High-temperature-resistant pressure sensor packaging structure and packaging method thereof

Abstract

This invention discloses a high-temperature resistant pressure sensor packaging structure and method, including a sensor head assembly, a ferrule connector, and a tail-end fixing device. The sensor head assembly includes a sensor cap, a high-temperature resistant ceramic adhesive, a SiC ceramic substrate, a sensor base, a metal extension tube, a gold-plated optical fiber, a metal sealing ring, an optical fiber ferrule, and a SiC sensing element. In this invention, the SiC sensing element and the SiC ceramic substrate are connected by nickel (Ni) diffusion bonding, which is simpler and more reliable than compression sealing. The SiC sensing element and the SiC ceramic substrate have the same coefficient of thermal expansion, ensuring good airtightness of the bonding interface at high temperatures without leakage. The tight fit of the metal sealing ring achieves gap sealing between the three-layer SiC sensing structure and the encapsulated sensor cap. Laser welding is used to seal the sensor cap and sensor base, and the sensor base and metal extension tube. These three methods achieve airtight encapsulation of the sensor, avoiding the risk of sensor leakage.

Description

Technical Field

[0001] This invention relates to the field of sensor packaging technology, and in particular to a high-temperature pressure sensor packaging structure and packaging method thereof. Background Technology

[0002] To address the pressure measurement needs in extreme environments such as the combustion chambers of aero-engines or the high-temperature zones of chemical machinery, research is being conducted on fiber optic Fabry-Perot pressure sensors that are resistant to high temperatures, corrosion, and electromagnetic interference. This is of great significance for monitoring pressure conditions in extreme environments such as high temperatures. However, existing silicon-based pressure sensors are limited by the materials themselves and cannot be used for pressure measurement in high-temperature environments; the simple structure of the sensing element and optical fiber is easily damaged by impact in the high-temperature zones of engine combustion chambers or chemical machinery; and the lack of hermetic sealing in the overall sensor structure makes the sensor a leakage channel for the engine, thus seriously affecting pressure measurement.

[0003] CN110146203A discloses a high-temperature resistant fiber optic pressure sensor packaging structure. The pressure-sensitive element is mounted in a positioning cap and an adapter post, and sealed by threaded fastening. The positioning cap and adapter post are sealed using laser welding. The threaded fastening seal requires a high degree of flatness in the contact surface between the pressure-sensitive element and the packaging structure. The applied force is difficult to adjust; excessive force may crush the element, while insufficient force may cause gas leakage through the narrow through-hole of the adapter post. Inconsistent thermal expansion coefficients between the pressure-sensitive element and the packaging structure can also cause gas leakage at high temperatures. The optical fiber is only fixed at the adapter post; the entire optical fiber lacks encapsulation protection, making it susceptible to breakage under stress.

[0004] CN205228702U discloses a fiber optic high-voltage sensor based on the FP interferometry principle. The sensing diaphragm is glued to the metal fiber ferrule with epoxy resin, and the sides of the metal fiber ferrule and the base are sealed with epoxy resin. However, this method is prone to leakage under extreme conditions in fields such as petroleum and chemical industries.

[0005] CN115196582A discloses a high-pressure resistant MEMS pressure sensor packaging structure, which uses glass slurry sintering to seal the stepped pressure-sensitive unit to a Kovar alloy base, and then welds the Kovar alloy base to a stainless steel base for sealing. However, glass is not resistant to high temperatures, and the connection between the pressure-sensitive unit and the Kovar alloy base will fail and leak at high temperatures.

[0006] Existing pressure sensor packaging methods based on MEMS technology mostly involve threaded compression and adhesive sealing. Although these methods can detect pressure, their detection capabilities are limited by the packaging method, making it difficult to further apply them in high-temperature environments. Summary of the Invention

[0007] The purpose of this invention is to provide a high-temperature resistant pressure sensor packaging structure and method to solve the problems existing in the prior art. It utilizes bonding of the SiC sensing element to the SiC ceramic substrate, a metal sealing ring, and laser welding to achieve a sealing function, thus avoiding sensor leakage. Then, the three-layer sensing structure is encapsulated with a high-temperature resistant metal, and the gold-plated optical fiber is encapsulated with an optical fiber ferrule, a polytetrafluoroethylene tube, and a metal extension tube to achieve pressure and temperature detection at high temperatures.

