Ceramic substrate with annular supporting structure and capacitive pressure sensor

Abstract

The utility model relates to a ceramic substrate with an annular supporting structure and a capacitive pressure sensor, and belongs to the technical field of sensor electrodes. At least one of the problems of initial point drift, large non-linear error and precision reduction, poor measurement repeatability and the like caused by different thermal expansion coefficients of materials due to machining error accumulation of a capacitive vacuum gauge in the prior art is solved. The utility model discloses a ceramic base body with an annular supporting structure, the lower surface of the ceramic base body is provided with an annular supporting part, the annular supporting part extends downwards along the edge of the lower surface of the ceramic base body, and the supporting part is provided with an air guide notch. According to the ceramic substrate and the capacitive pressure sensor provided by the invention, a unique annular supporting structure and an integral forming technology are adopted, so that the phenomena of machining error accumulation and mechanical lag caused by expansion coefficient difference of parts made of different materials are avoided, the measurement precision and the measurement repeatability are remarkably improved, and the ceramic substrate and the capacitive pressure sensor are simple in preparation process and low in cost. The method is suitable for large-scale popularization.

Description

Technical Field

[0001] The utility model relates to the technical field of sensor electrodes, in particular to a ceramic substrate with an annular support structure and a capacitive pressure sensor. Background Art

[0002] The common structure of capacitive pressure sensor is to use alloy pressure strain diaphragm as one of the electrodes of capacitor, forming a capacitor with the conductive coating on the ceramic substrate. When the pressure on both sides of the alloy strain diaphragm changes, a pressure difference is generated, causing the alloy strain diaphragm to deform, thereby changing the distance between the alloy strain diaphragm and the conductive layer on the ceramic substrate, and changing the capacitance value. The pressure in the measured space is measured by measuring the capacitance value.

[0003] The principle of such pressure measurement is not complicated. However, with the development of technology, modern processing technology has extremely high requirements for the accuracy, sensitivity and stability of vacuum measurement. Especially in the semiconductor industry where the process size reaches the nanometer level, the accuracy of vacuum pressure measurement directly affects the success or failure of the process. Among the common structural parts of the capacitive vacuum gauge, the distance between the metal diaphragm and the ceramic electrode is determined by the thickness of one or more gaskets, and the accuracy and stability of the capacitance value depend on the processing accuracy of multiple gaskets. The error of the existing metal parts finishing process is 30um to 50um. There are two supporting structural parts between the metal diaphragm and the ceramic electrode, and the accumulated error of the parts will reach 60um to 100um or more. However, in the process of high-precision vacuum measurement, the maximum deformation of the diaphragm is only 5um or less. The processing error of technical parts will bring great initial value differences to high-precision vacuum measurement, which will make the initial zeroing of vacuum measurement extremely difficult. Moreover, the capacitance signal is a nonlinear curve, and the obvious difference in the initial point will also lead to excessive nonlinear errors.

[0004] Furthermore, the geometry may change slightly over time or with temperature changes. The coefficient of thermal expansion of metal parts is usually greater than that of ceramic electrodes. Therefore, changes in temperature can cause mutual internal stress or deformation of the capacitive sensor components. Mechanical stresses accumulate within a certain range during heating or cooling, and when the stress is large enough, the electrodes and housing will move relative to each other to relieve the stress. This movement is called "stick-slip" or "mechanical hysteresis". These stick-slip movements affect the geometry and may adversely affect the accuracy of the capacitive sensor assembly, with poor repeatability and unpredictable and uncompensable performance.

[0005] Therefore, it is necessary to design an internal part of a capacitive pressure sensor whose structure can reduce the number of components and the contact area of ​​components while reducing the accumulation of processing errors, prevent mechanical hysteresis between components caused by temperature drift and other reasons, and thus improve measurement accuracy.

