Silicon piezoresistive watertight pressure sensor and preparation method thereof

Abstract

The invention discloses a silicon piezoresistive watertight pressure sensor and a preparation method thereof.A sealing assembly is arranged at the joint of a waterproof cable and a sensor body, a sealed installation space is arranged on the inner side of the sensor body, a pressure-sensitive core and a support are both fixed in the installation space, and the bottom of the support surrounds the periphery of the pressure-sensitive core; the top of the support is connected with the circuit board, the pressure-sensitive core is connected with the circuit board through a lead, and the circuit board is connected with a wire of the waterproof cable. The pressure-sensitive core body adopts a piezoresistive pressure working principle, when the sensor is used for measuring underwater pressure, water pressure acts on the pressure-sensitive core body through a channel at the bottom of the sensor body, so that the output resistance value of the pressure-sensitive core body is changed, the potential change of a circuit board is further caused, a potential difference signal is processed by a conditioning circuit, and the pressure-sensitive core body is obtained. And finally, voltage or current signals are output through a lead and a waterproof cable, so that pressure measurement is realized. The device has the advantages of compact structure, high stability, good sealing and waterproof effects, high measurement precision and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of pressure sensor equipment, and in particular to a silicon piezoresistive watertight pressure sensor and a preparation method thereof. Background Art

[0002] Pressure sensors are widely used in aviation, aerospace, shipping, automobile and other important fields to measure the pressure of gas or liquid and convert the pressure signal into a readable electrical signal. In the aerospace field, pressure sensors are mainly used for aircraft air pressure control, cabin environment monitoring, and refrigeration component air pressure monitoring; in the shipping field, pressure sensors can be used for water depth monitoring, underwater exploration, and underwater explosion pressure testing; in the automotive field, pressure sensors are used in engine management systems, tire pressure monitoring systems, etc.

[0003] Pressure is an important parameter for underwater explosion measurement. It is an important data reflecting the external load on the ship when it is attacked by underwater explosion. It is also a necessary input parameter for the numerical simulation calculation of underwater explosion on the ship. The pressure time course generated by the underwater explosion of explosives is a high-speed changing process. Therefore, the sensor used to accurately measure pressure must have a wide bandwidth, high frequency response, strong mechanical strength, accurate and stable sensitivity, suitable range, low noise, good sealing and strong corrosion resistance. It can be said that the technical level of the sensor directly determines the accuracy of pressure measurement.

[0004] At present, most of the underwater pressure sensors used in the industry are imported products. Their disadvantages are that they are expensive, have a long procurement cycle, and incur high costs when used in batches. Summary of the invention

[0005] The technical problem to be solved by the present invention is as follows: In view of the above problems in the prior art, a silicon piezoresistive watertight pressure sensor with compact structure, high stability, good sealing and waterproof effect and high measurement accuracy and a preparation method thereof are provided.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A silicon piezoresistive watertight pressure sensor comprises: a sensor body, a pressure-sensitive core, a bracket, a circuit board, a waterproof cable and a sealing component; a sealing component is provided at the connection between the waterproof cable and the sensor body, a sealed installation space is provided inside the sensor body, the pressure-sensitive core and the bracket are both fixed in the installation space, the bottom of the bracket surrounds the periphery of the pressure-sensitive core, the top of the bracket is connected to the circuit board, the pressure-sensitive core is connected to the circuit board through a lead, and the circuit board is connected to the wire of the waterproof cable to realize the conversion of pressure signals into electrical signal transmission; the pressure-sensitive core adopts the piezoresistive pressure working principle, when the sensor performs underwater pressure measurement, the water pressure acts on the pressure-sensitive core through the channel at the bottom of the sensor body, so that the output resistance value of the pressure-sensitive core changes, thereby causing the potential of the circuit board to change, and the potential signal is then processed by the conditioning circuit in the circuit board, and finally the voltage or current signal is output through the wire and the waterproof cable to realize the pressure measurement.

