Ceramic suspended low-power consumption sensitive device and preparation method thereof

Abstract

The application discloses a kind of ceramic suspension type low-power consumption sensitive device and preparation method thereof.The ceramic suspension type low-power consumption sensitive device includes ceramic substrate, electric heating structure, insulating heat-conducting layer and sensitive structure which are stacked along specified direction;Ceramic substrate is formed by ceramic powder or ceramic slurry, forming porosity is 10-60%, including frame body, cantilever beam and suspension structure;Electric heating structure includes heating body, and sensitive structure includes sensitive material body, and heating body and sensitive material body are arranged in the projection area formed by the projection of suspension structure along specified direction.This application forms ceramic substrate with certain porosity, reduces the problem of high heat loss of conventional dense ceramic substrate, and the process is simpler, the forming rate is higher, the cost is greatly reduced, and the implementability is strong;According to the requirement of device heat dissipation, the composition, structure and process of ceramic powder and slurry can be adjusted to meet the performance requirements of device, and the process is flexible.

Description

Technical Field

[0001] This invention relates to the field of sensitive device technology, and in particular to a ceramic-suspended low-power sensitive device and its fabrication method. Background Technology

[0002] Sensitive devices encompass a wide variety of types, such as temperature sensors, gas sensors, and photoelectric sensors. Their main principle is to utilize the responsiveness of a sensitive material to environmental changes. A test circuit measures a series of changes in the sensitive material, such as resistance, capacitance, or voltage, to provide feedback on the changes in the physical quantity sensed by the material. Furthermore, in some sensitive devices, the sensitive material needs to be heated to maintain it within an appropriate temperature range for measurement accuracy. These heating circuit structures generate power consumption during use. Therefore, in practical applications, reducing power consumption through device structure design while ensuring effective heating is of paramount importance.

[0003] Gas sensors, as gas-sensitive devices, are widely used to detect flammable, toxic, and harmful gases, as well as atmospheric components. Currently, with the increasing integration of devices, the requirements for gas sensors are also becoming more stringent. Among them, micro-hot plate gas sensors based on MEMS technology have become a research hotspot in the field of low-power gas sensors due to their low power consumption, small size, and ease of integration.

[0004] Currently, commonly used semiconductor gas sensors include silicon substrate, glass substrate, and ceramic substrate gas sensors. The preparation process of ceramic substrates usually includes mixing, casting, pre-firing, pressing, and sintering. The process is complex, the sintering temperature is high, and the resulting ceramic substrate has high density, which leads to easy heat loss and high heat loss. For beam structures, ceramic substrate sensors are difficult to process and have high manufacturing difficulty.

[0005] Therefore, there is an urgent need in the field to develop a sensitive component that is simple to manufacture, has good performance, is easy to integrate, and has low power consumption, especially in applications such as consumer electronics and white goods. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a ceramic-suspended low-power sensitive device and its fabrication method.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] In a first aspect, the present invention provides a ceramic-suspended low-power sensitive device, comprising a ceramic substrate, an electrothermal structure, an insulating and thermally conductive layer, and a sensitive structure stacked along a specified direction; the ceramic substrate is formed at least of ceramic powder or ceramic slurry, with a molding porosity of 10-60%, and the ceramic substrate includes a frame, a cantilever beam, and a suspension structure, the frame surrounding the suspension structure and having a gap between the frame and the suspension structure, the cantilever beam being disposed in the gap space for connecting the frame and the suspension structure; the electrothermal structure includes a heating element, the sensitive structure includes a sensitive material body, and both the heating element and the sensitive material body are disposed in a projection area formed by the suspension structure projecting along the specified direction.

[0009] Secondly, the present invention also provides a method for fabricating a ceramic-suspended low-power sensing device, comprising:

[0010] A ceramic substrate is provided, the ceramic substrate being formed at least from ceramic powder or ceramic slurry and having a porous structure, and the ceramic substrate including a frame, a cantilever beam and a suspension structure, the frame being arranged around the suspension structure, and the cantilever beam being used to connect the frame and the suspension structure;

[0011] In addition, at least one step of sequentially covering the surface of the suspension structure with an electrothermal structure, an insulating and thermally conductive layer, and a sensitive structure.

