JP2012068054A - Capacitance type sensor and control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce detection errors of humidity sensors.SOLUTION: A humidity sensor 1 comprises a humidity sensitive membrane 60 that is so formed on one face 11 of a base plate 10 as to cover measuring electrodes 30a and 30b and physically adsorbs water vapor with a resultant rise in dielectric constant, and a water-repellent moisture permeable membrane 70 so formed as to cover the humidity sensitive membrane 60 from one side of the base plate 10 in a direction orthogonal thereto; the measuring electrodes 30a and 30b are so arranged as to cause tooth parts constituting comb teeth to engage with each other; a surface 71 of the water-repellent moisture permeable membrane 70 has an apex 70A protruding on one side of an orthogonal direction to the base plate 10, and the surface 71 is inclined from the apex 70A side thereof as to guide dew condensation water toward the outer edge side of the humidity sensitive membrane 60; therefore, even if dew condensation water sticks to the surface of the humidity sensor 1, the dew condensation water is guided by the inclination of the surface to flow from the apex 70A side toward the outer edge side of the humidity sensitive membrane 60.

Description

  The present invention relates to a capacitance type sensor and a control device that controls a heater provided in the sensor.

  Conventionally, a capacitance type humidity sensor has a sensor part composed of a pair of electrodes having an insulating film on the surface, and a change in the capacitance of the sensor part that occurs when water droplets adhere to the surface of the sensor part Is detected as adhesion of the water droplet (see Patent Document 1).

  Some humidity sensors include a heater that heats the entire detection unit, and the entire detection unit is heated by the heater to remove dirt attached to the entire detection unit (see Patent Document 2).

JP-A 63-309847 Japanese Utility Model Publication No. 62-62955

  In the above-mentioned Patent Document 1, when the surface of the insulating film is condensed, if dirt such as dust in the air adheres to the condensed water, the dirt diffuses over the entire surface of the sensor unit, and after the condensed water is dried, A dirt layer may be formed on the entire surface. In this case, the dielectric constant changes due to the dirt layer. For this reason, when a dirt layer is formed on the sensor unit, there is a problem that it causes a detection error.

  On the other hand, although the above-mentioned Patent Document 2 has a heater for heating and removing dirt adhering to the detection unit, the inorganic substance cannot be removed by heating. For this reason, when inorganic substances such as salts adhere to the condensed water as dirt, a residue remains widely on the surface of the detection unit after the condensed water is dried. The salt in the residue has a problem that a detection error occurs because the dielectric constant changes due to moisture absorption or deliquescence.

  Such a problem may occur not only in sensors that detect water droplets, but also in sensors that have a gas-sensitive film whose dielectric constant changes by acting on a test gas such as water vapor or carbon monoxide.

  The present invention has been made in view of the above points, and an object of the present invention is to reduce the detection error of a capacitive sensor.

In order to achieve the above object, the invention described in claim 1 has a substrate (10) and a pair of measurement electrodes (30a, 30b) provided on the substrate to detect capacitance. Comb electrode portions (32a, 32b, 32c, 34a, 34b) provided with detectors (10, 30a, 30b), wherein the pair of measurement electrodes are formed in a comb shape and are arranged to mesh with each other. In a capacitive sensor having
The detection part has a top part (70A) that is formed so as to protrude to one side in a direction orthogonal to the substrate and is arranged so as to overlap with the vicinity of the center of the comb electrode part,
The surface shape of the detection part is a shape having an inclination from the top part toward the outer edge side of the comb electrode part, and water adhering to the surface (71) of the detection part follows the inclination by gravity. And moving to the outer edge side.

  According to this invention, even if water, for example, condensed water adheres to the surface of the sensor, the condensed water is guided by the inclination of the surface by gravity and flows from the top side to the outer edge side of the comb electrode part. Detection error due to dew condensation water can be reduced. Here, the vicinity of the center of the comb electrode portion refers to the center portion of the comb electrode portion or a portion in the vicinity of the center portion.

  Specifically, according to a second aspect of the present invention, in the capacitance type sensor according to the first aspect, the detection unit is formed so as to cover the comb-tooth electrode unit and is orthogonal to the substrate. It has the oxide film (40) formed in the convex shape which becomes convex on one side, It is characterized by the above-mentioned. Thereby, a detection part can be formed so that it may protrude in the one side of the orthogonal direction with respect to a board | substrate.

  According to a third aspect of the present invention, in the capacitance type sensor according to the first or second aspect, the detection unit has a moisture sensitive film (60) formed so as to cover the comb electrode portion. It is characterized by having a hydrophilic film (80) disposed on the outer edge side of the moisture sensitive film and formed on a portion surrounding the periphery of the comb electrode portion.

  According to this invention, water, for example, condensed water does not stay on the moisture sensitive film, and the condensed water can be held by the hydrophilic film outside the moisture sensitive film. For this reason, even when vibration occurs in the sensor, the dew condensation water is difficult to move to the top side of the surface. In this case, if the hydrophilic film (80) has a groove that is recessed toward the substrate as in the invention described in claim 4, it becomes easier to hold the condensed water in the recess. Further, as in the invention described in claim 5, the inner edge pattern of the hydrophilic film (80) overlapping the moisture sensitive film (60) has a meandering shape reciprocating on the outer edge side of the moisture sensitive film. Then, similarly to the fourth aspect, the dew condensation water can be easily held in the meandering concave portion.

  A sixth aspect of the present invention is the electrostatic capacity sensor according to the first or second aspect, further comprising a heater (100) formed on the substrate (10), wherein the heater is formed on the surface. The vicinity of the top is formed by a heater pattern having a heat generation temperature higher than that of other portions.

  According to this invention, the amount of heat reaching the surface from the heater becomes smaller as it approaches the outer edge side of the measurement electrode portion from the top side. As a result, the condensed water evaporates first at the top, and the evaporation of the condensed water becomes slower as it approaches the outer edge side of the measurement electrode section. For this reason, the dirt contained in the dew condensation water can be collected on the outer edge side and away from the central part of the measurement electrode part.

The invention according to claim 7 is a control device for controlling the heater in the capacitance type sensor according to claim 5,
A determination means (S140) for determining whether or not a condition that causes condensation on the capacitance sensor continues for a certain period of time;
And a control means (S150) for causing a current to flow through the heater and generating heat from the heater when the judgment by the judgment means is affirmative.

