A method of manufacturing a capacitive displacement sensor

Abstract

A kind of capacitive displacement sensor manufacturing method, it is related to capacitive displacement sensor, it is related to a kind of capacitive displacement sensor.Capacitive displacement sensor manufacturing method compatible with semiconductor process is provided.There is probe, insulating substrate, upper shell, lower shell, cable.The probe is manufactured using semiconductor process, the conductive and insulating part of probe main body is integrated manufacturing, the front of probe is three conductive parts and two insulating parts mutually coplanar nesting, as measurement plane;Insulating layer is prepared on the back of probe, and conductive material is embedded in specific position, and is bonded and electrically connected with insulating substrate.Probe is fixedly connected with lower shell through insulating substrate, and cable is connected with the conductive material of insulating substrate through upper shell;The insulating substrate is bonded with the upper and lower shell of sensor metal, and the conductive material in it is connected with cable.It has the advantages of batch manufacturing, reducing cost, reducing assembly difficulty and improving assembly coaxiality.

Description

TECHNICAL FIELD

[0001] The present application relates to a capacitive displacement sensor, in particular to a manufacturing method of a capacitive displacement sensor with Kelvin guard ring structure probe. BACKGROUND

[0002] Capacitive displacement sensors are widely used in aerospace, military weapons, automobiles, biomedicine and manufacturing industries due to their non-contact measurement, excellent dynamic performance, high precision and other advantages. Due to its versatility, capacitive displacement sensors are mostly based on the principle of variable plate spacing of parallel plate capacitors, that is, when the distance between the sensor probe and the measured object changes, the capacitance between them also changes, so as to accurately measure the displacement change between them. In the ideal case, the relationship between the capacitance C and the plate spacing d is:

[0003] C = ε r 0Ad (1)

[0004] Where ε r is the relative dielectric constant, ε0 is the vacuum dielectric constant, and A is the relative area of the plate. The condition for formula (1) to hold is that the electric field lines between the plates are uniformly distributed. However, the plates often have a certain thickness, and due to the tip effect, the electric charge accumulates at the edge of the plate, which causes the electric field lines between the plates to twist at the edge, i.e. edge effect. The edge effect seriously reduces the linearity and accuracy of the sensor. Therefore, Kelvin guard ring structure is now used to make the electric field in the measurement electrode region uniformly distributed, and the key is to keep the guard ring and the measurement electrode at the same potential [W. Chr. Heerens and F. C. Vermeulen, “Capacitance of Kelvin guardring capacitors with modified edge geometry,” J. Appl. Phys., vol. 46, no. 6, pp. 2486-2490, Jun. 1975]. In the world's leading capacitive displacement sensor suppliers, such as Germany's Micro-Epsilon and the United Kingdom's Queensgate Instruments, the probe and sensor housing are manufactured as one, and the commonly used materials are aluminum, iron-nickel alloy, titanium and stainless steel, etc. This means that the sensor is mainly machined, which is less efficient. Subsequently, the measurement electrode, guard ring and housing need to be precisely aligned and assembled coaxially through insulating materials, which is not easy to fill insulating materials in a narrow area of tens to hundreds of microns and ensure the coaxiality of the rings. This may result in poor coaxiality of the measurement electrode and the guard ring, which is not conducive to the improvement of the edge effect [Zhou Wenxiang. Key technology research on single-pole high-frequency response capacitive displacement sensor [D]. Harbin Institute of Technology, 2016]. Therefore, this manufacturing scheme also has the disadvantage of difficult assembly. SUMMARY

[0005] The present application aims to overcome the low efficiency and difficult assembly of the existing capacitive displacement sensor manufacturing method, and provide a capacitive displacement sensor manufacturing method compatible with semiconductor technology, and a capacitive displacement sensor manufactured by the method.

[0006] The capacitive displacement sensor comprises a probe, an insulating substrate, an upper shell, a lower shell and a cable.

[0007] The probe is a flat cylinder and is manufactured by semiconductor technology. The main body of the probe comprises three coaxial conductive parts: a measurement electrode, a guard ring and a ground ring. The probe also comprises two coaxial insulating parts: an inner insulating ring and an outer insulating ring, which are used for insulation between the conductive parts. The conductive parts are made of semiconductor materials, such as silicon, silicon carbide or gallium nitride. The insulating parts are made of epoxy resin glue, glass or alumina ceramic. The probe is fixedly connected to the lower shell through the insulating substrate, and the cable is connected to the conductive material of the insulating substrate through the upper shell. The measurement electrode, the guard ring and the ground ring are respectively connected to the cable through the conductive material. The insulating substrate is provided with three through hole structures and filled with conductive material.

