CN117213668A - Ceramic capacitive pressure sensor and manufacturing method thereof - Google Patents
Ceramic capacitive pressure sensor and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses a ceramic capacitive pressure sensor and a manufacturing method thereof, and belongs to the technical field of capacitive pressure sensors. The ceramic capacitive pressure sensor includes: a base and a membrane; the front surface of the base is provided with a base measuring electrode, the front surface of the diaphragm is provided with a diaphragm measuring electrode, and the base measuring electrode and the diaphragm measuring electrode are arranged in parallel and opposite to each other to form two poles of a capacitor; the middle of the base measuring electrode is provided with a groove, so that the distance D between the middle position of the base measuring electrode and the diaphragm measuring electrode is larger than the distance D between other positions of the base measuring electrode and the diaphragm measuring electrode. The capacitive pressure sensor overcomes the technical defect of poor output linearity of the traditional capacitive pressure sensor, and improves measurement accuracy and stability.
Description
Technical Field
The invention relates to the technical field of capacitive pressure sensors, in particular to a non-contact ceramic capacitive pressure sensor and a manufacturing method thereof.
Background
A capacitive pressure sensor is a pressure sensor that uses a capacitive sensing element to convert measured pressure into an electrical output in a relationship therewith. The capacitive pressure sensor uses the principle that tiny deformation is generated when a measured object is pressed, so that capacitance is changed to measure pressure. Typically consisting of a pressure sensing diaphragm and a pair of metal electrodes. Under the action of external force, the pressure-sensitive membrane can deform, so that the distance between the pressure-sensitive membrane and the electrodes and the electric field intensity are changed, the capacitance value is changed, and the pressure of the measured object can be measured through the correlation between the capacitance value and the pressure after the change.
For the current capacitive pressure sensor, a circular parallel electrode design is generally adopted, the pressure sensing diaphragm deforms under the action of pressure, and as the circumference of the diaphragm is fixed, the distance change of different radius positions on the electrode is not parallel and uniform, but is nonlinear deflection change, the closer to the middle position of the diaphragm, the larger the deflection change is, the larger the electrode distance change is correspondingly, so that the nonlinear output is rapidly increased, and the reliability of the pressure result measured by the capacitive pressure sensor is reduced.
In view of this, a new solution is needed to solve the above-mentioned problems.
Disclosure of Invention
The invention mainly aims to provide a ceramic capacitive pressure sensor and a manufacturing method thereof, and aims to solve the technical problem that the reliability of results is reduced due to nonlinear output of the existing capacitive pressure sensor.
To achieve the above object, a first aspect of the present invention provides a ceramic capacitive pressure sensor, including a base and a diaphragm;
the front surface of the base is provided with a base measuring electrode, the front surface of the diaphragm is provided with a diaphragm measuring electrode, and the base measuring electrode and the diaphragm measuring electrode are arranged in parallel and opposite to each other to form two poles of a capacitor;
the middle of the base measuring electrode is provided with a groove, so that the distance D between the middle position of the base measuring electrode and the diaphragm measuring electrode is larger than the distance D between other positions of the base measuring electrode and the diaphragm measuring electrode.
As a further improvement, the distance D between the middle position of the base measuring electrode and the diaphragm measuring electrode and the distance D between the other positions of the base measuring electrode and the diaphragm measuring electrode satisfy the formula: d is more than or equal to 1.5D and less than or equal to 100D.
As a further improvement, the following relationship is satisfied between the radius R of the groove and the radius R of the base measuring electrode: r is more than or equal to 0.01 and less than or equal to R.
As a further improvement, the sealing device further comprises a sealing layer positioned between the base and the membrane, wherein the sealing layer is used for sealing and connecting the base and the membrane.
As a further improvement, the groove comprises a cylindrical groove or an arc-shaped groove.
As a further improvement, the front surface of the base is also provided with a first compensation electrode, and the front surface of the membrane is provided with a second compensation electrode opposite to the first compensation electrode.
As a further improvement, the front surface of the base is also provided with a first bonding pad and a second bonding pad;
the base measuring electrode is electrically connected with the first bonding pad, and the first bonding pad is led out to the back surface of the base through a first measuring lead pin;
the first compensation electrode is electrically connected with the second bonding pad, and the second bonding pad is led out to the back surface of the base through the second measurement lead pin.
As a further improvement, the front surface of the membrane is also provided with a third bonding pad and a fourth bonding pad;
the diaphragm measuring electrode is electrically connected with the third bonding pad, and the third bonding pad is led out to the back surface of the base through a third measuring lead pin;
the second compensation electrode is electrically connected with the fourth bonding pad, and the fourth bonding pad is led out to the back surface of the base through a fourth measurement lead pin.
