JP2016180601A - Humidity detection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a humidity detection unit that has a humidity sensor installable in a situation in which foreign substances are not easily attached.SOLUTION: A humidity sensor 5 is equipped to a first surface 2a of a substrate 2. On the first surface 2a, a case 10 is provided to cover the humidity sensor 5 and a leg part 11 extending downward from a side plate of the case 10 is interposed in the inside of a through-hole 3 penetrating the substrate 2. Between the through-hole 3 and the leg part 11, a ventilation path 4 is formed leading to the inside of the case 10. Further, the spaces between the side plates of the case 10 and the first surface 2a of the substrate 2 are sealed with a resin material 13.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a humidity detection unit in which a humidity sensor is mounted on a substrate.

Humidity sensors are used in various electrical and electronic products such as air conditioners and refrigerators.
As described in Patent Document 1, in the humidity sensor, a moisture-sensitive polymer that absorbs and releases moisture is disposed between the electrodes. The moisture-sensitive polymer has a dielectric constant that changes depending on the moisture held, and the humidity of the outside air to which the humidity sensor is exposed is measured by measuring the capacitance between the electrodes.

  Since the humidity sensor needs to be exposed to the outside air, in Patent Document 1, the conductive wires, ICs, and the like are covered with resin, but the sensor chip adopts a structure exposed to the outside air.

  Patent Document 2 describes an invention related to a gas sensor. In this gas sensor, a gas detection element is housed in a concave portion of a wiring board formed of a multilayer board. The wiring board and the gas detection element are covered with a protective cover, and a plurality of vent holes are formed in the protective cover.

International publication WO2010 / 113712 A1 JP 2012-2721 A

  The humidity sensor uses a moisture-sensitive polymer whose dielectric constant changes depending on the amount of moisture to be held, but this moisture-sensitive polymer has a problem of affecting the dielectric constant when foreign matter adheres. For example, if an organic substance such as oil or fat adheres as a foreign substance, the dielectric constant changes regardless of the retained moisture, and once attached organic substance does not easily leave, an error is always included in the measured humidity value. It will be.

  In the humidity sensor described in Patent Document 1, since the sensor chip is always exposed to the outside air, there is a very high possibility that foreign substances such as organic substances adhere to the moisture-sensitive polymer.

  It is also conceivable that the sensor chip of the humidity sensor is replaced with a gas detection element described in Patent Document 2 and the sensor chip of the humidity sensor is covered with a protective cover. However, in the protective cover shown in Patent Document 2, there is a high possibility that foreign matter entering from the through hole directly touches the sensor chip.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a humidity detection unit that can mount a humidity sensor in a state in which foreign matter hardly adheres.

The present invention provides a humidity detection unit in which a humidity sensor is mounted on one surface of a substrate.
A through hole is formed in the substrate;
A case that covers the humidity sensor is attached to the surface of the substrate, a leg portion provided in the case is inserted into the through hole, and at least a part of a side plate portion of the case and the surface of the substrate The gap is closed with resin material,
An air passage for allowing outside air to flow into the case is formed between the through hole and the leg portion.

  In the humidity detection unit of the present invention, the through hole has an outer inner wall and an inner inner wall, the leg portion is in contact with the outer inner wall, and the interior of the case is between the inner inner wall and the leg portion. It is preferable that the air passage that leads to is formed.

  In this case, it is preferable that the leg portion is elastically deformed and pressed against the outer inner wall when inserted into the through hole.

  The humidity detection unit of the present invention can be configured such that an electronic element is mounted in a region not covered with the case on the surface of the substrate, and the electronic element is covered with a resin material.

  In the humidity detection unit of the present invention, a humidity sensor is mounted on one surface of a substrate, and the humidity sensor is covered with a case, and a leg portion of the case is mounted in a through hole of the substrate. Therefore, it is difficult for foreign matter to enter directly into the case from the surface side of the substrate. Further, since the air passage is formed inside the through hole, the outside air is given to the humidity sensor from the other surface side of the substrate through the air passage. Since the air passage has an inflow distance corresponding to the thickness dimension of the substrate, when the humidity detection unit is held by hand, it is difficult for organic substances such as oil and fat adhering to the finger to reach the humidity sensor. . For this reason, the detection accuracy of the humidity sensor can always be kept high.

The perspective view which shows the whole structure of the humidity detection unit of embodiment of this invention, 1 is an exploded perspective view of the humidity detection unit shown in FIG. Sectional drawing which cut | disconnected the humidity detection unit shown in FIG. 1 by the III-III line | wire, FIG. 3 is an enlarged cross-sectional view of a part of FIG.