[0008] The manufacturing method of the capacitive displacement sensor comprises the following steps:

[0009] 1) The upper shell and the lower shell are manufactured by mechanical processing, and external threads are formed on the upper shell.

[0010] 2) Three through hole structures are manufactured on the insulating substrate, and the through hole positions correspond to the conductive material of the probe.

[0011] 3) The probe is manufactured by combining semiconductor technology:

[0012] (1) A semiconductor wafer is taken, and a ring-shaped cavity is obtained by using photolithography and etching process.

[0013] (2) The ring-shaped cavity is filled with insulating material, and the composite wafer is thinned and planarized.

[0014] (3) An insulating layer is prepared on the back of the composite wafer by PECVD process, a cavity is manufactured on the insulating layer by combining photolithography and etching process, and the cavity is filled with conductive material by using stripping process, thereby completing the manufacturing of the probe.

[0015] 4) The probe is aligned and bonded to the insulating substrate, the conductive material is filled in the through holes of the insulating substrate respectively, and reliable contact is ensured between the conductive material of the probe and the corresponding conductive material below, thereby realizing vertical electrical interconnection and ensuring the insulation between the paths of the measurement electrode, the guard ring and the ground ring.

[0016] 5) The probe is fixed to the lower shell with the insulating substrate, coaxially aligned, the probe does not interfere with the lower shell, the lower surface of the probe is higher than the lower surface of the lower shell;

[0017] 6) The cable is connected to the corresponding conductive material of the insulating substrate through the upper shell;

[0018] 7) The upper shell and the lower shell are assembled and welded;

[0019] 8) The cable is fixed to the upper shell, and the manufacturing of the capacitive displacement sensor is completed.

[0020] Compared with the prior art, the beneficial effects of the present application are:

[0021] 1) The probe is manufactured by semiconductor process, such as photolithography, etching, deposition, etc., which has the advantages of mass production, improves efficiency and reduces cost; realizes fine structure and high precision coaxiality.

[0022] 2) The conductive and insulating parts of the probe body are manufactured integrally, the front surface of the probe is three conductive parts and two insulating parts coplanarly nested, serving as a measurement plane; the conductive and insulating parts of the probe are manufactured integrally, omitting the assembly step, and in the precise photolithography step, ensuring extremely high coaxiality and significantly reducing edge effect.

[0023] 3) The back surface of the probe is prepared with an insulating layer, and conductive material is embedded at a specific position, which is bonded and electrically connected with the insulating substrate. The insulating layer on the back surface of the probe ensures reliable insulation between the conductive parts during assembly, improves the assembly yield of the sensor, and improves the performance and production efficiency of the entire sensor.

[0024] 4) The present application has the advantages of batch manufacturing, reducing cost, reducing assembly difficulty and improving assembly coaxiality. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is the overall schematic diagram of the capacitive displacement sensor.

[0026] Figure 2 It is Figure 1 The probe cross-sectional view of the capacitive displacement sensor.

[0027] Figure 3 It is Figure 2 The back view of the probe.

[0028] Figure 4 It is Figure 2 The manufacturing flow chart of the probe. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the following embodiments will be further described in combination with the drawings. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0030] Referring to Figures 1 to 3 The capacitive displacement sensor comprises a probe 1, an insulating substrate 2, an upper shell 5, a lower shell 6 and a cable 4.

[0031] The probe 1 is a flat cylinder with a thickness of 200-800 μm and a diameter of about 5-40 mm related to the required measurement range and performance, and the specific size can be conveniently and flexibly adjusted in semiconductor process. The probe 1 main body comprises three conductive parts (a measurement electrode 11, a guard ring 12 and a ground ring 13) and two insulating parts (an inner insulating ring 14 and an outer insulating ring 15). The cylinder formed by the three conductive parts and the two insulating parts is in the same plane on the upper and lower sides, and there is an insulating layer 16 on one side (such as the back) of the cylinder. The insulating layer 16 has a cavity at the position corresponding to each of the measurement electrode 11, the guard ring 12 and the ground ring 13, respectively, and the lower surface of the cavity exposes the corresponding conductive part, and the cavity is filled with a first conductive material 31, a second conductive material 32 and a third conductive material 33, which are insulated from each other.

[0032] The insulating substrate 2 has a vertical through hole at the position corresponding to each of the first conductive material 31, the second conductive material 32 and the third conductive material 33, respectively, and is filled with a fourth conductive material 34, a fifth conductive material 35 and a sixth conductive material 36, which are insulated from each other. The fourth conductive material 34, the fifth conductive material 35 and the sixth conductive material 36 can also be used together with the conductive pins.

