled into the pressure measuring chamber 150 to reduce acoustic wave sensing loss. When the vent 22 is located on the bottom wall of the accommodating base 20, the vent 22 is connected to the pressure measuring chamber 150, but with the substrate 17 and the piezoelectric substrate 11 fixed, the other spaces in the packaging structure are sealed spaces. In this case, the space between the cover plate 19 and the piezoelectric substrate 11 can be further set as a sealed space. The external air pressure enters the packaging structure through the vent 22 and forms a pressure difference with the reference air pressure in the packaging structure to measure the pressure. In this case, inert gas can be filled into the sealed space to reduce acoustic wave sensing loss.

[0099] The vent 22 is directly connected to the inside of the encapsulation structure, which can balance the internal and external air pressure, ensure that the external pressure is transmitted without delay, and avoid overload causing the pressure measuring chamber to fail.

[0100] like Figures 5 to 7 As shown, as an example, the surface acoustic wave sensor packaging structure 18 further includes an overload damping block 23, which is disposed on the inner wall of the cover plate 19 (e.g., Figure 6 and Figure 7 (as shown) and / or the inner side of the bottom wall of the accommodating base 20 (as shown) Figures 5 to 7 (As shown) and corresponding to the acceleration measurement reflection grating region of the surface acoustic wave sensor 10. When the cantilever beam 113 vibrates up and down under acceleration impact, the encapsulation space of the cantilever beam 113 region reserves a buffer gap. When the amplitude is large and it collides with the overload damping block 23, the overload damping block 23 will absorb the mechanical impact, prevent the cantilever beam 113 from breaking, and reduce the impact of mechanical impact on measurement accuracy. Preferably, the material of the overload damping block 23 is a viscoelastic material, such as silicone rubber. The energy dissipation mechanism of the viscoelastic material will absorb the impact vibration and prevent the cantilever beam from breaking.

[0101] In summary, this invention provides a surface acoustic wave (SAW) sensor and its packaging structure. Based on a POI piezoelectric substrate and a multifunctional reflective grating layout, it highly integrates temperature, pressure, and acceleration sensing units onto a single chip. The design not only considers the structural optimization of individual sensors in existing technologies but also addresses issues such as cross-coupling between multiple sensors. To achieve decoupling of multiple sensing quantities, two sets of reference reflective gratings are designed: two reference gratings located on either side of a uniform interdigital transducer, and a set of acceleration measurement reflective gratings, temperature measurement reflective gratings, and pressure measurement reflective gratings. The two reference gratings are used for differential time delay measurement of the sensing quantities. The temperature measurement reflective grating is positioned close to the reference gratings to effectively ensure that temperature measurement is not affected by other sensing quantities and to effectively suppress environmental noise interference. The acceleration and pressure measurement reflective gratings are positioned on either side of the uniform interdigital transducer, enabling the measurement of pressure and acceleration while effectively avoiding cross-sensitivity effects between these physical quantities. The response signal of the temperature measurement reflective grating not only provides an independent temperature measurement value but also serves as a reference parameter for pressure measurement. Dynamic compensation is performed on force and acceleration signals. For example, the time delay change of the pressure measurement reflector includes the thermal expansion effect of the piezoelectric single crystal layer caused by temperature. By subtracting the linear contribution of the temperature component, the net deformation caused by pressure can be accurately extracted. The sensitivity of the acceleration measurement reflector is affected by temperature drift. The change in the elastic modulus of the cantilever beam is corrected in real time using the temperature signal to ensure the temperature stability of acceleration measurement. This achieves efficient separation and synchronous detection of multiple parameter signals such as temperature, pressure, and acceleration, avoiding the electromagnetic coupling problem of traditional multi-interdigital transducer structures. The surface acoustic wave sensor uses an SMD packaging structure, resulting in a compact overall device structure that significantly reduces installation difficulty and system maintenance costs in complex environments. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. In the above embodiments, the descriptions of each embodiment have different emphases; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A surface acoustic wave sensor, characterized in that, The surface acoustic wave (SAW) sensor includes: a piezoelectric substrate, a uniform interdigital SAW transducer, a temperature measurement reflective grating, a pressure measurement reflective grating, an acceleration measurement reflective grating, and two reference gratings disposed on the piezoelectric substrate, and bonded to a substrate under the piezoelectric substrate; wherein... The uniform interdigital transducer is used to excite and receive surface acoustic waves. The piezoelectric substrate is a POI piezoelectric substrate composed of a high-resistivity substrate layer, an insulating layer and a piezoelectric single crystal layer; The two reference grids are respectively disposed on both sides near the uniform interdigital transducer; The pressure measurement reflective grating and the acceleration measurement reflective grating are respectively disposed on two sides away from the uniform interdigital transducer; The temperature measurement reflective grid is disposed between the reference grid and the pressure measurement reflective grid, which are located on the same side of the uniform interdigital transducer as the pressure measurement reflective grid. The substrate exposes at least the piezoelectric substrate beneath the acceleration measurement reflective grating to form a cantilever beam; A pressure measuring cavity is formed in the piezoelectric substrate between the temperature measuring reflective grating and the pressure measuring reflective grating, penetrating the high-resistivity substrate layer and the insulating layer.