[0006] The patent with application number 201911212383.8 provides an annular support structure and a ceramic capacitive pressure sensor using the same. The above structure and pressure sensor alleviate the problem of accumulated processing errors to a certain extent, but in actual implementation, there are still defects such as "mechanical lag", difficulty in parts processing, low yield, and difficulty in replacing spare parts.

[0007] Therefore, it is necessary to design a new internal part of a capacitive pressure sensor to overcome at least one of the above-mentioned drawbacks. Utility Model Content

[0008] In view of the above analysis, the utility model aims to provide a ceramic substrate and a capacitive pressure sensor with an annular support structure to solve at least one of the problems of existing capacitive sensors, such as accumulated processing errors, temperature drift, mechanical hysteresis, difficulty in parts processing, and inconvenient use.

[0009] The purpose of this utility model is mainly achieved through the following technical solutions:

[0010] The utility model discloses a ceramic substrate 2 with an annular support structure. The lower surface of the ceramic substrate 2 has an annular support portion 8, which extends downward along the edge of the lower surface of the ceramic substrate 2. An air guide notch 201 is provided on the support portion.

[0011] Specifically, the annular support portion 8 and the main body of the ceramic substrate 2 are formed in one piece; wherein the material of the annular support portion 8 and the main body of the ceramic substrate 2 is ceramic.

[0012] Specifically, the thickness of the annular support portion 8 is not less than 1 mm.

[0013] Preferably, the main cross section of the ceramic substrate 2 is circular.

[0014] Specifically, the air guiding slots 201 are arranged at equal intervals along the circumference of the support portion; and the number of the air guiding slots 201 is more than two.

[0015] Specifically, the ratio of the total circumference of the air guide slot 201 to the total circumference of the annular support portion 8 is 0.8-1.2:1.

[0016] Specifically, the lower surface of the annular support portion 8 is chamfered.

[0017] The utility model also discloses a ceramic capacitive pressure sensor, comprising the above-mentioned ceramic substrate 2 and a housing 1 having an annular convex portion 3;

[0018] The annular protrusion 3 is protrudingly arranged along the inner peripheral wall of the housing 1 , and the annular supporting portion 8 of the ceramic substrate 2 is connected to the annular protrusion 3 .

[0019] Specifically, the pressure sensor further includes:

[0020] A metal diaphragm 6 is disposed below the annular protrusion 3 of the housing 1 and is used to form a variable electrode;

[0021] The standard pressure chamber 5 is formed in the space formed by the shell 1 above the metal diaphragm 6; wherein, the two sides of the ceramic substrate 2 of the standard pressure chamber 5 are connected through the air guide groove 201 and the gap between the ceramic substrate 2 and the shell 1.

[0022] Specifically, the inner edge of the annular protrusion 3 is provided with a protrusion 301 extending upward; the radial dimension of the protrusion 301 matches the inner diameter of the annular support portion 8 of the ceramic substrate 2, and is used to position the ceramic substrate 2; the height of the protrusion 301 is not greater than 50% of the height of the annular support portion 8.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. The technical solution provided by the utility model directly processes the support structure on the ceramic substrate, the cumulative processing error is small and the capacitance fluctuation (capacitance spacing fluctuation) caused by the difference in expansion coefficient is greatly reduced.

[0025] The utility model directly processes an annular supporting structure on the lower surface of the ceramic substrate, and the supporting structure is also made of ceramic material. Therefore, the temperature drift phenomenon caused by the difference in expansion coefficient between the traditional metal gasket or the metal supporting structure and the ceramic substrate is greatly alleviated. At different temperatures, the capacitance spacing remains basically stable, ensuring the accuracy and stability of the measurement results; compared with traditional capacitive sensors, the number of parts is reduced, the contact area between parts is reduced overall, and the accumulation of processing errors is greatly reduced.

