High-temperature thin film pressure sensor based on precursor ceramic and preparation method of high-temperature thin film pressure sensor

Abstract

The invention discloses a precursor ceramic-based high-temperature film pressure sensor and a preparation method thereof, and belongs to the field of ceramic film pressure sensors. The pressure sensor comprises a metal substrate, an insulating layer, a conductive layer and a sensitive layer from bottom to top; the metal substrate is a metal pressure sensing substrate into which pressure gas can be introduced; the conductive layer is in a Wheatstone bridge shape; the sensitive layer is made of sensitive layer slurry formed by mixing polysilazane and nano carbon powder, the sensitive layer is connected through the conductive layer to form a Wheatstone bridge, and the position of the Wheatstone bridge is selected to be the maximum stress position or the minimum stress position in the actual work of the pressure sensor based on the piezoresistive effect. According to the thin film pressure sensor, the thin film sensitive layer and the conductive layer are prepared through the composite technology of femtosecond laser combined with coating, accurate positioning, adjustable line width and uniform thickness can be achieved on the micro-nano scale, in-situ preparation and high consistency of the film layer are achieved, the feasibility of quantitative processing is guaranteed, and the prepared device can achieve pressure measurement at the temperature of 530 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic thin film pressure sensor, in particular to a high-temperature thin film pressure sensor based on precursor ceramic and a preparation method thereof. BACKGROUND

[0002] The piezoresistive pressure sensor is widely used in the fields of aerospace key part monitoring, mechanical automation technology, human health monitoring, etc. due to its unique advantages. However, the existing pressure sensor is mostly based on silicon or metal material and prepared by traditional MEMS process, which is generally complex and has high cost and time cost.

[0003] The precursor ceramic is a new type of material synthesized by high-temperature pyrolysis of polymer precursor, and the silicon-based precursor ceramic is commonly used. The precursor ceramic has amorphous properties on the macro level and inhomogeneity on the micro-nano scale, so it has excellent high-temperature performance, such as oxidation resistance, creep resistance, high-temperature stability, high-temperature semiconductor electrical properties, etc. In addition, the precursor ceramic is formed by a unique liquid phase conversion method, so the preparation process is more diverse, such as pressure-assisted forming, spin coating, dip-coating, screen printing, additive manufacturing, etc. can be applied to the preparation and forming of the precursor ceramic. In the field of high-temperature sensors, the precursor ceramic has been used as a sensitive material for pressure sensors due to its high-temperature semiconductor properties and good piezoresistive effect. However, most of the precursor ceramic high-temperature sensors are independent bulk devices, and there are few reports on precursor ceramic thin film devices. SUMMARY

[0004] The present application aims to solve the above-mentioned problems in the prior art and provide a high-temperature thin film pressure sensor based on precursor ceramic and a preparation method thereof.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A high-temperature thin film pressure sensor based on precursor ceramic, the pressure sensor comprises, from bottom to top, a metal substrate, an insulating layer, a conductive layer, and a SiCN / C sensitive layer; the metal substrate is a metal pressure sensing substrate through which pressure gas can pass; the conductive layer is in the shape of a Wheatstone bridge and is provided with a lead-out end for signal output; the SiCN / C sensitive layer is prepared from a sensitive layer slurry formed by mixing polysilazane and nano-carbon powder, and the SiCN / C sensitive layer is connected into a Wheatstone bridge through the conductive layer, and the position is selected based on the maximum stress or minimum stress in the actual working of the pressure sensor under piezoresistive effect.

[0007] The present application further comprises a pressure connector connected to the metal substrate, the pressure connector is provided with a gas inlet and a thread, and the gas inlet is connected to a steel pipe with a sleeve thread through the thread.

[0008] The application also comprises a signal leading-out layer, which comprises an insulating solder point and a metal lead, and the insulating solder point adheres and fixes the leading-out end of the conductive layer to the metal lead.

[0009] The thickness of the SiCN / C sensitive layer is 20-60 microns.

[0010] The thickness of the insulating layer is 50-100 microns.