[0012] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention include at least the following:

[0013] The technical solution provided by this invention is based on the formation of cantilever beam structures from ceramic powder or slurry through injection molding or pressing. This can form ceramic substrates with a certain porosity, reducing the high heat loss problem of conventional dense ceramic substrates. Furthermore, injection-molded or pressed ceramic substrates can lower the molding temperature, save energy, have lower equipment requirements, and can be mass-produced. More importantly, compared to ceramic substrates formed by conventional processes, which are not easy to form cantilever beam structures for sensitive devices, ceramic powder or slurry can form cantilever beam structures in one step through injection molding or pressing. This process is simpler, has a higher forming rate, significantly reduces costs, and is highly feasible. The composition, structure, and process of the ceramic powder or slurry can be adjusted according to the device's heat dissipation requirements to meet the device's performance requirements, making the process flexible.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to enable those skilled in the art to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described below in conjunction with detailed drawings. Attached Figure Description

[0015] Figure 1This is a side view of a ceramic-suspended low-power sensitive device provided in a typical embodiment of the present invention.

[0016] Figure 2 This is a front structural schematic diagram of a ceramic-suspended low-power sensitive device provided in a typical embodiment of the present invention.

[0017] Figure 3 This is a schematic diagram of the overall fabrication process of a ceramic-suspended low-power sensitive device provided in a typical embodiment of the present invention;

[0018] Figures 4a-4g This is a schematic diagram of the step-by-step fabrication process of a ceramic-suspended low-power sensitive device provided in a typical embodiment of the present invention.

[0019] Explanation of reference numerals in the attached figures:

[0020] 101. Frame; 102. Cantilever beam; 103. Suspension structure; 200. Insulation layer; 301. Heating circuit; 302. Heating element; 303. Metal through hole; 400. Insulating and thermally conductive layer; 501. Test circuit; 502. Sensitive material. Detailed Implementation

[0021] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0023] See Figure 1 and Figure 2 This invention provides a ceramic-suspended low-power sensitive device, comprising a ceramic substrate, an electrothermal structure, an insulating and thermally conductive layer 400, and a sensitive structure stacked along a specified direction. The ceramic substrate includes a frame 101, a cantilever beam 102, and a suspension structure 103. The frame 101 surrounds the suspension structure 103, and there is a gap between the frame 101 and the suspension structure 103. The cantilever beam 102 is disposed in the gap and is used to connect the frame 101 and the suspension structure 103. The electrothermal structure includes a heating element 302, and the sensitive structure includes a sensitive material body 502. Both the heating element 302 and the sensitive material body 502 are disposed in the projection area formed by the suspension structure 103 projected along the specified direction.

[0024] Of course, in order to further reduce heat loss, an insulation layer 200 can be provided between the ceramic substrate and the electrothermal structure, but this insulation layer 200 is not necessary.

[0025] In some embodiments, the frame 101, cantilever beam 102, and suspension structure 103 are integrated; viewed radially along the designated axis, the width of the cantilever beam 102 is less than 10-1000 μm, and its thickness is less than 300 μm. To form a low-power ceramic substrate with good thermal barrier properties, the present invention uses the cantilever beam 102 to support the suspension structure 103 within the frame 101. Heat is primarily dissipated through thermal conduction via the cantilever beam 102. Therefore, to achieve the optimal balance between strength and low-power performance, the dimensional parameters of the cantilever beam 102 are preferably within the aforementioned range.

[0026] More specifically, in some embodiments, in the specified direction, the thickness of the cantilever beam 102 is 1 / 10 to 3 / 4 of the thickness of the suspension structure 103. If the thickness is too thin, it is insufficient to support the weight of the suspension structure 10; if the thickness is too thick, it increases heat loss.