As a further refinement, the second measurement pin merges with the fourth measurement pin.
A second aspect of the present invention provides a method of manufacturing a ceramic capacitive pressure sensor, comprising:
step one, arranging a groove in the middle of the front surface of a base, and arranging a base measuring electrode covering the groove;
step two, arranging a diaphragm measuring electrode on the front surface of the diaphragm;
step three, sealing the membrane and the base face to face;
wherein the sequence of the first step and the second step can be exchanged.
As a further improvement, the method of disposing the base measurement electrode covering the recess includes: coating, spraying or depositing the metal slurry on the front surface of the base to obtain a base measuring electrode;
the method for arranging the diaphragm measuring electrode on the front surface of the diaphragm comprises the following steps: and coating, spraying or depositing the front surface of the diaphragm by adopting metal slurry to obtain a diaphragm measuring electrode.
As a further improvement, the step of coating, spraying or depositing the metal paste on the front surface of the base to obtain the base measuring electrode further comprises: coating, spraying or depositing metal slurry on the front surface of the base to obtain a first bonding pad and a second bonding pad;
the step of coating, spraying or depositing the front surface of the diaphragm by adopting the metal slurry to obtain the diaphragm measuring electrode further comprises the following steps: and coating, spraying or depositing the front surface of the membrane by adopting metal slurry to obtain a third bonding pad and a fourth bonding pad.
As a further improvement, further comprising:
a first compensation electrode is arranged around the base measurement electrode;
a second compensation electrode is disposed around the diaphragm measurement electrode.
As a further improvement, further comprising:
penetrating a first measuring lead through the base to the front surface of the base so as to be electrically connected with a first bonding pad; and
penetrating a second measurement lead through the base to the front surface of the membrane, and enabling the second measurement lead to be electrically connected with the second bonding pad and the fourth bonding pad; and
and penetrating a third measuring lead through the base to the front surface of the diaphragm, so that the third measuring lead is electrically connected with a third bonding pad.
As a further improvement, the method for sealing the membrane to the base face to face comprises:
and printing a sealing layer on the front surface of the base and/or the front surface of the membrane, and sintering and solidifying the sealing layer to realize the joint connection of the base and the membrane.
As a further improvement, a sinking table is arranged on the front face of the base, and the depth of the sinking table is equal to the preset electrode spacing.
The invention has the beneficial effects that:
the front middle of the base is provided with a groove, so that the base measuring electrode is divided into a middle groove area and a surrounding annular area; when pressure acts on the diaphragm, the nonlinear deflection deformation of the central point part of the diaphragm is the largest, and the part of the diaphragm measuring electrode is opposite to the middle groove area of the base measuring electrode.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a cross-sectional view of a ceramic capacitive pressure sensor of the present invention;
FIG. 2 shows a cross-sectional view of the mount of FIG. 1 (including the mount measurement electrode);
FIG. 3 shows a schematic front view of the mount of FIG. 1 (including the mount measurement electrode);
FIG. 4 shows a cross-sectional view of the diaphragm (including the diaphragm measurement electrode) of FIG. 1;
FIG. 5 shows a schematic diagram of the front structure of the diaphragm (including the diaphragm measurement electrode) of FIG. 1;
FIG. 6 shows a cross-sectional view of a base of another ceramic capacitive pressure sensor of the invention;
FIG. 7 shows a schematic diagram of the present invention with compensation electrodes;
FIG. 8 shows a schematic diagram of the measurement results of a prior art parallel circular pressure sensor of a dimple-less design (where the red line is a fitted function curve and the black line is a calculated curve);
FIG. 9 shows a schematic diagram of the measurement results of a pressure sensor with a pit depth of 50 μm (wherein the red line is a fitted function curve and the black line is a calculated curve);
FIG. 10 shows a schematic diagram of the measurement results of a pressure sensor with a pit depth of 100 μm (wherein the red line is a fitted function curve and the black line is a calculated curve);
FIG. 11 shows a graph of variance of measurements (using normal distribution) for a pressure sensor without pits, 50 μm deep, 100 μm deep.
