JPH05232061A - Humidity sensor - Google Patents

Abstract

PURPOSE:To provide a humidity sensor with small characteristic dispersion at mass production whose linearity of output voltage against humidity in a certain range is improved and size is small by directly fixing one humidity-sensitive element and more than two thermistors and a fixed resistor on an insulating substrate with a conductive pattern and a bonding material so as to constitute a circuit. CONSTITUTION:On one face of one porous humidity-sensitive element 2, two electrodes are provided, and an electrode is provided over the whole surface of the other side. More than two thermistors 3 and 4, a fixed resistor 6 and an element 2 are directly fixed to an alumina substrate with a conductive pattern 5 and a bonding material 7 so as to constitute a circuit. Thus, linearity of output voltage against humidity in the rage from 30% RH to 95% RH is improved. Next, as one of the electrode and the whole-surface electrode, and the other electrode and the whole-surface electrode of the element 2 work as two, the size can be reduced. Also, as the element 2 is not in touch with the substrate and the thermistors 3 and 4 other than the contact of the two electrodes, bleeding is eliminated at impregnation of a humidity-sensitive material, dispersion in humidity characteristic is reduced, characteristics in mass production are stabled and responsiveness of a humidity sensor can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor used for humidity control such as air conditioning and cooking.

[0002]

2. Description of the Related Art Conventionally, this type of moisture sensitive element has a structure as shown in the perspective view of FIG. In FIG. 7, 21 is an alumina substrate, 22 is a hole on the alumina substrate, 23 is a moisture sensitive element, and a moisture sensitive material is held in the hole of the moisture sensitive element 23. Reference numeral 24 is a thermistor, 25 is a conductive pattern, and 26 is a platinum lead wire that connects the conductive pattern 25 to the moisture sensitive element 23 and the thermistor 24 by using a conductive bonding material. 27, 28, and 29 are conductive terminals.

The operation of the conventional humidity sensor configured as described above will be described. FIG. 8 is an equivalent circuit of the above-mentioned conventional humidity sensor, where 30 is the impedance of the humidity sensitive element 23, 31 is the impedance of the thermistor 24, 32 is the first terminal corresponding to the conductive terminal 27, and 33 is the conductive terminal 2.
8 is a second terminal corresponding to 8, and 34 is a third terminal corresponding to the conductive terminal 29. Impedance 30 of humidity sensitive element 23
Has a characteristic that it changes according to a change in humidity, but since the impedance also changes with temperature, by configuring in series a thermistor 24 having a temperature characteristic equivalent to the temperature characteristic of the impedance 30 of the humidity sensitive element 23. Monitoring the voltage applied between the first terminal 32 and the third terminal 34, which appears between the first terminal 32 and the second terminal 33 or between the second terminal 33 and the third terminal 34. This makes it possible to stably detect changes in humidity even in an environment where the temperature fluctuates.

The change in the divided voltage with respect to the change in humidity at 25 ° C. of the conventional humidity sensor as described above is as follows.
By applying an AC voltage of Sin wave, 1V, 1 kHz between the second terminal 33 and the third terminal 34 and monitoring the voltage appearing between the second terminal 33 and the third terminal 34, 25 ° C in FIG.
In the response characteristics to the rapid humidity change between 40% RH and 80% RH, the Sin wave, 1 V, and 1 kHz AC voltage are applied between the first terminal 32 and the third terminal 34, and the second terminal By monitoring the change in the voltage appearing between 33 and the third terminal 34, the curves shown in FIG. 10 are obtained.

[0005]

However, since the humidity sensor having the above structure uses the lead wire and the humidity sensing element and the thermistor are formed on the insulating substrate, the area can be smaller than these areas. There is a problem that it cannot be miniaturized because it has no property.

Further, the humidity characteristic of the conventional humidity sensor is 40% RH to 60% RH (at) as already shown in FIG.
25 ° C), the second terminal 33 and the third terminal 34 with respect to humidity
There is linearity of the voltage between and, but otherwise there is no linearity. On the other hand, in recent years, the demand for linearity of the output voltage with respect to humidity at 30% RH to 90% RH has increased, particularly from the market related to air conditioners, which has become a problem.

Further, the response characteristic of the conventional humidity sensor is about 2 although it is different on the adsorption side and the desorption side as already shown in FIG.
It takes about 50 seconds to stabilize, which is a problem.

Further, since the moisture-sensitive element is attached to the insulating substrate, when the moisture-sensitive element is impregnated into the moisture-sensitive element as an aqueous solution, there is a phenomenon that the impregnating liquid causes stains on the insulating substrate to cause characteristic variations. It is a problem above.

The present invention solves these problems and improves the linearity of the output voltage with respect to humidity in the range of 30% RH to 90% RH, and is a miniaturized humidity sensor with small characteristic variations during mass production. Is provided.