[0027] The ceramic substrate can be composed of conventional ceramic slurry or ceramic powder, such as powdered Al2O3. In order to reduce thermal conductivity, the ceramic slurry or ceramic powder can also be made of porous materials, such as porous zirconium dioxide, porous alumina, or porous silicon dioxide, and is not limited to these.

[0028] Regarding the microstructure of the ceramic substrate, the porosity is 10-60%; in some embodiments, the ceramic substrate is a porous structure with a pore size of 5-500 μm; the porous ceramic structure is of great help in preventing heat conduction and can block heat loss through heat conduction. In practical applications, the above-mentioned porous structure is usually formed through the preparation process of the ceramic substrate.

[0029] In a more preferred embodiment, the porosity of different parts of the ceramic substrate is set differently. For example, at least the porosity of the cantilever beam 102 is higher than that of the suspension structure 103, while the porosity of the suspension structure 103 can be set lower, around 10-30%. The cantilever beam, as a primary heat dissipation channel, forms a heat-insulating structure by increasing its porosity, thus blocking the main heat generated during conduction. Setting the suspension structure 103 with lower porosity allows for a smaller cross-sectional area while maintaining its mechanical load-bearing capacity. Furthermore, the suspension structure 103 can be configured as a multi-layer structure, with different porosities selected for each layer. For example, the lower layer farther from the electrothermal structure has a higher porosity than the upper layer closer to the electrothermal structure. This ensures the load-bearing capacity of the suspension structure while further reducing heat loss and energy consumption. Specific methods for differentiating porosity can be achieved through different forming processes at different locations, as illustrated in the specific examples of the preparation methods below, but are not limited to these.

[0030] The above describes the structure and composition of the ceramic substrate. Regarding heating and sensing functions, in some embodiments, the electrothermal structure further includes multiple heating circuits 301 electrically connected to the heating element 302, and the sensing structure further includes multiple test circuits 501 electrically connected to the sensitive material body 502. The heating circuits 301 and test circuits 501 are disposed on the surface of the cantilever beam 102 and extend away from the suspension structure 103. Thus, the cantilever beam 102 not only serves as a fixed structure for the suspension structure 103 but also provides an extension carrier for the test circuits 501 and heating circuits 301. The test circuits 501 and heating circuits 301 extend along the extension direction of the cantilever beam 102, making full use of the structural space and resulting in a more orderly connection between the device and the external circuitry.

[0031] In some embodiments, at least four cantilever beams 102 are radially arranged around the suspension structure 103; each of the plurality of heating circuits 301 and test circuits 501 is disposed on a different cantilever beam 102. For example… Figure 1 and Figure 2 As shown ( Figure 1 From Figure 2 (Viewed from one corner), in a specific example... Figure 2 There are four cantilever beams 102 on each side, top, bottom, left, and right. The top and bottom pairs of cantilever beams 102 are used to lay two circuits of the test circuit 501, and the left and right pairs of cantilever beams 102 are used to lay two circuits of the heating circuit 301. This specific structure allows different circuits to be led out separately through different orientations, making the arrangement of external circuits very clear and convenient.

[0032] See merger Figure 3 Corresponding to the structural characteristics of the aforementioned ceramic-suspended low-power sensing device, this embodiment of the invention also provides a method for fabricating a ceramic-suspended low-power sensing device, which includes the following steps:

[0033] A ceramic substrate is provided, the ceramic substrate including a frame 101, a cantilever beam 102 and a suspension structure 103, the frame 101 being arranged around the suspension structure 103, and the cantilever beam 102 being used to connect the frame 101 and the suspension structure 103.

[0034] In addition, at least one step of sequentially covering the surface of the suspension structure 103 with an electrothermal structure, an insulating and thermally conductive layer 400, and a sensitive structure.

[0035] In some implementations, the preparation method specifically includes the following sub-steps:

[0036] Provide ceramic powder and form the ceramic substrate by injection molding or pressing and sintering process;

[0037] The injection molding process includes the step of mixing the ceramic powder with a binder and then injection molding it.