Reference numerals illustrate:
the achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, "and/or" throughout this document includes three schemes, taking a and/or B as an example, including a technical scheme, a technical scheme B, and a technical scheme that both a and B satisfy; in addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
Referring to fig. 1-5, the present invention provides a ceramic capacitive pressure sensor, wherein a groove 2 is disposed in a front middle position of a base 1, and an original base measuring electrode 34 is divided into two parts, wherein a corresponding part of the groove 2 is defined as a groove electrode 4, other area parts are defined as a base electrode 3, and a certain height difference exists between the two parts of electrodes on the surface of the base 1, and the height difference is actually the depth of the groove 2. During measurement, the groove electrode 4 is opposite to the central point of the diaphragm 8, namely, the area with larger deflection change of the diaphragm 8, and the seat electrode 3 is opposite to the area near the central point of the diaphragm 8, namely, the area with smaller deflection change of the diaphragm 8. The measured value of the sensor is related to the ratio of the deformation amount of the diaphragm 8 to the distance between the two electrodes, because the distance between the two electrodes corresponding to the groove electrode 4 is larger than the distance between the two electrodes corresponding to the seat electrode 3, the deformation amount of the diaphragm 8 corresponding to the groove 2 is a small value relative to the distance between the electrodes, and the change of the ratio of the deformation amount of the diaphragm 8 to the deformation amount is very small and corresponds to no change, so that the diaphragm 8 corresponding to the groove 2 is equivalent to the movement of the diaphragm 8 which is wholly parallel to the groove electrode 4, in other words, the diaphragm 8 part corresponding to the groove electrode 4 can be regarded as the movement which is approximately parallel to the bottom wall of the groove 2, thereby overcoming the technical defect of poor output linearity of the traditional ceramic capacitive pressure sensor.
Referring to fig. 1 to 5, a specific structure of the ceramic capacitive pressure sensor will be described below.
Referring to fig. 1 in detail, fig. 1 is a schematic cross-sectional structure of a ceramic capacitive pressure sensor according to an embodiment of the invention.
In this embodiment, the ceramic capacitive pressure sensor comprises a base 1 and a diaphragm 8;
the front surface of the base 1 is provided with a base measuring electrode 34, the front surface of the diaphragm 8 is provided with a diaphragm measuring electrode 9, and the base measuring electrode 34 and the diaphragm measuring electrode 9 are arranged in parallel and opposite to form two poles of a capacitor;
wherein the middle of the base measuring electrode 34 is provided with a groove 2, so that the distance D between the middle position of the base measuring electrode 34 and the diaphragm measuring electrode 9 is larger than the distance D between the other positions of the base measuring electrode 34 and the diaphragm measuring electrode 9.
Specifically, the base 1 and the diaphragm 8 are made of ceramic materials, and the accuracy and stability of the pressure sensor can be improved based on the characteristics of high elasticity, corrosion resistance, abrasion resistance, impact resistance and vibration resistance of the ceramic.
By designing the recess 2 in the middle of the front face of the base 1, the base measuring electrode 34 is divided into a middle recess region and a surrounding annular region, which are defined as a recess electrode 4 and a base electrode 3, respectively; when a pressure acts on the membrane 8, it deforms, changing the distance between the two electrodes and thus the measured capacitance, and the pressure sensor is made by this principle. The nonlinear deflection deformation of the central point part of the diaphragm 8 is the largest, and the part of the diaphragm measuring electrode 9 is opposite to the middle groove area of the base measuring electrode 34, because the distance D between the middle position of the base measuring electrode 34 and the diaphragm measuring electrode 9 is larger than the distance D between other positions of the base measuring electrode 34 and the diaphragm measuring electrode 9, the part near the central point of the diaphragm 8 can be equivalent to the deformation of the bottom wall of the groove 2 which is wholly parallel to the whole, so as to replace the actual nonlinear deflection deformation of the part, and further realize the purpose of reducing the nonlinearity of the measuring result of the whole pressure sensor.
Specifically, the initial total capacitance value of the ceramic capacitive pressure sensor is:
wherein C is 0 For the initial total capacitance value, ε is the dielectric constant, d is the distance between the other positions of the base measuring electrode 34 except the groove 2 and the diaphragm measuring electrode 9, S1 is the area of the base electrode 3, and S2 is the projected area of the groove electrode 4 on the diaphragm 8.
During measurement, the diaphragm 8 deforms, and the deflection nonlinearity of the deformation gradually becomes smaller from the center point of the diaphragm 8 to the periphery. It should be noted that: in practical application, the deformation Δd of the diaphragm 8 in the direction perpendicular to the diaphragm 8 is smaller than the electrode spacing d, and the ratio of the deformation Δd to the electrode spacing d is not greater than 0.2.