[0026] 2. The processing difficulty is greatly reduced, the yield rate is improved, and the production cost is greatly reduced. Compared with the prior art, the utility model uses ceramic materials to form an annular support structure in one piece, and then uses a tool to fine-tune the support part. Since the support part is protruding from the lower surface of the ceramic substrate, the processing difficulty is greatly reduced, and there is no need to use special small-sized tools, which reduces the wear rate of the tool, greatly improves the yield rate overall, and reduces the production cost.

[0027] 3. The utility model adopts a ceramic substrate with an annular support structure, so that during use, technicians can replace different ceramic substrates according to the required range, and adjust the capacitor spacing and the sensor range by selecting annular support parts of different heights. In addition, when the annular support part has defects such as wear and tear, missing corners, etc., it can also be replaced without scrapping the entire part, saving resources.

[0028] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the following content, and some advantages can be obvious from the description or understood by implementing the present invention. The purpose and other advantages of the present invention can be achieved and obtained through the contents specifically pointed out in the text and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are only used for the purpose of illustrating specific embodiments and are not to be considered as limiting the present invention. In the entire drawings, the same reference symbols represent the same components.

[0030] Figure 1 A cross-sectional schematic diagram of a ceramic capacitive sensor according to an embodiment of the present utility model;

[0031] Figure 2 for Figure 1 A partial enlarged view of the annular convex portion;

[0032] Figure 3 It is a three-dimensional schematic diagram of a ceramic substrate structure with an annular support structure.

[0033] Reference numerals:

[0034] 1-shell; 2-ceramic substrate; 3-annular convex portion; 4-detection port; 5-standard pressure chamber; 6-metal diaphragm; 7-conductive layer; 8-annular support portion; 201-air guide groove; 301-convex portion. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0036] In the structure of the commonly used thin film capacitive vacuum gauge, the distance d between the two electrodes of the capacitor is adjusted by the outer dimensions of the support washer and the support gasket. Alloy materials of different grades are processed into different shapes and used in superposition to achieve the function of support and distance adjustment. However, the processing error exists in every part and every processing surface. Therefore, the distance d between the two electrodes of the capacitor will be directly affected by the processing error of the parts. The range of capacitance measurement depends on the deformation of the strain diaphragm. Considering the linearity characteristics of the load-deformation of the metal material itself. When the capacitance is measured at full scale, the maximum deformation of the strain diaphragm will be ≤20 microns. However, the limit of the processing error of the parts is between 15 microns and 50 microns (depending on the processing technology and equipment performance). This leads to the cumulative error of multiple parts when multiple parts are used in superposition, resulting in the initial distance range of the capacitor being about 50 microns to 150 microns. This will cause the zeroing and full-scale nonlinear compensation of vacuum measurement to exceed the adjustable range of hardware and circuit, seriously affecting the performance, stability, and even yield of the vacuum gauge. In addition, different capacitor spacings as starting points will bring huge nonlinear differences and differences in capacitance changes.

[0037] Patent application number 201911212383.8 provides an annular support structure and a ceramic capacitive pressure sensor using the same. The above structure and pressure sensor alleviate the problem of machining error accumulation to a certain extent, but still have the following defects:

[0038] (1) The annular support structure of the above patent is made of alloy, which still has a difference in expansion rate compared with ceramic materials, and the "stick-slip" or "mechanical hysteresis" phenomenon caused by stress release will still occur.

[0039] (2) The annular support structure of the above-mentioned patent needs to be processed on the annular convex portion of the inner cavity of the shell. The processing of the precision structure inside the narrow cavity is difficult. In addition, since the size of the special tool to be used is less than 2 mm and the thickness of the support structure is generally around 1 mm, the tool will be uncontrollably deformed due to stress in different directions during the processing, which in turn causes the error of the annular support structure of the alloy part to be uncontrollable to a certain extent, resulting in a low yield and a high tool wear rate.