[0033] The upper shell 5 has external threads to facilitate the installation and use of the sensor.

[0034] The cable 4 is a radio frequency three coaxial cable.

[0035] The probe 1 is bonded (including electrical connection) with the insulating substrate 2, the insulating substrate 2 is fixed with the lower shell 6, the lower shell 6 is spliced with the upper shell 5, the cable 4 is connected with the conductive materials of the insulating substrate 2, the cable 4 is fixed with the upper shell 5, and the lower surface of the probe 1 is higher than the lower surface of the lower shell 6. The measurement electrode 11, the guard ring 12 and the ground ring 13 of the probe 1 are vertically interconnected by the first conductive material 31, the second conductive material 32 and the third conductive material 33 of the probe 1, and the fourth conductive material 34, the fifth conductive material 35 and the sixth conductive material 36 in the insulating substrate 2.

[0036] The material of the measuring electrode 11, the guard ring 12 and the ground ring 13 is a semiconductor material, such as silicon, silicon carbide or gallium nitride.

[0037] The material of the inner insulating ring 14 and the outer insulating ring 15 is epoxy glue, glass or alumina ceramic. The temperature of the epoxy glue is lower than 200℃, the temperature of the glass can reach 450℃ (such as BF33) and the alumina ceramic can be applied to an environment of more than 1000℃.

[0038] The material of the insulating layer 16 is silicon dioxide or silicon nitride.

[0039] The material of the first conductive material 31, the second conductive material 32 and the third conductive material 33 is aluminum, gold or platinum gold.

[0040] The material of the insulating substrate 2 is alumina or aluminum nitride.

[0041] The material of the fourth conductive material 34, the fifth conductive material 35 and the sixth conductive material 36 is carbon paste, gold paste, silver paste or copper paste.

[0042] The material of the upper shell 5 and the lower shell 6 is stainless steel, copper and copper alloy, aluminum and aluminum alloy, nickel-based alloy, molybdenum alloy or tantalum alloy.

[0043] The manufacturing method of the capacitor displacement sensor embodiment includes the following steps:

[0044] 1) The upper shell 5 and the lower shell 6 are manufactured by mechanical processing, and the outer threads are machined on the upper shell 5;

[0045] The upper shell and the lower shell are the outer shell of the sensor, which is used to protect the internal components; the upper shell is manufactured by mechanical processing, and the outer threads are machined on it; which is convenient for the installation and use of the sensor; the lower shell is also manufactured by mechanical processing, which ensures that the size and shape match the upper shell and are suitable for the internal components.

[0046] 2) The through hole is manufactured at a specific position of the insulating substrate 2, and the through hole position corresponds to the first conductive material 31, the second conductive material 32 and the third conductive material 33 of the probe 1 respectively;

[0047] The through hole corresponds to the three conductive materials on the probe, and during assembly, the probe and the substrate are aligned to ensure electrical connection between the probe and the substrate.

[0048] 3) Refer to Figure 4 , the probe 1 is manufactured by combining semiconductor process, including the following steps:

[0049] (A) Take half of the semiconductor wafer 7, get the precise inner and outer insulating ring pattern by photolithography process, then measure the electrode 11, the protection ring 12, the ground ring 13 pattern is also defined, and then use etching process to manufacture the inner insulating ring cavity 8, the outer insulating ring cavity 9, the insulating ring width range is 50-200 μm;

[0050] (B) Fill the insulating material 10 in the inner insulating ring cavity 8 and the outer insulating ring cavity 9 to form a composite wafer;

[0051] (C) Double-sided thinning and planarization is performed on the composite wafer to form the measurement electrode 11, the protection ring 12, and the ground ring 13 with extremely high coaxiality;

[0052] (D) Use PECVD process to deposit an insulating layer 16 on the back of the composite wafer, with a thickness range of 100-500 nm;

[0053] (E) Manufacture the first cavity 171, the second cavity 172, and the third cavity 173 at specific positions of the insulating layer 16 by photolithography and etching process, and expose them respectively corresponding to the measurement electrode 11, the protection ring 12, and the ground ring 13;

[0054] (F) Fill the conductive material in the cavities prepared in step (E) by using magnetron sputtering or thermal evaporation method combined with stripping process to obtain the first conductive material 31, the second conductive material 32, and the third conductive material 33, and complete the manufacturing of the probe 1;

[0055] 4) Align and bond the probe 1 with the insulating substrate 2, then fill the fourth conductive material 34, the fifth conductive material 35, and the sixth conductive material 36 in the through holes of the insulating substrate 2 respectively to ensure reliable contact with the first conductive material 31, the second conductive material 32, and the third conductive material 33 of the probe 1 below, realize vertical electrical interconnection, and ensure the mutual insulation of the through paths where the measurement electrode 11, the protection ring 12, and the ground ring 13 are located;

[0056] The different conductive materials filled in the through holes of the insulating substrate are to establish vertical electrical connection and also to provide mechanical support for different parts of the probe. The conductive material should have good conductivity and appropriate viscosity to facilitate filling and curing. The filled conductive material must ensure reliable contact between different parts of the probe (measurement electrode, protection ring, ground ring) and the corresponding circuit path to realize effective electrical interconnection.