Specifically, the total capacitance value of the range change of the ceramic capacitive pressure sensor is as follows:
wherein C is the total capacitance value of the range change, epsilon is the dielectric constant, d is the distance between the other positions of the base measuring electrode 34 except the groove 2 and the diaphragm measuring electrode 9, R is the radius of the groove electrode 4, n (x) is the deflection of the diaphragm at the position x from the center, x is the arbitrary radius position from the center of the diaphragm, R is not less than x is not more than R,the capacitance value corresponding to the seat electrode 3; n (y) is the deflection of the diaphragm at a position y away from the center, y is any radial position away from the center of the diaphragm, and y is less than or equal to r, < >>The capacitance value corresponding to the groove electrode 4.
The deflection nonlinearity of the deformation of the diaphragm 8 corresponding to the seat electrode 3 is low, the deflection nonlinearity of the deformation of the diaphragm 8 corresponding to the groove electrode 4 is high, and the electrode spacing of the corresponding part of the groove electrode 4 is artificially increased, so that the compression condition of the diaphragm 8 is equivalent to the deformation (parallel deformation is equivalent to no deflection) of the whole part near the center point of the diaphragm 8 parallel to the bottom wall of the groove 2, and the nonlinearity of the whole pressure sensor measurement result is reduced instead of the actual nonlinear deflection deformation.
The specific working process of the existing ceramic capacitive pressure sensor comprises the following steps: the diaphragm 8 of the sensor deforms under the action of pressure, and the deformation causes a nonlinear problem; and the larger the amount of deformation of the diaphragm 8, the more pronounced the problem of nonlinearity of the measurement results. For controlling nonlinearity of the result, a method of reducing the measuring range is generally adopted, that is, the pressure sensor with a higher measuring range is reduced to be used in a range of practical application measuring range, so as to reduce the deformation of the diaphragm 8, and meanwhile, the full-range output signal of the sensor is greatly reduced. Therefore, the existing ceramic capacitive pressure sensor cannot solve the problem of nonlinearity caused by deflection, or can only control the nonlinearity of the result in a manner of reducing the range. When the pressure sensor is used in a range-reducing manner, a conditioning circuit connected with the rear end of the pressure sensor needs larger amplification factor, so that the measurement stability of the sensor is affected.
In comparison with the conventional ceramic capacitive pressure sensor, the typical nonlinear value pair of the ceramic capacitive pressure sensor in this embodiment is shown in table 1 (nonlinear value after circuit compensation).
TABLE 1
Note that: FS represents full scale, full scale (non-linear value after compensation by the same circuit).
It can be seen that, in terms of reducing nonlinearity, the ceramic capacitive pressure sensor in this embodiment can reduce the nonlinearity error of the measurement result by 40% compared with the existing sensor, and greatly improve the performance of the ceramic capacitive pressure sensor.
Referring to fig. 6, the recess 2 may be a cylindrical recess or an arc recess. The size of the groove 2 is determined according to the size design and the measuring range of the pressure sensitive element. Preferably, the radius R of the recess 2 is equal to or smaller than the radius R of the base measuring electrode 34, and is equal to or larger than R/2, namely, satisfies the following formula: r is more than or equal to 0.01 and less than or equal to R.
The inventors have found that the radius r of the groove 2 is related to the distance d between the two electrodes, the elastic properties of the membrane 8 itself. Under the condition that the electrode distance d is constant, the diaphragm 8 deforms under the action of pressure, and the nonlinear deflection deformation of the diaphragm 8 is highest at the center point of the diaphragm 8 and gradually becomes smaller from the center point to the periphery. Simulation calculation proves that the area with higher nonlinear deflection deformation is concentrated in the range of a circular area taking the center point of the diaphragm 8 as the center, the nonlinear deflection deformation exceeding the area is lower, and the influence on the measurement result of the pressure sensor is limited. Therefore, the idea of the invention is to equivalently replace the part of the diaphragm 8 with higher nonlinear deflection deformation by arranging the groove electrode 4, and theoretically, the radius of the groove 2 is larger than zero and limited by processing conditions, and the minimum value of the radius of the groove 2 can be set to be 0.01R, so that the area opposite to the groove electrode 4 covers all areas with high nonlinear deflection deformation, and the nonlinearity of the measurement result is reduced as a whole.