[0008] As a further improvement of the present invention, the pressure-sensitive core is a SOI silicon piezoresistive pressure-sensitive core made of semiconductor elastic material, and four parallel resistors R1, R2, R3, and R4 are provided on the silicon cup diaphragm of the pressure-sensitive core to form a force-sensitive full bridge; when the force-sensitive full bridge is excited by voltage or current, the strain caused by the pressure on the elastic material is converted into a differential-mode voltage output that is approximately linearly related to the pressure.

[0009] As a further improvement of the present invention, when the pressure-sensitive core made of semiconductor material is subjected to external force, the relative change of its resistance is:

[0010]

[0011] in, is the change in solid resistivity caused by the piezoresistive effect, It is the resistance change caused by the strain effect, π is the piezoresistive coefficient matrix, E is the elastic modulus of the material, μ is the Poisson's ratio of the material, ε is the strain, K=πE+1+2μ, which is the sensitivity coefficient of the resistance change caused by strain ε.

[0012] As a further improvement of the present invention, the sensor body includes a base and a shell, the lower part of the shell is sealed and connected to the upper part of the base, a channel is provided at the bottom of the base, the pressure-sensitive core is fixed to the base by electron beam welding, the bracket is fixed to the base by laser welding, and the circuit board is fixed to the bracket by insulating pads and screws.

[0013] As a further improvement of the present invention, the sealing assembly includes a waterproof joint and a waterproof adhesive layer. The waterproof joint is arranged at the connection between the outer shell and the waterproof cable. The waterproof adhesive layer is arranged at the inner end of the outer shell and is close to the waterproof joint to achieve sealing of the inner side of the outer shell. The wire passes through the waterproof adhesive layer and is connected to the waterproof cable.

[0014] As a further improvement of the present invention, the shielding layer stripped from the waterproof cable extending into the housing is crimped onto the housing through the waterproof connector to achieve electromagnetic shielding.

[0015] As a further improvement of the present invention, the signal conditioning circuit in the circuit board includes a 4mA~20mA current output type and a 1V~5V voltage output type. The signal conditioning circuit is used to amplify the mV level signal to the V level to realize a current or voltage output signal.

[0016] As a general technical concept, the present invention also provides a method for preparing the above-mentioned silicon piezoresistive watertight pressure sensor, comprising the following steps:

[0017] Step S1, welding the pressure-sensitive core to the base, placing the pressure-sensitive core on the base, and welding the pressure-sensitive core by electron beam welding;

[0018] Step S2, connecting the pressure-sensitive core to the lead wire;

[0019] Step S3, welding the bracket to the base, placing the bracket on the base, and welding the bracket by laser welding;

[0020] Step S4, fixing the circuit board, welding the circuit components on the circuit board, passing the leads of the pressure-sensitive core through the mounting holes of the circuit board, and welding them to the circuit board;

[0021] Step S5, connecting the waterproof connector to the housing and the waterproof cable;

[0022] Step S6, coating the front and back sides of the circuit board with silica gel for protection;

[0023] Step S7, connecting the wire of the waterproof cable to the circuit board;

[0024] Step S8: The housing and the base are fixed by welding.

[0025] As a further improvement of the present invention, in step S1, the welding depth is 0.8±0.1 mm; in step S3, the welding depth is 0.5±0.1 mm.

[0026] As a further improvement of the present invention, in step S4, after welding, the safety distance between the lead and the base is greater than 1 mm.

