阅读说明：本技术 一种共烧结构的电涡流式高温转速传感器用敏感探头及制备方法 (Sensitivity probe with co-firing structure for eddy current type high-temperature rotating speed sensor and preparation method thereof ) 是由 文吉延 刘玺 程振乾 刘洋 周明军 金鹏飞 王永刚 杨永超 于 2019-11-12 设计创作，主要内容包括：一种共烧结构的电涡流式高温转速传感器用敏感探头及制备方法,涉及一种高温转速传感器用敏感探头。目的是解决电涡流式转速传感器温度范围窄、探头尺寸大、电涡流场一致性差和可靠性低的问题。敏感探头由陶瓷基板、敏感线圈、线圈保护层、信号引出线、焊盘保护层和焊盘构成。制备：氧化铝生瓷带冲孔并印刷成线圈图形,叠放得到平面线圈生坯块或多层线圈生坯块；在氧化铝生瓷带表面涂覆保护层浆料,进行排胶和一次高温烧结,金属信号引出线和焊盘封接,进行二次高温烧结；封接处覆盖玻璃浆料,进行三次高温烧结,形成焊盘保护层。敏感探头具有高温下可靠性高,一致性好,微型化,耐振动性能高,耐温度冲击性能好等优点。本发明适用于制备敏感探头。(A sensitivity probe with a co-firing structure for an eddy current type high-temperature rotating speed sensor and a preparation method thereof relate to a sensitivity probe for a high-temperature rotating speed sensor. The eddy current type rotating speed sensor aims to solve the problems of narrow temperature range, large probe size, poor eddy current field consistency and low reliability of the eddy current type rotating speed sensor. The sensitive probe comprises a ceramic substrate, a sensitive coil, a coil protective layer, a signal outgoing line, a bonding pad protective layer and a bonding pad. Preparation: punching an alumina green porcelain strip, printing the alumina green porcelain strip into a coil pattern, and stacking the coil pattern to obtain a planar coil green block or a multilayer coil green block; coating protective layer slurry on the surface of the alumina green porcelain tape, carrying out glue removal and primary high-temperature sintering, sealing the metal signal outgoing line and the bonding pad, and carrying out secondary high-temperature sintering; and covering the sealing part with glass slurry, and performing high-temperature sintering for three times to form a pad protective layer. The sensitive probe has the advantages of high reliability at high temperature, good consistency, miniaturization, high vibration resistance, good temperature impact resistance and the like. The invention is suitable for preparing the sensitive probe.)

1. The utility model provides a burn sensing probe for eddy current type high temperature rotational speed sensor of structure altogether which characterized in that: the sensitive probe is a plane coil probe or a multilayer coil probe; the planar coil probe or the multilayer coil probe is composed of a ceramic substrate (1), a sensitive coil (2), a coil protective layer (3), a signal outgoing line (4), a bonding pad protective layer (5) and a bonding pad (6); the sensitive probe is a plane coil probe or a multilayer coil probe;

in the planar coil probe: the surface of the ceramic substrate (1) is provided with a sensitive coil (2), two ends of the sensitive coil (2) on the ceramic substrate (1) are respectively provided with a through hole perpendicular to the surface of the main body of the ceramic substrate (1), a cylindrical bonding pad (6) is arranged in the through hole, and the two ends of the sensitive coil (2) are respectively fixedly connected with the side wall of the bonding pad (6); the upper end of the bonding pad (6) extends out to the upper surface of the ceramic substrate (1), the upper end of the bonding pad (6) is fixedly connected with one end of the signal leading-out wire (4), the sensitive coil (2) is coated with the coil protective layer (3), and the bonding pad protective layer (5) covers the joint of the upper end of the bonding pad (6) and the signal leading-out wire (4);