The distance D between the middle position of the base measuring electrode 34 and the diaphragm measuring electrode 9 is larger than the distance D between the other positions of the base measuring electrode 34 and the diaphragm measuring electrode 9, and generally, d=1.5d to 100D. Namely, the distance D between the groove electrode 4 and the diaphragm measuring electrode 9 is set to exceed the original electrode distance D artificially, so that the purpose of neglecting the influence of the deformation of the diaphragm 8 on the measuring result is achieved: as already described above, in practice the deformation of the membrane 8 is a few tenths or hundredths of the D value, which is further reduced by a factor of 1.5 to 100 compared to the case without the grooves 2.
Referring to fig. 1, the ceramic capacitive pressure sensor of the present invention further includes a sealing layer 13, wherein the sealing layer 13 is located between the base 1 and the diaphragm 8 and is used for sealing and connecting the base 1 and the diaphragm 8, and the height of the sealing layer 13 is equal to the distance d between the two electrodes.
The sealing layer 13 may be made of ceramic or glass material, and is formed by sintering low-temperature ceramic slurry or glass slurry, wherein the ceramic slurry or glass slurry may be printed on the front surface of the base 1, or may be printed on the front surface of the membrane 8, or printed on the front surfaces of the base 1 and the membrane 8 at the same time, and then the front surfaces of the base 1 and the membrane 8 are bonded together, and sintering is performed at low temperature to realize sealing of the base 1 and the membrane 8. The low temperature corresponds to different slurries, each slurry has a corresponding sintering temperature range, and the technology related to low temperature sintering is the prior art and will not be described herein.
In other embodiments, the sealing layer 13 may be integrally formed on the base 1, i.e. a sinking platform is dug on the front surface of the base 1, the depth of the sinking platform is equal to d, and the membrane 8 is directly connected to the top surface of the sinking platform in a sealing manner. At this time, the front surface of the base 1 is the bottom surface of the sinking table.
Referring to fig. 3 and 5, specifically, the front surface of the base 1 is further provided with a first compensation electrode 5, and the front surface of the membrane 8 is provided with a second compensation electrode 10 opposite to the first compensation electrode 5. The first compensation electrode 5 and the second compensation electrode 10 are each provided in the shape of a ring, the first compensation electrode 5 being spaced apart from the base measurement electrode 34, and the second compensation electrode 10 being spaced apart from the diaphragm measurement electrode 9.
More specifically, the front surface of the chassis 1 is further provided with a first pad 6 and a second pad 7, wherein the chassis measurement electrode 34 is electrically connected to the first pad 6, and the first pad 6 is led out to the back surface of the chassis 1 through the first measurement lead 14. The first compensation electrode 5 is electrically connected with the second bonding pad 7, and the second bonding pad 7 is led out to the back surface of the base 1 through the second measurement lead 15. It should be noted that, the first bonding pad 6 and the second bonding pad 7 are both disposed at the periphery of the first compensation electrode 5, so that the first bonding pad 6 needs to pass through the first compensation electrode 5 to be connected to the base measurement electrode 34, and during manufacturing, the first compensation electrode 5 is subjected to disconnection processing so that the first bonding pad 6 is connected to the base measurement electrode 34; the two ends of the disconnected first compensation electrode 5 are connected and connected with the second bonding pad 7.
The front surface of the diaphragm 8 is further provided with a third bonding pad 11 and a fourth bonding pad 12, wherein the diaphragm measurement electrode 9 is electrically connected with the third bonding pad 11, and the third bonding pad 11 is led out to the back surface of the base 1 through a third measurement lead 16. The second compensation electrode 10 is electrically connected with a fourth bonding pad 12, and the fourth bonding pad 12 is led out to the back surface of the base 1 through a fourth measurement lead. It should be noted that, the third bonding pad 11 and the fourth bonding pad 12 are both disposed at the periphery of the second compensation electrode 10, so that the third bonding pad 11 needs to pass through the second compensation electrode 10 to be connected to the diaphragm measurement electrode 9, and during manufacturing, the second compensation electrode 10 is subjected to disconnection processing so that the third bonding pad 11 is connected to the diaphragm measurement electrode 9; the two ends of the disconnected second compensation electrode 10 are connected and connected with the fourth bonding pad 12.
During packaging, the membrane 8 is oppositely connected with the front surface of the base 1, wherein the first bonding pad 6 and the third bonding pad 11 are staggered up and down, and the second bonding pad 7 and the fourth bonding pad 12 are opposite up and down. Preferably, the second measurement pin 15 is combined with the fourth measurement pin into one pin.
After packaging, the base measuring electrode 34 and the diaphragm measuring electrode 9 form one capacitance unit, and the first compensating electrode 5 and the second compensating electrode 10 form another capacitance unit. The purpose of providing the two compensation electrodes is to set the initial value of the measured value of the capacitance formed by the two measurement electrodes equal to the reference with the measured value of the capacitance formed by the two compensation electrodes as the reference.