[0008] To achieve the above objectives, the present invention provides the following solution:

[0009] This invention provides a high-temperature resistant pressure sensor packaging structure, including a sensor head device, a ferrule connector, and a tail end fixing device;

[0010] The sensing head device includes a sensing cap, a high-temperature resistant ceramic adhesive, a SiC ceramic substrate, a sensing base, a metal extension tube, a gold-plated optical fiber, a metal sealing ring, an optical fiber ferrule, and a SiC sensing element. The sensing base is disposed at the tail end of the sensing cap. The SiC ceramic substrate is encapsulated within the cavity formed by the sensing base and the sensing cap. The bonding surfaces of the SiC sensing element and the head end of the SiC ceramic substrate are bonded together via nickel diffusion bonding to form a three-layer SiC sensing structure. The head end of the sensing cap has a pressure-sensing hole opposite to the SiC sensing element. The metal sealing ring is disposed between the SiC ceramic substrate and the sensing cap, and the abutting surface at the head end of the sensing base contacts and abuts against the substrate. The metal sealing ring; the SiC ceramic substrate has a ferrule mounting hole at the first end and an adhesive dispensing hole at the last end, the optical fiber ferrule is inserted into the ferrule mounting hole and contacts the SiC sensing element; the metal extension tube is connected to the last end of the sensing base, one end of the gold-plated optical fiber passes through the inner hole of the optical fiber ferrule and contacts the SiC sensing element, the other end of the gold-plated optical fiber passes through the metal extension tube and extends out of the metal extension tube, the optical fiber ferrule and the SiC ceramic substrate are fixed in the adhesive dispensing hole by the high-temperature resistant ceramic adhesive, and the gold-plated optical fiber and the optical fiber ferrule are fixed in the adhesive dispensing hole by the high-temperature resistant ceramic adhesive.

[0011] The ferrule connector is movably connected to the metal extension tube, and the tail end fixing device is disposed at the tail end of the metal extension tube for radial positioning of the gold-plated optical fiber.

[0012] Preferably, the sensor cap has three stepped holes with gradually increasing diameters arranged from the first end to the last end, namely inner hole one, inner hole two, and inner hole three. The outer wall of the SiC ceramic base is provided with a positioning shoulder surface, which is engaged with the shoulder surface of the hole between inner hole one and inner hole two. The inner hole at the first end of the sensor base has the same diameter as inner hole two. The outer diameter of the SiC ceramic base at the first end of the positioning shoulder surface is the same as the diameter of inner hole one. The outer diameter of the SiC ceramic base at the last end of the positioning shoulder surface is the same as the diameter of inner hole two. The last end face of the SiC ceramic base abuts against the bottom of the inner hole at the first end of the sensor base. The first end of the sensor base is a plug-in part that is inserted into inner hole three. The outer diameter of the plug-in part is smaller than the outer diameter of the sensor base body, so that a shoulder surface is formed between them. The connecting surface at the last end of the sensor cap is connected to the shoulder surface on the outer wall of the sensor base.

[0013] Preferably, the metal sealing ring is disposed between the outer wall of the SiC ceramic substrate and the wall of the inner hole three, and the abutting surface of the first end of the sensing seat contacts and abuts the non-opening surface of the metal sealing ring.

[0014] Preferably, the tail end of the sensor base is a connecting part that connects to the metal extension tube, and the connecting part is provided with a threaded hole, and the metal extension tube is threaded into the threaded hole.

[0015] Preferably, the connection between the sensor cap and the sensor base, and the connection between the sensor base and the metal extension tube, are sealed by laser welding.

[0016] Preferably, the SiC sensing element includes a SiC sensing film and a SiC sensing substrate, wherein the SiC sensing film is bonded to the SiC sensing substrate, the outer portion of the SiC sensing film is a pressure-sensitive part, and the inner side of the SiC sensing film opposite to the SiC sensing substrate is a vacuum Fabry-Perot cavity.

[0017] Preferably, the tail end fixing device is a polytetrafluoroethylene (PTFE) tube, the outer wall of the PTFE tube is fixed to the inner wall of the metal extension tube with glue, the diameter of the gold-plated optical fiber is equal to the inner diameter of the PTFE tube, and the gold-plated optical fiber passes through the inner hole of the PTFE tube.