[0027] As a further improvement of the present invention, in step S5, the connection between the waterproof connector and the waterproof cable includes the following steps:

[0028] Step S51, inserting the waterproof cable into the waterproof connector;

[0029] Step S52, peeling off the outer insulation layer of the waterproof cable extending into the housing to expose the shielding layer and the conductor;

[0030] Step S53, peeling off the shielding layer of the waterproof cable extending into the shell, leaving only the shielding layer extending into the shell by 100 mm±10 mm, so as to expose the power line and the conductor;

[0031] Step S54, twist the remaining 100 mm ± 10 mm shielding layer into two small strands and overlap them on the threads of the waterproof joint;

[0032] Step S55, apply thread glue to the thread tail of the waterproof connector, put a protective cover on the hexagon of the waterproof connector, tighten and fix the housing and the waterproof connector with a vise and a wrench, and crimp the two small shielding layers onto the housing;

[0033] Step S56, after the waterproof glue is stirred evenly, the waterproof glue is poured into the shell with a pouring thickness of 100 mm±10 mm, covering the shielding layer extending into the shell, leaving only the power cord and the conductor exposed.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] 1. The silicon piezoresistive watertight pressure sensor of the present invention realizes a sealed connection between a waterproof cable and a sensor body by setting a sealing component. A sealed installation space is provided on the inner side of the sensor body, and the pressure-sensitive core, bracket and circuit board are all installed in the installation space. The pressure-sensitive core adopts the piezoresistive pressure working principle. The circuit board is installed above the pressure-sensitive core through the bracket. The pressure-sensitive core is connected to the circuit board through a lead, and the circuit board is connected to the wire of the waterproof cable, thereby realizing the conversion of the pressure signal in the pressure-sensitive core into an electrical signal for transmission. When the sensor performs underwater pressure measurement, the water pressure acts on the pressure-sensitive core through the channel at the bottom of the sensor body, so that the resistance value of the pressure-sensitive core changes, thereby causing the potential of the circuit board to change, and the potential difference signal is output through the wire and the waterproof cable, thereby realizing the accurate measurement of pressure in a deep water environment, and at the same time solving the sealing and waterproofing problems of the pressure sensor in a deep water environment and the large-range pressure measurement problem of underwater explosion.

[0036] 2. The preparation method of the silicon piezoresistive watertight pressure sensor of the present invention adopts welding to firmly install the pressure-sensitive core, bracket and circuit board in the base, realizes the sealed connection between the waterproof cable and the shell through the waterproof joint, and fills the inside of the shell with a waterproof adhesive layer to ensure a high-sealing connection between the sensor body and the waterproof cable, solves the problem of sealing and waterproofing of underwater large-range pressure sensors at a low cost, and meets the use requirements of the sensor in deep water environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1It is a schematic diagram of the structural principle of a silicon piezoresistive watertight pressure sensor in a specific embodiment of the present invention;

[0038] Figure 2 It is a schematic diagram of the structural principle of the pressure-sensitive core in a specific embodiment of the present invention;

[0039] Figure 3 It is a schematic diagram of the circuit principle of the pressure-sensitive core body in a specific embodiment of the present invention;

[0040] Figure 4 It is a functional block diagram of a pressure detection component in a specific embodiment of the present invention;

[0041] Figure 5 It is a fixture used for detecting the watertight performance of a sensor device in a specific embodiment of the present invention.

[0042] Legend: 1. Base; 2. Pressure-sensitive core; 3. Bracket; 4. Insulation pad; 5. Screw; 6. Circuit board; 7. Housing; 8. Waterproof connector; 9. Wire; 10. Waterproof adhesive layer; 11. Waterproof cable; 100. Pressure sensor; 200. Fixture; 201. Pressurization hole; 300. Cable connector. DETAILED DESCRIPTION

[0043] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0044] In the description of the present invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0046] Example 1

