A thermal shock resistant oxygen sensor chip and a method of manufacturing the same

Abstract

The application discloses an anti-thermal shock oxygen sensor chip, which comprises a sensing layer, a thermal improvement layer in close contact with the sensing layer and a skin layer covering the thermal improvement layer arranged on a functional area in sequence; the thermal improvement layer comprises a lower insulating layer, a heating circuit layer, an upper insulating layer and a porous structure layer arranged in sequence and in close contact with the sensing layer; the porous structure layer is arranged on one side edge or both side edges of the thermal improvement layer; the porous structure layer arranged on the edges of the lower insulating layer, the heating circuit layer and the upper insulating layer realizes a weak connection between the porous structure layer and the sensing layer; the chip is prepared by a silk screen printing method, different pastes are used to print the lower insulating layer, the heating circuit layer, the upper insulating layer, the porous structure layer and the skin layer on the sensing layer in sequence, and then sintering is carried out to obtain the oxygen sensor chip; the chip is provided with a weak connection structure, so that the thermal stress of an alumina layer in service of the chip is reduced from the structural arrangement, and the thermal shock performance of the chip is improved.

Description

Technical Field

[0001] This invention relates to the field of oxygen sensor fabrication technology, and in particular to a thermal shock resistant oxygen sensor chip and a method for fabricating the thermal shock resistant oxygen sensor chip. Background Technology

[0002] Automotive oxygen sensor chips primarily consist of a zirconia substrate and several functional thick-film layers. The zirconia substrate is mainly formed using casting or rolling methods, while the thick-film functional areas are obtained primarily through screen printing. Alumina-zirconia multilayer co-fired ceramic chips can be used in structural devices, primarily utilizing their high strength and toughness; they can also be used to fabricate functional devices, such as automotive oxygen sensor chips, leveraging the gas-sensitive properties of zirconia. As automotive oxygen sensor chips require rapid heating to a stable operating temperature of 600–800℃ or higher, this condition places higher demands on the thermal shock resistance of multilayer ceramic sensing chips, and thermal shock fracture is one of the important failure modes of oxygen sensor chips. Existing methods for improving the thermal shock resistance of chips mostly focus on material selection or optimization through controlling chip heating strategies. Among these, oxygen sensor chips using alumina as the main material typically employ a stepped heating method for optimized use in heating control strategies.

[0003] However, the above methods still have some shortcomings. The alumina material in the sensing chip needs to consider insulation, thermal conduction, and compatibility with zirconium oxide and Pt, and the adjustable space is very small. Moreover, the method of reducing the heating rate in the heating strategy will lead to a reduction in ignition time, which will affect the performance of the product. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a thermal shock resistant oxygen sensor chip, as well as a method for fabricating the thermal shock resistant oxygen sensor chip. By using a screen printing method to set a weak connection structure between the sensing layer and the thermal improvement layer, the thermal stress of the alumina layer during chip service is reduced from the structural design, thereby improving the thermal shock performance of the chip.

[0005] To achieve the above objectives, the present invention provides a thermal shock resistant oxygen sensor chip, comprising, starting from one side of the functional area of ​​the chip, a sensing layer, a thermal improvement layer in close contact with the sensing layer, and a skin layer covering the thermal improvement layer, arranged sequentially on the functional area; the thermal improvement layer comprises a lower insulating layer, a heating circuit layer, an upper insulating layer, and a porous structure layer arranged sequentially in close contact with the sensing layer; the porous structure layer is disposed on one or both edges of the thermal improvement layer; the porous structure layer disposed at the edges of the lower insulating layer, the heating circuit layer, and the upper insulating layer forms a weak connection structure with the sensing layer.

[0006] As a further improvement, the heating circuit layer is disposed between the lower insulating layer and the upper insulating layer to achieve insulation isolation, and the width of the lower insulating layer, the heating circuit layer and the upper insulating layer is smaller than that of the sensing layer; the porous structure layer is disposed on one or both edges of the lower insulating layer, the heating circuit layer and the upper insulating layer; the skin layer covers the surface of the upper insulating layer and the porous structure layer to isolate them from the outside world and protect the heat improvement layer.