[0011] The preparation method of the high-temperature thin-film pressure sensor based on the precursor ceramic comprises the following steps:

[0012] (1) cleaning the substrate: ultrasonic cleaning of the metal substrate and then drying;

[0013] (2) preparing the insulating layer: coating the insulating medium paste on the surface of the dried metal substrate, and then preparing the insulating layer through high-temperature pyrolysis in an air atmosphere;

[0014] (3) preparing the conductive layer: etching the shape of the Wheatstone bridge on the mask by using the femtosecond laser, coating the high-temperature silver paste on the surface of the insulating layer corresponding to the shape area, then placing it in an air atmosphere for high-temperature curing, and finally performing annealing to prepare the conductive layer;

[0015] (4) preparing the SiCN / C sensitive layer: mixing polysilazane and nano-carbon powder, and then performing magnetic stirring and ultrasonic treatment to obtain a sensitive layer paste without air bubbles; coating the sensitive layer paste on the surface of the conductive layer corresponding to the shape area by etching the shape of the bridge resistor on the mask by using the femtosecond laser, solidifying first, and then placing it in a nitrogen atmosphere for high-temperature pyrolysis to prepare the SiCN / C sensitive layer;

[0016] (5) preparing the signal leading-out layer: adhering the leading-out end of the conductive layer to the metal lead by using the insulating solder point, placing it in an air atmosphere for heat preservation and curing to form the signal leading-out layer;

[0017] (6) laser resistance adjustment: performing micro-etching on the surface of the SiCN / C sensitive layer by using the femtosecond laser to adjust the resistance values of the four resistors made of the SiCN / C sensitive layer in the Wheatstone bridge to be approximately or equal, and thus completing the preparation of the high-temperature thin-film pressure sensor.

[0018] In step (2), the temperature for high-temperature pyrolysis is 880-920℃.

[0019] In step (3), the temperature for high-temperature curing is 400-600℃.

[0020] In step (4), the temperature for solidification is 150-250℃, and the temperature for high-temperature pyrolysis is 700-800℃.

[0021] In step (4), the mixed nano-carbon powder has a mass fraction of 50-80 wt%.

[0022] Compared with the prior art, the technical scheme of the application has the following beneficial effects:

[0023] 1. The thin film pressure sensor has excellent performance: it can work stably at 30-300 DEG C and 700 KPa, and work for a short time at 530 DEG C and 700 KPa, thereby realizing cost reduction and efficiency increase compared with the pressure sensor prepared by the traditional process.

[0024] 2. The thin film pressure sensor has excellent processing performance: the thin film sensitive layer and the conductive layer are prepared by the composite process of femtosecond laser and coating, and precise positioning, adjustable line width and uniform thickness can be realized on the micro-nano scale, thereby realizing in-situ preparation of the film layer.

[0025] 3. The thin film pressure sensor has excellent consistency: the sensor prepared is micro-processed by femtosecond laser, thereby realizing high consistency of the sensitive area. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a film layer structure schematic diagram of the high-temperature thin film pressure sensor based on the precursor ceramic of the application; wherein, 1 - gas inlet, 2 - thread, 3 - pressure connector, 4 - metal base, 5 - insulating layer, 6 - conductive layer, 7 - SiCN / C sensitive layer, 8 - insulating welding point, 9 - metal lead.

[0027] Figure 2 It is a preparation process schematic diagram of the thin film pressure sensor of the application.

[0028] Figure 3 It is a test schematic diagram of the thin film pressure sensor of the application.

[0029] Figure 4 It is a cross-section SEM diagram of the SiCN / C sensitive layer and the conductive layer connection of the embodiment of the application.

[0030] Figure 5 It is a relationship diagram of the output potential of the embodiment of the application changing with pressure strength at normal temperature.

[0031] Figure 6 It is a relationship diagram of the output potential of the embodiment of the application changing with pressure strength in the full range at 300 DEG C.

[0032] Figure 7 It is a relationship diagram of the output potential of the embodiment of the application changing with pressure strength in the full range at 530 DEG C. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer and more apparent, the present application will be further described in detail below in combination with the drawings and examples, but the protection scope of the present application is not limited to these examples. The same reference signs in the text always represent the same elements, and similar reference signs represent similar elements.