[0018] Preferably, the sensor base, sensor cap, and metal extension tube are all made of Inconel alloy.

[0019] Based on the above-mentioned high-temperature resistant pressure sensor packaging structure, the present invention also provides a packaging method for the high-temperature resistant pressure sensor packaging structure, comprising the following steps:

[0020] Step 1: Using reactive ion etching technology, a Fabry-Perot cavity blind hole is fabricated on the SiC chip to create a SiC sensing film. Then, the SiC sensing film and the SiC sensing substrate are subjected to wet surface treatment, pre-bonded in air, and then transferred into a bonding machine for direct bonding to form a SiC sensing element.

[0021] Step 2: Nickel diffusion bonding between SiC sensing element and SiC ceramic substrate; the surface roughness Ra of the bonding surface of SiC ceramic substrate is polished to less than 20nm, and then wet surface treatment is performed on SiC sensing element; 500nm nickel is sputtered on the lower surface of SiC sensing element and pre-bonded with the bonding surface of SiC ceramic substrate before being moved into bonding machine to complete the preparation of SiC sensing three-layer structure.

[0022] Step 3: The outer surface of the SiC ceramic substrate and the inner hole of the sensor cap are polished to a surface roughness Ra of less than 0.2 μm; first, the metal sealing ring is installed on the outer wall of the SiC ceramic substrate, and then it is installed at the inner hole of the first end of the sensor substrate; using the abutting surface of the sensor substrate to abut against the non-opening surface of the metal sealing ring, the metal sealing ring is pushed into the depth of the mounting groove formed by the outer wall of the SiC ceramic substrate and the inner hole of the sensor cap, until the positioning shoulder surface of the SiC ceramic substrate contacts the hole shoulder surface of the sensor cap and cannot be pushed further.

[0023] Step 4: Fix the outer wall of the PTFE tube to the inner wall of the metal tube end with glue, and connect the threaded hole of the sensor base to the front thread of the metal extension tube; pass the gold-plated optical fiber through the PTFE tube, the metal extension tube and the sensor base in sequence, and insert it into the inner hole of the optical fiber ferrule; install the optical fiber ferrule and the gold-plated optical fiber in the ferrule mounting hole of the SiC ceramic substrate, so that the end face of the gold-plated optical fiber is in contact with the inner surface of the SiC sensing element, and then use high-temperature resistant ceramic glue in the glue dispensing hole of the SiC ceramic substrate to fix the gold-plated optical fiber and the optical fiber ferrule.

[0024] Step 5: After the high-temperature resistant ceramic adhesive has completely cured, move the sensor base to connect with the sensor cap; use laser welding to connect and seal the connecting surface of the sensor cap's tail end to the shoulder surface on the sensor base, and use laser welding to seal the connection between the sensor base and the metal extension tube.

[0025] Preferably, in step one, the bonding temperature is 1100℃, the bonding pressure is 50MPa, the bonding time is 3 hours, and the bonding vacuum is less than 50Pa; in step two, the bonding temperature is 900℃, the bonding pressure is 50MPa, and the bonding time is 3 hours.

[0026] The present invention achieves the following beneficial technical effects compared to the prior art:

[0027] 1. The high-temperature pressure sensor packaging structure and packaging method provided by the present invention connect the SiC sensing element and the SiC ceramic substrate through nickel (Ni) diffusion bonding, which is simpler and more reliable than compression sealing.

[0028] 2. The SiC sensing element and the SiC ceramic substrate have the same coefficient of thermal expansion, ensuring good hermeticity at high temperatures after bonding without leakage. A tight fit of the metal sealing ring seals the gap between the three-layer SiC sensing structure and the encapsulated sensing cap. Laser welding is used to seal the sensing cap and sensor base, and the sensor base and metal extension tube. These three methods achieve hermetic encapsulation of the sensor, mitigating the risk of sensor leakage.