  According to the present invention, it is possible to appropriately obtain the effect of the invention according to claim 6 by starting heating by the heater assuming that water, for example, dew condensation water, is attached to the entire surface of the sensor. it can.

It is a front view of the humidity sensor in a 1st embodiment of the present invention. It is AA sectional drawing in FIG. It is a figure which shows the manufacturing process of the humidity sensor in 1st Embodiment. It is a figure which shows the manufacturing process of the humidity sensor in 1st Embodiment. It is a figure which shows the structure of the humidity detection apparatus using the humidity sensor of 1st Embodiment. It is a figure which shows the modification of the hydrophilic film in 1st Embodiment. It is the front view and sectional drawing of the humidity sensor in 2nd Embodiment of this invention. It is a figure which shows the heater single-piece | unit of FIG. It is a figure which shows the structure of the humidity detection apparatus of 2nd Embodiment. It is a flowchart which shows the heater control process in the humidity detection apparatus of 2nd Embodiment. It is a figure for demonstrating arrangement | positioning of the board | substrate of a humidity sensor in the modification of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other are given the same reference numerals in the drawings in order to simplify the description.

(First embodiment)
1 and 2 show a first embodiment of a humidity sensor 1 according to the present invention. 1 is a top view of the humidity sensor 1, and FIG. 2 is a cross-sectional view taken along the line AA in FIG.

  The humidity sensor 1 constitutes a sensor that detects the relative humidity in the air. As shown in FIGS. 1 and 2, the substrate 10, the insulating protective films 20 and 21, the measurement electrodes 30 a and 30 b, and the oxide film 40. The insulating protective film 50, the moisture sensitive film 60, the water-repellent moisture permeable film 70, and the hydrophilic film 80 are configured. In the present embodiment, a silicon substrate is used as the substrate 10.

  The insulating protective film 20 is formed on the one surface 11 side of the substrate 10, and is provided in a film shape along the one surface 11 of the substrate 10. The insulating protective film 20 is formed in a substantially circular shape when viewed from the direction orthogonal to the substrate 10. The insulating protective film 20 plays a role of achieving electrical insulation between the substrate 10 and the measurement electrodes 30a and 30b. The insulating protective film 21 is disposed on the outer peripheral side of the insulating protective film 20 and is formed so as to surround the insulating protective film 20 via the space 22.

  The measurement electrodes 30a and 30b constitute a pair of electrodes made of a metal film such as aluminum. The measurement electrodes 30a and 30b generate capacitance according to the dielectric constant of the moisture sensitive film 60 when a potential difference is applied between the measurement electrodes 30a and 30b. As shown in FIG. 1, the measurement electrodes 30 a and 30 b are formed in a comb shape and are arranged so as to mesh with each other.

  Specifically, the measurement electrode 30a includes a base 31 and tooth portions 32a, 32b, and 32c. The measurement electrode 30b includes a base 33 and tooth portions 34a and 34b.

  The tooth portions 32a, 32b, and 32c constitute a comb-tooth electrode portion of the measurement electrode 30a, and are disposed on one side of the insulating protective film 20 in the direction orthogonal to the substrate 10 as shown in FIG. . As shown in FIG. 1, the tooth portions 32 a, 32 b, and 32 c are formed so as to protrude from the base portion 31 toward the base portion 33. The tooth portions 32a, 32b, and 32c are arranged in the order of the tooth portions 32a, 32b, and 32c from the one end 31a of the base portion 31 toward the other end 31b. The tooth portions 32a, 32b, and 32c are arranged in parallel at intervals. As a result, the measurement electrode 30a is formed in a comb-teeth shape.

  The base 31 is formed in an elongated plate shape, and one end 31 a side thereof is disposed on one side in the orthogonal direction with respect to the insulating protective film 20. The base 31 extends on the outer peripheral side of the hydrophilic film 80 on the other end 31b side through insulating protective films 52 and 53 described later. A pad 35 a is connected to the other end 31 b of the base 31. The pad 35a is exposed on one side in the orthogonal direction.

  The tooth portions 34a and 34b constitute a comb electrode portion of the measurement electrode 30b, and are arranged on one side in the orthogonal direction with respect to the insulating protective film 20, as shown in FIG. As shown in FIG. 1, the tooth portions 34 a and 34 b are formed so as to protrude from the base portion 33 toward the base portion 31. The tooth portions 34a and 34b are arranged so as to be parallel with a gap therebetween. The tooth portion 34a is disposed on the one end 33a side of the base portion 33, and is located between the tooth portions 32a and 32b of the measurement electrode 30a. The tooth portion 34b is disposed on the other end 33b side of the base portion 33 with respect to the tooth portion 34a, and is located between the tooth portions 32b and 32c of the measurement electrode 30a. Accordingly, the measurement electrode 30b is formed in a comb-like shape, and the comb-tooth electrode portions (34a, 34b) are engaged with the comb-tooth electrode portions (32a, 32b, 32c) of the measurement electrode 30a. Will be placed. This increases the facing area between the measurement electrodes 30a and 30b, and increases the capacitance between the measurement electrodes 30a and 30b.

  The base portion 33 is formed in an elongated plate shape, and one end 33 a side thereof is disposed on one side in the orthogonal direction with respect to the insulating protective film 20. The other end 33 b side of the base 33 extends to the outer peripheral side of the hydrophilic film 80 through insulating protective films 52 and 53 described later. A pad 35 b is connected to the other end 33 b of the base 33. The pad 35b is exposed on one side in the orthogonal direction.

  The oxide film 40 in FIG. 2 is disposed on one side in the orthogonal direction with respect to the insulating protective film 20, and is located on the radially inner side of the insulating protective film 20. The oxide film 40 is formed so as to cover the tooth portions 32a, 32b, 32c of the measurement electrode 30a and the tooth portions 34a, 34b of the measurement electrode 30b. The oxide film 40 is formed in a convex shape (convex lens shape) that is convex on one side in the orthogonal direction. As will be described later, the oxide film 40 plays a role of forming the surface of the humidity sensor 1 so as to protrude to one side in the orthogonal direction. As the oxide film 40 of this embodiment, for example, an insulating film (that is, a BPSG film) made of a silicon oxide film containing boron and phosphorus is used.