[0047] like Figure 1As shown, the silicon piezoresistive watertight pressure sensor of the present invention includes: a sensor body, a pressure-sensitive core 2, a bracket 3, a circuit board 6, a waterproof cable 11 and a sealing assembly. A sealing assembly is provided at the connection between the waterproof cable 11 and the sensor body, and a sealed installation space is provided inside the sensor body. The pressure-sensitive core 2 and the bracket 3 are both fixed in the installation space. The bottom of the bracket 3 surrounds the outer periphery of the pressure-sensitive core 2, and the top of the bracket 3 is connected to the circuit board 6. The pressure-sensitive core 2 is connected to the circuit board 6 through a lead (not shown in the figure), and the circuit board 6 is connected to the wire 9 of the waterproof cable 11 to realize the conversion of pressure signals into electrical signals for transmission. The pressure-sensitive core 2 adopts the piezoresistive pressure working principle. Figure 4 As shown, when the sensor performs underwater pressure measurement, the water pressure acts on the pressure-sensitive core 2 through the channel at the bottom of the sensor body, causing the pressure-sensitive core 2 to deform, thereby causing the output resistance value of the pressure-sensitive core 2 to change, thereby causing the potential of the circuit board 6 to change. The potential signal is then processed by the conditioning circuit in the circuit board 6, and finally the voltage or current signal is output through the wire 9 and the waterproof cable 11 to achieve pressure measurement.

[0048] In this embodiment, the waterproof cable 11 is sealed and connected to the sensor body by setting a sealing component. By setting a sealed installation space inside the sensor body, the pressure-sensitive core 2, the bracket 3 and the circuit board 6 are all installed in the installation space. The pressure-sensitive core 2 adopts the piezoresistive pressure working principle. The circuit board 6 is installed above the pressure-sensitive core 2 through the bracket 3. The pressure-sensitive core 2 is connected to the circuit board 6 through a lead wire, and the circuit board 6 is connected to the wire 9 of the waterproof cable 11, that is, the pressure signal in the pressure-sensitive core 2 is converted into an electrical signal for transmission. When the sensor performs underwater pressure measurement, the water pressure acts on the pressure-sensitive core 2 through the channel at the bottom of the sensor body, so that the resistance value of the pressure-sensitive core 2 changes, which in turn causes the potential change of the circuit board 6, and the potential difference signal is output through the wire 9 and the waterproof cable 11, so that the accurate measurement of pressure in the deep water environment is realized, and at the same time, the sealing and waterproofing problems of the pressure sensor in the deep water environment and the large-range pressure measurement of underwater explosions are solved.

[0049] like Figure 2 and Figure 3As shown, in this embodiment, the pressure-sensitive core 2 is a SOI silicon piezoresistive pressure-sensitive core made of semiconductor elastic material. Inside the core, the sealed cavity between the corrugated sheet and the base is filled with high-temperature silicone oil; when external pressure acts on the corrugated sheet, the corrugated sheet will have a linear displacement. Due to the incompressibility of silicone oil, the silicone oil converts the displacement of the corrugated sheet into an equivalent pressure that directly acts on the pressure chip to achieve pressure transmission. The operating temperature of the pressure-sensitive core 2 is -55℃~125℃, and the accuracy requirement in the full temperature range is better than ±0.8%. During the sensor production process, by calibrating the circuit board 6, the accuracy of the sensor output can reach 0.2%FS, achieving high-precision measurement. Four parallel resistors R1, R2, R3, and R4 are provided on the silicon cup diaphragm of the pressure-sensitive core 2 to form a force-sensitive full bridge. When the force-sensitive full bridge is excited by voltage or current, the strain generated by the elastic material under pressure is converted into a differential voltage output that is approximately linearly related to the pressure.

[0050] In this embodiment, when the pressure-sensitive core 2 made of semiconductor material is subjected to external force, the relative change of its resistance is:

[0051]

[0052] in, is the change in solid resistivity caused by the piezoresistive effect, It is the resistance change caused by the strain effect, π is the piezoresistive coefficient matrix, E is the elastic modulus of the material, μ is the Poisson's ratio of the material, ε is the strain, K=πE+1+2μ, which is the sensitivity coefficient of the resistance change caused by strain ε.