[0029] 3. The SiC sensing three-layer structure and optical fiber are protected by high-temperature resistant metal encapsulation, avoiding the impact of external shocks on the sensor and ensuring the sensor's working stability at high temperatures. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the high-temperature pressure sensor packaging structure in this invention;

[0032] Figure 2 This is an assembly diagram of the sensor head device in this invention;

[0033] Figure 3 This is an assembly diagram of the tail end fixing device in this invention;

[0034] Figure 4 This is a schematic diagram of the structure of the SiC sensing element in this invention;

[0035] Figure 5 This is an assembly diagram of the three-layer SiC sensing structure in this invention;

[0036] Figure 6 This is a cross-sectional view of the SiC ceramic substrate in this invention;

[0037] Figure 7 This is a cross-sectional view of the sensor cap in this invention;

[0038] Figure 8 This is a cross-sectional view of the sensor base in this invention;

[0039] In the diagram: 1-Sensor head device, 2-Compression fitting, 3-Tail end fixing device, 4-Sensor cap, 4A-Pressure sensing hole, 4B-Hole shoulder surface, 4C-Inner hole three, 4D-Connecting surface, 4E-Inner hole one, 4F-Inner hole two, 5-High temperature resistant ceramic adhesive, 6-SiC ceramic base, 6A-Outer wall of SiC ceramic base, 6B-Flange mounting hole, 6C-Dispensing hole, 6D-Bonding surface, 6E-Positioning shaft shoulder surface, 7-Sensor seat, 7A-Threaded hole, 7B-Abutting surface, 7C-Head end inner hole, 7D-Shoulder surface, 8-SiC sensing element, 9-Fiber optic ferrule, 10-Metal sealing ring, 11-Metal extension tube, 12-Gold-plated fiber, 13-PTFE tube, 14-SiC sensing film, 14A-Pressure sensitive part, 14B-Vacuum Fabry-Perot cavity, 15-SiC sensing substrate. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] The purpose of this invention is to provide a high-temperature resistant pressure sensor packaging structure and packaging method to solve the problems existing in the prior art.

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The high-temperature pressure sensor packaging structure in this embodiment is as follows: Figures 1-8 As shown, it includes a sensor head device 1, a ferrule connector 2, and a tail end fixing device 3;

[0044] The sensor head device 1 includes a sensor cap 4, a high-temperature resistant ceramic adhesive 5, a SiC ceramic substrate 6, a sensor base 7, a metal extension tube 11, a gold-plated optical fiber 12, a metal sealing ring 10, an optical fiber ferrule 9, and a SiC sensing element 8. The sensing base 7 is located at the tail end of the sensor cap 4. The SiC ceramic substrate 6 is encapsulated within the cavity formed by the sensing base 7 and the sensor cap 4. The bonding surface 6D of the SiC sensing element 8 and the head end of the SiC ceramic substrate 6 are bonded together by nickel diffusion bonding to form a three-layer SiC sensing structure. The head end of the sensor cap 4 is provided with a pressure-sensing hole 4A opposite to the SiC sensing element 8. The metal sealing ring 10 is located between the SiC ceramic substrate 6 and the sensor cap 4, and the head end of the sensing base 7 abuts against... The surface 7B contacts and abuts against the metal sealing ring 10; the SiC ceramic base 6 is provided with a ferrule mounting hole 6B at the first end and a dispensing hole 6C at the last end. The fiber optic ferrule 9 is inserted into the ferrule mounting hole 6B and contacts the SiC sensing element 8; the metal extension tube 11 is connected to the last end of the sensing base 7. One end of the gold-plated fiber 12 passes through the inner hole of the fiber optic ferrule 9 and contacts the SiC sensing element 8. The other end of the gold-plated fiber 12 passes through the metal extension tube 11 and extends out of the metal extension tube 11. The fiber optic ferrule 9 and the SiC ceramic base 6 are fixed in the dispensing hole 6C by high-temperature resistant ceramic adhesive 5. The gold-plated fiber 12 and the fiber optic ferrule 9 are fixed in the dispensing hole 6C by high-temperature resistant ceramic adhesive 5.

[0045] The ferrule 2 is movably connected to the metal extension tube 11. In order to measure different high-temperature zone positions, the ferrule 2 can be moved on the metal extension tube 11. In order to cope with different equipment interfaces, the ferrule 2 can be replaced with different sizes.

[0046] The tail end fixing device 3 is set at the tail end of the metal extension tube 11 and is used for radial limiting of the gold-plated optical fiber 12.

