A high temperature resistant inductive angle sensor

Abstract

The present application relates to a kind of high-temperature-resistant inductive angle sensor, belong to angle sensor technical field.The sensor includes: gradient composite ceramic substrate Al2O3-ZrO2-Al2O3, realize thermal expansion coefficient gradient matching by intermediate layer zirconium oxide doped yttrium oxide, reduce thermal stress cracking risk;Substrate surface is formed with micro-arc oxidation porous layer in turn titanium nitride nanocrystalline layer, improve surface bonding force;Atomic layer deposition process is used to prepare TiN or TiN / Ag composite film coil, improve temperature resistance;Through electron beam welding and transient liquid phase bonding composite process coil and circuit;Insulating encapsulation layer is made of boron nitride nanosheet and high-temperature-resistant resin, improve thermal conductivity and breakdown field strength.The present application is through gradient substrate design, thin film coil integration and composite process optimization, solves the thermal stress failure of traditional inductive sensor under high temperature, coil oxidation and insulation aging problem, suitable for angle measurement under extreme environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of angle sensors and relates to a high-temperature-resistant inductive angle sensor. BACKGROUND

[0002] Industrial equipment working in extreme temperature environments have strict requirements for the high-temperature resistance of sensors. Inductive angle sensors are widely used in high-temperature scenarios due to their non-contact measurement and resistance to electromagnetic interference. However, when the temperature exceeds 200℃, the thermal stress caused by the difference in the coefficient of thermal expansion (CTE) between the substrate material and the metal wire (such as copper) of the traditional PCB-based sensor can cause electrode detachment and coil deformation, severely affecting the measurement accuracy. Although CN117109640A proposes fixing the device on a ceramic test board, the angle sensor uses screen-printed silver paste electrodes, which are prone to electrode detachment and coil deformation due to the mismatch in the coefficient of thermal expansion when the temperature exceeds 200℃. The organic silane resin insulation layer has a dielectric constant that drifts in a continuous high-temperature environment, causing signal attenuation. The mechanical stress matching between the ceramic substrate and the metal wire is poor, and the interfacial bonding strength decreases in the 200-300℃ thermal shock cycle, reducing the service life.

[0003] Another study attempts to deposit an AlN coating on the ceramic surface to reduce the coefficient of thermal expansion, but due to the lattice mismatch between the coating and the substrate (the CTE difference between AlN and Al2O3 is -4.5 x 10 -6 / ℃ vs 5.7 x 10 -6 / ℃), the interfacial shear strength decreases. In terms of insulation layer modification, the SiC ceramic-filled epoxy resin system can improve the temperature resistance to 350℃, but its high-frequency dielectric loss exceeds 0.02 at 2MHz, making it difficult to meet the sensor signal transmission requirements. More importantly, the coils prepared by the existing process use traditional copper foil winding technology, with a line width uniformity control within ±15μm, leading to coil turn-to-turn short circuits at 500℃ due to metal recrystallization, severely restricting the expansion of the sensor to higher temperature ranges.

[0004] The essence of the current technical bottleneck lies in the fundamental contradiction between the traditional manufacturing process and the physical and chemical properties of materials in a high-temperature environment: the porosity of the silver paste after sintering by the screen printing process leads to poor electrode conductivity stability; the metal thin film prepared by physical vapor deposition can avoid thermal stress, but cracks are easily produced when the film thickness exceeds 50μm; and the chemical vapor deposition process is costly and difficult to implement on a large scale. In addition, existing research focuses on improving individual components, lacking a coordinated design of the overall sensor system (substrate-electrode-coil-insulation). For example, the influence of gradient interfacial thermal expansion matching on multi-physical field coupling characteristics is not considered. This leads to insufficient service life of existing high-temperature sensors under high-temperature working conditions, failing to meet the stringent demands of high-temperature scenarios. SUMMARY

[0005] The application solves the problems of thermal stress failure, coil oxidation and insulation aging of traditional inductive sensors under high temperature through gradient substrate design, thin film coil integration and composite process optimization, and is suitable for angle measurement under extreme environment.

[0006] The purpose of the application can be achieved by the following technical solutions.