[0053] like Figure 3 As shown in the figure, a certain voltage or current is given to the force-sensitive full bridge of the pressure-sensitive core 2 to excite the elastic material caused by the pressure, and the strain generated by the pressure is converted into a differential-mode voltage output that is approximately linearly related to the pressure. The sensitive core is connected to the circuit board 6 through a lead, and the electrical signal of the sensitive core is temperature compensated, amplified, and debugged by the conditioning circuit, and the processed signal is transmitted to the terminal control system. At the same time, the control system supplies power to the circuit board 6, and finally the mV level signal is amplified to the V level to obtain a current or voltage output signal, which is the result of pressure measurement.

[0054] like Figure 1 As shown, in this embodiment, the sensor body includes a base 1 and a shell 7, the lower part of the shell 7 is sealed and connected to the upper part of the base 1, and a sealed installation space is formed inside the shell 7. A channel is provided at the bottom of the base 1, the pressure-sensitive core 2 is fixed to the base 1 by electron beam welding, and the pressure-sensitive core 2 is connected to the channel at the bottom of the base 1, the bracket 3 is fixed to the base 1 by laser welding, and the circuit board 6 is fixed to the bracket 3 by an insulating pad 4 made of polytetrafluoroethylene and screws 5.

[0055] Furthermore, the outer side of the lower part of the base 1 can be designed with external threads of different specifications according to installation requirements, for example, external threads of specifications such as M5, M6, M7, M8, M10, M12, and M18 can be designed. A compression flange can also be designed on the outer side of the base 1 according to installation requirements to achieve installation in various application scenarios, and the installation method is flexible.

[0056] like Figure 1 As shown, the sealing assembly includes a waterproof joint 8 and a waterproof adhesive layer 10. The waterproof joint 8 is arranged at the connection between the outer shell 7 and the waterproof cable 11. The waterproof adhesive layer 10 is arranged at the inner end of the outer shell 7 and is close to the waterproof joint 8 to achieve sealing of the inner side of the outer shell 7. The wire 9 passes through the waterproof adhesive layer 10 and is connected to the waterproof cable 11.

[0057] In this embodiment, in order to realize underwater detection, a special waterproof cable 11 and a Hummel connector (i.e., a waterproof connector 8) are used. A shielding layer is added to the outside of the waterproof cable 11, which is composed of a metal braided mesh. The shielding layer can effectively block external electromagnetic radiation and noise signals, reduce the influence of interference on signal transmission, and can provide a good electromagnetic shielding effect, effectively resisting external electromagnetic interference. The Hummel connector used is made of nickel-plated brass. When used, it is tightened and fixed after passing through the wire 9 of the waterproof cable 11, and its protection level is IP-68-10. At the connection between the waterproof cable 11, the housing 7 and the waterproof connector 8, an O-ring is used, and thread glue is applied to the thread. Finally, through the potting process, the waterproof glue layer 10 is potted inside the housing 7 to achieve high-pressure sealing and waterproof performance.

[0058] In order to achieve the measurement of extreme environments such as large-scale blasting pressure under water and reduce the difficulty of production process, the selection of glue is very important. Before the glue is cured, it should have good fluidity and have sufficient hardness after curing. In terms of performance, the glue is not easy to volatilize in the ambient temperature range of -40℃ to 85℃ (to avoid volatiles attached to the circuit board and cause short circuit); in terms of material, it does not corrode the cable sheath and the sensor housing 316L metal.

[0059] The signal conditioning circuit in the circuit board 6 is divided into current output type and voltage output type according to the output type of the pressure signal. The signal conditioning circuit is used to amplify the mV level signal to the V level to realize the current or voltage output signal. For the current output type sensor, only two cable cores, the positive power supply and the negative power supply, are needed; for the voltage type sensor, only three cable cores, the power supply, the output, and the ground wire, are needed. The power supply method is simple and reliable.