[0038] To achieve the aforementioned superior differentiated porosity distribution, in some more preferred embodiments, a first ceramic powder or a second ceramic powder may be provided, wherein the first ceramic powder is a porous powder and the second ceramic powder is a solid powder (or has a smaller pore size and / or lower porosity than the first ceramic powder), wherein the first ceramic powder is used at least to form the cantilever beam 102 and the second ceramic powder is used at least to form the suspension structure 103.

[0039] For example, in the pressing and sintering process, different ceramic powders are filled in different parts of the mold (different positions corresponding to the suspension structure 103 and the cantilever beam 102) to achieve a differential porosity distribution.

[0040] More specifically, the first ceramic powder and the second ceramic powder are preferably made of the same material, so that the two powders have better bonding properties.

[0041] In a more preferred embodiment, the suspension structure 103 may also adopt a vertically differentiated porosity distribution. For example, the side facing away from the heating element 302 (bottom layer) has low porosity, and the side facing the heating element 302 (surface layer) has high porosity. In the corresponding preparation method, the second ceramic powder is used to form the side facing away from the heating element 302 and the side facing the heating element 302.

[0042] For example, in the pressing and sintering process, the first ceramic powder and the second ceramic powder are filled in two layers in the mold position corresponding to the suspension structure 103. In this way, the first ceramic powder forms the bottom layer of the cantilever beam 102 and the suspension structure 103 in an integrated manner, which ensures the bonding strength, reduces heat loss, and ensures mechanical bonding.

[0043] In the corresponding preparation method, a first ceramic powder can be used to form the side facing away from the heating element 302, and a second ceramic powder can be used to form the side facing the heating element 302.

[0044] In some embodiments, the preparation method specifically includes the following steps:

[0045] Metal is deposited on the surface of the ceramic substrate and etched to form metal wires. The metal wires include a heating element 302 disposed at the suspension structure 103 and a heating circuit 301 electrically connected to the heating element 302 and extending along the surface of the cantilever beam 102 in a direction away from the suspension structure 103. The heating element 302 and the heating circuit 301 constitute the electrothermal structure.

[0046] Deposit an insulating and thermally conductive material to form an insulating and thermally conductive layer 400 that at least covers the heating element 302;

[0047] A plurality of test circuits 501 are formed by depositing metal and etching on the surface of the insulating and thermally conductive layer 400, and a sensitive material is coated between the ends of the corresponding test circuits 501 to form a sensitive material body 502. The test circuits 501 and the sensitive material body 502 constitute the sensitive structure.

[0048] Of course, if it is necessary to form the insulation layer 200, the insulation material can be deposited on the surface of the ceramic substrate first to form the insulation layer 200. The insulation layer 200 at least covers the surface of the suspension structure 103, and then metal is deposited on the surface of the insulation layer 200 and etched to form metal wires.

[0049] In some implementation schemes, the following steps / processes are also specifically included:

[0050] The steps include: depositing the test circuit 501 and then performing a first sintering process on the corresponding structure loaded with the test circuit 501; and / or coating the sensitive material and then performing a second sintering process to solidify the sensitive material.

[0051] As a typical application example of the above technical solution, the ceramic suspension type low-power sensitive device is, for example, a low-power ceramic gas sensor, with ceramic as the base, a ceramic suspension structure 103 in the middle, a heating structure, an insulating and thermally conductive layer 400, and a test structure formed sequentially on the suspension structure 103; and cantilever beams 102 around the perimeter to support and connect to the frame 101.

[0052] The above-mentioned method for preparing a porous ceramic gas sensor uses ceramic powder as a substrate, forms a corresponding cantilever beam 102 substrate structure by injection molding, then deposits a heating structure, and then prints an insulating and thermally conductive layer 400 and a test structure on the heating structure.