[0040] (3) In actual use, during the assembly or use of the sensor, the annular support structure of the above patent may be damaged, have missing corners or other defects. Since the above support structure is integrally formed with the shell, it is difficult to replace the parts and the entire structure can only be scrapped. Moreover, the height of the support structure cannot be adjusted as needed, that is, the capacitor spacing cannot be adjusted, resulting in the range being unable to be flexibly adjusted according to actual needs.

[0041] The utility model discloses a ceramic substrate 2 with an annular support structure, wherein the lower surface of the ceramic substrate 2 has an annular support portion 8, the annular support portion 8 extends downward along the edge of the lower surface of the ceramic substrate 2, and an air guide slot 201 is provided on the support portion. The air guide slot 201 is a notch on the annular support portion 8. In fact, due to the provision of the air guide slot 201, the annular support portion 8 can also be figuratively referred to as an "annular support foot". The design of the air guide slot 201 can reduce the contact area between the ceramic substrate 2 and the metal base (the ceramic substrate is in direct contact with the metal base through the annular support portion 8 / annular support foot), and on the other hand, it is to form a standard pressure chamber.

[0042] Specifically, the annular support portion 8 is integrally formed with the main body of the ceramic substrate 2; wherein the material of the annular support portion 8 and the main body of the ceramic substrate 2 is ceramic, so as to ensure that the thermal expansion coefficient of the component is small, thereby making the capacitor spacing as stable as possible, alleviating temperature drift and mechanical hysteresis.

[0043] Specifically, the thickness of the annular support portion 8 is not less than 1 mm, the outer diameter of the annular support portion 8 is the same as the outer diameter of the main body of the ceramic substrate 2, and the thickness of the annular support portion 8 should not be too small to ensure that no micro-tools are required for cutting during the processing process, to ensure the consistency of the overall processing size and the stability of the overall force. And by controlling the height of the support structure through processing, the processing error can be minimized; the height of the annular support portion 8 can be set according to the required range, and the ceramic substrate 2 with annular support portions 8 of different heights can also be manufactured for replacement.

[0044] Preferably, the main cross-section of the ceramic substrate 2 is circular. Generally speaking, a circular ceramic substrate 2 or fixed electrode is subjected to a more uniform force and has a good structural balance, and is a preferred shape commonly used in the art.

[0045] Specifically, the air guide grooves 201 are arranged at equal intervals along the circumference of the support portion; the number of the air guide grooves 201 is more than 2. In a specific implementation, in order to ensure the stability of the assembly of the ceramic substrate 2, the air guide grooves 201 are preferably arranged with more than 3 (corresponding to the annular support portion 8 having more than three "feet").

[0046] Specifically, the ratio of the total circumference of the air guide slot 201 to the total circumference of the annular support structure is 0.8-1.2:1, so as to ensure sufficient exhaust gaps while ensuring the support strength of the ceramic parts.

[0047] Specifically, the lower surface of the annular support portion 8 is chamfered to reduce the direct contact area between the ceramic and the metal shell, thereby minimizing the "mechanical hysteresis" effect caused by the thermal expansion difference.

[0048] The utility model also discloses a ceramic capacitive pressure sensor, comprising the above-mentioned ceramic substrate 2 and a housing 1 having an annular convex portion 3;

[0049] The annular protrusion 3 is protrudingly arranged along the inner peripheral wall of the housing 1 , and the annular supporting portion 8 of the ceramic substrate 2 is connected to the annular protrusion 3 to form a fixed electrode substrate.

[0050] Specifically, the ceramic capacitive pressure sensor further includes:

[0051] A metal diaphragm 6 is disposed below the annular protrusion 3 of the housing 1 and is used to form a variable electrode;

[0052] A standard pressure chamber 5 is formed in a space formed by the housing 1 above the metal diaphragm 6;

[0053] The two sides of the ceramic substrate 2 of the standard pressure chamber 5 are connected through the air guide slot 201 and the gap between the ceramic substrate 2 and the housing 1 .