[0060] Example 2

[0061] The method for preparing the silicon piezoresistive watertight pressure sensor of the present invention comprises the following steps:

[0062] Step S1, welding the pressure-sensitive core 2 to the base 1, placing the pressure-sensitive core 2 on the base 1, and welding the pressure-sensitive core 2 by electron beam welding. The welding depth is 0.8±0.1mm, and there is no damage or splash on the chip surface.

[0063] Step S2, connecting the pressure-sensitive core 2 to the lead wire.

[0064] Step S3, welding the bracket 3 to the base 1, placing the bracket 3 on the base 1, and welding the bracket 3 by laser welding; the welding depth is 0.5±0.1 mm.

[0065] Step S4, fix the circuit board 6, solder the circuit components on the circuit board 6, and check the circuit soldering points, components, leads, excess materials, safety spacing, etc.; pass the leads of the pressure-sensitive core 2 through the mounting holes of the circuit board 6 and solder them to the circuit board 6. After soldering, the safety spacing between the leads and the base 1 is greater than 1 mm.

[0066] Step S5, connecting the waterproof connector 8 to the waterproof cable 11.

[0067] Step S6: Apply about 1 mm of silicone on the front and back sides of the circuit board 6 for protection.

[0068] Step S7, connect the wire 9 of the waterproof cable 11 to the circuit board 6; connect the power line and the wire extending from the housing 7 to the circuit board 6, and the lead wire needs to pass through the circuit board via hole for welding.

[0069] Step S8, the shell 7 is welded and fixed to the base 1, and the shell 7 is welded to the base 1 by laser welding, and the welding depth is 0.7±0.1mm.

[0070] In step S5 of this embodiment, the connection between the waterproof connector 8, the housing 7 and the waterproof cable 11 includes the following steps:

[0071] Step S51 , insert the waterproof cable 11 into the waterproof connector 8 .

[0072] Step S52 , peeling off the outer insulation layer of the waterproof cable 11 extending into the housing 7 to expose the shielding layer and the wire 9 .

[0073] Step S53 , peel off the shielding layer of the waterproof cable 11 extending into the housing 7 , leaving only the shielding layer extending into the housing 7 by 100 mm±10 mm, so as to expose the power line and the conductor 9 .

[0074] Step S54 , twist the remaining 100 mm±10 mm shielding layer into two small strands and overlap them on the threads of the waterproof joint 8 .

[0075] Step S55, apply thread glue to the threaded tail of the waterproof connector 8, put a protective cover on the hexagon of the waterproof connector 8, tighten and fix the housing 7 and the waterproof connector 8 with a vise and a wrench, check the insulation between the shielding layer of the waterproof cable 11 and the housing 7, prevent the waterproof connector 8 from deformation, and crimp the two small shielding layers to the housing 7. The shielding layer of the waterproof cable inserted into the housing 7 is crimped to the housing 7 through the waterproof connector 8 to play the role of electromagnetic shielding; by applying thread glue on the thread of the waterproof connector 8, the external electromagnetic radiation and noise signals are effectively blocked, the influence of interference on signal transmission is reduced, and a good electromagnetic shielding effect is provided to effectively resist external electromagnetic interference.

[0076] Step S56, after the waterproof glue is stirred evenly, a waterproof glue layer 10 is poured inside the housing 7, with a pouring thickness of 100mm±10mm, covering the exposed shielding layer of the waterproof cable 11 inside the housing 7, leaving only the power line and the conductor 9 exposed, to achieve secondary sealing.

[0077] In this embodiment, the pressure-sensitive core 2, the bracket 3 and the circuit board 6 are firmly installed in the base 1 by welding, the waterproof cable 11 and the outer shell 7 are sealed by the waterproof connector 8, and the waterproof adhesive layer 10 is filled inside the outer shell 7 to ensure an efficient sealed connection between the sensor body and the waterproof cable 11. The problem of sealing and waterproofing of the underwater large-range pressure sensor is solved at a low cost, meeting the use requirements of the sensor in a deep water environment.