[0007] A preparation method of a high-temperature-resistant inductive angle sensor comprises the following steps:

[0008] (1) A gradient composite ceramic substrate is prepared by flow casting and laminated sintering, the substrate is composed of three layers of materials, the surface layer and the bottom layer are Al2O3, the thickness of each is 0.2-0.5mm, the middle layer is ZrO2 doped with Y2O3, the thickness is 0.4-1mm, and the thermal expansion coefficient of the middle layer is between the surface layer and the bottom layer;

[0009] (2) A functional transition layer is prepared on the surface of the substrate, specifically, a TiN nanocrystalline layer is prepared by plasma enhanced chemical vapor deposition, and an oxide layer is formed on the TiN nanocrystalline layer by micro-arc oxidation treatment;

[0010] (3) After depositing a TiN seed layer by magnetron sputtering, a coil pattern is formed on the TiN seed layer by photolithography, and a silver thickening coil is formed by electroplating, and a TiN protective layer is deposited on the surface of the electroplated silver coil by magnetron sputtering again;

[0011] (4) The end part of the coil is connected by electron beam welding positioning, and then transient liquid phase bonding is carried out at 200-300 DEG C;

[0012] (5) Boron nitride nanosheets are dispersed in a high-temperature-resistant polymer resistant to 200-400 DEG C to form a coating liquid, and an insulation packaging layer is formed from the coating liquid.

[0013] As a preferred technical solution of the application, the gradient composite ceramic substrate of step (1) comprises a surface layer, a middle layer and a bottom layer stacked in sequence, wherein the surface layer and the bottom layer are both Al2O3, and the middle layer is ZrO2 and Y2O3; the purity of Al2O3 in the surface layer and the bottom layer is ≥99%, the middle layer is ZrO2 doped with 3-8mol% Y2O3 to realize the gradient matching of the thermal expansion coefficient, and the thickness ratio of the surface layer, the middle layer and the bottom layer is 1:2:1.

[0014] As a preferred technical solution of the application, the thickness of the TiN nanocrystalline layer of step (2) is 50-200nm, the thickness of the oxide layer is 15-25μm, the pore size is 0.1-1μm, and the porosity is 10-30%.

[0015] As a preferred technical scheme of the present application, the thickness of the TiN seed layer of the coil in step (3) is 50-200 nm; the thickness of the electroplated Ag layer is 1-10 μm, and the thickness of the TiN protective layer is 50-500 nm.

[0016] As a preferred technical scheme of the present application, Sn-Bi alloy or In-Ag alloy is used in the transient liquid phase bonding process in step (4).

[0017] As a preferred technical scheme of the present application, in the insulating packaging layer in step (5), the mass fraction of the boron nitride nanosheet is 10-40%, and the high-temperature-resistant polymer is silicone resin or polyimide.

[0018] A high-temperature-resistant inductive angle sensor obtained by the preparation method.

[0019] The present application has the following beneficial effects:

[0020] (1) The present application designs a gradient composite ceramic substrate Al2O3-ZrO2-Al2O3, which has a gradually matched thermal expansion coefficient, reduces thermal cycle cracking, and improves the high-temperature resistance of the substrate; the TiN thin film coil, the titanium nitride nanocrystalline layer, and the porous oxide layer avoid metal oxidation or softening at high temperatures, and improve the temperature resistance of the coil.

[0021] (2) The boron nitride nanosheet composite insulating layer of the present application significantly improves the thermal conductivity and breakdown field strength, and has no carbonization risk at high temperatures; the gradient substrate and the boron nitride nanosheet cooperate to dissipate heat, the temperature rise of the sensor is reduced, and the service life is extended to 5000 high-temperature cycles.

[0022] (3) The present application realizes high-strength connection through the electron beam welding and transient liquid phase bonding composite process, improves the thermal fatigue life, and reduces the resistivity of the TiN / Ag composite thin film coil, reduces signal loss, and improves the sensitivity of the angle sensor. DETAILED DESCRIPTION

[0023] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purposes, the specific embodiments, structures, features and effects according to the present application are described in detail as follows in combination with examples.

[0024] The sources of the raw materials involved in the following examples and comparative examples are as follows: the az462 positive photoresist is purchased from Meikufu Microfluidic Technology Co., Ltd.; the Sn-Bi alloy and the In-Ag alloy are purchased from Angxing New Carbon Material Co., Ltd.; the silicone resin is purchased from Guangdong Linhua New Material Co., Ltd.; and the polyimide is purchased from Jettes Plastic Products Co., Ltd.