[0053] Regarding the specific material selection, the substrate material is a porous material with a pore size of 5-500 μm and a thickness of 100-2000 μm; the thickness of the insulating and thermally conductive layer 400 can be, for example, 100-5000 nm; the test electrode is a circuit formed by metals such as Au, Ag, Cu, and Ni, and a sensitive material body 502 connected to both ends of the two circuits; the diameter of the metal through-hole 303 used to connect or lead out the circuit between layers is 50-600 μm, especially the heating circuit can be connected to the upper layer pad through the metal through-hole 303 (the metal pillar connecting the layers); of course, other forms commonly used in the art, such as the method of wire exiting from the side of the frame, can also be used instead of metal through-holes; the heating circuit 301 is made of metals such as Pt, Au, Ag, and Cu, with a thickness of 100-5000 nm; the heating element 302 in the heating structure is, for example, a filamentary heating element 302 formed by arranging the above-mentioned metal fine wires, or it can be formed by coating with an electrothermal material.

[0054] It should be noted that some film layers may appear to be suspended in the attached figures. However, this is a phenomenon created for the convenience of drawing the image and does not indicate that the position is suspended. For example, the insulating and thermally conductive layer 400 is actually covered on the surface in the actual device and is not suspended.

[0055] The technical solution of the present invention will be further described in detail below through several embodiments and in conjunction with the accompanying drawings. However, the selected embodiments are only for illustrating the present invention and do not limit the scope of the present invention.

[0056] Example 1

[0057] This embodiment illustrates the structure and fabrication process of a ceramic-suspended low-power sensor, as shown below:

[0058] See Figure 3 and Figures 4a-4gAs shown, alumina ceramic powder is first prepared; then, the alumina ceramic powder is injection molded to form an integrated cantilever beam ceramic substrate. The outer periphery of the ceramic substrate is a square frame 101 with a side length of 1500μm, a frame width of 300μm, and a thickness of 500μm. The center of the frame 101 is a suspension structure 103, which is also a square sheet with a side length of 400μm and a thickness of 300μm. The frame 101 and the suspension structure 103 are connected by four cantilever beams 102, which have a thickness of 200μm and a width of 300μm.

[0059] The ceramic substrate is pre-fired at 350℃ to form a ceramic substrate with an overall porosity of about 30%.

[0060] An insulation layer 200 is deposited on the end face of the ceramic substrate. The insulation layer 200 is made of alumina and has a thickness of 50 μm.

[0061] A platinum heating circuit 301 with a thickness of 500 nm is deposited on the insulation layer 200. The circuit extends outward on the left and right cantilever beams 102 respectively, and at the position of the suspension structure 103, the circuit is a thin U-shaped reciprocating structure, forming the central heating element 302.

[0062] A 400-layer aluminum oxide insulating and thermally conductive layer with a thickness of 1000 nm is deposited on the upper surface.

[0063] The test circuit 501 formed by depositing metallic gold has a thickness of 500 nm. The test circuit 501 includes two sections (positive and negative circuits) and is attached to the upper and lower cantilever beams 102. The central area is an empty area for coating of sensitive material.

[0064] The sensitive material is coated, specifically zinc oxide, with a thickness of 20 μm, to form a sensitive material body 502, which is then electrically connected to the aforementioned test circuit 501.

[0065] The obtained structure was sintered at 800℃ for 30 minutes to finally obtain a ceramic-suspended low-power gas sensing device.

[0066] After batch trial production, the preparation method provided in this embodiment produces a ceramic cantilever sensor with a power consumption of 210mW, while in comparison, the sensor prepared using conventional ceramic substrates in the prior art has a power consumption of 500mW, resulting in a significant reduction in power consumption.

[0067] Example 2

[0068] This embodiment also illustrates the structure and fabrication process of a ceramic-suspended low-power sensing device, which is largely the same as that in Embodiment 1, with the main difference being:

[0069] By replacing the alumina ceramic powder with porous zirconium dioxide, the power consumption of the ceramic cantilever sensing device obtained in this embodiment is 180mW, which is lower than that in Example 1.

