Capacitive pressure sensitive element and sensor

Abstract

A capacitive pressure sensitive component includes a relatively rigid ceramic substrate and a relatively flexible ceramic diaphragm which are sealingly joined together and enclose a mounting cavity; the edges of the opposite inner surfaces of the ceramic substrate and the ceramic diaphragm are respectively provided with a first metal layer and a second metal layer, the second metal layer is welded with the second metal layer; the center of the opposite inner surfaces of the ceramic substrate and the ceramic diaphragm is respectively provided with a first electrode plate and a second electrode plate, and a gap is left between the first electrode plate and the second electrode plate. The capacitive pressure sensitive component can have a very small electrode plate spacing; and due to the plasticity in the thickness direction of the metal layer, the electrode plate can have a higher parallelism; in addition, by setting the second reference electrode on the outer surface of the ceramic substrate, not only the connection with the measurement circuit is facilitated, but also the support area of the periphery is fully utilized, the electrode plate can have a larger area, and the measurement accuracy is further improved.

Description

Technical Field

[0001] This application relates to the field of sensor technology, specifically to a capacitive pressure-sensitive element and sensor. Background Technology

[0002] Existing ceramic capacitive pressure sensors typically have two ceramic plates facing each other, one a rigid substrate and the other a flexible thin plate. Fixed and movable electrodes are respectively mounted on the opposing surfaces of the two ceramic plates, forming a variable capacitor. The flexible thin plate faces the pressure-receiving side and bends to one side under the pressure difference. This pressure difference can be obtained by measuring the capacitance of the variable capacitor. The outer edge of the flexible thin plate is pressure-sealed with a sealing ring to a support step formed on the sensor housing. To avoid a fixed gap between the two electrodes, a ceramic spacer ring is placed between the two ceramic plates. This ring ring is fused to the ceramic plates at high temperature using glass filler. The aforementioned ceramic capacitive pressure sensors are manufactured at high temperatures and with complex processes. To obtain a larger capacitance value to maximize measurement accuracy, the thickness of the spacer ring needs to be reduced. However, this often leads to warping of the ceramic spacer ring during sintering, affecting surface flatness, increasing the risk of poor sealing, and causing the surfaces of the two electrodes to become non-parallel, thus reducing measurement accuracy. In response, Japanese Patent Application Publication No. 8-240500 proposes a solution of adding ceramic or resin spheres between two ceramic plates, which leads to a complex process; while US20030221493A1 sets annular spacers around the electrodes, which not only leads to a complex process but also limits the usable area of ​​the capacitor plates; in addition, there is still room for improvement in the minimum spacing that they can achieve. Summary of the Invention

[0003] In view of the shortcomings of the prior art, this application provides a pressure sensor to solve at least one of the above-mentioned defects.

[0004] The capacitive pressure-sensitive component provided in this application includes a relatively rigid ceramic substrate and a relatively flexible ceramic diaphragm that are sealed together and form a mounting cavity. A first metal layer and a second metal layer are respectively disposed on the edges of the relatively inner surfaces of the ceramic substrate and the ceramic diaphragm, and the second metal layers are welded together. A first electrode plate and a second electrode plate are respectively disposed at the center of the relatively inner surfaces of the ceramic substrate and the ceramic diaphragm, and an electrode plate gap is left between the first electrode plate and the second electrode plate.

[0005] Preferably, at least one of the first metal layer, the second metal layer, the first electrode plate, and the second electrode plate is fabricated using a thick film process.

[0006] Preferably, the first metal layer and the first electrode plate are both obtained by sintering together a metal paste coated on a ceramic substrate.

[0007] Preferably, both the second metal layer and the first metal layer are obtained by sintering together a metal paste coated on a ceramic diaphragm.

[0008] Preferably, it further includes a second reference electrode, which is disposed on the outer surface of the ceramic substrate and faces the first metal layer.

[0009] Preferably, the first electrode plate and / or the second electrode plate are covered with an insulating film. More preferably, the insulating film is an organic film.

[0010] Preferably, the inner surface of the ceramic substrate is provided with a cavity, and the first electrode plate is disposed at the bottom of the cavity.

[0011] Preferably, the ceramic membrane is a light-transmitting material; the first metal layer and the second metal layer are welded together by a laser beam incident perpendicularly from the outside of the ceramic membrane.

[0012] This application also claims a pressure sensor comprising any of the capacitive pressure-sensitive components described above.

[0013] The capacitive pressure-sensitive component of this application can achieve a very small electrode spacing; and due to the plasticity in the thickness direction imparted by the metal layer, the electrode plates can have a high degree of parallelism; in addition, by setting the second reference electrode on the outer surface of the ceramic substrate, it is not only convenient to connect with the measurement circuit, but also makes full use of the peripheral support area, which can make the electrode plates have a larger area, further improving the measurement accuracy. Attached Figure Description

[0014] Figure 1 This is an axial cross-sectional view of a preferred embodiment of the capacitive pressure-sensitive component of the present invention.