[0057] 5) Bond and fix the insulating substrate 2 with the probe 1 to the lower shell 6, try to align coaxially, the probe 1 does not interfere with the lower shell 6, and the lower surface of the probe 1 is higher than the lower surface of the lower shell;

[0058] The insulating base is used to secure the probe and connect it to the rest of the circuit. It also ensures electrical isolation between the probe and the lower housing, avoiding short circuits. During the securing process, the probe and the lower housing are aligned coaxially as much as possible, ensuring that the probe detects the displacement correctly without being hindered by the lower housing. The lower surface of the probe is adjusted to a position higher than the lower surface of the lower housing, ensuring that the probe has enough space to move when in operation. The insulating base and the probe can be fixed to the lower housing using various methods, including the use of glue, epoxy resin or other adhesives. In addition, mechanical fasteners such as screws or clips can be used to increase stability.

[0059] 6) The cable 4 is connected to the corresponding conductive material of the insulating base 2 through the upper housing 5;

[0060] The cable transmits the capacitive variation signal detected by the probe to the external processing circuit; to protect the cable from damage and avoid any possible interference, the cable passes through the upper housing. In the design, the upper housing is provided with a hole or channel of appropriate size for the cable to pass through. The cable passes through the upper housing and is connected to the conductive material on the insulating base. The connection can be achieved by welding, crimping or using a dedicated connector.

[0061] 7) The upper housing 5 and the lower housing 6 are assembled and welded;

[0062] Ensuring that the sensor has good sealing performance, thereby ensuring the stability and durability of the entire sensor system.

[0063] 8) The cable 4 is fixed to the upper housing 5, completing the manufacture of an embodiment of a capacitive displacement sensor.

[0064] The sensor is subjected to final inspection and testing to ensure that all components have been properly installed and that the sensor is functioning correctly.

[0065] The probe is manufactured by semiconductor process, and the conductive and insulating parts of the probe body are manufactured integrally. The front surface of the probe is three conductive parts and two insulating parts which are mutually coplanar and nested, serving as a measurement plane. An insulating layer is prepared on the back surface of the probe, and conductive material is embedded at specific positions, bonded and electrically connected with the insulating substrate. By using semiconductor process to manufacture the probe, very precise geometric size and appearance can be achieved, which is crucial for improving the sensitivity and resolution of the sensor. By using double-sided thinning and planarization process during the manufacturing process of the probe, the measurement electrode, protection ring and ground ring can have high coaxiality, which helps to improve the stability and linearity of the sensor. By manufacturing through holes at specific positions and filling different conductive materials between the probe and the substrate, reliable electrical interconnection can be achieved while maintaining insulation between parts. By filling insulating material in the outer insulating ring cavity and depositing an insulating layer on the back surface of the probe, external electromagnetic interference can be effectively reduced and the noise immunity of the sensor can be improved. The insulating substrate is bonded with the sensor metal shell, and the conductive material therein is connected with the cable. The whole sensor structure is compact, and there is no interference between the probe and the shell, which is conducive to the installation and use of the sensor in limited space. By using physical deposition and etching technology, and filling conductive and insulating materials at key positions, the sensor can have high long-term stability and reliability. The capacitive displacement sensor has the advantages of batch manufacturing, reducing cost, reducing assembly difficulty and improving assembly coaxiality, and is suitable for various precision measurement occasions.

[0066] The above embodiments are only preferred embodiments of the present application and should not be considered as limiting the scope of the present application. Any equivalent changes and improvements made in accordance with the scope of the present application should still belong to the scope of the present application.