  The insulating protective film 50 is made of, for example, a SiN film, and is formed in a film shape having insulating protective films 51, 52, and 53. The insulating protective film 51 is formed in a film shape that covers the radially outer portion 20 a (see FIG. 2) of the oxide film 40 and the insulating protective film 20. Thereby, the insulating protective film 51 is formed so as to be substantially circular as viewed from one side in the orthogonal direction and to protrude to one side in the orthogonal direction. The insulating protective film 52 is formed so as to fill the space 22. The insulating protective film 52 is provided with a recess 52a that is recessed on the other side in the orthogonal direction. The insulating protective film 53 is formed so as to cover the insulating protective film 21 and to cover the outer peripheral side of the insulating protective film 21 on the one surface 11 of the substrate 10.

  The moisture sensitive film 60 is made of polyimide, for example, and has a dielectric constant that increases with the physical adsorption of water vapor. The moisture sensitive film 60 is formed so as to cover the insulating protective film 51 from one side in the orthogonal direction. As a result, the moisture sensitive film 60 is formed so as to be substantially circular when viewed from one side in the orthogonal direction and to protrude to one side in the orthogonal direction.

  The water-repellent moisture permeable film 70 is made of, for example, a fluorine polymer film, and repels water as a liquid while allowing water vapor as a gas to pass therethrough. The water-repellent moisture permeable film 70 is formed so as to be substantially circular when viewed from one side in the orthogonal direction and to cover the entire moisture sensitive film 60 from one side in the orthogonal direction. The water repellent and moisture permeable membrane 70 forms a top portion 70A whose surface 71 protrudes to one side in the orthogonal direction, and between the top portion 70A side and the outer edge side of the water repellent and moisture permeable membrane 70, it is between the substrate 10. Inclined to shorten the distance. The surface 71 is a surface formed on one side in the orthogonal direction of the water-repellent moisture permeable film 70 and constitutes a surface located on one side in the orthogonal direction of the humidity sensor 1. Such a water repellent and moisture permeable film 70 includes a substrate 10, an insulating protective film 20, measurement electrodes 30 a and 30 b, an oxide film 40, an insulating protective film 50, and a moisture sensitive film 60, and a detection unit that detects capacitance. Is configured.

  Here, the top portion 70A of the surface 71 overlaps with the vicinity of the center of the comb electrode portions (32a, 32b, 32c, 34a, 34b) of the measurement electrodes 30a, 30b in the orthogonal direction. The vicinity of the center refers to a central portion of the comb electrode portion or a portion in the vicinity thereof. In FIG. 1, the center portion of the comb electrode portion is a location where the tooth portion 32 b and an instruction line (a dashed line in the drawing) of the AA crossing line intersect.

  Therefore, according to the configuration described above, the shape of the surface 71 (that is, the surface shape of the detection portion) is inclined from the top portion 70A protruding to one side in the direction orthogonal to the substrate 1 toward the outer edge side of the comb electrode portion. The shape has.

  The hydrophilic film 80 is made of, for example, TiO 2 or a hydrophilic group-modified polymer film, and holds water in the form of a film. The hydrophilic film 80 is disposed on the outer peripheral side of the moisture sensitive film 60 and is formed in an annular shape. The inner edge side of the hydrophilic film 80 is in contact with the outer edge side of the moisture sensitive film 60. That is, the inner edge side in contact with the moisture sensitive film 60 in the hydrophilic film 80 is formed in an annular shape. Therefore, the hydrophilic film 80 does not overlap with the comb electrode portions of the measurement electrodes 30a and 30b described above, and is formed in a portion surrounding the periphery of the comb electrode portions of the measurement electrodes 30a and 30b. The hydrophilic film 80 is disposed in the recess 52a of the insulating protective film 52, and forms a groove 80a that is recessed on the other side in the orthogonal direction. The bottom of the groove 80 a is located on the other side in the orthogonal direction with respect to the surface 71 of the water and moisture permeable membrane 70 and the insulating protective film 53.

  Next, the manufacturing process of the humidity sensor 1 of this embodiment is demonstrated.

  FIGS. 3A to 3D and FIGS. 4A to 4C are schematic cross-sectional views showing the manufacturing process of the humidity sensor 1.

  First, an insulating protective film is formed on the surface 11 side of the substrate 10 and patterned. As a result, insulating protective films 20 and 21 are formed on the surface 11 of the substrate 10 (see FIG. 3A). Thereafter, an electrode film is formed and patterned on the substrate 10 on which the insulating protective films 20 and 21 are thus formed. As a result, the measurement electrodes 30a and 30b are formed (see FIG. 3B). FIG. 3B shows the tooth portions 32a, 32b, and 32c of the measurement electrode 30a and the tooth portions 34a and 34b of the measurement electrode 30b.

  Next, an oxide film is formed on the insulating protective film 20 mounted on the surface 11 side of the substrate 10 and patterned. As a result, an oxide film 40a is formed on the insulating protective film 20 (see FIG. 3C). The oxide film 40a is formed in a thin plate shape covering the tooth portions 32a, 32b, 32c, 34a, 34b. Thereafter, the oxide film 40a is heated to soften the oxide film 40a. Accordingly, the oxide film 40a has a convex lens shape that is convex on one side in the orthogonal direction. As a result, an oxide film 40 is formed (see FIG. 3D).

  Next, an insulating protective film is formed and patterned on the oxide film 40 thus formed. As a result, an insulating protective film 50 composed of the insulating protective films 51, 52, and 53 is formed (see FIG. 4A).

  Next, a moisture-sensitive film and a water-repellent moisture-permeable film are formed on the thus-formed insulating protective film 50 and patterned. Thereby, the moisture sensitive film 60 and the water-repellent moisture permeable film 70 are formed (see FIG. 4B). Thereafter, a hydrophilic film is formed on the moisture-sensitive film 60 and the water-repellent moisture-permeable film 70 and patterned. Thereby, the hydrophilic film | membrane 80 is formed (refer FIG.4 (c)). As a result, the manufacture of the humidity sensor 1 is completed.

  Next, the humidity detection apparatus 2 for detecting humidity using the humidity sensor 1 of this embodiment is demonstrated. FIG. 5 is a diagram illustrating a configuration of the humidity detection device 2.