[0015] Figure 2 This is an inner front view of the ceramic substrate 3a and the ceramic film 3b according to a preferred embodiment of the present invention;

[0016] Figure 3 This is an axial cross-sectional view of a preferred embodiment of the capacitive pressure-sensitive component of the present invention.

[0017] Explanation of reference numerals in the attached drawings: 30a, cavity; 311, first conductive part; 312, second conductive part; 313, first metallized through-hole; 314, second metallized through-hole; 31a, first electrode plate; 31b, second electrode plate; 32a, first metal layer; 32b, second metal layer; 32, first reference electrode; 33, second reference electrode; 34, insulating film; 350, conductive trace; 351, circuit board; 352, bonding wire; 35a, conditioning element; 35b, other electronic components; 35d, window; 35, measurement circuit; 3a, ceramic substrate; 3b, ceramic diaphragm; 3, capacitive pressure sensitive component; Detailed Implementation

[0018] The following definitions should apply throughout the application document:

[0019] The terms “up,” “down,” “left,” “right,” “front,” “back,” “inner,” “outer,” “far,” “near,” and their combinations, indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are used only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the equipment or component referred to must have a specific orientation, or be constructed, operated, or used in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms “horizontal” and “horizontal plane,” when not specifically defined in relation to the direction of gravity, refer to a direction or plane that is approximately perpendicular to the “up” or “down”. The terms “longitudinal” and “horizontal,” when not specifically defined in terms of their plane, refer to two orthogonal directions on the “horizontal plane.”

[0020] The term "and / or" refers to any combination of one or more of the listed items, and all possible combinations thereof;

[0021] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] The term "comprising" means including but not limited to, and should be interpreted in the manner commonly used in the patent context;

[0023] When used with numbers, terms such as “about” or “approximately” may refer to a specific number, or alternatively, a range close to that specific number as understood by those skilled in the art; and if the specification states that a component or feature is “may,” “can,” “possibly,” “potentially,” “capable,” “preferably,” “best,” “especially,” “usually,” “optionally,” “for example,” “often,” “specifically” (or other such words) included or has a certain characteristic, then the particular component or feature is not necessarily included or has that characteristic, but is optional, that is, such component or feature may be optionally included in some embodiments or excluded;

[0024] The phrases “in one embodiment,” “according to one embodiment,” “in other embodiments,” “in yet another embodiment,” etc., generally mean that the specific feature, structure, or characteristic following the phrase may be included in at least one embodiment of the invention, and may be included in more than one embodiment of the invention (importantly, such phrases do not necessarily refer to the same embodiment); if the specification describes something as “exemplary” or “example,” it should be understood as referring to a non-exclusive example;

[0025] The technical solution of this application will now be clearly and completely described with reference to the accompanying drawings. The following embodiments are exemplary and are only used to explain this application, and should not be construed as limiting this application. In the following description, the same reference numerals are used to denote the same or equivalent elements, and repeated descriptions are omitted.

[0026] like Figure 1 , Figure 2 As shown, a preferred embodiment of the capacitive pressure-sensitive component 3 of this application includes a ceramic substrate 3a and a ceramic diaphragm 3b, which are sealed together to form a sealed cavity (not marked). The inner surface of the ceramic substrate 3a ( Figure 1 A first electrode 31a is disposed at the center of the lower surface of the ceramic diaphragm 3b, and a second electrode 31b is disposed correspondingly on the inner surface of the ceramic diaphragm 3b. The inner surfaces of the first electrode 31a and the second electrode 31b are preferably fully exposed within the sealed cavity, forming a variable first capacitor. A gap (which may be called the electrode gap) is left between the first electrode 31a and the second electrode 31b. The first electrode 31a is a rigid plate, and the ceramic diaphragm 3b has a certain degree of elasticity. Its outer surface is in contact with the pressure medium and, under the pressure difference between the medium and the pressure (reference pressure) within the sealed cavity, it elastically bends inward or outward, thereby causing a change in the capacitance of the first capacitor. The magnitude of this capacitance can characterize the pressure difference.