2. The surface acoustic wave sensor according to claim 1, characterized in that: The material of the piezoelectric single crystal layer in the piezoelectric substrate is lithium niobate, lithium tantalate, quartz, lead zirconate titanate, or aluminum nitride; the insulating layer is a silicon dioxide layer, a silicon nitride layer, or an aluminum oxide layer; and the high-resistivity substrate layer is a high-resistivity silicon layer, a high-resistivity silicon carbide layer, or a high-resistivity gallium arsenide layer.

3. The surface acoustic wave sensor according to claim 1, characterized in that: The high-resistivity substrate layer is a high-resistivity silicon layer, the substrate is a glass substrate, and the high-resistivity substrate layer and the substrate are pre-formed with an alumina transition layer at the bonding interface and bonded based on a low-temperature anodic bonding process.

4. The surface acoustic wave sensor according to claim 1, characterized in that: A mass block is fixed under the piezoelectric substrate below the acceleration measurement reflective grating.

5. The surface acoustic wave sensor according to claim 1 or 4, characterized in that: The cantilever beam extends at least to the reference gate near its side, and the cantilever beam is provided with a micro-pore slit sensitization structure in the acceleration sensitive region. The micro-pore slit sensitization structure is a plurality of micro-pores and / or micro-slits extending inward from the lower surface of the high-resistivity substrate towards the piezoelectric single crystal layer and extending to a depth not exceeding the thickness of the high-resistivity substrate.

6. The surface acoustic wave sensor according to claim 1, characterized in that: The metal electrodes of the uniform interdigital transducer are aluminum thin film electrodes with a linewidth of 0.5μm to 1.0 μm, a spacing of 0.5μm to 1.0 μm, 20 to 50 pairs of interdigitates, and a length of 50μm to 200μm. They are kept consistent along the direction of surface acoustic wave propagation and excite surface acoustic waves to both sides. The operating frequency is in the frequency range of 10MHz to 10GHz.

7. A surface acoustic wave sensor packaging structure, characterized in that, The packaging structure includes: a surface acoustic wave sensor, a cover plate, and a housing base as described in any one of claims 1 to 6; wherein... The surface acoustic wave sensor is housed in the accommodating base; The cover plate is fastened onto the receiving base to form an SMD packaging structure; An antenna is fixed below the accommodating base.

8. The surface acoustic wave sensor packaging structure according to claim 7, characterized in that: The cover plate is a glass cover plate, and the accommodating base is a ceramic base.

9. The surface acoustic wave sensor packaging structure according to claim 7, characterized in that: The packaging structure also includes solder bonding leads, which are electrically connected to the uniform interdigital transducer.

10. The surface acoustic wave sensor packaging structure according to claim 9, characterized in that: The welding bonding leads are gold wire, silicon-aluminum wire, or platinum wire.

11. The surface acoustic wave sensor packaging structure according to claim 7, characterized in that: The encapsulation structure further includes a vent hole, which is disposed on the cover plate or the bottom wall of the accommodating base. When the vent hole is disposed on the cover plate, it penetrates the cover plate and is located above the pressure measuring chamber. When the vent hole is disposed on the bottom wall of the accommodating base, it penetrates the bottom wall of the accommodating base and the substrate of the surface acoustic wave sensor to communicate with the pressure measuring chamber.

12. The surface acoustic wave sensor packaging structure according to claim 11, characterized in that: When the vent is located on the cover plate, the pressure measuring chamber forms a sealed space and is vented with inert gas; when the vent is located on the bottom wall of the accommodating base, a sealed space is formed between the cover plate and the piezoelectric substrate and is vented with inert gas.

13. The surface acoustic wave sensor packaging structure according to claim 7, characterized in that: The encapsulation structure also includes an overload damping block, which is disposed on the inner wall of the cover plate and / or the inner side of the bottom wall of the accommodating base and corresponds to the acceleration measurement reflection grating area of ​​the surface acoustic wave sensor.

14. The surface acoustic wave sensor packaging structure according to claim 13, characterized in that: The overload damping block is made of silicone rubber.

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