[0047] In this specific embodiment, the sensor cap 4 has three stepped holes with gradually increasing diameters arranged from the first end to the last end, namely inner hole one 4E, inner hole two 4F, and inner hole three 4C. A positioning shoulder surface 6E is provided on the outer wall 6A of the SiC ceramic base, and the positioning shoulder surface 6E is engaged with the shoulder surface 4B between inner hole one 4E and inner hole two 4F. The diameter of the inner hole 7C at the first end of the sensor base 7 is equal to that of the inner hole two 4F. The SiC ceramic base 6 at the first end of the positioning shoulder surface 6E... The outer diameter of the sensor base 6 is equal to the diameter of the inner hole 4E. The outer diameter of the SiC ceramic base 6 at the tail end of the positioning shoulder surface 6E is equal to the diameter of the inner hole 4F. The tail end face of the SiC ceramic base 6 abuts against the bottom of the inner hole 7C at the head end of the sensor base 7. The head end of the sensor base 7 is a plug-in part inserted into the inner hole 4C. The outer diameter of the plug-in part is smaller than the outer diameter of the sensor base 7 body, so that a shoulder surface 7D is formed between the two. The connecting surface 4D at the tail end of the sensor cap 4 is connected to the shoulder surface 7D on the outer wall of the sensor base 7.

[0048] In this specific embodiment, the metal sealing ring 10 is disposed between the outer wall 6A of the SiC ceramic substrate and the hole wall of the inner hole 4C. The abutting surface 7B of the first end of the sensor seat 7 contacts and abuts against the non-opening surface of the metal sealing ring 10. The metal sealing ring 10 has a "C" shaped cross-section and consists of a compressible spring and a thin metal ring. It is tightly fitted in the mounting groove and can compensate for the gap between the SiC ceramic substrate 6 and the sensor cap 4 caused by thermal expansion at high temperatures.

[0049] In this specific embodiment, the tail end of the sensor base 7 is a connecting part that is connected to the metal extension tube 11. A threaded hole 7A is provided in the connecting part, and the metal extension tube 11 is threadedly connected to the threaded hole 7A.

[0050] In this specific embodiment, the connection between the sensor cap 4 and the sensor base 7, and the connection between the sensor base 7 and the metal extension tube 11, are both sealed by laser welding. When pressurized gas enters from the pressure-sensing hole 4A of the sensor cap 4, it ensures that the pressurized gas only contacts the sensing diaphragm and does not leak along the sensor pipe.

[0051] In this specific embodiment, the SiC sensing element 8 includes a SiC sensing film 14 and a SiC sensing substrate 15. The SiC sensing film 14 and the SiC sensing substrate 15 are bonded together. The outer part of the SiC sensing film 14 is a pressure-sensitive part 14A, and the inner side of the SiC sensing film 14 opposite to the SiC sensing substrate 15 is a vacuum Fabry-Perot cavity 14B.

[0052] In this specific embodiment, the tail-end fixing device 3 is a polytetrafluoroethylene (PTFE) tube 13. The outer wall of the PTFE tube 13 is fixed to the inner wall of the metal extension tube 11 with glue. The diameter of the gold-plated optical fiber 12 is equal to the inner diameter of the PTFE tube 13, and the gold-plated optical fiber 12 passes through the inner hole of the PTFE tube 13. That is, the front end of the gold-plated optical fiber 12 is fixed, and the rear end is kept in a centered state. The gold-plated optical fiber 12 cannot move radially, but can freely expand axially at high temperatures without breaking.

[0053] In this specific embodiment, the sensor base 7, sensor cap 4, and metal extension tube 11 are all made of Inconel alloy to meet the requirements for use at high temperatures.

[0054] Based on the above-described high-temperature resistant pressure sensor packaging structure, this embodiment also provides a packaging method for the high-temperature resistant pressure sensor packaging structure, including the following steps:

[0055] Step 1: Using reactive ion etching (RIE) technology, a Fabry-Perot cavity blind via is fabricated on the SiC chip to create a SiC sensing film 14. Subsequently, the SiC sensing film 14 and the SiC sensing substrate 15 are subjected to wet surface treatment, pre-bonded in air, and then transferred to a bonding machine. The bonding temperature is 1100℃, the bonding pressure is 50 MPa, the bonding time is 3 hours, and the bonding vacuum degree is less than 50 Pa. The SiC sensing element 8 is directly bonded to form the SiC sensing element 8.