[0010]

[Means for Solving the Problems] Solving these problems
Therefore, in the present invention, in the pore portion of the porous body having a large number of pores,
Holds a moisture sensitive material whose electrical resistance changes when it absorbs water
Two electrodes on one side of the moisture sensitive element by coating, vapor deposition, etc., on the other side
One humidity sensitive element with electrodes on the entire surface and two or more thermistors
Conductor and fixed resistor are electrically conductive without using leads on an insulating substrate
Direct fixing using pattern and conductive bonding material
Also, the moisture-sensitive element to be used is coated or vapor-deposited on one side.
Two electrodes, the other surface is provided with an electrode on the entire surface, and the two electrodes are directly disconnected.
It is fixed to the edge board or thermistor and each electrode,
RuO on the other side is full glass electrode ₂ Of conductive material such as
It is conductively bonded to the insulator substrate using a bonding material.
By doing so, one of the two electrodes and the whole electrode, the other and the whole electrode
It has the function of two moisture-sensitive elements called surface electrodes.
It

In the pores of a porous body having a large number of pores, two electrodes are formed by coating or vapor deposition on one surface of a moisture sensitive element holding a moisture sensitive material whose electric resistance changes when absorbing moisture, and the entire surface is formed on the other surface. One moisture-sensitive element having electrodes provided on it, two or more thermistors and fixed resistors are directly fixed on an insulating substrate using a conductive pattern and a conductive bonding material without using leads, and the circuit shown in FIG. Is configured.

The humidity sensing element is not attached to the insulating substrate and the thermistor except for the contacts of the two electrodes, and the two electrodes provided on one surface of the moisture sensing element by coating or vapor deposition make line contact with the respective electrodes of the insulating substrate or the thermistor. Fixed in place.

[0013]

In the present invention, in the pores of a porous body having a large number of pores, two electrodes are formed by coating, vapor deposition or the like on one side of a moisture sensitive element holding a moisture sensitive material whose electric resistance changes when absorbing moisture. On the surface, one humidity sensitive element having electrodes on the entire surface, two or more thermistors and fixed resistors are directly fixed on the insulating substrate by using a conductive pattern and a conductive bonding material without using leads. The humidity-sensitive element to be used has two electrodes by coating or vapor deposition on one side, and electrodes on the other side, and the two electrodes are directly connected.
The insulating substrate or thermistor is fixed to each electrode, and the whole surface electrode on the other surface is conductively bonded to the insulating substrate by using a bonding material of a conductive substance such as RuO ₂ containing glass. The miniaturization can be achieved by making the moisture-sensitive elements for the two electrodes, that is, the entire surface electrode and the other and the entire surface electrode.

In the pores of a porous body having a large number of pores, two electrodes are formed by coating, vapor deposition, etc. on one surface of a moisture sensitive element holding a moisture sensitive material whose electric resistance changes when absorbing moisture, and the other surface is entirely covered. One moisture-sensitive element having electrodes provided on it, two or more thermistors and fixed resistors are directly fixed on an insulating substrate using a conductive pattern and a conductive bonding material without using leads, and the circuit shown in FIG. By configuring 30% RH ~ 9
It is possible to enhance the linearity of the output voltage with respect to humidity at 5% RH.

The humidity sensing element is not attached to the insulating substrate and the thermistor except for the contacts of the two electrodes, and the two electrodes provided on one surface of the moisture sensing element by coating or vapor deposition are in line contact with the respective electrodes of the insulating substrate or the thermistor. By fixing the humidity sensor with the humidity sensor, it is possible to eliminate the bleeding when the moisture sensitive material is impregnated, reduce variations in humidity characteristics, stabilize characteristics during mass production, and improve the response characteristics of the humidity sensor.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1, 2 and 3 are a perspective view, an AA sectional view and a BB sectional view in an embodiment of the present invention. In FIGS. 1, 2 and 3, 1 is an alumina substrate, 2 is a humidity sensitive element, and MgCrO ₄ —Ti is used in this experimental example.
A MgCrO ₄ —TiO ₂ -based polycrystal having a porosity of 35% obtained by firing the O ₂ -based mixture in air at 1300 ° C. for 2 hours was used. Reference numeral 11 is a porous electrode, and two electrodes are provided on one surface of the moisture sensitive element 2.
An electrode is provided on the entire other surface, and in this experimental example, R
The uO ₂ paste was screen-printed and baked at 800 ° C. for 10 minutes to form the porous electrode 11. 3 and 4 are thermistors, and in this experimental example, 3 to 7 kΩ (at 25 ° C.)
Then, an NTC thermistor having a B constant of 4300 and a B constant of 4300 at 20 kΩ (at 25 ° C.) was used. 12 and 13 are formed on both side surfaces of the thermistors 3 and 4, respectively.
The electrodes 12 and 13 made of Pd are formed by printing on the thermistors 3 and 4 by screen printing or the like, and then baking at 800 to 850 ° C. At this time, the thickness of each of the electrodes 12 and 13 is 10 μm.
It is a degree. Reference numeral 5 is a conductive pattern, and Ag-P is used in this experimental example.
The d paste was screen-printed and baked at 800 ° C. for 10 minutes to form it. 6 is a fixed resistor, which is R in this experimental example.
The glaze resistance of uO ₂ was used and the resistance value was adjusted to 1 MΩ. 7 is a conductive bonding material, which is RuO ₂ in this experimental example.
An inorganic adhesive made of glass and glass was used. 8, 9, 10
Are conductive terminals, respectively.

