Gas sensor based on porous ceramic

By using porous ceramic materials and ceramic powder injection molding technology, the problems of MEMS gas sensors in high stress and thermal expansion are solved, higher strength and high temperature resistance are achieved, and the production process is simplified.

CN222618540UActive Publication Date: 2025-03-14JIANGSU FURUI MICRO NANO SENSOR TECH CO LTD
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Patent Information

Application Number
CN202420448701.0
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Priority Date
2023-03-24
Filing Date
2024-03-08
Publication Date
2025-03-14
Estimated Expiration
2034-03-08

AI Technical Summary

Technical Problem

Existing MEMS gas sensors have problems such as high stress causing device failure, as well as device damage caused by mismatch in the thermal expansion coefficient of the material. Meanwhile, the suspended structure is susceptible to damage when printing sensitive materials.

Method used

Porous ceramics are used as the substrate and cover plate, and a porous structure is formed by injection molding of ceramic powder. Combined with the electrical connection between metal passages and pads, a heating electrode and a test electrode are formed, and a pore is opened on the porous ceramic cover plate to form a closed cavity.

Benefits of technology

It improves the thermal insulation and strength of the gas sensor, avoids the fragility of the suspended structure, enhances the high-temperature resistance, can be used in harsh environments, and simplifies the production process.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model discloses a gas sensor based on porous ceramics. The porous ceramic-based gas sensor comprises a sensitive test structure and a packaging structure, the packaging structure comprises a porous ceramic cover plate and a porous ceramic substrate, and the sensitive test structure comprises a gas sensitive structure, a test electrode, an insulating layer and a heating electrode which are stacked on the substrate; wherein the gas sensitive structure is also electrically connected with a test electrode arranged on the insulating layer; the porous ceramic cover plate is provided with a packaging chamber and air holes communicated with the packaging chamber, and the porous ceramic cover plate can be combined with the porous ceramic substrate in a sealed mode so that the gas sensitive structure can be packaged in the packaging chamber. The gas sensor based on the porous ceramic, provided by the utility model, has good heat insulation property and is easier to form; the structure effectively avoids a fragile suspended structure, the strength and reliability are higher, the high temperature resistance is good, and the cable can be used in a more severe environment.
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Description

Technical Field

[0001] The utility model relates to a gas sensor, in particular to a gas sensor based on porous ceramics, belonging to the technical field of electronic devices. Background Art

[0002] Gas sensors are widely used to detect combustible gases, toxic gases and atmospheric components.

[0003] Micro-hotplate gas sensors based on MEMS technology have become a research hotspot in the current gas sensor field due to their low power consumption, small size and easy integration.

[0004] The commonly used silicon-based MEMS gas sensors currently have some defects: the deposition of multiple layers of thin films on silicon-based materials, especially the multi-layer composite of metal films and thin films such as silicon oxide and silicon nitride, can easily form high stress and cause device failure; secondly, the current MEMS gas sensors need to work at a certain temperature, and the superposition of multiple materials can easily cause mismatches in thermal expansion coefficients between materials, causing device damage. In addition, most MEMS gas sensors use platinum as the heating wire and use back-side bulk silicon processing technology to achieve the suspension of the micro-hotplate. After etching the cavity on the back, the suspended structure will also be damaged when printing sensitive materials. Utility Model Content

[0005] In view of the deficiencies of the prior art, the purpose of the utility model is to provide a gas sensor based on porous ceramics.

[0006] In order to achieve the above-mentioned utility model purpose, the technical solution adopted by the utility model includes:

[0007] The utility model provides a gas sensor based on porous ceramics, comprising: a porous ceramic substrate,

[0008] A porous ceramic cover plate, which is arranged on the substrate, a groove-shaped structure is formed on the bottom surface of the porous ceramic cover plate, and is arranged opposite to the top surface of the substrate, and the groove-shaped structure cooperates with the top surface of the substrate to form a closed cavity, and the closed cavity is connected to the pores opened on the porous ceramic cover plate;

[0009] And, a sensitive test structure includes a heating electrode, an insulating layer and a gas sensitive structure which are sequentially stacked on the top surface of the substrate, wherein the gas sensitive structure is exposed in the closed cavity and is electrically connected to the test electrode.

[0010] In a specific embodiment, the heating electrode is electrically connected to the outside via a first conductive path penetrating the substrate, and the testing electrode is electrically connected to the outside via a second conductive path penetrating the porous ceramic cover plate.

[0011] In a specific embodiment, the first conductive path penetrates the substrate along the thickness direction, and the heating electrode is electrically connected to a first metal pad disposed on the bottom surface of the substrate via the first conductive path.