[0025] Example 1

[0026] A preparation method of a high-temperature-resistant inductive angle sensor, comprising the following steps:

[0027] (1) Al2O3 slurry, ZrO2 doped with 5 mol% Y2O3 are used to prepare each layer of green ceramic sheet by tape casting, and the green ceramic sheet is sintered at 1600 DEG C for 3 hours after lamination to prepare a substrate with a surface layer and a bottom layer of Al2O3, each with a thickness of 0.3 mm, and an intermediate layer of ZrO2 and Y2O3 with a thickness of 0.6 mm;

[0028] (2) a 100 nm TiN nanocrystalline layer is formed on the surface of the substrate by plasma enhanced chemical vapor deposition, the reaction gas is TiCl4, NH3 and H2, the flow rates are 10 sccm, 30 sccm and 60 sccm respectively, the radio frequency power is 300 W, and the deposition temperature is 400 DEG C, so as to improve the surface conductivity and provide a substrate for subsequent micro-arc oxidation treatment;

[0029] (3) a 20 μm thick porous Al2O3-TiN composite layer is formed by micro-arc oxidation treatment with a 5% Na2SiO3 and 2% KOH aqueous solution as an electrolyte, a voltage of 500 V and a pulse frequency of 1000 Hz, the pore diameter is 0.5 μm, and the porosity is 20%;

[0030] (4) a TiN seed layer is deposited by a magnetron sputtering system, pure titanium is used as a target material, the chamber vacuum degree is 5*10 -3 Pa, argon is 50 sccm, nitrogen is 10 sccm, the deposition temperature is 200 DEG C, the deposition rate is 20 nm / min, the deposition time is 5 min, and annealing is performed in a nitrogen atmosphere;

[0031] (5) az462 positive photoresist is spin-coated, the thickness is 2 μm, ultraviolet light is used to form a coil pattern with a line width of 50 μm and a pitch of 50 μm, AZ 400K developing solution is used for developing for 60 seconds, and the photoresist in the unexposed area is removed;

[0032] (6) a 5 μm silver plating layer is formed on the coil pattern after the photoetching by electroplating, the electroplating solution is cyanide silver potassium 40 g / L and cyanide potassium 80 g / L, the temperature is 25 DEG C, the current density is 0.5 A / dm 2 ;

[0033] (7) a 200 nm thick TiN protective layer is deposited on the surface of the silver coil by magnetron sputtering in the manner of step (4);

[0034] (8) the coil end is positioned and connected by electron beam welding, the welding area is locally heated to 2000 DEG C, a 0.2 mm diameter welding spot is formed, and then Sn-Bi alloy transient liquid phase bonding is performed at 220 DEG C under a bonding pressure of 5 MPa;

[0035] (9) 30wt% boron nitride nanosheet is dispersed in silicone resin to form a coating liquid, and a thickness of 20 μm is formed by spin coating, and a step curing of 80℃, 30min, 150℃, 2h is performed to form an insulating packaging layer.

[0036] Example 2

[0037] A preparation method of a high-temperature-resistant inductive angle sensor, comprising the following steps:

[0038] (1) Al2O3 slurry, ZrO2 doped with 3mol% Y2O3 are used to prepare each layer of green ceramic sheet by tape casting, and the green ceramic sheet is laminated and sintered at 1600℃ for 3 hours to prepare a substrate with a surface layer and a bottom layer of Al2O3, each with a thickness of 0.3mm, and an intermediate layer of ZrO2 and Y2O3 with a thickness of 0.6mm;

[0039] (2) A 105nm TiN nanocrystalline layer is formed on the surface of the substrate by plasma enhanced chemical vapor deposition, with TiCl4, NH3, and H2 as the reaction gases, flow rates of 10sccm, 30sccm, and 60sccm respectively, a radio frequency power of 300W, and a deposition temperature of 400℃, to improve the surface conductivity and provide a substrate for subsequent micro-arc oxidation treatment;

[0040] (3) A 15μm thick porous Al2O3-TiN composite layer is formed by micro-arc oxidation treatment with a 5% Na2SiO3 and 2% KOH aqueous solution as the electrolyte, a voltage of 500V, and a pulse frequency of 1000Hz, with a pore size of 0.5μm and a porosity of 20%;

[0041] (4) A TiN seed layer is deposited using a magnetron sputtering system, with pure titanium as the target material, a chamber vacuum degree of 5×10 -3 Pa, argon gas of 50sccm, nitrogen gas of 10sccm, a deposition temperature of 200℃, a deposition rate of 20nm / min for 3min, and annealing in a nitrogen atmosphere;