in the multilayer coil probe: the surface of the ceramic substrate (1) is provided with a sensitive coil (2), the interior of the ceramic substrate (1) is provided with a plurality of sensitive coils (2), the surface of the ceramic substrate (1) is parallel to the sensitive coils (2) in the ceramic substrate, two ends of the sensitive coils (2) on the surface of the ceramic substrate (1) are respectively provided with a through hole perpendicular to the main body surface of the ceramic substrate (1), a cylindrical bonding pad (6) is arranged in the through hole, and the interior of the ceramic substrate (1) and the two ends of the sensitive coils (2) on the surface of the ceramic substrate (1) are respectively fixedly connected with the side wall of the bonding pad (6); the upper end of the bonding pad (6) extends out to the upper surface of the ceramic substrate (1), the upper end of the bonding pad (6) is fixedly connected with one end of the signal leading-out wire (4), the outermost sensitive coil (2) is coated with the coil protective layer (3), and the joint of the upper end of the bonding pad (6) and the signal leading-out wire (4) is covered with the bonding pad protective layer (5).

2. The sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure of claim 1, wherein: the sensitive coil (2) is a plane single-turn spiral line or a plane multi-turn equidistant spiral line.

3. The method for preparing the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 1, wherein the method comprises the following steps:

the method comprises the following steps:

punching a design position of a pad (6) on the alumina green porcelain tape to obtain a punched alumina green porcelain tape; printing low-sheet resistance metal slurry into a coil pattern on the upper surface of the punched alumina green tape, and allowing the low-sheet resistance metal slurry to flow into the punched hole to form a bonding pad (6) during printing to obtain the alumina green tape with the coil pattern;

the printing of the coil pattern is carried out by adopting screen printing;

the coil pattern is a plane single-turn spiral line or a plane multi-turn equidistant spiral line; the thickness of lines in the spiral line is 5-25 mu m, the width is 75-250 mu m, the spacing is 50-100 mu m, and the maximum diameter of the spiral line is 15 mm;

the thickness of the alumina green porcelain strip is 0.08-0.35 mm;

the sheet resistance of the low sheet resistance metal slurry is 2-25 m omega/□, and the low sheet resistance metal slurry is prepared from 10-25 wt% of alumina powder, 6-30 wt% of solvent, 0.5-3 wt% of dispersant, 1-8 wt% of adhesive and the balance of metal powder;

step two:

when the planar coil probe is prepared, stacking 1 alumina green tape with a coil pattern and a plurality of punched alumina green tapes in the step one, wherein the alumina green tape with the coil pattern is arranged on the uppermost layer, punching holes of different alumina green tapes correspond to each other during stacking, and performing isostatic pressing treatment to obtain a planar coil green compact;

when a multilayer coil probe is prepared, stacking a plurality of alumina green porcelain tapes with coil patterns in the step one, wherein punched holes of different alumina green porcelain tapes correspond to each other when the alumina green porcelain tapes are stacked, and performing isostatic pressing treatment to obtain a multilayer coil green compact;

the isostatic pressing treatment process comprises the following steps: keeping the temperature and the pressure for 10-50 min at 65-85 ℃ and 2500-4000 psi;

step three:

when the planar coil probe is prepared, coating a layer of protective layer slurry on the surface of the aluminum oxide green tape with the coil pattern of the planar coil green block in the step two until the coil pattern is completely coated; when a multilayer coil probe is prepared, coating a layer of protective layer slurry on the surface of the outermost layer of the aluminum oxide green tape with the coil pattern in the multilayer coil green block in the step two until the coil pattern is completely coated; then, carrying out glue discharging and primary high-temperature sintering to obtain a sensitive core body, and converting the protective layer slurry into a coil protective layer (3);

the thickness of the protective layer slurry is 10-150 mu m;

the protective layer slurry is formed by mixing 55-75 wt% of alumina powder or aluminum-magnesium spinel powder, 1-8 wt% of binder, 0.5-2 wt% of dispersant and the balance of solvent;

step four:

taking the same low sheet resistance metal slurry obtained in the first step, sealing the metal signal outgoing line (4) and the bonding pad (6) in the sensitive core by using the low sheet resistance metal slurry, and performing secondary high-temperature sintering after sealing;

step five:

and covering glass slurry at the sealing part of the bonding pad (6) and the metal signal outgoing line (4) until the end part of the bonding pad (6) is completely covered by adopting a dispensing mode, and performing high-temperature sintering for three times to form a bonding pad protective layer (5).

4. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step one, the metal powder is one or a mixture of Ag powder, Au powder and Pt powder; the solvent is one or a mixture of more of terpineol, diethylene glycol monobutyl ether and benzyl alcohol in any proportion; the dispersant is castor oil; the adhesive is one or a mixture of more of ethyl cellulose, polyvinyl butyral and polyamide resin in any proportion.

5. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step three, the binder is ethyl cellulose; the dispersant is triglyceride; the solvent is terpineol.

6. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step three, the concrete process of the binder removal is as follows: firstly, heating to 130 ℃ at a heating rate of 0.5-2 ℃/min, then heating to 280 ℃ at a heating rate of 0.5-1 ℃/min, finally heating to 600 ℃ at a heating rate of 0.2-1 ℃/min, and keeping the temperature for 60-1440 min.

7. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step three, the specific process of primary high-temperature sintering is as follows: heating to 950-1500 ℃ at a heating rate of 1-10 ℃/min and preserving heat for 1-10 h.

8. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step four, the specific process of the secondary high-temperature sintering is as follows: heating to 900-1450 ℃ at a heating rate of 1-10 ℃/min and preserving heat for 0.5-4 h.

9. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: fifthly, the specific process of the third high-temperature sintering comprises the following steps: heating to 500 ℃ at a heating rate of 0.2-5 ℃/min, then heating to 850-1350 ℃ at a heating rate of 1-10 ℃/min, and preserving heat for 1-10 h.

10. The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-fired structure according to claim 3, wherein the method comprises the following steps: step five, mixing 25-50 wt% of glass powder, 1-4 wt% of micron alumina powder, 2-25 wt% of nano alumina powder, 1-7 wt% of binder and the balance of solvent to form the glass slurry;

the solvent is one or a mixture of more of terpineol, diethylene glycol monobutyl ether and benzyl alcohol in any proportion; the binder is one or a mixture of more of ethyl cellulose, polyvinyl butyral and polyamide resin in any proportion; the grain diameter of the micron alumina powder is 0.8-5 mu m, and the grain diameter of the nanometer alumina powder is 100-300 nm.

Technical Field

The invention relates to a sensitive probe for a high-temperature rotating speed sensor

Background

The eddy current rotating speed sensor can continuously and accurately acquire the parameters of the rotating track of the engine impeller by accurately measuring the eddy current-like induced current generated in the conductor when the static and dynamic relative displacement between the metal conductor and the end surface of the sensitive probe changes in the analysis and measurement of the rotating speed of the engine impeller (particularly for non-contact rotating signals). Eddy current speed sensors have been widely used for early diagnosis of mechanical problems such as imbalance, misalignment, bearing wear, shaft cracks, etc. of engine impellers.

At present, most of common eddy current speed sensors on the market are metal wire winding structures, wherein copper wires and alloy wire winding structures are common. Some researches on eddy current type rotation speed sensors have been carried out at home and abroad, and most of the currently researched eddy current type rotation speed sensors are low-temperature rotation speed sensors or medium-temperature rotation speed sensors. For example: a high-temperature resistant eddy current sensor system of the Bentley company in America belongs to an eddy current rotating speed sensor with a metal wire winding structure, adopts a closed sealing ceramic structure, and can continuously bear the service temperature of +350 ℃ under extreme conditions. Patent CN201897601U discloses a revolution speed sensor for eddy current buffer, belongs to the eddy current revolution speed sensor of metal wire winding structure, and the sensor structure is cavity structure, is equipped with the signal generator who has solenoid, is equipped with magnet in the accommodation space, is convenient for change.

The eddy current speed sensor with the metal wire winding structure has the following common problems:

1. the application temperature range is narrow, the sensitive probe of the existing rotating speed sensor is of a metal wire winding structure, and the metal wire winding can be oxidized or melted to cause sensor failure after long-term use in a high-temperature environment, so that the sensor cannot be applied to the high-temperature environment. Wherein the use temperature range of the low-temperature rotation speed sensor is-60-100 ℃, and the use temperature range of the medium-temperature rotation speed sensor is-50-240 ℃.