[0012] In a specific embodiment, the second conductive path penetrates the porous ceramic cover plate in the thickness direction, and the test electrode is electrically connected to a second metal pad disposed on the top surface of the porous ceramic cover plate via the second conductive path.

[0013] In a specific embodiment, the pores are opened on the top surface of the porous ceramic cover plate.

[0014] In a specific embodiment, the heating electrode is also exposed in the closed cavity.

[0015] In a specific embodiment, the thickness of the substrate is 100-1000 μm.

[0016] In a specific embodiment, the pores of the substrate have a diameter of 5-500 μm.

[0017] In a specific embodiment, the diameter of the pores is 50-1000 μm.

[0018] In a specific embodiment, the thickness of the porous ceramic cover plate is 100-1000 μm.

[0019] In a specific embodiment, the diameter of the through holes used to form the first conductive path and the second conductive path is 50-500 μm.

[0020] In a specific embodiment, the material of the test electrode includes any one of Au, Ag, Cu, and Ni, or a combination of two or more thereof.

[0021] In a specific embodiment, the material of the heating electrode includes any one of Pt, Au, Ag, and Cu, or a combination of two or more thereof.

[0022] In a specific embodiment, the thickness of the insulating layer is 100 nm-1000 nm.

[0023] In a specific embodiment, the test electrode has a thickness of 100 μm-1000 μm.

[0024] In a specific embodiment, the thickness of the heating electrode is 100nm-5000nm.

[0025] Compared with the prior art, the advantages of the utility model include: the substrate in the gas sensor based on porous ceramics provided by the utility model is a ceramic substrate with a porous structure, which has good thermal insulation and is easier to shape; and the manufacturing process is simple and has a high degree of automation. And compared with the cantilever beam structure formed by etching, the structure of a gas sensor based on porous ceramics effectively avoids the relatively fragile suspended structure, has higher strength and reliability, good high temperature resistance, and can be used in more severe environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a structural schematic diagram of a gas sensor in the prior art;

[0027] Figure 2 A schematic diagram of the structure of a gas sensor based on porous ceramics provided by the utility model;

[0028] Figure 3 It is a schematic structural diagram of a porous ceramic substrate having a plurality of first through holes in the step of preparing the porous ceramic substrate of the utility model;

[0029] Figure 4 It is a schematic structural diagram of the first metal path filling the first through hole in the step of preparing the porous ceramic substrate of the utility model;

[0030] Figure 5 It is a schematic structural diagram of forming a heating electrode on a porous ceramic substrate in the step of preparing a porous ceramic substrate according to the utility model;

[0031] Figure 6 It is a schematic structural diagram of forming a bottom metal pad on a porous ceramic substrate in the step of preparing a porous ceramic substrate according to the utility model;

[0032] Figure 7 It is a schematic diagram of the structure of forming an insulating layer on a heating electrode in the step of preparing a porous ceramic substrate of the utility model;

[0033] Figure 8 It is a schematic diagram of the structure of forming a test electrode on an insulating layer in the step of preparing a porous ceramic substrate according to the utility model;

[0034] Fig. 9 It is a schematic diagram of the structure of forming a gas sensitive structure on a test electrode in the step of preparing a porous ceramic substrate according to the utility model;

[0035] Fig.10 It is a structural schematic diagram of a porous ceramic cover plate having a plurality of second through holes in the step of manufacturing a porous ceramic cover plate of the utility model;

[0036] Fig.11This is a schematic diagram of the structure of the second metal path filling the second through hole in the step of manufacturing the porous ceramic cover plate of the utility model;

[0037] Fig.12 It is a schematic diagram of the structure of forming a surface metal pad on a porous ceramic substrate in the step of manufacturing a porous ceramic cover plate of the utility model;

[0038] Fig.13 The utility model provides a flow chart of a method for preparing a gas sensor based on porous ceramics.

[0039] Explanation of the accompanying drawings: 1. porous ceramic substrate; 2. porous ceramic cover plate; 21. pores; 3. gas sensitive structure; 4. test electrode; 5. insulating layer; 6. heating electrode; 7. surface metal pad; 8. bottom metal pad; 9. first metal path; 10. second metal path. DETAILED DESCRIPTION

[0040] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the utility model after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0041] Example

[0042] See also Figure 1 , is a gas sensor based on porous ceramics provided in this embodiment, including a porous ceramic substrate 1, a porous ceramic cover plate and a sensitive test structure, the porous ceramic cover plate 2 is arranged on the porous ceramic substrate 1, a groove-like structure is formed on the bottom surface of the porous ceramic cover plate 2, and is arranged opposite to the top surface of the porous ceramic substrate 1, and the groove-like structure cooperates with the top surface of the porous ceramic substrate 1 to form a closed cavity, and the closed cavity is connected to the pores 21 opened on the porous ceramic cover plate 2; the sensitive test structure includes a heating electrode 6, an insulating layer 5 and a gas sensitive structure 3 stacked in sequence on the top surface of the porous ceramic substrate 1, the gas sensitive structure 3 is exposed in the closed cavity, and is electrically connected to the test electrode 4.