[0007] As a further improvement, the heating circuit layer, which performs the electric heating connection and heating function, is disposed between the lower insulating layer and the upper insulating layer, which is used for external insulation and isolation from the heating circuit layer, to achieve electrical insulation isolation and thermal conduction protection. Furthermore, the porous structure layer disposed on the side buffers and optimizes the heating conduction speed and uniformity between the lower and upper insulating layers and the heating circuit layer, reducing the thermal stress caused by the heat conduction speed during heating and cooling processes, reducing the thermal gradient between different areas, thereby greatly improving the thermal shock resistance of the oxygen sensor chip.

[0008] Preferably, the lower insulating layer and the upper insulating layer are aluminum oxide layers printed from aluminum oxide paste. The aluminum oxide material provides insulation properties. Nanoparticles of 30nm to 500nm are selected. Alternatively, doping with zirconium oxide powder and silicon dioxide powder can better match the sintering performance with the zirconium oxide matrix.

[0009] Preferably, the heating circuit layer is formed by printing multiple conductive lines with Pt paste, and more preferably four conductive lines.

[0010] Preferably, the porous structure layer is an alumina layer made of alumina material, located 0.1–0.2 mm from the edge of the heating region of the thermal improvement layer. The porous structure layer is formed using alumina slurry with a particle size of 5–10 μm, or by doping with carbon black pore-forming agents. The porous structure layer is achieved through screen printing, adhesive removal, and sintering. This forms a porous alumina structure while ensuring certain insulation properties. The slurry is prepared using large-grained alumina powder, ultimately achieving a porosity of 10–40% in the porous structure. At the normal chip sintering temperature of 1350–1450°C, the integrity of the overall chip structure is maintained while a weak connection with the zirconium oxide layer is formed, thereby reducing the thermal stress at the edge of the alumina layer during the heating process.

[0011] As a further improvement, a porous structure layer with a width of 0.1–0.2 mm is formed at the edges of the alumina layers of the lower and upper insulating layers to achieve a weak connection with the sensing layer. This reduces the constraint of the zirconium oxide layer on the alumina layer during heating, thereby reducing thermal stress and improving the overall thermal shock performance of the chip. The core sensing unit of the chip is located at the center of the sensing layer, while the porous structure is set at the edge of the heating layer. This porous structure has no negative impact on the rapid heating of the sensing unit and its electrical performance indicators; since the porous structure reduces the overall heat capacity, it is more conducive to the rapid heating of the sensing unit. A weak connection structure is formed between the alumina layer and the zirconium oxide layer to reduce thermal stress during heating, thereby improving the thermal shock performance of the chip; this structure is implemented through a screen printing process.

[0012] Preferably, the sensing layer is a zirconia layer made of zirconia powder. The zirconia powder is mixed and ball-milled according to a certain ratio to prepare a slurry, then cast and naturally dried to form a green strip. One to three layers of the green strip are then laminated using a mold to form a zirconia sensing layer, and various functional areas (such as reference channels, diffusion barriers, etc.) are integrated within it according to product performance requirements. The thickness of a single layer of the green strip is 0.1–0.3 mm. The length of the blank of the sensing layer made of zirconia is 20–70 mm, the width is 3–5 mm, and the thickness is 0.8–1.5 mm. Its main function is to realize the sensing function of the oxygen sensor chip. Depending on the requirements of different products, there are various internal features such as diffusion barriers, channels, reference electrodes, and external sensing electrodes.

[0013] Preferably, the skin layer is also made of zirconia powder material, and zirconia slurry can be prepared using 5YSZ powder (5 mol yttrium-stabilized zirconia) or other proportions of YSZ powder.

[0014] To achieve the above objectives, the present invention also provides the following technical solution: a method for fabricating a thermal shock resistant oxygen sensor chip, comprising the following steps:

[0015] S1 green belt preparation: First, 5YSZ zirconia powder is mixed and ball-milled according to the formula to prepare a slurry, then cast and naturally dried to make a green belt with a thickness of 0.1 to 0.3 mm. Then, 1 to 3 layers of the green belt are laminated with a mold to form a zirconia green body, that is, the green body of the sensing layer.