[0034] Referring to Figure 1 A precursor ceramic-based high-temperature thin film pressure sensor comprises a pressure connector 3 from bottom to top, a metal substrate 4, an insulating layer 5, a conductive layer 6 and a SiCN / C sensitive layer 7; the conductive layer is in the shape of a Wheatstone bridge and is provided with a lead-out end for signal output; the SiCN / C sensitive layer is made of a sensitive layer slurry formed by mixing polysilazane and nano-carbon powder, and the SiCN / C sensitive layer is connected into a Wheatstone bridge through the conductive layer, and the position is selected based on the maximum stress or the minimum stress in the actual working of the pressure sensor under the piezoresistive effect.

[0035] The pressure connector 3 is connected with the metal substrate 4, and the pressure connector 3 is provided with an air inlet 1 and a thread 2, wherein the air inlet 1 is threadedly connected with a breathable steel pipe provided with a sleeve thread, thereby providing a pressure gas source conveying channel for the thin film pressure sensor, and realizing surface multi-membrane structure pressure sensing test.

[0036] The insulating layer 5 is used to provide insulation blocking effect between the conductive layer and the metal surface, the conductive layer 6 is used to connect and conduct the SiCN / C sensitive layer 7, the SiCN / C sensitive layer 7 is used to realize pressure sensing function, and the insulating solder joint 8 and the metal lead 9 are used to realize signal output. The above-mentioned multi-layer structure is prepared in turn by high-temperature thin film process and is closely attached to the surface of the previous layer.

[0037] The insulating layer 5 is prepared by coating high-temperature blue medium slurry on the surface of the metal substrate 4 and pyrolyzing, and the blue medium slurry is used to clearly show the multi-membrane structure morphology.

[0038] The thickness of the insulating layer 5 is 50-100 μm, and the thickness of the SiCN / C sensitive layer 7 is 20-60 μm.

[0039] A preparation method of a precursor ceramic-based high-temperature thin film pressure sensor comprises the following steps:

[0040] (1) Cleaning the substrate: ultrasonic cleaning the metal substrate and then drying.

[0041] (2) Preparing the insulating layer: coating a blue insulating medium slurry with uniform thickness on the metal substrate, and then pyrolyzing at a high temperature of 880-920 ℃ in an air atmosphere to obtain the insulating layer, the heating rate is 2-5 ℃ / min, the holding time is 15-30 min, and the cooling rate is 2-10 ℃ / min.

[0042] (3) Preparation of conductive layer: using femtosecond laser to prepare a Wheatstone bridge shape on the mask, coating high-temperature silver paste on the surface of the insulating layer corresponding to the shape area, and curing at high temperature in air atmosphere to obtain the conductive layer; the high-temperature curing heating rate is 2~15℃ / min, the temperature is raised to 400~600℃, and then annealing is performed after holding for 15~60min.

[0043] (4) Preparation of sensitive layer paste: uniformly mixing polysilazane solution and nano-carbon powder in proportion, and then preparing the sensitive layer paste after magnetic stirring and ultrasonic treatment; the mass fraction of the added nano-carbon powder is 50~80wt%.

[0044] (5) Preparation of SiCN / C sensitive layer: using femtosecond laser to prepare a bridge resistance shape on the mask, coating the sensitive layer paste of step (4), curing at 150~250℃ for 5~15min, and then high-temperature pyrolysis in N2 atmosphere, with a pyrolysis heating rate of 2~8℃ / min, the temperature is raised to 700~800℃, holding for 10~20min, and the cooling rate is 2~12℃ / min, to obtain the SiCN / C sensitive layer.

[0045] (6) Signal leading-out: using insulating solder points to bond the leading-out end of the conductive layer and the metal lead, and curing at 200~300℃ in air atmosphere for 15~30min.

[0046] (7) Laser resistance adjustment: using femtosecond laser to adjust the resistance of the prepared SiCN / C sensitive layer, so that the resistance values of the four resistances made of SiCN / C sensitive layer in the bridge are approximately equal or equal.

[0047] The coating methods in steps (3) and (5) include but are not limited to screen printing, direct writing printing, etc.