After the above assembly, the moisture sensitive element 2 is impregnated with a 5% aqueous solution of sodium polyacrylate having a degree of polymerization of 2000 to 5000 as a moisture sensitive material, and then the moisture sensitive element 2 is heated to 40 ° C.
After drying for 5 hours, the humidity sensor was formed by holding it in the pores of the moisture sensitive element 2 which is a porous body.

The operation of the humidity sensor constructed as above will be described below. FIG. 4 is an equivalent circuit of the humidity sensor according to the above-described embodiment, in which 14a and 14b are two impedances of the humidity sensitive element 2 and 14a and 14b are substantially the same value. 15 is the impedance of the fixed resistor 6, 16
Is the impedance of the thermistor 3 and 17 is the thermistor 4
Impedance, 18 is the first corresponding to the conductive terminal 8.
Terminals, 19 are second terminals corresponding to the conductive terminals 9, and 20 are third terminals corresponding to the conductive terminals 10. As shown in FIG. 5, the humidity characteristic of the humidity sensor at 25 ° C. is 30% RH as compared with the humidity characteristic of the conventional humidity sensor (FIG. 9).
The linearity at 0% RH is improved. The humidity characteristic is that Sin wave, 1V, 1k is applied between the first terminal 18 and the third terminal 20.
AC voltage of Hz is applied to the second terminal 19 and the third terminal 20.
The voltage is monitored during the period between. The response characteristic is as shown in FIG. 6, which is improved as compared with the response characteristic of the conventional humidity sensor (FIG. 10). The response characteristic is that the Sin is between the first terminal 18 and the third terminal 20 of the humidity sensor.
Waves, 1V, 1kHz AC voltage is applied, and the humidity sensor is left in an atmosphere of 25 ° C and 40% RH for 30 minutes while monitoring the voltage divided between the second terminal 19 and the third terminal 20. , Put it in the atmosphere of 80% RH,
The minute voltage change with time between the second terminal 19 and the third terminal 20 at that time was measured.

As described above, this humidity sensor can be assembled by stacking parts without using lead wires.
The size can be reduced by using two moisture sensitive elements as one moisture sensitive element. In addition, since the moisture-sensitive element is in line contact with the alumina substrate and the thermistor and is not in contact with anything else, the contact area is small, and the moisture-sensitive material does not leak from the moisture-sensitive element when impregnated with the moisture-sensitive element.

When 30 units of the conventional humidity sensor and 30 units of the humidity sensor of the present invention are manufactured and the divided voltage value between the second terminal and the third terminal at 25 ° C. and 60% RH is examined, it becomes as shown in (Table 1). It can be seen that the variation is smaller than that of the conventional humidity sensor.

[0022]

[Table 1]

In the present experimental example, the moisture sensitive element 2 is made of MgCrO.
_{Although the 4-} TiO ₂ -based porous polycrystal (ceramics) was used, it goes without saying that other ceramics, inorganic substances, and organic substances can also be used as long as they are porous bodies that can be impregnated with the moisture sensitive material.

In this embodiment, Ru is used as a fixed resistor.
Although the O ₂ glaze resistance is used, it is needless to say that any shape and any material such as a square chip resistor and a melf type chip resistor can be used as long as a predetermined resistance value can be secured.

Further, the impedance 15 of the fixed resistor, the impedance 16 of the thermistor 3 and the impedance 17 of the thermistor 4 shown in FIG. 4 have the above-mentioned values in this experimental example. As a result, the humidity of FIG. Any combination can be used as long as the characteristics can be realized.

Further, sodium polyacrylate was used as the moisture sensitive material, but the resistance is changed with respect to the change of humidity, and it is not limited to the inorganic substance and the organic substance as long as it can impregnate the pores of the porous body. Anything can be used.