Claims

1. A capacitive displacement sensor characterized by The probe, the insulating substrate, the upper shell, the lower shell and the cable are provided. The probe is a flat cylinder, which includes three coaxial conductive parts and two coaxial insulating parts to insulate each other. The three coaxial conductive parts are a measuring electrode, a protection ring and a ground ring. The two coaxial insulating parts are an inner insulating ring and an outer insulating ring. The material of the conductive parts is a semiconductor material, i.e. silicon, silicon carbide or gallium nitride. The material of the insulating parts is epoxy resin glue, glass or alumina ceramic. The probe is fixedly connected with the lower shell through the insulating substrate, and the cable is connected with the conductive material of the insulating substrate through the upper shell. The insulating substrate is provided with three through-hole structures and filled with conductive materials. The cylinder formed by the three coaxial conductive parts and the two coaxial insulating parts is in the same plane on the upper and lower sides, and an insulating layer is arranged on one side of the cylinder. The insulating layer has a cavity corresponding to the measuring electrode, the protection ring and the ground ring respectively, and the lower surface of the cavity exposes the corresponding conductive part. The cavity is filled with the first conductive material, the second conductive material and the third conductive material respectively, and they are insulated from each other. The insulating substrate has a vertical through-hole corresponding to the first conductive material, the second conductive material and the third conductive material respectively, and is filled with the fourth conductive material, the fifth conductive material and the sixth conductive material respectively, and they are insulated from each other. The probe is bonded with the insulating substrate, the insulating substrate is fixed with the lower shell, the lower shell is spliced with the upper shell, the cable is connected with the conductive material of the insulating substrate, the cable is fixed with the upper shell, and the lower surface of the probe is higher than the lower surface of the lower shell. The measuring electrode, the protection ring and the ground ring of the probe are connected with the first conductive material, the second conductive material and the third conductive material of the probe and the fourth conductive material, the fifth conductive material and the sixth conductive material in the insulating substrate respectively, so as to realize vertical electrical interconnection.

2. A capacitance displacement sensor as claimed in claim 1, wherein The cable is a radio frequency three-coaxial cable.

3. A method of manufacturing a capacitive displacement sensor, characterized by The method comprises the following steps: 1) The upper shell and the lower shell are manufactured by mechanical processing, and the outer thread of the upper shell is machined; 2) Three through-hole structures are manufactured on the insulating substrate, and the through-hole positions correspond to the conductive materials of the probe; 3) The probe is manufactured by combining the semiconductor process: (1) A semiconductor wafer is taken, and a ring cavity is obtained by using the photoetching and etching process; (2) The ring cavity is filled with insulating material, and the composite wafer is thinned and planarized; (3) The insulating layer is prepared on the back of the composite wafer by the PECVD process, the cavity is manufactured on the insulating layer by combining the photoetching and etching process, the conductive material is filled in the cavity by using the stripping process, and the manufacturing of the probe is completed; 4) The probe is aligned and bonded with the insulating substrate, the conductive material is filled in the through-hole of the insulating substrate respectively, the reliable contact of the conductive material of the probe corresponding to the lower surface is ensured, the vertical electrical interconnection is realized, and the paths of the measuring electrode, the protection ring and the ground ring are insulated from each other; 5) The insulating substrate with the probe is bonded and fixed with the lower shell, and is coaxially aligned. The probe does not interfere with the lower shell, and the lower surface of the probe is higher than the lower surface of the lower shell. 6) The cable is connected with the corresponding conductive material of the insulating substrate through the upper shell; 7) The upper shell and the lower shell are assembled and welded; 8) The cable is fixedly bonded with the upper shell, and the manufacturing of the capacitive displacement sensor is completed.

4. The method of claim 3, wherein In step 2), the through hole positions correspond to the conductive materials of the probe, and the through holes are manufactured at specific positions of the insulating substrate, and the through hole positions correspond to the first conductive material, the second conductive material and the third conductive material of the probe respectively.

5. The method of claim 3, wherein In step 3), the cavities are manufactured on the insulating layer by combining the photoetching and etching processes, and the conductive materials are filled in the cavities by using the stripping process. Specifically, the first cavity, the second cavity and the third cavity are manufactured at specific positions of the insulating layer by using the photoetching and etching processes, and the cavity positions correspond to the measuring electrode, the guard ring and the ground ring respectively, and are exposed; then the first conductive material, the second conductive material and the third conductive material are filled in the first cavity, the second cavity and the third cavity by using the magnetic control sputtering or the thermal evaporation method in combination with the stripping process, so as to complete the manufacturing of the probe.

6. The method of claim 3, wherein In step 4), the through holes in the insulating substrate are respectively filled with the conductive materials to ensure reliable contact with the conductive materials of the corresponding probe below, and vertical electrical interconnection is realized; specifically, the fourth conductive material, the fifth conductive material and the sixth conductive material are respectively filled in the through holes of the insulating substrate to ensure reliable contact with the first conductive material, the second conductive material and the third conductive material of the corresponding probe below, realize vertical electrical interconnection, and ensure that the paths where the measuring electrode, the guard ring and the ground ring are located are mutually insulated.

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