[0016] S2 prepares an insulating layer paste by mixing alumina powder and other doped powders in a certain proportion to prepare an alumina paste for screen printing. Then, the alumina paste is used to print the lower insulating layer alumina layer and the upper insulating layer alumina layer on the green zirconia layer described in step S1.

[0017] S3 is a porous slurry, which is prepared by using large-particle alumina to form a porous slurry, or by doping the alumina insulating layer slurry in step S2 with an appropriate proportion of pore-forming agent to form a porous slurry; the large-particle alumina is alumina powder with a purity of 99.7% and a particle size of 3-5 μm, and the pore-forming agent is made by doping with more than 10%-40% carbon black (by volume).

[0018] S4 is mixed with Pt paste to prepare Pt paste that meets the requirements of resistance and other electrical properties, and is used for printing the heating circuit layer;

[0019] S5 is a zirconia paste, which is prepared by using 5YSZ powder or other proportions of YSZ powder for printing the zirconia surface layer.

[0020] S6 Screen printing: On the induction layer of the zirconium oxide of the green body obtained in step S1, the pastes from steps S2 to S5 are selected to sequentially print the lower insulating layer, heating circuit layer, upper insulating layer, porous structure layer and skin layer to obtain the chip substrate.

[0021] S7 Sintering: The chip substrate obtained in step S6 is dried, debonded, and sintered to obtain a thermal shock resistant oxygen sensor chip. The sintering is carried out in an air environment at a temperature of 1350℃~1450℃ for 2~3 hours.

[0022] As a further improvement, the thickness of the single layer of the green strip in step S1 is 0.1–0.3 mm; while the length of the zirconia green body is 20–70 mm, the width is 3–5 mm, and the thickness is 0.8–1.5 mm. Its main function is to realize the sensing function of the oxygen sensor chip. Depending on the requirements of different products, there are various internal configurations such as diffusion barriers, channels, reference electrodes, and external sensing electrodes. The core objective of this invention is to improve chip thermal shock performance. The configuration of different functional areas of the chip does not affect the chip's thermal shock performance, so they will not be described in detail here.

[0023] As a further improvement, the alumina slurry in step S2 provides insulation properties. It is preferred to use nano or submicron powders with a diameter of 30nm to 500nm. Alternatively, it can be doped with zirconia powder and silica powder to better match the sintering performance with the zirconia matrix.

[0024] As a further improvement, a porous structure of alumina is formed in step S3 while ensuring certain insulation properties; a slurry is prepared by using large-particle alumina powder, or a pore-forming agent is added to the slurry in step S2, ultimately achieving a porosity of 10-40% in the porous structure.

[0025] As a further improvement, step S4 is to heat the circuit paste, and step S5 is an optional step. The skin layer structure is a structure that can be printed according to the chip usage requirements. The purpose of this skin layer is to obtain a better chip appearance. A single layer of zirconium oxide paste with a thickness of 10 to 30 μm is printed.

[0026] Compared with the prior art, the thermal shock resistant oxygen sensor chip of the present invention has the following advantages:

[0027] 1. The thermal shock resistant oxygen sensor chip of the present invention reduces the thermal stress of the alumina layer during chip service by setting a weak connection structure between the sensing layer and the thermal improvement layer, thereby improving the thermal shock performance of the chip; the porous structure at the edge of the heating area can also reduce the overall heat capacity of the heating area, which is more conducive to the rapid heating of the sensing unit and improves product performance.

[0028] 2. Thermal shock failure of oxygen sensor chips originates from thermal stress at the chip edges caused by the heating process of the heating circuit. This invention improves thermal shock failure by addressing the chip structure and implements this improvement through specific manufacturing processes. At startup, the Pt heating circuit raises the temperature of the sensing area to the normal operating temperature of 600–800°C. During this process, the edges of the alumina layer are under tensile stress in the planar direction. Figure 2 The figure shows the longitudinal tensile stress S22. This tensile stress is mainly caused by the temperature gradient and the constraint of the zirconia layer on the deformation of the alumina layer. Failure caused by S22 tensile stress is also a major mode of chip failure. This invention, while ensuring the temperature and heating rate of the sensing area, appropriately reduces the constraint of the zirconia layer on the alumina heating layer, thereby reducing the tensile stress at the edge of the alumina layer; improving the chip's resistance to thermal shock fracture, and achieving this through specific fabrication processes. Attached Figure Description