[0027]

INDUSTRIAL APPLICABILITY As described above, the pores of a porous body having a large number of pores are coated or vapor-deposited on one side of a moisture sensitive element holding a moisture sensitive material whose electric resistance changes when water is absorbed. Electrodes, one humidity sensitive element with electrodes on the other side, two or more thermistors and fixed resistors are directly fixed on the insulating substrate by using conductive patterns and conductive bonding materials without using leads. Also, the humidity sensitive element to be used has two electrodes on one side by coating, vapor deposition, etc., and electrodes on the other side are directly attached to the insulating substrate or thermistor and each electrode, and the entire surface of the other side is fixed. The electrodes are conductively bonded to the insulating substrate by using a bonding material of a conductive substance such as RuO ₂ containing glass, so that the humidity sensitive element for two electrodes, one of the two electrodes and the whole electrode, and the other and the whole electrode. By acting as a The sensor can be miniaturized.

In addition, in the pores of the porous body having a large number of pores, the humidity sensitive element holding the moisture sensitive material whose electric resistance changes when absorbing moisture is applied to one surface of the moisture sensitive element, and two electrodes are applied to the other surface by vapor deposition or the like. Shows that one humidity sensitive element with electrodes on the entire surface and two or more thermistors and fixed resistors are directly fixed on the insulating substrate using conductive patterns and conductive bonding materials without using leads. 30% by configuring the circuit shown
It was possible to improve the linearity of the output voltage with respect to humidity at RH to 95% RH.

The moisture-sensitive element is not attached to the insulating substrate and the thermistor except for the contact of two electrodes, and the two electrodes provided on one surface of the moisture-sensitive element by coating or vapor deposition make line contact with the respective electrodes of the insulating substrate or the thermistor. By fixing the humidity sensor, it was possible to eliminate bleeding when impregnating the moisture-sensitive material, reduce variations in humidity characteristics, stabilize characteristics during mass production, and improve the response characteristics of the humidity sensor.

[Brief description of drawings]

FIG. 1 is a perspective view of a humidity sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of the humidity sensor according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view taken along the line BB of the humidity sensor according to the embodiment of the present invention.

FIG. 4 is an equivalent circuit diagram of a humidity sensor according to an embodiment of the present invention.

FIG. 5 is a graph of humidity characteristics at 25 ° C. of a humidity sensor according to an embodiment of the present invention.

FIG. 6 is a graph of response characteristics of a humidity sensor according to an embodiment of the present invention.

FIG. 7 is a perspective view of a conventional humidity sensor.

FIG. 8 is an equivalent circuit diagram of a conventional humidity sensor.

FIG. 9 is a graph of humidity characteristics of a conventional humidity sensor at 25 ° C.

FIG. 10 is a graph of response characteristics of a conventional humidity sensor.

[Explanation of Codes] 1 Alumina substrate 2 Moisture sensitive element 3 Thermistor 4 Thermistor 5 Conductive pattern 6 Fixed resistor 7 Conductive bonding material 8 Conductive terminal 9 Conductive terminal 10 Conductive terminal 11 Porous electrode 12 Ag-Pd electrode 13 Ag-Pd electrode 14a Impedance 14b Impedance 15 Impedance 16 Impedance 17 Impedance 18 First terminal 19 Second terminal 20 Third terminal 21 Alumina substrate 22 Hole 23 Moisture sensitive element 24 Thermistor 25 Conductive pattern 26 Lead wire 27 Conductive terminal 28 Conductive Sex terminal 29 conductive terminal 30 impedance 31 impedance 32 first terminal 33 second terminal 34 third terminal

Front page continuation (72) Inventor Ryoichi Makimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Tetsuji Tsuji, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. Inventor Hiromitsu Taki 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A porous body having a large number of pores, wherein an electrode is provided on one side of a moisture sensitive element holding a moisture sensitive material whose electric resistance changes when absorbing moisture, and an electrode is formed on the entire other side. A humidity sensor characterized in that one humidity sensitive element provided with, two or more thermistors and a fixed resistor are directly fixed on an insulating substrate by using at least one of a conductive pattern and a conductive bonding material. 2. A moisture-sensitive element is coated on one side by vapor deposition or the like.
An electrode is provided on the entire surface of the other surface, and the two electrodes are directly fixed to the insulating substrate or the thermistor and the respective electrodes. The entire surface of the other surface is made of a glass-containing RuO ₂ or other conductive material bonding material. The humidity sensor according to claim 1, wherein the humidity sensor serves as two humidity-sensitive elements, one of the two electrodes and the entire surface electrode, and the other of the two electrodes, the other surface and the entire surface electrode, by being conductively connected to the insulating substrate. 3. The humidity sensor according to claim 1, wherein the humidity sensitive element is not in contact with the insulating substrate and the thermistor except for the contacts of the two electrodes. 4. The two electrodes provided on one surface of the moisture sensitive element by coating, vapor deposition or the like are fixed in line contact with the respective electrodes of the insulating substrate or the thermistor.
The described humidity sensor.