[0070] Example 3

[0071] This embodiment also illustrates the structure and fabrication process of a ceramic-suspended low-power sensing device, which is largely the same as that in Embodiment 1, with the main difference being:

[0072] The thickness of the cantilever beam 102 was adjusted to 100μm, and the power consumption was 200mW, which is lower than that of Example 1.

[0073] Example 4

[0074] This embodiment also illustrates the structure and fabrication process of a ceramic-suspended low-power sensing device, which is largely the same as that in Embodiment 1, with the main difference being:

[0075] In preparing the ceramic substrate, two types of powder are provided: solid alumina powder and hollow alumina powder. A mold pressing method is used. The hollow alumina powder is completely filled into the mold at the position corresponding to the cantilever beam 102. At the position corresponding to the suspension structure 103, the bottom layer of hollow alumina powder is first filled, approximately half the height of the suspension structure 103. The remaining portion is then filled with solid alumina powder until completely filled. After pressing in the mold, the substrate is sintered to obtain a ceramic substrate with different porosities at different locations.

[0076] The remaining steps and materials are the same as in Example 1.

[0077] The device obtained in this embodiment still achieves lower power consumption, only 170mW, which is significantly lower than that in the above embodiments.

[0078] Based on the above embodiments, it is clear that the technical solution provided by the embodiments of the present invention is based on the formation of a cantilever beam structure from ceramic raw materials. Not only is the cantilever structure integrally formed and formed quickly, greatly reducing the power consumption of the device; by controlling the proportion of ceramic components and the size of the cantilever beam, low-power sensitive devices can be flexibly obtained, and the processing technology is simple and the cost is low.

[0079] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A ceramic-suspended low-power sensing device, characterized in that, A ceramic substrate, an electrothermal structure, an insulating and thermally conductive layer, and a sensitive structure are stacked at least in a specified direction; The ceramic substrate is formed from at least ceramic powder or ceramic slurry, and the molded substrate has a porous structure. The pore size of the ceramic substrate is 5-500 μm, and the porosity is 10-60%. The ceramic substrate includes a frame, a cantilever beam, and a suspension structure, which are integrally formed in one piece. The frame surrounds the suspension structure, and there is a space between the frame and the suspension structure. The cantilever beam is disposed in the space and is used to connect the frame and the suspension structure. The porosity of the cantilever beam is higher than that of the suspension structure. The suspension structure is a multi-layer structure, in which the lower layer farther from the electrothermal structure has a higher porosity than the upper layer closer to the electrothermal structure, and the thickness of the lower layer is half that of the suspension structure. The electrothermal structure includes a heating element, and the sensitive structure includes a sensitive material body. Both the heating element and the sensitive material body are disposed in the projection area formed by the projection of the suspension structure along the specified direction.

2. The ceramic-suspended low-power sensing device according to claim 1, characterized in that, In the specified direction, the thickness of the cantilever beam is 1 / 10 to 3 / 4 of the thickness of the suspension structure.

3. The ceramic-suspended low-power sensing device according to claim 1, characterized in that, The ceramic substrate comprises a porous ceramic material.

4. The ceramic-suspended low-power sensing device according to claim 1, characterized in that, The electrothermal structure further includes multiple heating circuits electrically connected to the heating element, and the sensitive structure further includes multiple test circuits electrically connected to the sensitive material body; The heating circuit and the testing circuit are disposed on the cantilever beam and extend away from the suspension structure. Each of the plurality of heating circuits and testing circuits is disposed on a different cantilever beam.

5. A method for fabricating a ceramic-suspended low-power sensing device according to any one of claims 1-4, characterized in that, include: A ceramic substrate is provided, the ceramic substrate being formed at least from ceramic powder or ceramic slurry and having a porous structure, and the ceramic substrate including a frame, a cantilever beam and a suspension structure, the frame being arranged around the suspension structure, and the cantilever beam being used to connect the frame and the suspension structure; In addition, at least one step of sequentially covering the surface of the suspension structure with an electrothermal structure, an insulating and thermally conductive layer, and a sensitive structure.

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