[0042] (5) An az462 positive photoresist is spin-coated to a thickness of 2μm, and an ultraviolet light is used to form a coil pattern with a line width of 50μm and a pitch of 50μm, and the photoresist is developed for 60 seconds using an AZ 400K developer to remove the photoresist in the unexposed area;

[0043] (6) A 5μm silver plating layer is electroplated on the coil pattern after the photoetching, with a cyanide silver potassium solution of 40g / L and a cyanide potassium solution of 80g / L, a temperature of 25℃, and a current density of 0.5A / dm 2 ;

[0044] (7) A 240nm thick TiN protective layer is deposited on the surface of the silver-plated coil by magnetron sputtering in the manner of step (4);

[0045] (8) The coil end is positioned and connected by electron beam welding, the welding area is locally heated to 2000℃, a 0.2mm diameter welding spot is formed, and then Sn-Bi alloy transient liquid phase bonding is performed at 220℃ under a bonding pressure of 5MPa;

[0046] (9) 30wt% boron nitride nanosheet is dispersed in silicone resin to form a coating liquid, the thickness is 20μm by spin coating, and the insulation packaging layer is formed by step curing at 80℃ for 30min and at 150℃ for 2h.

[0047] Comparative Example 1

[0048] On the basis of Example 1, no zirconium oxide and yttrium oxide are added for substrate preparation, the surface layer and the bottom layer are 0.3mm Al2O3 layers, the middle layer is a 0.6mm Al2O3 layer, and the rest remains the same as Example 1.

[0049] Comparative Example 2

[0050] On the basis of Example 1, the coil is prepared by screen printing Ag paste instead of magnetron sputtering and electroplating process, the screen with the coil pattern is fixed on the printing machine frame, the substrate is placed on the printing table to ensure accurate alignment of the pattern, the Ag paste is uniformly coated on the screen, the paste is deposited on the substrate surface through the screen holes, and after demolding and drying, it is heated from 350℃ to 850℃ at a heating rate of 3℃ / min, and sintered for 30min, and the rest remains the same as Example 1.

[0051] Comparative Example 3

[0052] On the basis of Example 1, the Sn-Bi alloy is not used for connecting the coil and the external circuit, but Sn-37Pb alloy is used instead, and the rest remains the same as Example 1.

[0053] Comparative Example 4

[0054] On the basis of Example 2, the In-Ag alloy is not used for connecting the coil and the external circuit, but Sn-37Pb alloy is used instead, and the rest remains the same as Example 2.

[0055] Comparative Example 5

[0056] On the basis of Example 1, the TiN thin film deposited by magnetron sputtering system is replaced by magnetron sputtering Cu, and the rest remains the same as Example 1.

[0057] Example 6

[0058] On the basis of Example 1, no boron nitride nanosheet is added to the insulation packaging layer, and the rest remains the same as Example.

[0059] Performance test:

[0060] Temperature resistance test: the initial resistance of the samples prepared from Example 1-2 and Comparative Example 1-6 was tested by a digital multimeter, placed in a high temperature aging test box at 300℃ for 500 hours, taken out and cooled to 25℃, then tested by a digital multimeter after aging, and the resistance change rate was calculated:

[0061] Resistance change rate = (initial resistance - resistance after aging) / initial resistance x 100%;

[0062] Thermal cycle life test: the samples prepared from Example 1-2 and Comparative Example 1-6 were placed in a thermal shock test box, and the set temperature cycle range was set as: -40℃ for 30 minutes, and then heated to 350℃ for 30 minutes, and the cycle was repeated for 5000 times. The crack rate of the interface between the substrate and the coil was observed by an optical microscope, and the crack rate was counted.

[0063] Coil resistivity test: the thickness t of the coil was measured by a step meter, the square resistance Rs was measured by a four-probe method, and the resistivity p = Rs x t was calculated.

[0064] Insulating layer breakdown field strength test: a voltage resistance tester was used, an electrode was placed on the surface of the insulating layer with a spacing of 1mm, the voltage was increased at a rate of 500V / s until breakdown occurred, and the breakdown voltage V was recorded. bd , and the breakdown field strength E bd = V bd / d; (d: the thickness of the insulating layer, measured by a micrometer)

[0065] Thermal conductivity test: the thermal conductivity of the samples of Example 1-2 and Comparative Example 1-6 was tested according to the standard of ASTM E1461-13(2022).