  In addition to the humidity sensor 1, the humidity detection device 2 includes a temperature sensor 90, a humidity conversion circuit 91, a temperature conversion circuit 92, and a signal processing circuit 93.

  The humidity conversion circuit 91 converts the capacitance of the humidity sensor 1 into a voltage. The temperature sensor 90 is formed in the vicinity of the above-described comb electrode portion in the humidity sensor 1. A thermistor is used as the temperature sensor 90 of the present embodiment. The temperature conversion circuit 92 supplies a constant current to the thermistor and amplifies and outputs the output voltage of the thermistor.

  Here, the capacitance of the humidity sensor 1 and the relative humidity around the humidity sensor 1 have a one-to-one relationship. In addition, in the humidity sensor 1, there is an error between the detected humidity and the actual humidity, and this error has a characteristic that changes with temperature.

  The signal processing circuit 93 includes a CPU, a memory, and the like. The signal processing circuit 93 obtains the humidity detected by the humidity sensor 1 based on the output voltage of the humidity conversion circuit 91 and outputs the obtained humidity to the temperature conversion circuit 92. A process for obtaining a humidity with a small error by performing correction based on the voltage is executed.

  Next, the operation of the temperature detection device will be described for an example in which the substrate 10 of the humidity sensor 1 of the present embodiment is arranged in parallel to the horizontal direction.

  First, when the temperature of the air around the humidity sensor 1 is higher than the dew point temperature, the water vapor passes through the water-repellent moisture permeable film 70 and is physically adsorbed on the moisture sensitive film 60 in the humidity sensor 1. Along with this, the dielectric constant of the moisture sensitive film 60 increases. That is, the humidity sensor 1 acts on water vapor to increase the capacitance between the measurement electrodes 30a and 30b. The humidity conversion circuit 91 converts the capacitance of the humidity sensor 1 into a voltage. The temperature conversion circuit 92 amplifies the output voltage of the temperature sensor 90 and outputs it. Next, the signal processing circuit 93 obtains the relative humidity detected by the humidity sensor 1 based on the output voltage of the humidity conversion circuit 91 and corrects the obtained relative humidity with the output voltage of the temperature conversion circuit 92. Output.

  Thereafter, when the temperature of the air around the humidity sensor 1 falls below the dew point temperature, condensed water is generated on the surface of the humidity sensor 1. The condensed water is guided from the top portion 70 </ b> A side by the inclination of the surface 71 of the water repellent and moisture permeable membrane 70 and flows to the outer edge side of the water repellent and moisture permeable membrane 70. That is, the dew condensation water adhering to the surface 71 of the water-repellent moisture permeable membrane 70 flows to the outer edge side of the comb electrode portions (32a, 32b, 32c, 34a, 34b) of the measurement electrodes 30a, 30b due to gravity. . Thereafter, the condensed water enters the groove 80 a of the hydrophilic film 80. In the groove 80a, the dew condensation water is formed into a film and held.

  Thereafter, when the temperature of the air around the humidity sensor 1 becomes higher than the dew point temperature, the condensed water in the groove 80a of the hydrophilic film 80 evaporates. For this reason, the dirt contained in the dew condensation water remains in the groove 80a as a residue.

  According to the present embodiment described above, the humidity sensor 1 covers the measurement electrodes 30a and 30b mounted on the one surface 11 side of the substrate 10 and the measurement electrodes 30a and 30b on the one surface 11 side of the substrate 10. A moisture sensitive film 60 that is physically adsorbed to increase the dielectric constant by water vapor adsorption, and a water repellent and moisture permeable film 70 that is formed so as to cover the moisture sensitive film 60 from one side in a direction orthogonal to the substrate 10. Prepare. The measurement electrodes 30a and 30b are arranged so that the comb electrode portions (32a, 32b, 32c, 34a and 34b) mesh with each other. An output voltage indicating the dielectric constant of the moisture sensitive film 60 is output from between the measurement electrodes 30a and 30b. The surface 71 (that is, the surface of the humidity sensor 1) of the water-repellent moisture permeable film 70 protrudes on one side in the direction orthogonal to the substrate 10 and has a top portion 70A, and the surface 71 has a comb electrode portion (from the top portion 70A side) 32a, 32b, 32c, 34a, 34b) are inclined so as to guide the dew condensation water to the outer edge side. The top portion 70A is formed so as to overlap with the vicinity of the center of the comb electrode portions (32a, 32b, 32c, 34a, 34b).

  Therefore, even if condensed water adheres to the surface of the humidity sensor 1, the condensed water is guided by the inclination of the surface and flows from the top 70A side to the outer edge side of the moisture sensitive film 60. For this reason, even if dirt adheres to the dew condensation water, the dirt can be moved to the outer edge side of the moisture sensitive film 60. In the present embodiment, as described above, the top portion 70A is arranged so as to overlap with the vicinity of the center of the comb electrode portions of the measurement electrodes 30a and 30b meshing with each other. Thereby, dirt can be kept away from the center vicinity of the comb-tooth electrode part of measurement electrode 30a, 30b. For this reason, the influence which the stain | pollution | contamination contained in dew condensation water has with respect to the output voltage output from between the electrodes 30a and 30b for measurement can be decreased. Thereby, the humidity sensor 1 which made the detection error of relative humidity small can be provided.

  In the present embodiment, a groove 80 a of the hydrophilic film 80 is provided on the outer peripheral side of the water repellent and moisture permeable film 70. The groove 80 a of the hydrophilic film 80 holds the condensed water that has been guided to the surface 71 of the water-repellent moisture permeable film 70 and has flowed to the outer edge side of the surface 71 in a film shape.

  Here, when a water-repellent film made of a water-repellent material that makes the condensed water spherical is used instead of the hydrophilic film 80, when vibration occurs in the humidity sensor 1, the condensed water is easily formed on the top portion 70 </ b> A side of the surface 71. There is a possibility of flowing.

  On the other hand, in this embodiment, as described above, the groove 80a of the hydrophilic film 80 is provided on the outer peripheral side of the water-repellent moisture permeable film 70. For this reason, even if vibration occurs in the humidity sensor 1, the groove 80a of the hydrophilic film 80 holds the condensed water in the form of a film, so that it is possible to suppress the movement of the condensed water toward the top portion 70A of the surface 71. .