Specifically, for the compensation principle of the compensation electrode, the following is:
referring to fig. 7, a and B represent a pair of measurement electrodes, respectively.
The area of the measuring electrode is of a limited size, and at the edge position of the measuring electrode, the electromagnetic field direction and the intensity are distorted, so that the capacitance value changes nonlinearly along with the change of the gap (as shown in fig. 7).
Meanwhile, the capacitor is easily affected by external electromagnetic radiation interference, and parasitic capacitance and coupling capacitance existing in the capacitance signal conditioning circuit, so that the output of the sensor is unstable or greatly deviates.
The annular compensation electrode is designed on the periphery of the measurement capacitor to form a compensation capacitor signal, and as the initial value of the compensation capacitor is the same as the initial value of the measurement capacitor, the influence of electromagnetic radiation interference, parasitic capacitance and the like received by the measurement capacitor and the compensation capacitor are consistent, the capacitance value between the measurement electrode and the compensation electrode is compensated by utilizing the capacitance difference value between the real-time measurement electrode and the compensation electrode, the influence of edge effect can be effectively eliminated, the capacitance value between the measurement electrode and the real-time measurement electrode is compensated by utilizing the difference value between the initial value of the compensation electrode and the real-time measurement electrode, and the external influence of electromagnetic radiation, parasitic capacitance, coupling capacitance and the like can be effectively eliminated, so that the stable measurement of pressure is realized.
The compensation principle can be implemented in a conditioning circuit. The conditioning circuit is a rear-end circuit connected with the measuring pin, is a special conditioning circuit ASIC (Application Specific Integrated Circuit) for capacitance signal processing, and is used for finishing standardized processing and output of pressure electric signals. The conditioning circuit belongs to the prior art and is not described in detail herein.
The electrode, the bonding pad and the connecting wire thereof can be realized by adopting coating, spraying or deposition technology, and the material can be gold, silver or other metals or alloys with good conductivity. It should be noted that the coating, spraying or depositing techniques are well known in the art for forming functional circuits, and the present invention will not be repeated.
The following specific examples are presented to illustrate the most readily achievable case in accordance with the teachings of the present invention and are not meant to be limiting.
Example 1
The embodiment provides a manufacturing method of a ceramic capacitive pressure sensor.
In this embodiment, the main structure of the ceramic capacitive pressure sensor includes a base 1, a diaphragm 8, and a sealing layer 13. The overall appearance of the sensor is flat cylindrical, and the distance between the two electrodes (i.e. the height of the sealing layer 13) is d=20 μm.
The manufacturing method comprises the following steps:
(1) After flattening the front surface of the base 1, arranging an arc-shaped groove 2 in the middle of the base 1, wherein the radius of the groove 2 is R/2, R is the radius of a base measuring electrode 34, and the depth of the groove 2 is 10 mu m;
(2) Coating a seat electrode 3, a groove electrode 4, a first compensation electrode 5, a first bonding pad 6 and a second bonding pad 7 on the front surface of the base 1 by adopting a coating mode by adopting gold slurry, and then sintering and solidifying to finish the manufacture of a functional layer of the base 1; the groove electrode 4 covers the side wall and the bottom wall of the groove 2 and keeps connected with the seat electrode 3;
(3) Coating, sintering and solidifying the diaphragm measuring electrode 9, the second compensating electrode 10, the third bonding pad 11 and the fourth bonding pad 12 on the diaphragm 8 in the same way as in the step (2), and completing the manufacture of a functional layer of the diaphragm 8;
(4) And then coating the sealing layer 13 on the front surface of the base 1 again, attaching the front surface of the membrane 8 manufactured by the functional layer to the front surface of the base 1, and sintering at a low temperature, wherein the specific sintering temperature is determined according to the slurry formula of the sealing layer 13, and the sintering temperature is generally 300-650 ℃.
(5) After the sealing is finished, the first bonding pad 6, the second bonding pad 7, the third bonding pad 11 and the fourth bonding pad 12 are connected by using the lead pins, and the electrode of the ceramic capacitor is led out to the back of the base 1 so as to be connected into a special ASIC conditioning circuit for capacitor signal processing, thereby finishing the standardized processing and output of the pressure electric signal.
(6) Thus, the manufacturing of the ceramic capacitive pressure sensor is completed.
Example two
The present embodiment provides another method for manufacturing a ceramic capacitive pressure sensor.