[0066]

[0067] According to the thermal cycle cracking rate results of Comparative Example 1-2 and Comparative Example 1, the cracking rate was significantly reduced by the gradient composite ceramic substrate (Al2O3-ZrO2-Al2O3) design of the application; and in Comparative Example 2, the traditional screen printing Ag paste process caused the substrate to deform due to high temperature sintering, the interfacial bonding force was insufficient, and the cracking rate further increased to 20%, highlighting the advantages of the functional transition layer.

[0068] In terms of coil performance, Example 1-2 used a magnetron sputtering and electroplated TiN / Ag composite film, with a resistivity as low as 1.8μΩ·cm, and the TiN protective layer effectively inhibited the high temperature oxidation of Ag (resistance change rate 2-3% after 300℃ / 500h, while Comparative Example 2 reached 18%), while in Comparative Example 5, the Cu coil had a low initial resistivity (1.7μΩ·cm), but lacked a TiN protective layer, and the resistivity increased to 5.0μΩ·cm after high temperature oxidation, further proving the innovativeness of the material combination of the application.

[0069] In the bonding process, the embodiment adopts Sn-Bi, n-Ag alloy composite bonding, the strength exceeds 150MPa, which is significantly improved compared with Sn-37Pb alloy of comparative examples 3-4, and is not easy to creep failure at high temperature.

[0070] In addition, the breakdown field strength of the boron nitride nanosheet composite insulating layer in example 1 reaches 32kV / mm, and the thermal conductivity is improved to 5.5W / mK, fully embodying the systematic breakthrough of the material system design.

[0071] In summary, through the gradient substrate structure, thin film coil process, composite bonding technology and the synergistic innovation of high-conductivity insulation system, the high-temperature reliability, signal stability and environmental adaptability of the sensor are comprehensively improved.

[0072] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any indirect modification, equivalent change and modification of the above embodiment according to the technical essence of the present application still belong to the scope of the technical solution of the present application.

Claims

1. A method for fabricating a high-temperature resistant inductive angle sensor, characterized in that: Includes the following steps: (1) Gradient composite ceramic substrates were prepared by tape casting and lamination sintering; (2) Plasma-enhanced chemical vapor deposition of TiN nanocrystalline layer and micro-arc oxidation treatment of TiN nanocrystalline layer are performed sequentially on the substrate surface to form an oxide layer; (3) After depositing a TiN seed layer by magnetron sputtering, photolithography is performed on the TiN seed layer to form a coil pattern and silver is electroplated to thicken the coil. Then, magnetron sputtering is performed again to deposit a TiN protective layer on the surface of the silver-plated coil. (4) The coil ends are positioned and connected by electron beam welding, followed by transient liquid phase bonding at 200-300℃; (5) Disperse boron nitride nanosheets in a high-temperature polymer resistant to 200-400℃ to form a coating liquid, and form an insulating encapsulation layer from the coating liquid.

2. The method for fabricating a high-temperature resistant inductive angle sensor according to claim 1, characterized in that: The gradient composite ceramic substrate in step (1) includes a surface layer, an intermediate layer and a bottom layer stacked sequentially, wherein the surface layer and the bottom layer are both Al2O3, and the intermediate layer is ZrO2 and Y2O3; the purity of Al2O3 in the surface layer and the bottom layer is ≥99%, and the ZrO2 in the intermediate layer is doped with 3-8 mol% Y2O3; the thickness ratio of the surface layer, the intermediate layer and the bottom layer is 1:2:

1.

3. The method for fabricating a high-temperature resistant inductive angle sensor according to claim 1, characterized in that: The thickness of the TiN nanocrystalline layer in step (2) is 50-200 nm, the thickness of the oxide layer is 15-25 μm, the pore size is 0.1-1 μm, and the porosity is 10-30%.

4. The method for fabricating a high-temperature resistant inductive angle sensor according to claim 1, characterized in that: The thickness of the TiN seed layer of the coil in step (3) is 50-200 nm; the thickness of the electroplated silver layer is 1-10 μm; and the thickness of the TiN protective layer is 50-500 nm.

5. The method for fabricating a high-temperature resistant inductive angle sensor according to claim 1, characterized in that: The transient liquid phase bonding process described in step (4) uses Sn-Bi alloy or In-Ag alloy.

6. The method for fabricating a high-temperature resistant inductive angle sensor according to claim 1, characterized in that: In step (5), the boron nitride nanosheets in the insulating encapsulation layer have a mass fraction of 10-40%, and the high-temperature polymer resistant to 200-400℃ is a silicone resin or polyimide.

7. A high-temperature resistant inductive angle sensor, characterized in that, Obtained by the preparation method described in claim 1.

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