[0056] Step 2: Nickel (Ni) diffusion bonding of SiC sensing element 8 to SiC ceramic substrate 6; the surface roughness Ra of bonding surface 6D of SiC ceramic substrate 6 is polished to less than 20 nm, and then wet surface treatment is performed on SiC sensing element 8; 500 nm of nickel (Ni) is sputtered on the lower surface of SiC sensing element 8 and pre-bonded with bonding surface 6D of SiC ceramic substrate 6, and then it is moved into a bonding machine. The bonding temperature is 900℃, the bonding pressure is 50 MPa, and the bonding time is 3 hours to complete the preparation of SiC sensing three-layer structure.

[0057] Step 3: The outer surface of the SiC ceramic base 6 and the inner hole 4C of the sensor cap 4 are polished to a surface roughness Ra of less than 0.2 μm; first, the metal sealing ring 10 is installed on the outer wall 6A of the SiC ceramic base, and then it is installed at the inner hole 7C at the beginning of the sensor base 7; using the abutting surface 7B of the sensor base 7 to abut against the non-opening surface of the metal sealing ring 10, the metal sealing ring 10 is pushed into the depth of the mounting groove formed by the outer wall 6A of the SiC ceramic base and the inner hole 4C of the sensor cap 4, until the positioning shoulder surface 6E of the SiC ceramic base 6 contacts the hole shoulder surface 4B of the sensor cap 4 and cannot be pushed;

[0058] Step 4: Fix the outer wall of the PTFE tube 13 to the inner wall of the metal tube end with glue. Connect the threaded hole 7A of the sensor base 7 to the front end of the metal extension tube 11. The gold-plated optical fiber 12 passes through the PTFE tube 13, the metal extension tube 11 and the sensor base 7 in sequence and is inserted into the inner hole of the optical fiber ferrule 9. Install the optical fiber ferrule 9 and the gold-plated optical fiber 12 in the ferrule mounting hole 6B of the SiC ceramic base 6 so that the end face of the gold-plated optical fiber 12 is in close contact with the inner surface of the SiC sensing element 8. Then, use high-temperature resistant ceramic glue 5 to fix the gold-plated optical fiber 12 and the optical fiber ferrule 9 in the glue dispensing hole 6C of the SiC ceramic base 6.

[0059] Step 5: After the high-temperature resistant ceramic adhesive 5 has completely cured, move the sensor base 7 to connect with the sensor cap 4; the connecting surface 4D at the tail end of the sensor cap 4 and the shoulder surface 7D on the sensor base 7 are connected and sealed by laser welding, and the connection between the sensor base 7 and the metal extension tube 11 is sealed by laser welding.

[0060] In the above embodiments:

[0061] Reactive ion etching (RIE): Applying radio frequency voltage between planar electrodes to chemically and physically etch the sample using the generated plasma.

[0062] Wet surface treatment: 1. Alternate ultrasonic cleaning with acetone / ethanol / deionized water solution, each cleaning 3 times, 5 minutes each time;

[0063] 2. Treat with piranha solution at 80℃ for 10 min;

[0064] The solution ratio is sulfuric acid: hydrogen peroxide = 3:1;

[0065] 3. Standard cleaning solution No. 1 (SC1) at 80℃ for 10 min;

[0066] The solution ratio is ammonia: hydrogen peroxide: deionized water = 1:1:5;

[0067] 4. Standard cleaning solution No. 2 (SC2) at 80℃ for 10 min;

[0068] The solution ratio is hydrochloric acid: hydrogen peroxide: deionized water = 1:1:6;

[0069] 5. Rinse three times with deionized water.

[0070] Pressure and temperature measurement principle: The sensor is based on the Fabry-Perot interference principle. The sensing element has three reflective interfaces: the lower surface of the SiC sensing substrate 15, the upper surface of the SiC sensing substrate 15, and the lower surface of the SiC sensing film 14. These three interfaces form an interference spectrum through multi-beam interference. Therefore, the lower surface of the SiC sensing film 14 and the lower surface of the SiC sensing film 14 constitute a vacuum Fabry-Perot cavity 14B. When pressure is applied, the pressure-sensitive part 14A of the SiC sensing film 14 deforms, causing a change in the length of the vacuum Fabry-Perot cavity 14B. The magnitude of the pressure can be deduced by demodulating the optical path difference of the vacuum Fabry-Perot cavity 14B. Due to the thermal expansion and thermo-optical effects of SiC material, it is sensitive to temperature. Therefore, the SiC sensing substrate 15 can be used as a temperature-sensing Fabry-Perot cavity. Thus, the temperature value can be obtained by demodulating the optical path difference of the SiC sensing substrate 15 Fabry-Perot cavity.