[0027] In this embodiment, a first metal layer 32a is provided at the opposite edges of the inner surface of the ceramic substrate 3a, and a second metal layer 32b, opposite to the first metal layer 32a, is provided at the opposite edges of the inner and outer surfaces of the ceramic diaphragm 3b. The first metal layer 32a and the second metal layer 32b are connected to form a first reference electrode 32. A second reference electrode 33 is provided on the outer surface of the ceramic substrate 3a. The second reference electrode 33 and the first reference electrode 32 are opposite to each other in the thickness direction of the ceramic substrate 3a and form a second capacitor (i.e., a reference capacitor). The second capacitor does not change with the pressure difference, but it changes with temperature. Therefore, it can be used as a reference capacitor to reflect the relative error caused by temperature. The capacitance measured by the first capacitor can be used as a reference for error compensation.

[0028] Unlike existing technologies that use a ceramic ring to connect two ceramic plates via high-temperature sintering with low-temperature glass filler, this embodiment uses a sealed welding method for the first metal layer 32a and the second metal layer 32b. This can be achieved, for example, by laser welding or friction welding. The aforementioned electrode plates 31a and 31b, and metal layers 31b and 32b, can be applied to the ceramic substrate 3a or ceramic film 3b using various known suitable methods, such as vapor deposition, thick film deposition, sputtering, and deposition processes. Preferably, they can be fabricated using a thick film process, which allows for the production of a consistent and sufficient thickness (metal layers 31b and 32b are preferably each greater than or equal to 0.2 mm, or together greater than or equal to 0.4 mm) at a lower manufacturing cost. Preferably, the first electrode 31a and the second metal layer 32b have the same thickness, which facilitates their fabrication together; alternatively, metal pastes are coated (e.g., screen-printed) onto the ceramic film 3b to different thicknesses, and then sintered together. The second electrode 31b and the first metal layer 32a can also have the same thickness; or metal pastes are printed onto the ceramic film 3b to different thicknesses, and then sintered together. The second reference electrode 33 can also be fabricated on the outer surface of the ceramic substrate 3a using a similar method. The metal paste can be aluminum paste or a paste made of other metals suitable for laser welding; preferably, the metal paste is aluminum paste, and both the ceramic substrate 3a and the ceramic film 3b are alumina.

[0029] In other embodiments, preferably, the inner surfaces of the second electrode plate 31b and / or the first electrode plate 31a are covered with an insulating film 34. The insulating film 34 can be made of organic materials with high insulation strength, low dielectric properties, and high plasticity, such as polyimide film, polyester film, polytetrafluoroethylene film, polypropylene film, etc.; their thickness can be as low as 0.1 mm, and they can be fixed to the inner surface of the corresponding ceramic substrate 3a or ceramic film 3b by means of bonding, heat shrinking, etc. In other embodiments, they can also be inorganic materials suitable for the above-mentioned surface by known methods, such as spreading powdered inorganic non-metallic material powder (such as low temperature glass) on the above-mentioned surface by rolling or scraping and then sintering, or sputtering an inorganic non-metallic target material on the above-mentioned surface.

[0030] A measurement circuit 35 is disposed on the outer surface of the ceramic substrate 3a. The measurement circuit 35 includes a conditioning element 35a for processing electrical signals and other electronic components 35b. They are electrically connected together through conductive traces 350 formed on the outer surface of the ceramic substrate 3a. The measurement circuit 35 is electrically connected to the first electrode 31a and the second electrode 31b, and to the second reference electrode 33 and the first reference electrode 32, respectively. For example, the ceramic substrate 3a is provided with a first metallized via 313 and a second metallized via 314. The first electrode 31a is connected to the conductive trace 350 through the second metallized via 314. A second conductive portion 312 is formed by radially inwardly extending the first metallized layer 32a, and the second conductive portion 312 is electrically connected to the conductive trace 350 through the first metallized via 313. The second electrode 31b can be electrically connected to the second metal layer 32b through the radially extending first conductive portion 311. In some other embodiments, preferably, the first conductive part 311 may not be connected to the second metal layer 32b, but may instead be in contact or welded to a contact island 315 formed separately on the first metal layer 32a. The contact island is electrically connected to the conductive trace 350 through another metallized through-hole 316 provided in the ceramic substrate 3a, which can reduce the influence of parasitic capacitance.

[0031] The second reference electrode 33 can be directly extended and electrically connected to the conductive trace 350. Of course, in some other embodiments, the first electrode 31a and the first metal layer 32a can also be electrically connected to the conductive trace 350 after penetrating the ceramic substrate 3a through other electrical feed structures toward the measurement circuit 35. For example, a via can be formed in the ceramic substrate 3a, and the first electrode 31a and the first metal layer 32a can be electrically connected to the conductive trace 350 through a metal pin. The metal pin passes through the ceramic substrate 3a and is sealed to the ceramic substrate 3a through a glass plate.