[0029] Figure 1 This is a schematic cross-sectional view of the heating region of the thermal shock resistant oxygen sensor chip of the present invention;

[0030] Figure 2 This is a simulation test diagram illustrating the improvement of the thermal shock resistant oxygen sensor chip of the present invention;

[0031] Figure 3 This is a schematic cross-sectional view of the finished product of the thermal shock resistant oxygen sensor chip of the present invention;

[0032] Reference numerals: 1-functional area; 2-sensing layer; 3-thermal improvement layer; 31-lower insulation layer; 32-heating circuit layer; 33-upper insulation layer; 34-porous structure layer; 4-skin layer. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, this invention will be further described in detail so that those skilled in the art can fully understand its technical content. It should be noted that this invention is a research and development result formed based on the company's actual situation, combined with customer needs, and through continuous practice and summarization in the development of automotive oxygen sensor chips and related processes. The specific embodiments described herein are only for explaining the invention and are not intended to limit it. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All powders and additives used are commercially available conventional products.

[0034] like Figure 1 and 3 As shown, the thermal shock resistant oxygen sensor chip of the present invention, starting from one side of the functional area 1 of the chip, includes a sensing layer 2, a thermal improvement layer 3 in close contact with the sensing layer 2, and a skin layer 4 covering the thermal improvement layer 3, which are sequentially disposed on the functional area 1. The thermal improvement layer 3 includes a lower insulating layer 31, a heating circuit layer 32, an upper insulating layer 33, and a porous structure layer 34, which are sequentially disposed in close contact with the sensing layer 2. The porous structure layer 34 is disposed on one or both edges of the thermal improvement layer 3. The porous structure layer 34 disposed at the edges of the lower insulating layer 31, the heating circuit layer 32, and the upper insulating layer 33 forms a weak connection structure with the sensing layer 2. The heating circuit layer 32 is disposed between the lower insulating layer 31 and the upper insulating layer 33 to achieve insulation isolation, and the width of the lower insulating layer 31, the heating circuit layer 32 and the upper insulating layer 33 is smaller than that of the induction layer 2; the porous structure layer 34 is disposed on one or both edges of the lower insulating layer 31, the heating circuit layer 32 and the upper insulating layer 33; the skin layer 4 covers the surface of the upper insulating layer 33 and the porous structure layer 34 to isolate them from the outside world and protect the heat improvement layer.

[0035] As another embodiment of the present invention, such as Figure 1The heating circuit layer 32, which provides both electrical heating and heating function, is positioned between the lower insulating layer 31 and the upper insulating layer 33, which provides external insulation and protection against heat conduction. Furthermore, a porous structure layer 34 on the side buffers and optimizes the heating conduction speed and uniformity between the lower and upper insulating layers 31 and 33 and the heating circuit layer 32, reducing thermal stress caused by the heat conduction speed during heating and cooling, and lowering the thermal gradient between different areas, thereby significantly improving the thermal shock resistance of the oxygen sensor chip. The lower insulating layer 31 and upper insulating layer 33 are alumina layers printed from alumina paste. The alumina material provides insulation properties. Nanoparticles of 30nm–500nm are selected, or doped with zirconium oxide powder and silicon dioxide powder for better sintering performance matching with the zirconium oxide substrate. The heating circuit layer 32 is printed with multiple conductive lines, preferably four, using Pt paste. The porous structure layer 34 is an alumina layer made of alumina material, positioned 0.1–0.2 mm from the edge of the heating region of the thermal improvement layer 3. The porous structure layer 34 is formed using alumina slurry with a particle size of 5–10 μm, or by doping with carbon black pore-forming agents. The porous structure layer 34 is achieved through screen printing, adhesive removal, and sintering. This process forms a porous alumina structure while ensuring certain insulation properties. The slurry is prepared using large-grain alumina powder, ultimately achieving a porosity of 10–40% in the porous structure. At the normal chip sintering temperature of 1350–1450 °C, this ensures the integrity of the overall chip structure while forming a weak connection with the zirconium oxide layer, thereby reducing thermal stress at the edge of the alumina layer during the heating process.