[0048] Example 1

[0049] Reference Figures 1-2 A preparation method of a high-temperature-resistant thin film pressure sensor based on a precursor ceramic, comprising the following steps:

[0050] (1) The metal substrate and the pressure joint are sequentially cleaned with alcohol and deionized water, ultrasonic treatment for 5min, and dried with nitrogen, and then placed in a constant temperature drying box for 1h, and the substrate is dried, and a metal substrate 4 with high cleanliness is obtained on the surface of the pressure joint 3.

[0051] (2) Blue insulating medium paste is coated on the metal substrate, and then is placed on a heating table to perform pre-curing at 300 DEG C for 120 min, to generate a pre-cured insulating layer with a thickness of about 60 microns; the prepared pre-cured insulating layer is subjected to heat treatment in an air atmosphere, to obtain an insulating layer 5; the heat treatment process is that the temperature is raised at a speed of 5 DEG C / min, is raised to 900 DEG C, is kept for 30 min, and then is subjected to high-temperature annealing;

[0052] (3) A femtosecond laser is used to prepare a conductive layer bridge shape on a mask, high-temperature silver paste is coated on the surface of the insulating layer in a silk screen printing manner, and high-temperature heat treatment is performed in an air atmosphere, to obtain a conductive layer 6; the heat treatment process is that the temperature is raised at a speed of 5 DEG C / min, is raised to 550 DEG C, is kept for 30 min, and then is subjected to high-temperature annealing.

[0053] (4) Polysilazane and nano-carbon powder are mixed in a mass ratio of 3:7, and after magnetic stirring and ultrasonic treatment, a uniform mixed bubble-free sensitive layer paste is obtained, wherein the particle size of the nano-carbon powder is 50-100 nm.

[0054] (5) A femtosecond laser is used to prepare a bridge resistance shape on a mask, the sensitive layer paste is coated on the surface in a silk screen printing manner, is cured at 150 DEG C for 10 min, and then is subjected to high-temperature pyrolysis in an N2 atmosphere, the pyrolysis temperature is raised at a speed of 5 DEG C / min, is raised to 750 DEG C, is kept for 15 min, and the temperature is lowered at a speed of 8 DEG C / min, to obtain a SiCN / C sensitive layer 7 with a thickness of about 21.6 microns.

[0055] (6) Alumina is used as an insulating solder point 8 to bond the lead-out end of the conductive layer and a metal lead 9, the metal lead is Ag, is cured in an air atmosphere at 200 DEG C for 20 min, and the preparation of the signal lead-out layer is completed.

[0056] (7) A femtosecond laser is used to perform resistance adjustment treatment on the prepared SiCN / C sensitive layer, specifically, laser micro-etching is performed on the surface of the SiCN / C sensitive layer by the femtosecond laser, the resistance values of the four resistances are adjusted, the resistance values of the four resistances prepared from the SiCN / C sensitive layer in the bridge are approximately equal or equal, and thus the preparation of a thin film pressure sensor based on a precursor ceramic is completed.

[0057] The test system of the embodiment of the present application is as shown in Figure 3 The pressure sensor is connected to a temperature-controlled furnace tube of a tube furnace through an air pipe, the pressure input size is controlled by a pressure controller, a group of lead wires are connected to a power supply and a collection card of a signal collection system to realize signal testing.

[0058] The cross-sectional SEM image of the connection between the conductive layer and the SiCN / C sensitive layer in the embodiment of the present application is as shown in Figure 4As shown, it can be seen from the figure that the connection between the two layers is close, forming a conductive network.

[0059] The output response of the embodiment of the present application at room temperature with pressure input is as shown in the figure Figure 5 As shown, the output potential presents obvious ladder shape, indicating that the sensor has pressure response ability.

[0060] The full-range output response of the embodiment of the present application at 300 DEG C with pressure input is as shown in the figure Figure 6 As shown, the output potential has good response under the full-range input of 101~700KPa at 300 DEG C, indicating that the pressure sensor has high-temperature test ability above 300 DEG C.

[0061] The full-range output response of the embodiment of the present application at 530 DEG C with pressure input is as shown in the figure Figure 7 As shown, the output potential has good response under the full-range input of 101~700KPa at 530 DEG C, but has certain noise, indicating that the pressure sensor has high-temperature test ability at 530 DEG C for a short time.