2. The diameter of the metal wire in the sensitive probe of the existing metal wire-wound structure rotating speed sensor is larger, generally larger than 0.3mm, and a thicker insulating structure with at least 0.2mm is needed between the metal wires, so that the size of the probe is large, and the sensor is not easy to realize miniaturization.

3. In the long-term use process, because the coefficient of thermal expansion mismatches can continuously produce the tensile force between wire winding and the pottery, lead to the wire to take place to warp or even break, cause sensor output signal drift or even no signal problem's appearance, consequently the reliability is poor under the high temperature, is unfavorable for long-term use.

4. The metal wire winding and the alumina ceramic substrate in the conventional rotating speed sensor sensing probe are respectively and independently manufactured, and in the wire winding process of each sensing probe, because the errors of the metal wire winding and the alumina ceramic substrate in the function matching process and the processing process are caused, the consistency of the metal wire winding and the alumina ceramic substrate is far lower than that of the ceramic substrate and the sensing coil formed by one-time co-firing, and the current eddy current field induction intensity of the rotating speed sensor with the conventional metal wire winding structure has more than 5 percent of deviation.

Disclosure of Invention

The invention aims to solve the problems of narrow temperature range, large probe size, poor consistency of an eddy current field and low reliability of a product at high temperature of an eddy current type rotating speed sensor, and provides a sensitive probe for the eddy current type high-temperature rotating speed sensor with a co-fired structure and a preparation method thereof.

The sensing probe for the eddy current type high-temperature rotating speed sensor with the co-firing structure is a planar coil probe or a multilayer coil probe; the planar coil probe or the multilayer coil probe consists of a ceramic substrate, a sensitive coil, a coil protective layer, a signal outgoing line, a bonding pad protective layer and a bonding pad; the sensitive probe is a plane coil probe or a multilayer coil probe;

in the planar coil probe: the surface of the ceramic substrate is provided with a sensitive coil, two ends of the sensitive coil on the ceramic substrate are respectively provided with a through hole vertical to the surface of the ceramic substrate body, a cylindrical bonding pad is arranged in the through hole, and the two ends of the sensitive coil are respectively fixedly connected with the side wall of the bonding pad; the upper end of the bonding pad extends out to the upper surface of the ceramic substrate, the upper end of the bonding pad is fixedly connected with one end of the signal leading-out wire, the sensitive coil is coated with a coil protective layer, and the bonding pad protective layer covers the joint of the upper end of the bonding pad and the signal leading-out wire;

in the multilayer coil probe: the surface of the ceramic substrate is provided with a sensitive coil, the interior of the ceramic substrate is provided with a plurality of sensitive coils, the surface of the ceramic substrate and the sensitive coils in the ceramic substrate are parallel to each other, two ends of the sensitive coils on the surface of the ceramic substrate are respectively provided with a through hole vertical to the surface of the ceramic substrate body, a cylindrical bonding pad is arranged in each through hole, and the two ends of the sensitive coils on the interior of the ceramic substrate and the surface of the ceramic substrate are respectively fixedly connected with the side wall of each bonding pad; the upper end of the bonding pad extends out to the upper surface of the ceramic substrate, the upper end of the bonding pad is fixedly connected with one end of the signal leading-out wire, the outermost sensitive coil is coated with a coil protective layer, and the joint of the upper end of the bonding pad and the signal leading-out wire is covered with the bonding pad protective layer.