[0036] As another embodiment of the present invention, such as Figure 1 and 3A porous structure layer 34 with a width of 0.1–0.2 mm is formed at the edge of the alumina layer of the lower insulating layer 31 and the upper insulating layer 33 to achieve a weak connection with the sensing layer 2. This reduces the constraint of the zirconium oxide layer on the alumina layer during heating, thereby reducing thermal stress and improving the overall thermal shock performance of the chip. The core sensing unit of the chip is located at the center of the sensing layer, while the porous structure is set at the edge of the heating layer. This porous structure has no negative impact on the rapid heating and electrical performance of the sensing unit; since the porous structure reduces the overall heat capacity, it is more conducive to the rapid heating of the sensing unit. A weak connection structure is formed between the alumina layer and the zirconium oxide layer to reduce thermal stress during heating, thereby improving the thermal shock performance of the chip; this structure is implemented through screen printing. The sensing layer 2 is a zirconia layer made of zirconia powder. The zirconia powder is mixed according to a specific ratio, ball-milled into a slurry, then cast and naturally dried to form a green strip. One to three layers of green strips are then laminated using a mold to form the zirconia sensing layer, and various functional areas (such as reference channels and diffusion barriers) are integrated within it according to product performance requirements. The thickness of a single green strip layer is 0.1–0.3 mm. The length of the blank of the sensing layer 2 made of zirconia is 20–70 mm, the width is 3–4 mm, and the thickness is 0.8–1.0 mm. Its main function is to realize the sensing function of the oxygen sensor chip. Depending on the requirements of different products, there are various internal configurations such as diffusion barriers, channels, reference electrodes, and external sensing electrodes. The core objective of this invention is to improve chip thermal shock performance. The configuration of different functional areas does not affect the chip's thermal shock performance, so they will not be described in detail here. The outer skin layer 4 is also made of zirconia powder material, and zirconia slurry can be prepared using 5YSZ powder (5 mol% yttrium stabilized zirconia) or other proportions of YSZ powder.

[0037] To achieve the structure and performance of the thermal shock resistant oxygen sensor chip described above, the fabrication method of the thermal shock resistant oxygen sensor chip includes the following steps:

[0038] (1) To prepare the green strip, firstly, 5YSZ zirconia powder is mixed and ball-milled according to the formula to prepare a slurry, then cast and naturally dried to make a green strip with a thickness of 0.1-0.3 mm. Then, 1-3 layers of green strip are laminated with a mold to form a zirconia green body, that is, the green body of the sensing layer 2. In step (1), the thickness of a single layer of green strip is 0.1-0.3 mm; while the length of the zirconia green body is 20-70 mm, the width is 3-5 mm, and the thickness is 0.8-1.5 mm. Its main function is to realize the sensing function of the oxygen sensor chip. According to the requirements of different products, there are various settings such as diffusion barrier, channel, reference electrode, and external sensing electrode inside. The core purpose of this invention is to improve the thermal shock failure of the chip. The setting of the functional area of ​​different chips does not affect the thermal shock performance of the chip, so they are not described one by one here.

[0039] (2) Prepare insulating layer paste. Prepare alumina powder and other doped powders into alumina paste for screen printing according to the ratio. Then use the alumina paste to print the lower insulating layer 31 alumina layer and the upper insulating layer 33 alumina layer on the green zirconia layer in step (1). The alumina paste in step (2) provides insulating properties. It is preferred to use nano or submicron powders of 30nm to 500nm. Alternatively, it can be doped with zirconia powder and silicon dioxide powder to better match the sintering performance with the zirconia matrix.

[0040] (3) Prepare a porous structure slurry. A porous structure slurry is prepared by using large-particle alumina, or by adding a suitable proportion of pore-forming agent to the alumina insulating layer slurry in step (2) to form a porous structure slurry. The large-particle alumina is 99.7% pure alumina powder with a particle size of 3-5 μm. Alternatively, 10-40% carbon black (volume ratio) is added to the alumina insulating slurry in step 2, including but not limited to carbon black pore-forming agents. A porous structure of alumina is formed in step (3) while ensuring certain insulation performance. A slurry is prepared by using large-particle alumina powder, or by adding pore-forming agent to the slurry in step S2, ultimately achieving 10-40% porosity in the porous structure.