In this embodiment, the ceramic capacitive pressure sensor comprises a base 1, a diaphragm 8 and a sealing layer 13. The overall appearance is flat cylindrical, the distance between the two electrodes is d=20 μm.
The manufacturing method comprises the following steps:
(1) After flattening the front surface of the base 1, arranging a cylindrical groove 2 in the middle of the base 1, wherein the radius of the groove 2 is 0.707R, R is the radius of the base measuring electrode 34, and the depth of the groove 2 is 10 mu m;
(2) Coating a seat electrode 3, a groove electrode 4, a first compensation electrode 5, a first bonding pad 6 and a second bonding pad 7 on the front surface of the base 1 by adopting silver paste in a coating mode, and then sintering and solidifying to finish the manufacture of a functional layer of the base 1;
(3) Coating arrangement and sintering of the diaphragm measuring electrode 9, the second compensating electrode 10, the third bonding pad 11 and the fourth bonding pad 12 are completed on the diaphragm 8 in the same way as in the step (2), and the manufacture of a functional layer of the diaphragm 8 is completed;
(4) Then, simultaneously printing sealing layers 13 on the base 1 and the membrane 82, attaching the front surface of the membrane 8 manufactured by the functional layer to the front surface of the base 1, and aligning and bonding the two sealing layers 13; and then sintering, wherein the specific sintering temperature is determined according to the slurry formula of the sealing layer 13, and the general sintering temperature is 300-650 ℃.
(5) After the sealing is finished, the first bonding pad 6, the second bonding pad 7, the third bonding pad 11 and the fourth bonding pad 12 are connected by using the lead pins, and the electrode of the ceramic capacitor is led out to the back of the base 1 so as to be connected into a special ASIC conditioning circuit for capacitor signal processing, thereby finishing the standardized processing and output of the pressure electric signal.
(6) Thus, the manufacturing of the ceramic capacitive pressure sensor is completed.
Taking a 70bar measuring range as an example, the sensors manufactured by the prior art and the invention are measured, and the results are compared as follows:
referring to fig. 8, which shows a prior art parallel circular pressure sensor of dimple-less design, electrode spacing 40 μm, diaphragm 8 linearity r2=99.63%, maximum error=6.12%.
Referring to fig. 9, which shows a pressure sensor with a dimple depth of 50 μm, an electrode spacing of 20 μm, a diaphragm 8 linearity r2=99.87%, and a maximum error=3.43%.
Referring to fig. 10, which shows a pressure sensor with a pit depth of 100 μm, an electrode spacing of 20 μm, a linearity r2=99.96% of the diaphragm 8, and a maximum error=1.9%.
The above error is defined as: the maximum value (absolute value) of the difference between the fit function curve and the calculated curve is divided by the capacitance value corresponding to the maximum range. The fitted function curve is a theoretical value and a reference, the calculated curve is a simulation calculated value and represents an actual measured value.
The three above illustrations can be seen: with the increase of pit depth, the fitting degree of the calculated curve and the fitting function is increased.
The linearity error is measured by calculating the variance and using a normal distribution as shown in fig. 11. It can be seen that as pit depth increases, the variance of the error decreases significantly and the accuracy improves significantly, i.e. the linearity improves significantly (non-linearity decreases). For example, a pit depth of 100 μm is about 1866.7 times as large as the latter, and the measurement reliability is improved by about 43.2 times as compared with the case without pit.
Indeed, the parameters of the measuring range, the electrode spacing d, the groove depth and the elastic modulus of the diaphragm of the ceramic capacitive pressure sensor are related to each other, and influence on the nonlinearity of the sensor together, and the invention provides a new idea: namely, by arranging the groove in the middle of the base measuring electrode, the actual electrode distance at the base measuring electrode is artificially increased, the nonlinearity of the measured value of the whole sensor can be reduced, and the reliability of the measuring result of the sensor is further improved.
In the manufacturing process of the groove electrode 4, the smaller the radius of the groove 2 is, the greater the manufacturing difficulty is, so that the requirements on manufacturing equipment are also increased. The grooves 2 with different radiuses can be formed on the basis of modifying the existing coating, spraying or depositing equipment.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the specification and drawings of the present invention or direct/indirect application in other related technical fields are included in the scope of the present invention.