  As shown in FIGS. 1 to 4, the humidity detection unit 1 according to the embodiment of the present invention has a substrate 2. The substrate 2 is a glass epoxy substrate, and has a first surface 2a facing upward in each figure and a second surface 2b facing downward in the opposite direction. A wiring pattern is formed of copper foil on the first surface 2a. The humidity sensor 5 and various electronic elements described below are connected on a wiring pattern, and an electronic circuit is configured by the humidity sensor 5, various electronic elements, and the wiring pattern.

  As shown in FIGS. 2 and 3, a humidity sensor 5 is mounted on the first surface 2 a of the substrate 2. The humidity sensor 5 is a humidity sensor chip, and has a pair of electrodes provided on the surface of a small substrate and a moisture sensitive polymer sandwiched between the electrodes.

  The electrodes forming a pair are arranged at intervals in a direction along the surface of the surface of the small substrate, and the moisture-sensitive polymer between the electrodes is arranged on the surface. Alternatively, the electrode, the moisture-sensitive polymer, and the electrode are three-dimensionally stacked in the direction perpendicular to the surface of the small substrate.

  The moisture-sensitive polymer has a function of absorbing and releasing moisture according to the humidity of the outside air, and the dielectric constant of the moisture-sensitive polymer changes depending on the amount of moisture contained. In the humidity sensor 5, the moisture-sensitive polymer is exposed to the outside air on a small substrate.

  The humidity sensor 5 has a plurality of terminal portions electrically connected to the electrodes on the lower surface of the small substrate, and each terminal portion is soldered to a wiring pattern formed on the first surface 2a. Has been.

  Electronic elements 6 a and 6 b such as IC elements are mounted on the first surface 2 a of the substrate 2 along with the humidity sensor 5. The terminal portions of the electronic elements 6a and 6b are also soldered to the wiring pattern formed on the first surface 2a.

  A case 10 covering the humidity sensor 5 and the electronic elements 6a and 6b is mounted on the first surface. Case 10 is formed of a synthetic resin or a metal plate. The case 10 of the embodiment is made of synthetic resin. The case 10 is a cube that is open at the bottom, and has a ceiling plate portion 10a and four side plate portions 10b, 10c, 10d, and 10e.

  The two side plate portions 10b and 10c facing the case 10 are integrally formed with a leg portion 11 projecting downward from the skirt portion 12 of the case. A latching claw 11 a that protrudes outward from the case 10 is integrally formed at the lower end of the leg 11.

  As shown in FIGS. 2 and 3, the substrate 2 is formed with a pair of through holes 3 and 3. The through holes 3 and 3 are formed at positions sandwiching a region where the humidity sensor 5 and the electronic elements 6a and 6b are mounted. As shown in FIG. 2, the opening shape of each through-hole 3 and 3 is a rectangle (rectangle).

  As shown in FIGS. 3 and 4, each through hole 3 has an outer inner wall 3 a located on the outer surface side of the case 10 and an inner inner wall 3 b located on the inner side of the case 10.

  The case 10 is attached to the first surface 2a of the substrate 2 so as to cover the humidity sensor 5 and the electronic elements 6a and 6b. At this time, the pair of leg portions 11 and 11 are inserted into the through holes 3 and 3 formed in the substrate 2. The legs 11 have elasticity and are inserted into the through holes 3 with an external force applied so as to narrow the interval between them. Therefore, the leg 11 after being inserted into the through hole 3 is given an elastic force E toward the outer inner wall 3a of the through hole 3, and the leg 11 is pressed against the outer inner wall 3a. A latching claw 11 a at the lower end of 11 is latched on the second surface 2 b of the substrate 2.

  As shown in an enlarged view in FIG. 4, as a result of the leg 11 being pressed against the outer inner wall 3 a, an air passage 4 is formed between the inner inner wall 3 b of the through hole 3 and the leg 11. Since the air passage 4 is open on the inner surface side of the leg 11, the outside air A on the second surface 2b side of the substrate 2 is guided to the internal space of the case 10 through the air passage 4, It is given to the humidity sensor 5.

  As shown in FIG. 4, there is a portion where a gap δ <b> 2 is formed between the skirt 12 of the case 10 and the first surface 2 a of the substrate 2, and the width dimension of the air passage 4 with respect to the gap δ <b> 2. δ1 is formed wider. As shown in FIGS. 1, 3, and 4, on the first surface 2 a of the first substrate 2, the space between the lower ends of the side plate portions 10 b, 10 c, 10 d, and 10 d of the case 10 and the first surface 2 a is obtained. The resin material 13 is supplied to the gap δ2 between the skirt portion 12 and the first surface 2a.