[0041] (4) Prepare Pt paste to meet the requirements of resistance and other electrical properties for printing of heating circuit layer 32;

[0042] (5) Prepare zirconia paste. Use 5YSZ powder or other proportions of YSZ powder to prepare zirconia paste for printing the outer skin layer 4 zirconia. Step (5) is an optional step. The structure of the outer skin layer can be selected for printing according to the chip usage requirements. The purpose of this outer skin layer is to obtain a better chip appearance. Print a single layer of zirconia paste with a thickness of 10 to 30 μm.

[0043] (6) Screen printing: On the zirconium oxide sensing layer 2 of the green body obtained in step (1), the pastes from step (2) to step (5) are selected to print the lower insulating layer 31, heating circuit layer 32, upper insulating layer 33, porous structure layer 34 and skin layer 4 in sequence to obtain the chip substrate.

[0044] (7) Sintering: The chip substrate obtained in step (6) is dried, debonded and sintered to obtain a thermal shock resistant oxygen sensor chip. The sintering is carried out in an air environment at a temperature of 1350℃~1450℃ for 2~3 hours.

[0045] To further illustrate the fabrication method of this thermal shock resistant oxygen sensor chip, a specific embodiment is as follows:

[0046] Example 1:

[0047] Preparation of the zirconia layer: 100 parts of 5YSZ zirconia powder are mixed with 3 parts of alumina powder (99.7% purity, particle size 0.3-1μm), ball-milled to prepare a slurry, then cast using a double-blade technique. After natural drying, a 0.3mm thick green strip is formed. The three green strips are then stamped into a 1.0mm thick zirconia blank (length * width: 20-40mm * 3-4mm) using a mold. Before lamination, suitable Pt sensing circuitry, diffusion barriers, and air channels can be screen-printed onto the multi-layer green strip to meet the requirements of gas detection performance.

[0048] Preparation of upper and lower insulating alumina layers: Alumina powder with a purity of 99.7% and a particle size of 0.3–0.5 μm was prepared into an alumina paste for screen printing. The lower insulating layer of alumina was formed on the surface of the zirconia layer by screen printing, followed by the printing of a Pt heating circuit layer, and then the printing of the upper insulating layer on the other side; the thickness of both insulating layers was 20 μm.

[0049] Porous layer preparation: A porous layer printing paste was prepared using 99.7% pure alumina powder with a thickness of 3–5 μm. After the upper insulating layer of alumina was printed and dried, the porous layer with a thickness of 50 μm was printed.

[0050] Zirconia outer layer: A screen printing paste of 0.3 μm 5YSZ was prepared, printed on the porous layer and dried, and then the zirconia outer layer with a thickness of 10 μm was printed.

[0051] Multi-layered ceramic co-firing: Sintering at 1350℃~1400℃ for 3 hours in air environment yields flat multi-layered co-fired ceramic chips. The porous layer has a porosity of approximately 10%, which can significantly improve thermal shock failure.

[0052] Example 2:

[0053] Preparation of the zirconia layer: 100 parts of 5YSZ zirconia powder were mixed with 6 parts of alumina powder (99.7% purity, particle size 0.3–1 μm), ball-milled to prepare a slurry, and then cast using a double-blade technique. After natural drying, a green strip with a thickness of 0.15 mm was formed. The six layers of green strip were then stamped into a 0.9 mm zirconia blank (length * width: 60–70 mm * 3–4 mm) using a mold. Before lamination, suitable Pt sensing circuitry, diffusion barriers, and air channels can be screen-printed onto the multi-layer green strip to meet the requirements of gas detection performance.