[0062] The present application relies on the preparation basis of high-temperature thin film sensor, and proposes a new process for reducing cost and increasing efficiency, which is used for preparing high-temperature-resistant PDC thin film pressure sensor, and is used for high-temperature application in a larger range, and meets the current development trend.

[0063] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit it; although the present application is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high temperature thin film pressure sensor based on a precursor ceramic, characterized in that: The pressure sensor comprises, from bottom to top, a metal substrate, an insulating layer, a conductive layer, and a SiCN / C sensitive layer; the metal substrate is a metal pressure sensing substrate through which pressure gas can pass; the conductive layer is in the shape of a Wheatstone bridge and is provided with lead-out ends for signal output; the SiCN / C sensitive layer is made of a sensitive layer slurry formed by mixing polysilazane and nano-carbon powder, and the SiCN / C sensitive layer is connected into a Wheatstone bridge through the conductive layer, and the position of the SiCN / C sensitive layer is selected based on the maximum stress or minimum stress in the actual working of the pressure sensor under the piezoresistive effect.

2. A high temperature thin film pressure sensor based on a precursor ceramic according to claim 1, characterized in that: The pressure sensor further comprises a pressure connector connected to the metal substrate, the pressure connector being provided with a gas inlet and a thread, and the gas inlet being connected to a steel pipe with a threaded sleeve through the thread.

3. A high temperature thin film pressure sensor based on a precursor ceramic according to claim 1, characterized in that: The pressure sensor further comprises a signal lead-out layer, the signal lead-out layer comprising insulating solder points and metal leads, and the insulating solder points being used to bond and fix the lead-out ends of the conductive layer to the metal leads.

4. A high temperature thin film pressure sensor based on a precursor ceramic according to claim 1, characterized in that: The thickness of the SiCN / C sensitive layer is 20-60 μm.

5. A precursor ceramic based high temperature thin film pressure sensor as claimed in claim 1, wherein: The thickness of the insulating layer is 50-100 μm.

6. A method of manufacturing a high temperature thin film pressure sensor based on a precursor ceramic according to any one of claims 1 to 5, characterized in that, The method comprises the following steps: (1) cleaning the substrate: ultrasonic cleaning of the metal substrate followed by drying; (2) preparing the insulating layer: coating of an insulating medium slurry on the surface of the dried metal substrate, followed by preparation of the insulating layer by high-temperature pyrolysis in an air atmosphere; (3) preparing the conductive layer: etching of a Wheatstone bridge shape on a mask using a femtosecond laser, coating of high-temperature silver paste on the surface of the insulating layer in the corresponding shape area, subsequent high-temperature curing in an air atmosphere, and finally annealing to prepare the conductive layer; (4) preparing the SiCN / C sensitive layer: mixing of polysilazane and nano-carbon powder, magnetic stirring and ultrasonic treatment to obtain a bubble-free sensitive layer slurry; etching of a bridge resistance shape on a mask using a femtosecond laser, coating of the sensitive layer slurry on the surface of the conductive layer in the corresponding shape area, solidification, and then high-temperature pyrolysis in a nitrogen atmosphere to prepare the SiCN / C sensitive layer; (5) preparing the signal lead-out layer: bonding of the lead-out ends of the conductive layer to the metal leads using insulating solder points, curing in an air atmosphere, and formation of the signal lead-out layer; (6) laser resistance adjustment: micro-etching of the surface of the SiCN / C sensitive layer using a femtosecond laser, adjustment of the resistance values of the four resistors made of the SiCN / C sensitive layer in the Wheatstone bridge to make the resistance values of the four resistors approximately equal or equal, and completion of the preparation of the high-temperature thin-film pressure sensor.

7. The production method according to claim 6, characterized by: In step (2), the temperature for high-temperature pyrolysis is 880-920 ℃.

8. The production method according to claim 6, characterized by: In step (3), the temperature for high-temperature curing is 400-600 ℃.

9. The production method according to claim 6, wherein: In step (4), the temperature for solidification is 150-250 ℃, and the temperature for high-temperature pyrolysis is 700-800 ℃.

10. The production method according to claim 6, wherein: In step (4), the mass fraction of the mixed nano-carbon powder is 50-80 wt%.

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