  The resin material 13 is preferably a resin having moisture resistance, that is, water resistance, and is composed of a polyimide resin or an epoxy resin. By applying the resin material 13, the gap δ <b> 2 between the skirt portion 12 of the case 10 and the first surface 2 a can be sealed, and foreign matter or the like is not easily mixed into the case 10 from the first surface 2 a side. Become.

  The resin material 13 preferably closes the entire circumference of the skirt portion 12 of the case 10 in the entire region of the side plate portions 10b, 10c, 10d, and 10e. However, the resin material 13 may be partially applied to a necessary portion without being applied to a portion where the gap δ2 between the skirt portion 12 and the first surface 2a is narrow.

  As shown in FIG. 2, since the through holes 3 and 3 are formed at positions sandwiching the area where the humidity sensor 5 and the electronic elements 6 a and 6 b are mounted, the leg portions 11 and 11 are formed in the through holes 3 and 3. Is inserted in the direction in which the pair of leg portions 11 and 11 are pressed against each other toward the outer inner wall 3a by the elastic force E that urges the leg portions 11 and 11 toward the outer inner wall 3a of the through holes 3 and 3. The case 10 can be fixed to the board 2 without rattling (reliably), and an air passage through which outside air flows into the case 10 between the legs 11 and 11 and the inner inner wall 3b is ensured. Can be formed.

  As shown in FIGS. 1 and 2, an electronic element 21 is mounted on the first surface 2 a of the substrate 2 on the outside of the case 10. The electronic element 21 is a chip electronic component such as a resistor or a capacitor or an IC element. These electronic elements 21 are connected to a wiring pattern formed on the first surface 2a. These electronic elements 21 are covered with a resin material 23, which is formed of the same material as the resin material 13.

  A connector portion 25 is formed on the first surface 2 a of the substrate 2, and each wiring pattern is connected to the connector portion 25. A mounting hole 26 is opened in the substrate 2 as necessary.

  The humidity detection unit 1 is housed inside various electric products and electronic devices, and the substrate 2 is fixed inside the product using mounting holes 26 and the like.

  The humidity detection unit 1 is installed in a place where the outside air where humidity is to be measured is touched. The outside air A hardly enters the inside of the case 10 from the first surface 2a of the substrate 2, and the through hole 3 penetrating the substrate 2 from the second surface 2b side of the substrate 2 as shown in FIG. It enters the inside of the case 10 through the internal ventilation path 4. Since the leg portion 11 extending from the case 10 is pressed against the outer inner wall 3 a of the through hole 3 by the elastic force E, the air passage 4 leading to the inside of the case 10 is surely provided between the inner inner wall 3 b and the leg portion 11. It can be opened.

  However, the ventilation path 4 has a path length corresponding to the thickness of the substrate 2, and the outside air on the second surface 2 b side passes through the inside of the ventilation path 4 and then reaches the inside of the case 10. Foreign matter such as fats and oils and other organic substances is difficult to reach the humidity sensor 5 from the second surface 2b side. On the other hand, the foreign matter reaching the first surface 2 a of the substrate 2 is blocked by the resin material 13 and is difficult to enter the case 10.

  Therefore, it is possible to reduce the possibility of foreign matter adhering to the moisture-sensitive polymer provided in the humidity sensor 5 and to maintain high detection accuracy of the humidity sensor 5.

DESCRIPTION OF SYMBOLS 1 Humidity detection unit 2 Board | substrate 2a 1st surface 2b 2nd surface 3 Through-hole 3a Outer inner wall 3b Inner inner wall 4 Air passage 5 Humidity sensor 6a, 6b, 21 Electronic element 10 Case 10b, 10c, 10d, 10e Side plate part 11 Leg part 11a Hanging claw 12 Bottom part 13, 23 Resin material

Claims (4)

In the humidity detection unit where the humidity sensor is mounted on one surface of the board,
A through hole is formed in the substrate;
A case that covers the humidity sensor is attached to the surface of the substrate, a leg portion provided in the case is inserted into the through hole, and at least a part of a side plate portion of the case and the surface of the substrate The gap is closed with resin material,
A humidity detection unit, wherein an air passage through which outside air flows into the case is formed between the through hole and the leg.   The through hole has an outer inner wall and an inner inner wall, the leg portion is in contact with the outer inner wall, and the air passage leading to the inside of the case is formed between the inner inner wall and the leg portion. The humidity detection unit according to claim 1.   The humidity detection unit according to claim 2, wherein the leg portion is elastically deformed and pressed against the outer inner wall when inserted into the through hole.   The humidity detection unit according to any one of claims 1 to 3, wherein an electronic element is mounted on a surface of the substrate that is not covered with the case, and the electronic element is covered with a resin material.

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