  Furthermore, in this embodiment, after the condensed water in the groove 80a of the hydrophilic film 80 evaporates, a residue of dirt remains in the groove 80a. When salts are contained in the residue, the dielectric constant of the salts changes due to moisture absorption or deliquescence. Here, when the residue is located near the center of the comb electrode portions of the measurement electrodes 30a and 30b, the influence of the residue on the output voltage of the humidity sensor 1 becomes large.

  On the other hand, in this embodiment, the hydrophilic film 80 is offset in the orthogonal direction with respect to the vicinity of the center of the comb electrode portion of the measurement electrodes 30a and 30b. Thereby, a residue is kept away from the center vicinity of the comb-tooth electrode part of measurement electrode 30a, 30b. For this reason, in the detection humidity of the humidity sensor 1, the influence which a residue has can be reduced further.

  The bottom of the groove 80 a of the hydrophilic film 80 according to the present embodiment is located on the other side in the orthogonal direction from the surface 71 of the water-repellent moisture permeable film 70 and the insulating protective film 53. For this reason, it can suppress that the dew condensation water in the groove part 80a moves to the outer side of the groove part 80a.

  In the first embodiment, the example in which the inner edge side of the hydrophilic film 80 is formed in an annular shape has been described. Alternatively, the hydrophilic film 80 may be configured as shown in FIG.

  FIG. 6 is a view of the hydrophilic film 80 and the moisture sensitive film 60 viewed from one side (see FIG. 2) orthogonal to the substrate 10 with the water repellent and moisture permeable film 70 omitted. The hydrophilic film 80 in FIG. 6 is not provided with the groove 80a and is disposed so as to overlap the moisture sensitive film 60 from one side in the orthogonal direction. The inner edge portion of the hydrophilic film 80 is formed in a meandering shape in which convex portions 80b and concave portions 80c are alternately arranged. That is, the inner edge of the hydrophilic film 80 is formed in a meander pattern. The convex portion 80 b is formed so as to protrude toward the top portion 70 </ b> A (not shown in FIG. 6) of the water-repellent moisture permeable film 70. The recess 80c is formed so as to be recessed on the opposite side of the top portion 70A (not shown in FIG. 6) of the water-repellent moisture permeable membrane 70. The inner edge portion of the hydrophilic film 80 in FIG. 6 is composed of 16 convex portions 80b and 16 concave portions 80c. Condensed water that has flowed from the top portion 70 </ b> A side of the water-repellent moisture permeable membrane 70 can be retained in the plurality of concave portions 80 c that constitute the inner edge portion of the hydrophilic film 80 configured as described above.

  Furthermore, as the hydrophilic film | membrane 80, the inner edge part may be formed in a meandering shape, and the groove part 80a may be formed. Thereby, much more condensed water can be hold | maintained.

(Second Embodiment)
In the second embodiment, an example in which a heater is added to the humidity sensor 1 of the first embodiment will be described.

  7A is a view of the humidity sensor 1 when the heater 100 is seen through the measurement electrodes 30a and 30b (shown by chain lines in the figure) from one side in the direction orthogonal to the substrate 10. FIG. In FIG. 7A, the insulating protective films 20 and 21, the oxide film 40, the insulating protective film 50, the moisture sensitive film 60, the water-repellent moisture permeable film 70, and the hydrophilic film 80 are omitted. FIG.7 (b) is a figure corresponded to BB sectional drawing in Fig.7 (a). 7B, the same reference numerals as those in FIG. 2 denote the same elements.

  The humidity sensor 1 of the present embodiment is the same as the humidity sensor 1 of FIG. 1 except that a recess 12 is provided in a substrate 10 and a heater 100 and an insulating film 120 are formed in the recess 12. Hereinafter, the heater 100 and the insulating film 120 will be described. FIG. 8 shows a view of the heater 100 alone viewed from one side in the direction orthogonal to the substrate 10.

  The heater 100 includes pads 101 and 102 and wiring portions 110, 111, 112, 113, 114, 115, 116, 117, and 118. As shown in FIG. 7B, the heater 100 covers the entire range corresponding to the groove portion 80 a of the water-repellent moisture permeable film 70 and the hydrophilic film 80 on the other side in the orthogonal direction with respect to the insulating protective film 20. It is arranged.

  In FIG. 7B, the wiring portions 110, 111,..., 117, 118 are located on the other side in the orthogonal direction with respect to the water repellent and moisture permeable film 70. The wiring part 114 is located on the other side in the orthogonal direction with respect to the top part 70 </ b> A of the water-repellent moisture permeable film 70. The wiring portions 110 and 118 are located on the other side in the orthogonal direction with respect to the groove portion 80 a of the hydrophilic film 80.

  As shown in FIG. 7A, the pads 101 and 102 are disposed between the pad 35a of the measurement electrode 30a and the pad 35b of the measurement electrode 30b. The pads 101 and 102 are exposed on one side in the orthogonal direction. The pad 101 is connected to the wiring part 110. The pad 102 is connected to the wiring part 118.

  The wiring portions 110, 111, 112, 113, 114, 115, 116, 117, 118 constitute a current path between the pads 101, 102.

  As shown in FIG. 8, the wiring portions 110, 111, 112, and 113 are each formed in an arc shape that is convex in the same direction. The wiring portions 110, 111, 112, and 113 are arranged at intervals in the radial direction. The wiring portions 115, 116, 117, and 118 are each formed in an arc shape that is convex in the same direction. The wiring portions 115, 116, 117, and 118 are arranged at intervals in the radial direction.

  The wiring portions 110, 111, 112, and 113 and the wiring portions 115, 116, 117, and 118 are arranged so as to protrude in opposite directions. The wiring portions 110, 111, 112, 113, 114, 115, 116, 117, 118 are connected so as to form a current path between the pads 101, 102 in a meandering manner.

  The wiring parts 110 and 111 are connected, the wiring parts 111 and 112 are connected, and the wiring parts 112 and 113 are connected. The wiring part 114 is connected between the wiring parts 113 and 115. The wiring portions 116 and 117 are connected, and the wiring portions 117 and 118 are connected.