[0032] Please refer to the following: Figure 3Unlike the first preferred embodiment, the measuring circuit 35 is disposed on a circuit board 351, which can be fixed to the upper surface of the ceramic substrate 3a at opposite midpoints by means of bonding or other methods. A window 35d or opening may be provided on the circuit board 351 to allow one end of the second metallized via 314 and the first metallized via 313 to be electrically connected to the conductive trace 350 through a bonding wire 352 passing through the window 35d or opening.

[0033] In the above embodiments, when laser welding the first metal layer 32a and the second metal layer 32b, the laser can be injected approximately along the joint gap between the two, as shown in direction W1. In other embodiments, the ceramic diaphragm 3b can preferably be made of a transparent material or a material with a certain degree of light transmittance, such as transparent alumina ceramic, transparent magnesium oxide ceramic, transparent yttrium oxide ceramic, transparent magnesium aluminum spinel ceramic, transparent aluminum nitride ceramic, etc. This allows the laser to be injected perpendicularly from one side of the ceramic diaphragm 3b, from its outer surface, and through the ceramic diaphragm 3b to irradiate the second metal layer 32b (as shown in direction W2). This allows the radial width of the welding surface between the first metal layer 32a and the second metal layer 32b to be unrestricted, thereby improving the sealing reliability. In other embodiments, preferably, a reference pressure hole (not shown) penetrating the ceramic substrate 3a along the thickness direction can be formed on the ceramic substrate 3a to introduce a reference pressure (e.g., the pressure inside the sensor housing, or atmospheric pressure) into the sealing cavity. In the above embodiments, as long as the electrode spacing is appropriately spaced to allow for the deformation of the ceramic diaphragm 3b, the electrode spacing can be made extremely small or even close to zero. Furthermore, a cavity 30a can be formed inside the ceramic substrate 3a, and the first electrode 31a can be disposed at the bottom of the cavity 30a. This further reduces the thickness of the metal layer to save costs while ensuring an appropriate electrode spacing for the deformation of the ceramic diaphragm 3b. The cavity 30a can be fabricated on the ceramic substrate 3a during pressing or injection molding.

[0034] In the above embodiments, the ceramic substrate 3a, ceramic diaphragm 3b, first electrode 31a, and second electrode 31b are preferably substantially circular. The first metal layer 32a and the second metal layer 32b are preferably substantially annular.

[0035] The scope of this disclosure is not limited by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be included in this disclosure.

Claims

1. A capacitive pressure-sensitive component, characterized in that, The assembly includes a relatively rigid ceramic substrate (3a) and a relatively flexible ceramic diaphragm (3b) that are sealed together and form a mounting cavity, and a second reference electrode (33). A first metal layer (32a) and a second metal layer (32b) are respectively disposed on the edges of the relatively inner surfaces of the ceramic substrate (3a) and the ceramic diaphragm (3b), and the second metal layers (32b) are welded together. A first electrode plate (31a) and a second electrode plate (31b) are respectively disposed at the center of the relatively inner surfaces of the ceramic substrate (3a) and the ceramic diaphragm (3b), and an electrode plate gap is left between the first electrode plate (31a) and the second electrode plate (31b). The second reference electrode (33) is disposed on the outer surface of the ceramic substrate (3a) and is directly opposite to the first metal layer (32a).

2. The capacitive pressure-sensitive component according to claim 1, characterized in that, At least one of the first metal layer (32a), the second metal layer (32b), the first electrode plate (31a), and the second electrode plate (31b) is fabricated using a thick film process.

3. The capacitive pressure-sensitive component according to claim 2, characterized in that, Both the first metal layer (32a) and the first electrode plate (31a) are obtained by sintering together a metal paste coated on a ceramic substrate (3a).

4. The capacitive pressure-sensitive component according to claim 2, characterized in that, Both the second metal layer (32b) and the first metal layer (32a) are obtained by sintering together a metal paste coated on a ceramic film (3b).

5. The capacitive pressure-sensitive component according to any one of claims 1 to 4, characterized in that, An insulating film (34) is covered on the first electrode plate (31a) and / or the second electrode plate (31b).

6. The capacitive pressure-sensitive component according to claim 5, characterized in that, The insulating film (34) is an organic film.

7. The capacitive pressure-sensitive component according to any one of claims 1 to 4, characterized in that, The inner surface of the ceramic substrate (3a) is provided with a cavity (30a), and the first electrode plate (31a) is disposed at the bottom of the cavity (30a).

8. The capacitive pressure-sensitive component according to any one of claims 1 to 4, characterized in that, The ceramic diaphragm (3b) is a light-transmitting material; the first metal layer (32a) and the second metal layer (32b) are welded together by a laser that is incident perpendicularly from the outside of the ceramic diaphragm (3b).

9. A pressure sensor, characterized in that, Includes the capacitive pressure-sensitive component according to any one of claims 1 to 8.

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