[0043] More specifically, the porous ceramic substrate 1 can be formed by injection molding of ceramic powder, the thickness of the porous ceramic substrate 1 is 100-1000 μm, and the diameter of the pores 21 on the porous ceramic substrate 1 is 50-1000 μm. The material of the porous ceramic cover plate 2 includes ceramic powder, and the thickness of the porous ceramic cover plate 2 is 100-1000 μm.

[0044] The heating electrode 6 is electrically connected to the outside through a first conductive path that penetrates the porous ceramic substrate 1, and the test electrode 4 is electrically connected to the outside through a second conductive path that penetrates the porous ceramic cover plate 2. The first conductive path penetrates the porous ceramic substrate 1 in the thickness direction, and the heating electrode 6 is electrically connected to a first metal pad disposed on the bottom surface of the porous ceramic substrate 1 through the first conductive path; the second conductive path penetrates the porous ceramic cover plate 2 in the thickness direction, and the test electrode 4 is electrically connected to a second metal pad disposed on the top surface of the porous ceramic cover plate 2 through the second conductive path.

[0045] The porous ceramic cover plate 2 is provided with a plurality of first through holes, in which a first metal path 9 is provided, and a surface metal pad 7 is provided on the porous ceramic cover plate 2, and the surface metal pad 7 and the test electrode 4 are electrically connected via the first metal path 9. The porous ceramic substrate 1 is provided with a plurality of second through holes, in which a second metal path 10 is provided, and a bottom metal pad 8 is provided on the porous ceramic substrate 1, and the bottom metal pad 8 and the heating electrode 6 are electrically connected via the first metal path 9.

[0046] Specifically, the diameter of the first through hole is 5-500 μm, the material of the test electrode 4 includes any one of Au, Ag, Cu, Ni or a combination of two or more thereof, the thickness of the test electrode 4 is 100 μm-1000 μm, and the thickness of the insulating layer 5 is 100 nm-1000 nm.

[0047] Specifically, the diameter of the second through hole is 50-1000 μm, the material of the heating electrode 6 includes any one of Pt, Au, Ag, and Cu or a combination of two or more thereof, and the thickness of the heating electrode 6 is 100 nm-5000 nm.

[0048] The substrate in the utility model is a ceramic substrate with a porous structure, which has good thermal insulation and is easier to shape; and the integrated molding manufacturing process of the gas sensor based on porous ceramics is simple and has a high degree of automation. Compared with the cantilever beam structure formed by etching, the structure of a gas sensor based on porous ceramics effectively avoids the relatively fragile suspended structure, has higher strength and reliability, good high temperature resistance, can be used in more severe environments, has simple raw materials, and can control the proportion.

[0049] Specifically, the present embodiment also provides a method for preparing a gas sensor based on porous ceramics, which specifically includes: preparing a porous ceramic substrate, preparing a cover, and pressing and sintering the porous ceramic substrate and the cover to form an integrated sensor. Figure 3-Figure 13 .

[0050] The steps of preparing the porous ceramic substrate include:

[0051] 1) injection molding a ceramic powder to form a porous ceramic substrate having a thickness of 100-1000 μm and a plurality of first through holes, wherein the porous ceramic substrate may be made of alumina ceramic powder;

[0052] 2) metallic silver as a first metal path filling the first through hole;

[0053] 3) forming a bottom metal pad on the porous ceramic substrate by deposition, wherein the metal pad may be made of metal gold;

[0054] 4) forming a heating electrode on a porous ceramic substrate by deposition, wherein the heating electrode may include a heating electrode, the material of the heating electrode includes any one of Pt, Au, Ag, and Cu or a combination of two or more thereof, and the thickness of the heating electrode is 100 nm-5000 nm;

[0055] 5) forming an aluminum oxide insulating layer on the heating electrode by deposition, wherein the thickness of the insulating layer is 100 nm-1000 nm, and the insulating layer is used to isolate the conductive path between the heating mechanism and the test electrode;