  Here, of the wiring portions 110, 111, 112, 113, 114, 115, 116, 117, 118, the wiring portion 114 is wider than the remaining wiring portions 110, 111, 112, 113, 115, 116, 117, 118. The direction length is shortened. The width direction length is a direction orthogonal to the direction of current flow in the wiring portion.

  Specifically, the wiring portions 110, 111, 112, 113, 114 are gradually shortened in the width direction in the order of the wiring portion 110, the wiring portion 111, the wiring portion 112, the wiring portion 113, and the wiring portion 114. Is set to The wiring portions 114, 115, 116, 117, 118 are set so that the length in the width direction gradually decreases in the order of the wiring portion 118, the wiring portion 117, the wiring portion 116, the wiring portion 115, and the wiring portion 114. .

  As a result, the wiring sections 110, 111, 112, 113, 114 gradually increase in electrical resistance in the order of the wiring section 110, the wiring section 111, the wiring section 112, the wiring section 113, and the wiring section 114. The wiring portions 114, 115, 116, 117, 118 gradually increase in electrical resistance in the order of the wiring portion 118, the wiring portion 117, the wiring portion 116, the wiring portion 115, and the wiring portion 114.

  The insulating film 120 is disposed between the heater 100 and the substrate 10 in the recess 12 of the substrate 10. As a result, electrical insulation between the heater 100 and the substrate 10 is achieved.

  The insulating film 120 is disposed in a gap between two adjacent wiring portions of the wiring portions 110, 111, 112, 113, 114, 115, 116, 117, 118 of the heater 100. As a result, electrical insulation of the gap between the two wiring portions is achieved.

  Next, the humidity detection device 2 of the present embodiment will be described. FIG. 9 is a diagram showing the configuration of the humidity detection device 2 of the present embodiment. 9, the same reference numerals as those in FIG. 5 denote the same components.

  The humidity detection device 2 of the present embodiment differs from the humidity detection device 2 of FIG. 5 in a humidity sensor 1 and a signal processing circuit (control device) 93. Therefore, the description of the configuration other than the humidity sensor 1 and the signal processing circuit 93 is omitted, and the humidity sensor 1 and the signal processing circuit 93 will be described below. The humidity sensor 1 is configured to include the heater 100 as described above.

  The signal processing circuit 93 includes a timer in addition to the CPU and the memory, and controls the heater 100 of the humidity sensor 1 in addition to the process of obtaining the relative humidity around the humidity sensor 1 as in the first embodiment. A heater control process is executed.

  Next, the operation of the humidity detection device 2 of the present embodiment will be described.

  FIG. 10 is a flowchart showing a heater control process in the humidity detection device 2. The humidity detection device 2 executes the heater control process according to the flowchart of FIG. The heater control process is repeatedly performed at regular intervals.

  First, in step S100, it is determined whether or not there is a concern that condensation has occurred on the surface 71 of the water-repellent moisture permeable film 70 of the humidity sensor 1.

  Specifically, as in the first embodiment, the relative humidity around the humidity sensor 1 is obtained based on the output voltage of the humidity conversion circuit 91, and the obtained relative humidity is used as the output voltage of the temperature conversion circuit 92. Based on the correction, the corrected relative humidity is obtained. It is determined whether or not the obtained relative humidity after correction is a threshold value (for example, 95%) or more.

  When the corrected relative humidity is less than the threshold value, it is determined that NO is not a concern that dew condensation has occurred on the surface 71 of the water-repellent moisture permeable membrane 70 of the humidity sensor 1, so that NO is determined and step S100 is performed. Return to.

  Further, when the corrected relative humidity is equal to or higher than the threshold value, it is determined as YES because it is a situation in which there is a concern that condensation has occurred on the surface 71 of the water-repellent moisture permeable film 70 of the humidity sensor 1.

  Here, if condensed water adheres to the surface 71 of the water-repellent moisture permeable membrane 70 of the humidity sensor 1, there is a possibility that the humidity detection of the humidity sensor 1 may be adversely affected due to the dielectric constant of the adhered condensed water. .

  Therefore, in the next step S120 to step S170, the heater 100 is controlled to evaporate the condensed water.

  First, in step S120, counting by a timer is started. As a result, the time elapsed after determining YES in step S100 is counted.

  In the next step S <b> 130, it is determined whether or not a situation in which condensation is generated on the surface 71 of the water-repellent moisture permeable film 70 of the humidity sensor 1 continues.

  Specifically, as in the above step S100, the corrected relative humidity is obtained based on the output voltage of the humidity conversion circuit 91 and the output voltage of the temperature conversion circuit 92, and the obtained corrected relative humidity is the threshold value. It is determined whether or not (for example, 95%) or more.

  When the corrected relative humidity is less than the threshold value, it is determined that the situation is that there is no concern that dew condensation has occurred on the surface 71 of the water-repellent moisture permeable membrane 70 of the humidity sensor 1, and NO is determined. The process proceeds to S170 and the timer is reset.

  When the corrected relative humidity is equal to or higher than the threshold value, it is determined that the situation that there is a concern about the occurrence of condensation on the surface 71 of the water-repellent moisture permeable film 70 of the humidity sensor 1 is determined as YES. The process proceeds to step S140. At this time, it is determined whether the time counted by the timer (hereinafter referred to as a timer value) is greater than a threshold value 1 or not. That is, after determining YES in step S100, it is determined whether or not a predetermined time has elapsed.

  In step S140, when the timer value is smaller than the threshold value 1 (timer value <threshold value 1), NO is determined, and the process returns to step S130. For this reason, as long as the situation in which the condensation of the humidity sensor 1 is a concern continues, the YES determination in step S130 and the timer value determination in step S140 are repeated. Thereafter, when the timer value is equal to or greater than the threshold value 1, it is determined YES in step S140.

  In this embodiment, when a situation in which it is feared that dew condensation has occurred on the surface 71 of the water-repellent moisture permeable membrane 70 of the humidity sensor 1 continues for a predetermined time or more, the surface 71 of the water-repellent moisture permeable membrane 70. Further, it is assumed that dew condensation water adheres over the entire hydrophilic film 80 and all the dew condensation water is connected and held on the surface 71 by surface tension. Then, whether the threshold value 1 is a state in which the dew condensation water adheres to the entire surface 71 of the water-repellent moisture permeable membrane 70 and the entire hydrophilic film 80, and all the dew condensation water is connected and held on the surface 71 by surface tension. This is a value for determining whether or not.