[0078] In this embodiment, after the pressure sensor is produced, the waterproof performance of the device needs to be tested. The pressure sensor of this embodiment can be used in an environment with a water depth of fifty meters or even a hundred meters. According to the formula p=ρgh (where p represents pressure, ρ represents liquid density, g is gravity acceleration, and h represents immersion depth), the water pressure that the sensor withstands at a water depth of 50 to 100 meters is 0.5MPa to 1MPa. When the immersion depth is higher, the pressure is greater. However, in the water tightness test of the sensor, the solution of directly placing the sensor in deep water is more complicated. Therefore, a tooling fixture device (such as Figure 5 As shown), it is used to detect the watertight performance of sensor devices.

[0079] One end of the pressure sensor 100 with an adapter is connected to an adapter ring, and the adapter ring is used to connect the fixture 200 and the pressure sensor 100. Matching adapter rings of different sizes can be selected according to sensors with different outer diameters; one end of the fixture 200 is connected to the adapter ring, and the other end is connected to a cable connector 300 of the same model. The sensor cable extends from the adapter ring and the inside of the fixture 200 to connect the cable connector 300; a pressurized hole 201 is opened on the side end of the fixture 200, and water pressure or air pressure can be injected into the fixture through the pressurized hole 201, or a leak detector can be connected to detect the leakage rate of the sensor, thereby achieving the purpose of watertight detection.

[0080] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A silicon piezoresistive watertight pressure sensor, characterized in that: include: A sensor body, a pressure-sensitive core (2), a bracket (3), a circuit board (6), a waterproof cable (11) and a sealing component; a sealing component is provided at the connection between the waterproof cable (11) and the sensor body; a sealed installation space is provided inside the sensor body; the pressure-sensitive core (2) and the bracket (3) are both fixed in the installation space; the bottom of the bracket (3) surrounds the outer periphery of the pressure-sensitive core (2); the top of the bracket (3) is connected to the circuit board (6); the pressure-sensitive core (2) is connected to the circuit board (6) via a lead; the circuit board (6) is connected to the waterproof cable (11) and the ... The pressure-sensitive core (2) is connected to the conductor (9) of the waterproof cable (11) to realize the conversion of pressure signals into electrical signals for transmission; the pressure-sensitive core (2) adopts the piezoresistive pressure working principle. When the sensor performs underwater pressure measurement, the water pressure acts on the pressure-sensitive core (2) through the channel at the bottom of the sensor body, causing the output resistance value of the pressure-sensitive core (2) to change, thereby causing the potential of the circuit board (6) to change. The potential signal is then processed by the conditioning circuit in the circuit board (6), and finally outputs a voltage or current signal through the conductor (9) and the waterproof cable (11), thereby realizing pressure measurement.

2. The silicon piezoresistive watertight pressure sensor according to claim 1, characterized in that: The pressure-sensitive core (2) is a SOI silicon piezoresistive pressure-sensitive core made of semiconductor elastic material. Four parallel resistors R1, R2, R3, and R4 are arranged on the silicon cup diaphragm of the pressure-sensitive core (2) to form a force-sensitive full bridge. When the force-sensitive full bridge is excited by voltage or current, the strain of the elastic material caused by pressure is converted into a differential voltage output that is approximately linearly related to the pressure.

3. The silicon piezoresistive watertight pressure sensor according to claim 2, characterized in that: When the pressure-sensitive core (2) made of semiconductor material is subjected to external force, the relative change of its resistance is: in, is the change in solid resistivity caused by the piezoresistive effect, It is the resistance change caused by the strain effect, π is the piezoresistive coefficient matrix, E is the elastic modulus of the material, μ is the Poisson's ratio of the material, ε is the strain, K=πE+1+2μ, which is the sensitivity coefficient of the resistance change caused by strain ε.