[0056] 6) forming a test electrode on the insulating layer by deposition, wherein the material of the test electrode includes any one of Au, Ag, Cu, and Ni or a combination of two or more thereof, and the thickness of the test electrode is 100 μm-1000 μm;

[0057] 7) coating a gas sensitive structure on the test electrode, wherein the thickness of the gas sensitive structure is 20 um;

[0058] 8) pre-sintering the porous ceramic substrate at 200° C.;

[0059] The steps of making the porous ceramic cover plate include:

[0060] 1) injection molding a ceramic powder to form a porous ceramic cover plate with a thickness of 100-1000 μm and a plurality of second through holes, wherein the porous ceramic cover plate may be made of alumina as powder and ethyl cellulose and pinene alcohol as additives;

[0061] 2) metallic silver as a second metal path filling the second through hole;

[0062] 3) A surface metal pad is formed on the porous ceramic substrate by deposition, and the material of the metal pad can be metal gold.

[0063] The porous ceramic cover plate and the porous ceramic substrate formed by the above method are pressed and sintered to form an integrated sensor.

[0064] It should be understood that the above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. A gas sensor based on porous ceramics, characterized in that: include: A porous ceramic substrate (1), A porous ceramic cover plate (2), which is arranged on the porous ceramic substrate (1), a groove-shaped structure is formed on the bottom surface of the porous ceramic cover plate (2), and is arranged opposite to the top surface of the porous ceramic substrate (1), and the groove-shaped structure cooperates with the top surface of the porous ceramic substrate (1) to form a closed cavity, and the closed cavity is connected to the pores (21) provided on the porous ceramic cover plate (2); And, a sensitive test structure, comprising a heating electrode (6), an insulating layer (5) and a gas sensitive structure (3) stacked in sequence on the top surface of the porous ceramic substrate (1), wherein the gas sensitive structure (3) is exposed in the closed cavity and electrically connected to the test electrode (4).

2. The porous ceramic-based gas sensor according to claim 1, characterized in that: The heating electrode (6) is electrically connected to the outside via a first conductive path penetrating the porous ceramic substrate (1), and the test electrode (4) is electrically connected to the outside via a second conductive path penetrating the porous ceramic cover plate (2).

3. The porous ceramic-based gas sensor according to claim 2, characterized in that: The first conductive path penetrates the porous ceramic substrate (1) along the thickness direction, and the heating electrode (6) is electrically connected to a first metal pad arranged on the bottom surface of the porous ceramic substrate (1) via the first conductive path.

4. The porous ceramic-based gas sensor according to claim 2, characterized in that: The second conductive path penetrates the porous ceramic cover plate (2) in the thickness direction, and the test electrode (4) is electrically connected to a second metal pad arranged on the top surface of the porous ceramic cover plate (2) via the second conductive path.

5. The porous ceramic-based gas sensor according to claim 1, characterized in that: The pores (21) are provided on the top surface of the porous ceramic cover plate (2).

6. The porous ceramic-based gas sensor according to claim 1, characterized in that: The heating electrode (6) is also exposed in the closed cavity.

7. The porous ceramic-based gas sensor according to claim 1, characterized in that: The thickness of the substrate is 100-1000 μm.

8. The porous ceramic-based gas sensor according to claim 1, characterized in that: The holes of the substrate have a diameter of 5-500 μm.

9. The porous ceramic-based gas sensor according to claim 1, characterized in that: The diameter of the pores (21) is 50-1000 μm.

10. The porous ceramic-based gas sensor according to claim 1, characterized in that: The thickness of the porous ceramic cover plate (2) is 100-1000 μm.

11. The porous ceramic-based gas sensor according to claim 3, characterized in that: The diameter of the through holes used to form the first conductive path and the second conductive path is 50-500 μm.

12. The porous ceramic-based gas sensor according to claim 4, characterized in that: The material of the test electrode (4) includes any one of Au, Ag, Cu and Ni, or a combination of two or more thereof.

13. The porous ceramic-based gas sensor according to claim 3, characterized in that: The material of the heating electrode (6) includes any one of Pt, Au, Ag, and Cu, or a combination of two or more thereof.

14. The porous ceramic-based gas sensor according to claim 1, characterized in that: The thickness of the insulating layer (5) is 100nm-1000nm.

15. The porous ceramic-based gas sensor according to claim 1, characterized in that: The thickness of the test electrode (4) is between 100 μm and 1000 μm.

16. The porous ceramic-based gas sensor according to claim 1, characterized in that: The thickness of the heating electrode (6) is 100nm-5000nm.