In the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-firing structure, the sensitive coil has the functions as follows: when alternating current passes through the sensing coil, an alternating magnetic field can be generated in the sensing coil, the alternating magnetic field can generate induced current, namely eddy current, on the surface of the engine impeller nearby the alternating magnetic field, the eddy current can induce the alternating magnetic field in the sensing coil in the opposite direction to change with the impedance external magnetic field, and the rotating speed value of the engine impeller can be obtained by measuring the electrical impedance change speed value of the sensing coil. The ceramic substrate is formed by sintering a plurality of alumina green porcelain strips, the ceramic substrate made of alumina has good high-temperature insulation performance, the phenomenon of short circuit between the sensitive coils of adjacent layers can be effectively prevented, the number of true turns of the coils is reduced, the phenomenon that output signals of the rotating speed sensor are weakened or no signals and the like is avoided, and the ceramic substrate can also improve the service temperature range of the sensor prepared by the sensitive probe. The coil protective layer can prevent the outermost sensitive coil from being scratched due to external friction or collision, so that the output signal of the sensor is abnormal; and the sensor can be prevented from failing due to oxidation of the outermost sensitive coil at high temperature. The pad protective layer is used for sealing and reinforcing the pad of the sensitive core and the metal signal outgoing line, so that the tensile strength of the pad protective layer is improved.

The preparation method of the sensitive probe for the eddy current type high-temperature rotating speed sensor with the co-firing structure comprises the following steps:

the method comprises the following steps: punching a hole at the designed position of a bonding pad on the alumina green ceramic tape to obtain a punched alumina green ceramic tape; printing low-sheet resistance metal slurry into a coil pattern on the upper surface of the punched alumina green tape, and allowing the low-sheet resistance metal slurry to flow into the punched hole to form a bonding pad during printing to obtain the alumina green tape with the coil pattern;

the printing of the coil pattern is carried out by adopting screen printing;

the coil pattern is a plane single-turn spiral line or a plane multi-turn equidistant spiral line; the thickness of the lines in the spiral line is 5-25 μm, the width is 75-250 μm, the spacing is 50-100 μm, and the maximum diameter of the spiral line is 15 mm.

The thickness of the alumina green porcelain strip is 0.08-0.35 mm;

the sheet resistance of the low sheet resistance metal slurry is 2-25 m omega/□, and the low sheet resistance metal slurry is prepared from 10-25 wt% of alumina powder, 6-30 wt% of solvent, 0.5-3 wt% of dispersant, 1-8 wt% of adhesive and the balance of metal powder;

step two:

when the planar coil probe is prepared, stacking 1 alumina green tape with a coil pattern and a plurality of punched alumina green tapes in the step one, wherein the alumina green tape with the coil pattern is arranged on the uppermost layer, punching holes of different alumina green tapes correspond to each other during stacking, and performing isostatic pressing treatment to obtain a planar coil green compact;

when a multilayer coil probe is prepared, stacking a plurality of alumina green porcelain tapes with coil patterns in the step one, wherein punched holes of different alumina green porcelain tapes correspond to each other when the alumina green porcelain tapes are stacked, and performing isostatic pressing treatment to obtain a multilayer coil green compact;

the isostatic pressing treatment process comprises the following steps: keeping the temperature and the pressure for 10-50 min at 65-85 ℃ and 2500-4000 psi;

step three:

when the planar coil probe is prepared, coating a layer of protective layer slurry on the surface of the aluminum oxide green tape with the coil pattern of the planar coil green block in the step two until the coil pattern is completely coated; when a multilayer coil probe is prepared, coating a layer of protective layer slurry on the surface of the outermost layer of the aluminum oxide green tape with the coil pattern in the multilayer coil green block in the step two until the coil pattern is completely coated; then, carrying out glue discharging and primary high-temperature sintering to obtain a sensitive core body, and converting the protective layer slurry into a coil protective layer;

the thickness of the protective layer slurry is 10-150 mu m;

the protective layer slurry is formed by mixing 55-75 wt% of alumina powder or aluminum-magnesium spinel powder, 1-8 wt% of binder, 0.5-2 wt% of dispersant and the balance of solvent;

step four: taking the same low sheet resistance metal slurry obtained in the first step, sealing the metal signal outgoing line and the bonding pad in the sensitive core by using the low sheet resistance metal slurry, and performing secondary high-temperature sintering after sealing;

step five: and covering glass slurry at the sealing position of the bonding pad and the metal signal outgoing line by adopting a dispensing mode until the end part of the bonding pad is completely covered, and performing high-temperature sintering for three times to form a bonding pad protective layer.