[0054] Preparation of the upper and lower insulating alumina layers: Based on 100 parts of alumina powder (particle size 0.3–0.5 μm, purity 99.7%), 0.4 parts of zirconium oxide powder and 0.2 parts of silica powder (particle size approximately 0.3 μm) were doped. The doping process was achieved by chemical deposition on the surface of the alumina powder. The doped alumina powder was then used to prepare an alumina paste for screen printing. The lower insulating layer of alumina was formed on the surface of the zirconium oxide layer by screen printing, followed by the printing of a Pt heating circuit layer, and then the printing of the upper insulating layer of alumina on the other side; the thicknesses of the upper and lower insulating layers were 30 μm and 20 μm, respectively.

[0055] Porous layer preparation: A porous layer printing paste was prepared by doping 10% carbon black (volume ratio) with 99.7% pure alumina powder of 3-5 μm thickness. After the upper insulating layer of alumina was printed and dried, the porous layer with a thickness of 60 μm was printed.

[0056] Zirconia outer layer: A screen printing paste of 0.3 μm 5YSZ was prepared, printed on the porous layer and dried, and then the zirconia outer layer with a thickness of 10 μm was printed.

[0057] Multilayer ceramic co-firing: Sintering at 1380℃~1420℃ for 2.5 hours in air environment yields flat multilayer co-fired ceramic chips. The porous layer has a porosity of approximately 15%, which can significantly improve thermal shock failure.

[0058] Example 3:

[0059] Preparation of the zirconia layer: 5YSZ zirconia powder (0.3μm particle size) was ball-milled into a slurry, then cast using a double-blade technique. After natural drying, a green strip with a thickness of 0.3mm was formed. The three green strips were then stamped into a 1.2mm thick zirconia blank (length * width: 50mm * 4mm) using a mold. Before lamination, suitable Pt sensing circuitry, diffusion gaps, and air channels can be screen-printed onto the multi-layer green strips to meet the requirements of gas detection performance.

[0060] Preparation of upper and lower insulating alumina layers: Alumina powder with a purity of 99.7% and a particle size of 0.3–0.5 μm was prepared into an alumina paste for screen printing. The lower insulating layer of alumina was formed on the surface of the zirconia layer by screen printing, followed by the printing of a Pt heating circuit layer, and then the printing of the upper insulating layer on the other side; the thickness of both insulating layers was 20 μm.

[0061] Porous layer preparation: A porous layer printing paste is prepared by doping 30% (by volume) of carbon black or other pore-forming agents into the upper and lower insulating alumina paste. After the upper insulating alumina layer is printed and dried, the porous layer with a thickness of 50 μm is printed.

[0062] Zirconia outer layer: A screen printing paste of 0.3 μm 5YSZ was prepared, printed on the porous layer and dried, and then the zirconia outer layer with a thickness of 15 μm was printed.

[0063] Multilayer ceramic co-firing: Sintering at 1400℃~1450℃ for 2 hours in air environment yields flat multilayer co-fired ceramic chips. The porous layer has a porosity of approximately 10%, which can significantly improve thermal shock failure.

[0064] Since the thermal shock failure of oxygen sensor chips originates from the thermal stress at the chip edge caused by the heating process of the heating circuit, the oxygen sensor chip obtained by the present invention through the above embodiments improves the thermal shock failure from the chip structure and is implemented from the specific manufacturing process. Figure 1 This is a schematic diagram of the ceramic induction chip structure (only the cross-sectional diagrams of the alumina heating layer and the zirconium oxide induction layer are shown; other cavity structures within the induction layers, induction electrodes, and other elements are omitted). At startup, the Pt heating circuit raises the temperature of the induction area to the normal operating temperature of 600–800°C. During this process, the edges of the alumina layer are under tensile stress in the planar direction. Figure 2 The figure shows the longitudinal tensile stress (S22). This tensile stress is primarily caused by the temperature gradient and the constraint of the zirconium oxide layer on the deformation of the alumina layer. Failure caused by the S22 tensile stress (stress along the Y-axis) is also a major mode of chip failure. This invention, while ensuring the temperature and heating rate of the sensing area, appropriately reduces the constraint of the zirconium oxide layer on the alumina heating layer, thereby reducing the tensile stress at the edge of the alumina layer; improving the chip's resistance to thermal shock fracture, and achieving this through specific fabrication processes.