Claims (16)
1. A ceramic capacitive pressure sensor is characterized by comprising a base and a diaphragm;
the front surface of the base is provided with a base measuring electrode, the front surface of the diaphragm is provided with a diaphragm measuring electrode, and the base measuring electrode and the diaphragm measuring electrode are arranged in parallel and opposite to each other to form two poles of a capacitor;
the middle of the base measuring electrode is provided with a groove, so that the distance D between the middle position of the base measuring electrode and the diaphragm measuring electrode is larger than the distance D between other positions of the base measuring electrode and the diaphragm measuring electrode.
2. The ceramic capacitive pressure sensor of claim 1 wherein the distance D between the middle position of the base measurement electrode and the diaphragm measurement electrode, and the distance D between the other positions of the base measurement electrode and the diaphragm measurement electrode satisfy the formula: d is more than or equal to 1.5D and less than or equal to 100D.
3. The ceramic capacitive pressure sensor of claim 1 wherein the radius R of the recess and the radius R of the base measurement electrode satisfy the following relationship: r is more than or equal to 0.01 and less than or equal to R.
4. The ceramic capacitive pressure sensor of claim 1 further comprising a sealing layer between the base and the diaphragm, the sealing layer for sealingly connecting the base and the diaphragm.
5. The ceramic capacitive pressure sensor of claim 1 wherein the recess comprises a cylindrical or arcuate slot.
6. The ceramic capacitive pressure sensor of claim 1 wherein the front face of the base is further provided with a first compensation electrode and the front face of the diaphragm is provided with a second compensation electrode opposite the first compensation electrode.
7. The ceramic capacitive pressure sensor of claim 6 wherein the front face of the base is further provided with a first bonding pad and a second bonding pad;
the base measuring electrode is electrically connected with the first bonding pad, and the first bonding pad is led out to the back surface of the base through a first measuring lead pin;
the first compensation electrode is electrically connected with the second bonding pad, and the second bonding pad is led out to the back surface of the base through the second measurement lead pin.
8. The ceramic capacitive pressure sensor of claim 7 wherein the front face of the diaphragm is further provided with a third pad and a fourth pad;
the diaphragm measuring electrode is electrically connected with the third bonding pad, and the third bonding pad is led out to the back surface of the base through a third measuring lead pin;
the second compensation electrode is electrically connected with the fourth bonding pad, and the fourth bonding pad is led out to the back surface of the base through a fourth measurement lead pin.
9. The ceramic capacitive pressure sensor of claim 8 wherein the second measurement pin is merged with the fourth measurement pin.
10. A method of manufacturing a ceramic capacitive pressure sensor according to any one of claims 1 to 9, comprising:
step one, arranging a groove in the middle of the front surface of a base, and arranging a base measuring electrode covering the groove;
step two, arranging a diaphragm measuring electrode on the front surface of the diaphragm;
step three, sealing the membrane and the base face to face;
wherein the sequence of the first step and the second step can be exchanged.
11. The method of manufacturing of claim 10, wherein the method of providing a base measurement electrode covering a recess comprises: coating, spraying or depositing the metal slurry on the front surface of the base to obtain a base measuring electrode;
the method for arranging the diaphragm measuring electrode on the front surface of the diaphragm comprises the following steps: and coating, spraying or depositing the front surface of the diaphragm by adopting metal slurry to obtain a diaphragm measuring electrode.
12. The method of manufacturing as set forth in claim 11, further comprising:
coating, spraying or depositing metal slurry on the front surface of the base to obtain a first bonding pad and a second bonding pad;
and coating, spraying or depositing the front surface of the membrane by adopting metal slurry to obtain a third bonding pad and a fourth bonding pad.
13. The method of manufacturing as set forth in claim 12, further comprising:
a first compensation electrode is arranged around the base measurement electrode;
a second compensation electrode is disposed around the diaphragm measurement electrode.
14. The method of manufacturing as set forth in claim 12, further comprising:
penetrating a first measuring lead through the base to the front surface of the base so as to be electrically connected with a first bonding pad; and
penetrating a second measurement lead through the base to the front surface of the membrane, and enabling the second measurement lead to be electrically connected with the second bonding pad and the fourth bonding pad; and
and penetrating a third measuring lead through the base to the front surface of the diaphragm, so that the third measuring lead is electrically connected with a third bonding pad.
15. The method of manufacturing of claim 10, wherein the method of face-to-face sealing the membrane to the base comprises:
and printing a sealing layer on the front surface of the base and/or the front surface of the membrane, and sintering and solidifying the sealing layer to realize the joint connection of the base and the membrane.
16. The method of manufacturing of claim 10, further comprising, prior to step one:
and a sinking table is arranged on the front surface of the base, and the depth of the sinking table is equal to the preset electrode spacing.
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