[0054] Specifically, the ceramic capacitive pressure sensor further includes an end cap; a vacuum pumping component is disposed on the end cap of the housing 1 away from the detection port 4; and is used to exhaust the air in the standard pressure chamber 5 so as to maintain the standard pressure in the standard pressure chamber 5. Since the end cap and the vacuum pumping component are common designs, the utility model does not mark them in the drawings, and technicians can design the shape and specific position of the end cap and the vacuum pumping component according to actual implementation needs.

[0055] Specifically, the ceramic capacitive pressure sensor further includes a detection port 4, which is disposed at one end of the housing 1 close to the metal diaphragm 6 and is used to allow a measuring medium to pass therethrough to apply pressure to deform the metal diaphragm 6.

[0056] Specifically, the ceramic capacitive pressure sensor further includes a conductive layer 7 , which is disposed on a side of the ceramic substrate 2 opposite to the metal diaphragm 6 and is used to combine with the ceramic substrate 2 to form a fixed electrode.

[0057] Specifically, the inner edge of the annular protrusion 3 is provided with a protrusion 301 extending upward; the radial dimension of the protrusion 301 matches the inner diameter of the annular support portion 8 of the ceramic substrate 2, and is used to position the ceramic substrate 2; the height of the protrusion 301 is not greater than 50% of the height of the annular support portion 8 to avoid blocking the air guide groove and causing poor airflow.

[0058] It should be noted that due to the provision of the raised portion, an axial annular groove is actually formed on the radial annular protrusion on the inner wall of the shell. During assembly or fitting, the annular support portion of the ceramic substrate should be placed in the annular groove. After the assembly is stable, subsequent assembly steps or measurements can be carried out.

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A ceramic substrate (2) having an annular support structure, characterized in that: The lower surface of the ceramic substrate (2) has an annular support portion (8), the annular support portion (8) extends downward along the edge of the lower surface of the ceramic substrate (2), and an air guide slot (201) is provided on the support portion; The annular support portion (8) is integrally formed with the main body of the ceramic substrate (2).

2. The ceramic substrate (2) according to claim 1, characterized in that: The thickness of the annular support portion (8) is not less than 1 mm.

3. The ceramic substrate (2) according to claim 1, characterized in that: The main cross section of the ceramic substrate (2) is circular.

4. The ceramic substrate (2) according to claim 1, characterized in that: The air guide slots (201) are arranged at equal intervals along the circumference of the support portion; and the number of the air guide slots (201) is more than two.

5. The ceramic substrate (2) according to claim 4, characterized in that: The ratio of the total circumference of the air guide slot (201) to the total circumference of the annular support portion (8) is 0.8 to 1.2:

1.

6. The ceramic substrate (2) according to claim 1, characterized in that: The lower surface of the annular support portion (8) is chamfered.

7. A ceramic capacitive pressure sensor, characterized in that: Comprising the ceramic substrate (2) according to any one of claims 1 to 6 and a shell (1) having an annular protrusion (3); The annular protrusion (3) is arranged to protrude along the inner peripheral wall of the shell (1), and the annular support portion (8) of the ceramic base (2) is connected to the annular protrusion (3).

8. The ceramic capacitive pressure sensor according to claim 7, characterized in that: Also includes: A metal diaphragm (6) is arranged below the annular protrusion (3) of the housing (1) and is used to form a variable electrode; A standard pressure chamber (5) is formed in the space formed by the shell (1) above the metal diaphragm (6); wherein two sides of the ceramic substrate (2) of the standard pressure chamber (5) are connected through the air guide groove (201) and the gap between the ceramic substrate (2) and the shell (1).

9. The ceramic capacitive pressure sensor according to claim 7, characterized in that: The inner edge of the annular protrusion (3) is provided with a protrusion (301) extending upwards; The radial dimension of the protrusion (301) matches the inner diameter of the annular support portion (8) of the ceramic substrate (2), and is used to position the ceramic substrate (2); The height of the protruding portion (301) is no greater than 50% of the height of the annular supporting portion (8).

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