[0065] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this patent.

Claims

1. A thermal shock resistant oxygen sensor chip, characterized in that, Starting from one side of the functional area (1) of the chip, it includes a sensing layer (2) disposed sequentially on the functional area (1), a heat improvement layer (3) in close contact with the sensing layer (2), and a skin layer (4) covering the heat improvement layer (3); the heat improvement layer (3) includes a lower insulating layer (31), a heating circuit layer (32), an upper insulating layer (33), and a porous structure layer (34); the heating circuit layer (32) is disposed between the lower insulating layer (31) and the upper insulating layer (33), and the width of the lower insulating layer (31), the heating circuit layer (32), and the upper insulating layer (33) is smaller than that of the sensing layer (2); the porous structure layer (34) is disposed on one or both edges of the lower insulating layer (31), the heating circuit layer (32), and the upper insulating layer (33); the skin layer (4) covers the surface of the upper insulating layer (33) and the porous structure layer (34).

2. The thermal shock resistant oxygen sensor chip according to claim 1, characterized in that: The lower insulating layer (31) and the upper insulating layer (33) are aluminum oxide layers printed from aluminum oxide paste.

3. The thermal shock resistant oxygen sensor chip according to claim 1, characterized in that: The heating circuit layer (32) is made of Pt paste printed with multiple conductive lines.

4. The thermal shock resistant oxygen sensor chip according to claim 1, characterized in that: The porous structure layer (34) is an alumina layer made of alumina material, and the porous structure layer (34) is disposed at a position of 0.1 to 0.2 mm on the side edge of the heat improvement layer (3).

5. The thermal shock resistant oxygen sensor chip according to claim 4, characterized in that: The porous structure layer (34) is made of alumina slurry with a particle size of 5 to 10 μm, or alumina insulating slurry doped with a similar carbon black pore-forming agent.

6. The thermal shock resistant oxygen sensor chip according to claim 3, characterized in that: A porous structure layer (34) with a width of 0.1 to 0.2 mm is provided at the edge of the alumina layer of the lower insulating layer (31) and the upper insulating layer (33) to achieve a weak connection with the sensing layer (2).

7. The method for fabricating a thermal shock resistant oxygen sensor chip according to any one of claims 1 to 6, characterized in that, It includes the following steps: S1 green belt preparation: First, 5YSZ zirconia powder is mixed and ball-milled according to the formula to prepare a slurry, then cast and naturally dried to form a green belt. Then, 1 to 3 layers of the green belt are laminated into a zirconia green body using a mold. S2 prepares an insulating layer paste by preparing an alumina paste for screen printing by mixing alumina powder and other doped powders in a certain proportion. Then, the alumina paste is used to print the lower insulating layer (31) and the upper insulating layer (33) on the green zirconia layer described in step S1. S3 is a porous slurry, which is prepared by using large-particle alumina to form a porous slurry, or by adding a suitable proportion of pore-forming agent to the alumina insulating layer slurry in step S2 to form a porous slurry. S4 is mixed with Pt paste to prepare Pt paste that meets the requirements of resistance and other electrical properties, and is used for printing the heating circuit layer (32); S5 is prepared with zirconia paste, using 5YSZ powder or other proportions of YSZ powder to prepare zirconia paste for printing the skin layer (4) of zirconia; S6 Screen printing: On the induction layer (2) of the zirconium oxide of the green body obtained in step S1, the pastes from steps S2 to S5 are selected to sequentially print the lower insulating layer (31), heating circuit layer (32), upper insulating layer (33), porous structure layer (34) and skin layer (4) to obtain the chip substrate; S7 Sintering: The chip substrate obtained in step S6 is dried, debonded, and sintered to obtain a thermal shock resistant oxygen sensor chip. The sintering is carried out in an air environment at a temperature of 1350℃~1450℃ for 2~3 hours.

8. The method for fabricating a thermal shock resistant oxygen sensor chip according to claim 7, characterized in that: In step S1, the thickness of a single layer of the green strip is 0.1–0.3 mm; while the length of the zirconia green body is 20–70 mm, the width is 3–5 mm, and the thickness is 0.8–1.5 mm.

Images