[0071] Usage: The sensor is installed at the reserved interface in the combustion chamber of an aircraft engine or chemical machinery equipment via the compression fitting 2. The sensor head device 1 extends to the desired measurement position, and the tail fiber is connected to the ASE broadband light source and spectrometer via a fiber optic circulator. The pressure-sensitive part 14A of the SiC sensing element 8 deforms under pressure, the cavity of the SiC sensing substrate 15 lengthens due to heat, and the vacuum Fabry-Perot cavity 14B shortens in the cavity length direction, resulting in a shift in the interference spectrum. Pressure and temperature are obtained by demodulating the spectrum.

[0072] This invention has illustrated its principles and implementation methods using specific examples. The descriptions of these embodiments are merely illustrative of the method and its core ideas; furthermore, those skilled in the art will recognize that modifications may be made to the specific implementation methods and application scope based on the principles of this invention. Therefore, the content of this specification should not be construed as limiting the invention.

Claims

1. A high-temperature resistant pressure sensor packaging structure, characterized in that: Includes sensor head assembly, ferrule connector, and tail end fixing device; The sensing head device includes a sensing cap, a high-temperature resistant ceramic adhesive, a SiC ceramic substrate, a sensing base, a metal extension tube, a gold-plated optical fiber, a metal sealing ring, an optical fiber ferrule, and a SiC sensing element. The sensing base is disposed at the tail end of the sensing cap. The SiC ceramic substrate is encapsulated within the cavity formed by the sensing base and the sensing cap. The bonding surfaces of the SiC sensing element and the head end of the SiC ceramic substrate are bonded together via nickel diffusion bonding to form a three-layer SiC sensing structure. The head end of the sensing cap has a pressure-sensing hole opposite to the SiC sensing element. The metal sealing ring is disposed between the SiC ceramic substrate and the sensing cap, and the abutting surface at the head end of the sensing base contacts and abuts against the substrate. The metal sealing ring; the SiC ceramic substrate has a ferrule mounting hole at the first end and an adhesive dispensing hole at the last end, the optical fiber ferrule is inserted into the ferrule mounting hole and contacts the SiC sensing element; the metal extension tube is connected to the last end of the sensing base, one end of the gold-plated optical fiber passes through the inner hole of the optical fiber ferrule and contacts the SiC sensing element, the other end of the gold-plated optical fiber passes through the metal extension tube and extends out of the metal extension tube, the optical fiber ferrule and the SiC ceramic substrate are fixed in the adhesive dispensing hole by the high-temperature resistant ceramic adhesive, and the gold-plated optical fiber and the optical fiber ferrule are fixed in the adhesive dispensing hole by the high-temperature resistant ceramic adhesive. The ferrule connector is movably connected to the metal extension tube, and the tail end fixing device is disposed at the tail end of the metal extension tube for radial limiting of the gold-plated optical fiber; the tail end fixing device is a polytetrafluoroethylene tube. The sensor cap has three stepped holes with gradually increasing diameters, arranged sequentially from the first end to the last end. These are inner hole one, inner hole two, and inner hole three. The outer wall of the SiC ceramic base has a positioning shoulder surface, which engages with the shoulder surface between inner hole one and inner hole two. The diameter of the inner hole at the first end of the sensor base is equal to that of inner hole two. The outer diameter of the SiC ceramic base at the first end of the positioning shoulder surface is equal to that of inner hole one. The outer diameter of the SiC ceramic base at the last end of the positioning shoulder surface is equal to that of inner hole two, and the last end face of the SiC ceramic base abuts against the bottom of the inner hole at the first end of the sensor base. The first end of the sensor base is a plug-in part that inserts into inner hole three. The outer diameter of the plug-in part is smaller than the outer diameter of the sensor base body, forming a shoulder surface between them. The connecting surface at the last end of the sensor cap connects with the shoulder surface on the outer wall of the sensor base.

2. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The metal sealing ring is disposed between the outer wall of the SiC ceramic substrate and the wall of the inner hole three. The abutting surface of the first end of the sensing seat contacts and abuts the non-opening surface of the metal sealing ring.

3. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The tail end of the sensor base is a connecting part that connects to the metal extension tube. The connecting part is provided with a threaded hole, and the metal extension tube is threaded into the threaded hole.

4. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The connection between the sensor cap and the sensor base, and the connection between the sensor base and the metal extension tube, are all sealed by laser welding.

5. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The SiC sensing element includes a SiC sensing film and a SiC sensing substrate. The SiC sensing film is bonded to the SiC sensing substrate. The outer portion of the SiC sensing film is a pressure-sensitive part, and the inner side of the SiC sensing film opposite to the SiC sensing substrate is a vacuum Fabry-Perot cavity.

6. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The outer wall of the polytetrafluoroethylene tube is fixed to the inner wall of the metal extension tube by potting adhesive. The diameter of the gold-plated optical fiber is equal to the inner diameter of the polytetrafluoroethylene tube, and the gold-plated optical fiber passes through the inner hole of the polytetrafluoroethylene tube.

7. The high-temperature pressure sensor packaging structure according to claim 1, characterized in that: The sensor base, sensor cap, and metal extension tube are all made of Inconel alloy.

8. A packaging method for a high-temperature resistant pressure sensor packaging structure, applied to the high-temperature resistant pressure sensor packaging structure according to any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Using reactive ion etching technology, a Fabry-Perot cavity blind hole is fabricated on the SiC chip to create a SiC sensing film. Then, the SiC sensing film and the SiC sensing substrate are subjected to wet surface treatment, pre-bonded in air, and then transferred into a bonding machine for direct bonding to form a SiC sensing element. Step 2: Nickel diffusion bonding between SiC sensing element and SiC ceramic substrate; the surface roughness Ra of the bonding surface of SiC ceramic substrate is polished to less than 20nm, and then wet surface treatment is performed on SiC sensing element; 500nm nickel is sputtered on the lower surface of SiC sensing element and pre-bonded with the bonding surface of SiC ceramic substrate before being moved into bonding machine to complete the preparation of SiC sensing three-layer structure. Step 3: The outer surface of the SiC ceramic substrate and the inner hole of the sensor cap are polished to a surface roughness Ra of less than 0.2 μm; first, the metal sealing ring is installed on the outer wall of the SiC ceramic substrate, and then it is installed at the inner hole of the first end of the sensor substrate; using the abutting surface of the sensor substrate to abut against the non-opening surface of the metal sealing ring, the metal sealing ring is pushed into the depth of the mounting groove formed by the outer wall of the SiC ceramic substrate and the inner hole of the sensor cap, until the positioning shoulder surface of the SiC ceramic substrate contacts the hole shoulder surface of the sensor cap and cannot be pushed further. Step 4: Fix the outer wall of the PTFE tube to the inner wall of the metal extension tube with glue, and connect the threaded hole of the sensor base to the front thread of the metal extension tube; pass the gold-plated optical fiber through the PTFE tube, the metal extension tube and the sensor base in sequence, and insert it into the inner hole of the optical fiber ferrule; install the optical fiber ferrule and the gold-plated optical fiber in the ferrule mounting hole of the SiC ceramic substrate, so that the end face of the gold-plated optical fiber contacts the inner surface of the SiC sensing element, and then use high-temperature resistant ceramic glue in the glue dispensing hole of the SiC ceramic substrate to fix the gold-plated optical fiber and the optical fiber ferrule. Step 5: After the high-temperature resistant ceramic adhesive has completely cured, move the sensor base to connect with the sensor cap; use laser welding to seal the connection surface of the sensor cap's tail end and the shoulder surface on the sensor base, and use laser welding to seal the connection between the sensor base and the metal extension tube.

9. The packaging method of the high-temperature pressure sensor packaging structure according to claim 8, characterized in that: In step one, the bonding temperature is 1100℃, the bonding pressure is 50MPa, the bonding time is 3 hours, and the bonding vacuum is less than 50Pa; in step two, the bonding temperature is 900℃, the bonding pressure is 50MPa, and the bonding time is 3 hours.

Images