The principle and the beneficial effects of the invention are as follows:

1. according to the invention, the ceramic substrate is formed by sintering a plurality of alumina green ceramic tapes, the alumina ceramic substrate has good high-temperature insulation performance, the phenomenon of short circuit between adjacent sensitive coils can be effectively prevented, the real number of turns of the coils is reduced, the phenomena of output signal attenuation or no signal and the like of the rotating speed sensor are avoided, and the ceramic substrate can also improve the service temperature range of the sensor prepared by the sensitive probe. The coil protective layer can prevent the outermost sensitive coil from being scratched due to external friction or collision, so that the output signal of the sensor is abnormal; and the sensor can be prevented from failing due to oxidation of the outermost sensitive coil at high temperature. The pad protective layer is used for sealing and reinforcing the pad of the sensitive core and the metal signal outgoing line, so that the tensile strength of the sensitive core is increased, and therefore, the sensitive probe has a higher use temperature range and high reliability at high temperature, and is beneficial to long-term use.

2. According to the invention, the sensitive probes suitable for different measuring distances and different use temperatures can be obtained by selecting the material of the coil patterns and selecting the width, thickness, space and number of turns of the coil patterns in the screen printing process; and the consistency of the width, the thickness, the spacing and the number of turns of the coil of the sensitive coil formed after the coil pattern is sintered is ensured by adopting a screen printing process, the manufacturing precision is improved, and the consistency of an eddy current field is ensured. The ceramic substrate and the sensitive coil are sintered simultaneously, so that the consistency of the eddy current field of the sensitive probe is improved.

3. The cross section of the line in the coil pattern is 5 microns multiplied by 75 microns at least, the thickness of the ceramic substrate is only about 0.1mm, and compared with a metal wire with the diameter of 0.3mm and an insulation structure with the diameter of at least 0.2mm in a rotating speed sensor with a metal wire winding structure, the micro-structure of the sensitive probe is realized.

4. In the sensing probe with the co-fired structure, the sensing coil and the ceramic substrate are deeply fused after being sintered at high temperature, the interlayer bonding force is provided by microscopic metal atoms and alumina particles, and the sensing coil and the alumina particles are not separated under high-frequency vibration, so that the signal output under the vibration environment is ensured, and the sensing probe has excellent vibration resistance.

5. The use temperature of the sensitive probe is-50 ℃ to +1200 ℃, the measuring distance is 0-3 mm (the distance between the measured object and the sensitive probe), and the measurement of the metal gear or the blade at the rotating speed of 0-10000 rpm can be realized.

6. According to the invention, the matching of the thermal expansion coefficients of the sensitive coil and the ceramic substrate is realized through the co-firing structure, and even if the sensitive coil and the ceramic substrate experience temperature impact in the use temperature range, due to the consistency of the thermal expansion coefficients, the sensitive coil and the ceramic substrate are always kept to expand or contract simultaneously, so that the phenomena of deformation, falling and even fracture of the coil are avoided, and the sensitive probe has excellent temperature impact resistance.

Description of the drawings:

FIG. 1 is a schematic structural view of a sensitive probe prepared in example 1;

FIG. 2 is a cross-sectional view taken at A-A of FIG. 1;

FIG. 3 is a schematic structural view of an alumina green tape having a coil pattern obtained in the first step of example 1;

FIG. 4 is a schematic view of a coil pattern on the surface of the alumina green tape of FIG. 3, wherein a is a punched hole;

FIG. 5 is a graph showing the rotational speed of the gear measured by the rotational speed sensor in example 1 at different ambient temperatures;

FIG. 6 is a resistance curve diagram of the sensing probe in example 1 at different ambient temperatures;

FIG. 7 is a schematic structural view of a sensing probe prepared in example 2;

FIG. 8 is a cross-sectional view taken at A-A of FIG. 7;

FIG. 9 is a schematic structural view of an alumina green tape having a coil pattern obtained in the first step of example 2;

fig. 10 is a schematic view of a coil pattern on the surface of the alumina green tape of fig. 9, in which a is a punched hole.

The specific implementation mode is as follows:

the technical scheme of the invention is not limited to the specific embodiments listed below, and any reasonable combination of the specific embodiments is included.