  For this reason, it determines with it being in the state currently hold | maintained on the surface 71 by surface tension by connecting all the dew condensation water adhering over the whole surface 71 of the water-moisture repellent film 70 by determining with YES in said step S140. Will do. Accordingly, in step S150, heating by the heater 100 is started. Specifically, a voltage is applied between the pads 101 and 102 of the heater 100. For example, when the pad 101 is a plus electrode and the pad 102 is a minus electrode, between the pads 101 and 102, the wiring part 110 → wiring part 111 → wiring part 112 → wiring part 113 → wiring part 114 → wiring part 115 → wiring The current flows in the order of the section 116 → the wiring section 117 → the wiring section 118. For this reason, the wiring parts 110, 111... 117, 118 generate heat. The generated heat is transmitted to the water- and moisture-repellent permeable film 70 through the insulating protective films 20 and 21, the measurement electrodes 30a and 30b, the oxide film 40, the insulating protective film 50, the moisture-sensitive film 60, and the like. In addition, heat generated from the wiring portions 110 and 118 is transmitted to the hydrophilic film 80 through the insulating protective film 50.

  Thereafter, in step S160, it is determined whether or not the timer value is greater than threshold value 2 (> threshold value 1). That is, it is determined whether heating by the heater 100 has continued for a predetermined time or more. In step S160, when the timer value is smaller than the threshold value 2, it is determined that the operating time of the heater 100 has not reached the predetermined time, and NO is determined. Accordingly, the process returns to step S160. For this reason, the determination in step S160 is repeated until the operating time of the heater 100 reaches a predetermined time.

  Here, the wiring sections 110, 111, 112, 113, and 114 of the heater 100 gradually increase in electrical resistance in the order of the wiring section 110, the wiring section 111, the wiring section 112, the wiring section 113, and the wiring section 114 as described above. growing. The wiring portions 114, 115, 116, 117, 118 gradually increase in electrical resistance in the order of the wiring portion 118, the wiring portion 117, the wiring portion 116, the wiring portion 115, and the wiring portion 114. Therefore, the amount of heat generated in the wiring portions 110,..., 114 gradually increases in the order of the wiring portion 110, the wiring portion 111, the wiring portion 112, the wiring portion 113, and the wiring portion 114. In the wiring portions 114,..., 118, the amount of generated heat gradually increases in the order of the wiring portion 118, the wiring portion 117, the wiring portion 116, the wiring portion 115, and the wiring portion 114. As described above, the wiring part 114 is located on the other side in the orthogonal direction with respect to the top part 70 </ b> A of the water-repellent moisture permeable film 70. That is, in the heater 100, the amount of generated heat decreases as the wiring portion 114 on the top portion 70A side approaches the wiring portions 110 and 118 on the hydrophilic film 80 side. For this reason, the amount of heat reaching the top portion 70 </ b> A of the water / moisture repellent film 70 is larger than that of the portion other than the top portion 70 </ b> A of the water / moisture repellent film 70. The closer to the outer edge side (that is, the hydrophilic film 80 side), the smaller the amount of heat that reaches.

  Thus, the condensed water is first evaporated at the top portion 70A of the water-repellent moisture permeable membrane 70 by the heat generated from the heater 100, and the outer edge side (that is, hydrophilic) of the surface 71 of the water-repellent moisture permeable membrane 70 with respect to the top portion 70A. On the membrane 80 side, the condensed water evaporates after the top 70A. That is, the closer to the outer edge side (that is, the hydrophilic film 80 side) of the surface 71 of the water-repellent moisture permeable film 70, the slower the condensation water evaporates.

  When the condensation water evaporates, dirt in the condensation water gradually flows to the outer edge side of the surface 71 due to gravity and is gradually collected and enters the groove 80 a of the hydrophilic film 80. Then, finally, the condensed water in the groove 80a evaporates, and the dirt remains as a residue.

  Thereafter, in step S160, when the timer value becomes larger than the threshold value 2 (> threshold value 1), it is determined that the operation time of the heater 100 has reached a predetermined time, YES. Accordingly, in step S170, voltage application between the pads 101 and 102 of the heater 100 is stopped, and heating by the heater 100 is stopped. Thereafter, the timer is reset in step S180 and the process returns to step S100.

  By repeating such processing of step S100 to step S180, the condensed water adhering to the surface of the water-repellent moisture permeable membrane 70 is evaporated by the heating of the heater 100, and dirt is collected in the groove 80a of the hydrophilic film 80. Become. Then, the signal processing circuit 93 is based on the output voltage of the humidity conversion circuit 91 in the state in which the condensed water evaporates and the dirt is collected in the groove 80a of the hydrophilic film 80 as described above. The relative humidity detected by the humidity sensor 1 is obtained, and the obtained relative humidity is corrected by the output voltage of the temperature conversion circuit 92 and output.

  In the present embodiment described above, the signal processing circuit 93 determines whether or not the situation in which condensation is generated on the surface 71 of the water-repellent moisture permeable film 70 of the humidity sensor 1 has continued for a predetermined period or longer. Determine whether. When it is determined that the situation in which the dew condensation has occurred on the surface 71 of the water / moisture repellent film 70 of the humidity sensor 1 has continued for a predetermined period or longer, the surface 71 of the water / moisture repellent film 70 and the hydrophilic film 80 Heating by the heater 100 is started on the assumption that the condensed water adheres to the entire surface and all the condensed water is connected and held on the surface 71 by surface tension.

  Here, the heater 100 has a larger amount of heat reaching the top portion 70 </ b> A of the water-repellent and moisture-permeable film 70 than the other portion other than the top portion 70 </ b> A of the water- and moisture-permeable and moisture-permeable film 70. The heater pattern is such that the amount of heat that reaches the surface 71 becomes closer to the hydrophilic film 80 side (that is, the outer edge side of the comb tooth portions of the measurement electrodes 30a and 30b) from the top portion 70A of the surface 71 of FIG. As a result, the condensed water evaporates first at the top portion 70A of the water-repellent moisture permeable membrane 70, and the condensed water evaporates as it approaches the outer edge side of the top portion 70A of the surface 71 of the water-repellent moisture permeable membrane 70. Becomes slower. As a result, dirt in the condensed water is gradually collected and remains in the groove 80a of the hydrophilic film 80, and finally, the condensed water in the groove 80a evaporates and the dirt remains as a residue. Therefore, as in the above embodiment, the dirt can be kept away from the vicinity of the center of the comb electrode portions of the measurement electrodes 30a and 30b. For this reason, the influence which the stain | pollution | contamination contained in dew condensation water has with respect to the output voltage output from between the electrodes 30a and 30b for measurement can be decreased.