4. The silicon piezoresistive watertight pressure sensor according to any one of claims 1 to 3, characterized in that: The sensor body comprises a base (1) and a shell (7), the lower part of the shell (7) is sealedly connected to the upper part of the base (1), a channel is provided at the bottom of the base (1), the pressure-sensitive core (2) is fixed to the base (1) by electron beam welding, the bracket (3) is fixed to the base (1) by laser welding, and the circuit board (6) is fixed to the bracket (3) by an insulating pad (4) and a screw (5).

5. The silicon piezoresistive watertight pressure sensor according to claim 4, characterized in that: The sealing component comprises a waterproof joint (8) and a waterproof adhesive layer (10); the waterproof joint (8) is arranged at the connection between the outer shell (7) and the waterproof cable (11); the waterproof adhesive layer (10) is arranged at the inner end of the outer shell (7) and close to the waterproof joint (8) to achieve sealing of the inner side of the outer shell (7); and the wire (9) passes through the waterproof adhesive layer (10) and is connected to the waterproof cable (11).

6. The silicon piezoresistive watertight pressure sensor according to any one of claims 1 to 3, characterized in that: The signal conditioning circuit in the circuit board (6) includes a 4mA-20mA current output type and a 1V-5V voltage output type, and the signal conditioning circuit is used to amplify the mV level signal to the V level to realize a current or voltage output signal.

7. A method for preparing a silicon piezoresistive watertight pressure sensor according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1, welding the pressure-sensitive core (2) and the base (1), placing the pressure-sensitive core (2) on the base (1), and welding the pressure-sensitive core (2) by electron beam welding; Step S2, connecting the pressure-sensitive core (2) to the lead wire; Step S3, welding the bracket (3) to the base (1), placing the bracket (3) on the base (1), and welding the bracket (3) by laser welding; Step S4, fixing the circuit board (6), welding the circuit components on the circuit board (6), passing the lead wires of the pressure-sensitive core (2) through the mounting holes of the circuit board (6), and welding them to the circuit board (6); Step S5, connecting the waterproof connector (8) to the housing (7) and the waterproof cable (11); Step S6, coating the front and back surfaces of the circuit board (6) with silica gel for protection; Step S7, connecting the conductor (9) of the waterproof cable (11) to the circuit board (6); Step S8: The housing (7) and the base (1) are fixed by welding.

8. The preparation method according to claim 7, characterized in that: In step S1, the welding depth is 0.8±0.1 mm; in step S3, the welding depth is 0.5±0.1 mm.

9. The preparation method according to claim 7, characterized in that: In the step S4, after welding, the safety distance between the lead wire and the base (1) is greater than 1 mm.

10. The preparation method according to claim 7, characterized in that: In step S5, the connection of the waterproof connector (8) with the housing (7) and the waterproof cable (11) comprises the following steps: Step S51, inserting the waterproof cable (11) into the waterproof connector (8); Step S52, peeling off the outer insulation layer of the waterproof cable (11) extending into the housing (7) to expose the shielding layer and the wire (9); Step S53, peeling off the shielding layer of the waterproof cable (11) extending into the housing (7), leaving only 100 mm±10 mm of the shielding layer extending into the housing (7), so as to expose the power line and the conductor (9); Step S54, twist the remaining 100 mm ± 10 mm shielding layer into two small strands and overlap them on the threads of the waterproof connector (8); Step S55, applying thread glue to the thread tail of the waterproof connector (8), putting a protective cover on the hexagon of the waterproof connector (8), tightening and fixing the housing (7) and the waterproof connector (8) with a vise and a wrench, and at the same time crimping the two small shielding layers onto the housing (7); Step S56, after the waterproof glue is stirred evenly, a waterproof glue layer (10) is poured inside the housing (7), with a pouring thickness of 100 mm±10 mm, covering the shielding layer extending into the housing (7), leaving only the power line and the conductor (9) exposed.

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