  In the first and second embodiments, the surface 11 of the substrate 10 of the humidity sensor 1 is made to flow to the hydrophilic film 80 side due to the inclination of the surface 71 of the condensed water adhering to the surface 71 of the water-repellent moisture permeable film 70. Although the example has been described so as to be directed upward in the vertical direction, the present invention is not limited to this, and the substrate 10 may be disposed so that one surface 11 thereof is directed in the horizontal direction, or as illustrated in FIG. The substrate 10 may be disposed obliquely with respect to the top-to-bottom direction with the one surface 11 facing upward in the top-to-bottom direction. FIG. 11 shows an example in which the humidity sensor 1 is arranged so that 0 ≦ θ ≦ 90, where θ is the angle formed clockwise with respect to the one surface 11 of the substrate 10 from the top-to-bottom direction.

  In the first and second embodiments described above, the example in which the top portion 70A of the water-repellent moisture permeable film 70 is disposed so as to overlap the vicinity of the center of the comb electrode portions of the measurement electrodes 30a and 30b has been described. First, the surface 71 of the water repellent and water permeable membrane 70 is formed so as to guide the condensed water adhering to the surface 71 of the water repellent and moisture permeable membrane 70 to the outer edge side of the comb electrode portions of the measurement electrodes 30a and 30b. For example, the top portion 70A of the water-repellent moisture permeable membrane 70 may be offset from the vicinity of the center of the comb electrode portion of the measuring electrodes 30a, 30b.

  In the first embodiment, the oxide film 40a is heated to soften the oxide film 40a to form the convex lens-shaped oxide film 40. However, the present invention is not limited to this, and a graduation mask technique for semiconductor manufacturing is used. Etching may be performed on the oxide film 40a to form the oxide film 40a into a convex lens shape. Alternatively, by utilizing the fact that the material becomes a convex lens shape (convex meniscus shape) when the fluid material is dropped, the oxide film 40a is heated to be fluid and then dropped to form a convex lens oxide film. 40 may be formed.

  In the said 1st, 2nd embodiment, when the moisture sensitive film | membrane 60 physically adsorb | sucked water vapor | steam, the example using the humidity sensor 1 from which the electrostatic capacitance between measurement electrodes 30a and 30b changes was shown, Instead of this, a humidity sensor in which the capacitance between the measurement electrodes 30a and 30b changes with the attachment (that is, the action) of water droplets on the sensor surface may be used.

  In the first and second embodiments, the oxide film 40 is formed in a convex lens shape in order to form the surface of the humidity sensor 1 so as to protrude to one side in the direction orthogonal to the substrate 10. Not limited to this, any one of the substrate 10, the insulating protective film 20, the insulating protective film 50, the moisture sensitive film 60, and the water-repellent moisture permeable film 70 may be formed in a convex lens shape.

  In the first and second embodiments, the example in which the humidity sensor 1 is used as the sensor of the present invention has been described. However, instead of this, it acts on a test gas other than water vapor such as carbon monoxide and oxygen to generate dielectric. A gas sensor with a variable rate may be used as the sensor of the present invention.

DESCRIPTION OF SYMBOLS 1 Humidity sensor 10 Board | substrate 20 Insulating protective film 21 Insulating protective film 30a Measuring electrode 30b Measuring electrode 31 Base 32a Tooth part 32b Tooth part 32c Tooth part 33 Base 34a Tooth part 34b Tooth part 40 Oxide film 50 Insulating protective film 51 Insulating protection film Film 52 Insulating protective film 53 Insulating protective film 60 Moisture sensitive film 70 Water-repellent moisture permeable film 70A Top part 71 Surface 80 Hydrophilic film 80a Groove part

Claims (7)

A pair of measurement electrodes (30a, 30b) provided on the substrate (10) and a detection unit (10, 30a, 30b) for detecting capacitance; In the capacitive sensor having comb-shaped electrode portions (32a, 32b, 32c, 34a, 34b) formed so as to be meshed with each other,
The detection part has a top part (70A) that is formed so as to protrude to one side in a direction orthogonal to the substrate and is arranged so as to overlap with the vicinity of the center of the comb electrode part,
The surface shape of the detection part is a shape having an inclination from the top part toward the outer edge side of the comb electrode part, and water adhering to the surface (71) of the detection part follows the inclination by gravity. The capacitive sensor is adapted to move to the outer edge side.   The said detection part has an oxide film (40) formed in the convex shape which is formed so that the said comb-tooth electrode part may be covered, and may become convex on the one side of the orthogonal direction with respect to the said board | substrate. 1. The capacitance type sensor according to 1. The detection unit has a moisture sensitive film (60) formed so as to cover the comb electrode unit,
The electrostatic capacitance according to claim 1 or 2, further comprising a hydrophilic film (80) disposed on an outer edge side of the moisture-sensitive film and formed in a portion surrounding the periphery of the comb electrode portion. Type sensor.   4. The capacitive sensor according to claim 3, wherein the hydrophilic film (80) has a groove that is recessed toward the substrate.   The hydrophilic film (80) is superimposed on the moisture sensitive film (60), and the inner edge pattern of the hydrophilic film superimposed on the moisture sensitive film has a meandering shape reciprocating on the outer edge side of the moisture sensitive film. The capacitance type sensor according to claim 3, wherein   It has a heater (100) formed on the substrate (10), and the heater is formed in a heater pattern in which the vicinity of the top portion of the surface is higher in heat generation temperature than other portions. The electrostatic capacity type sensor according to claim 1 or 2, characterized by the above-mentioned. A control device (93) for controlling the heater in the capacitive sensor according to claim 6,
A determination means (S140) for determining whether or not a condition that causes condensation on the capacitance sensor continues for a certain period of time;
And a control unit (S150) for causing a current to flow through the heater to generate heat from the heater when the determination by the determination unit is affirmative.

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