JPH0658900A - Moisture sensor - Google Patents

Abstract

PURPOSE:To enhance response and mass productivity by forming a dielectric film on a conductive substrate and forming a moisture-sensitive film thereon. CONSTITUTION:50ml of ethylsilicate (Si(OC2H5)4) is added with 34ml of ethanol and 16ml of 0.02N hydrochloric acid, for example, and stirred for one hour to produce a solution which is then applied on a stainless steel substrate 1 through spin coating and heat treated at 300 deg.C for one hour thus forming an SiO2 dielectric film 2 on the stainless steel substrate 1. On the other hand, 100ml of water is added with 100ml of ethanol, 80g of manganese acetate, 20g of lead acetate, 10g of potassium acetate, and stirred for one hour to prepare a moisture-sensitive coating liquid. The stainless steel substrate 1 formed with the dielectric film 2 is then dip coated with the moisture-sensitive coating liquid and heat treated at 500 deg.C for one hour thus forming a moisture-sensitive film 3 on the dielectric film 2. Ag paste is then screen printed on the moisture- sensitive film 3 to form a comb type electrodes 4. Since a moisture-sensitive film 3 is formed on the dielectric film 2 formed on a substrate 1, thermal response is enhanced, an inexpensive large substrate can be used and mass productivity is enhanced, resulting in unit cost reduction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity sensor for detecting humidity by changing electric characteristics of an element in response to humidity.

[0002]

2. Description of the Related Art In recent years, the number of fields requiring humidity measurement and humidity control has increased, and the importance of humidity sensors has come to be recognized.

Humidity sensors that detect humidity by changing the electrical characteristics of the element in response to humidity include electrolyte-based, metal-based, polymer-based, and ceramic-based humidity sensors, and various systems have been studied. However, polymer and ceramic humidity sensors are currently in practical use. All of them utilize the property that the resistance value or capacitance of the element changes due to the adsorption and desorption of water with respect to the element.

An insulator such as alumina or glass is used for the substrate, and a comb-shaped electrode or a moisture sensitive film is formed on this substrate.
A sandwich type structure in which a lower electrode, a moisture sensitive film and an upper electrode are formed on a substrate is generally used.

[0005]

However, the conventional humidity sensor has a problem that the alumina substrate is more expensive than a conductive substrate such as silicon, and the glass substrate is weak against heat and is easily broken. Further, in order to manufacture a sensor inexpensively and in a large amount, it is desirable to make a large number of elements on a large-sized substrate and then cut and use them, but a substrate such as alumina or glass has a problem such as warpage and is large. There was no cheap board. Furthermore, since the insulator has a smaller thermal conductivity than the conductor, there is a problem that the thermal response of the humidity sensor becomes slow.

[0006]

The humidity sensor of the present invention comprises:
An insulating film is formed on a conductive substrate, and a moisture sensitive film is formed on the insulating film. The humidity sensor of the present invention is characterized in that an insulating film is formed on a conductive substrate, an electrode is formed on the insulating film, and a moisture sensitive film is formed on the insulating film on which the electrode is formed. . In the humidity sensor of the present invention, an insulating film is formed on a conductive substrate, an electrode is formed on the insulating film, a moisture sensitive film is formed on the electrode, and an electrode is formed on the moisture sensitive film. It is characterized by

When at least one terminal portion is on the surface opposite to the moisture sensitive film with respect to the conductive substrate, the space factor is good, the cost is low, and the application to small equipment is easy.
In this case, the electrode on the surface of the conductive substrate on the moisture sensitive film side and the terminal portion on the surface on the side opposite to the moisture sensitive film are formed through holes formed in the conductive substrate or an insulating film on the side surface of the conductive substrate. Is formed, and a conductive path is formed on this insulating film so that they are electrically connected. Also,
The electrode on the surface of the conductive substrate facing the moisture sensitive film and the terminal on the surface of the conductive substrate opposite to the moisture sensitive film may be electrically connected by utilizing the conductivity of the conductive substrate. .

The conductive substrate may be a metal plate such as stainless steel, copper or aluminum, or conductive ceramics. When silicon is used for the conductive substrate, a silicon process suitable for mass production can be used, which is preferable in terms of mass productivity and reliability.

By forming the fluorine-containing polymer film so that at least the moisture-sensitive film is entirely covered, a highly reliable humidity sensor whose characteristics do not change even when immersed in an electrolyte solution can be obtained. it can.

[0010]

【Example】

(Example 1) Ethyl silicate _{(Si (OC 2 H 5)} 4) 5
34 ml of ethanol and 16 ml of 0.02N hydrochloric acid in 0 ml
Was added and spin-coated with a solution stirred for 1 hour and heat-treated at 300 ° C. for 1 hour to form a SiO ₂ insulating film on the stainless plate.

Next, 100 ml of water was added to 100 ml of ethanol.
ml, 80 g of manganese acetate, 20 g of lead acetate, and 10 g of potassium acetate were added, and the mixture was stirred for 1 hour to prepare a coating liquid for moisture-sensitive film.

The stainless steel plate having the insulating film formed thereon is dip-coated with this moisture-sensitive film coating solution,
A moisture sensitive film was formed on the insulating film by heat treatment at 500 ° C. for 1 hour. A comb-shaped electrode was formed on the moisture-sensitive film by screen-printing an Ag paste.

A cross-sectional view of the humidity sensor thus manufactured is shown in FIG. In FIG. 1, 1 is a substrate (stainless plate), 2 is an insulating film, 3 is a moisture sensitive film, and 4 is an electrode. The humidity sensitivity characteristics of this humidity sensor are shown in FIG.

Example 2 SiO ₂ was sputtered on a silicon substrate to form an insulating film. Cr, Cr,
Au was vapor-deposited to form a comb-shaped electrode. The silicon substrate was screen-printed with the coating liquid for a moisture-sensitive film used in Example 1 and heat-treated at 700 ° C. for 1 hour,
A moisture sensitive film was formed on the insulating film on which the comb electrodes were formed. A cross-sectional view of the humidity sensor thus manufactured is shown in FIG. In FIG. 3, 1 is a substrate, 2 is an insulating film, 3 is a moisture sensitive film, and 4 is an electrode.

FIG. 4 shows the humidity-sensitive characteristics of this humidity sensor. It can be seen from FIG. 4 that the humidity sensor of the present invention has a low resistance value, an appropriate change width of the resistance value, and the characteristics do not change with temperature, and thus is easy to use. The humidity sensor was left for 1000 hours in a constant temperature and humidity chamber at 60 ° C. and 90%, and the characteristics were measured. Therefore, it can be seen that this humidity sensor has high durability and reliability. Also, the response to temperature change is 1.
Within 0 seconds, the response to changes in humidity was sufficiently fast, within 5 seconds. Further, since the humidity sensor has a simple manufacturing process, it can be easily mass-produced and can be manufactured at low cost.

(Example 3) The humidity sensor prepared in Example 2 was covered with a solution (7% by weight) of a solvent-soluble fluorine-containing polymer dissolved in a perfluoro solvent so that at least the portion of the moisture-sensitive film was covered. Screen-printed on 180 ℃
And heat-treated for 1 hour to form a fluorine-containing polymer film. A cross-sectional view of the humidity sensor thus manufactured is shown in FIG.
In FIG. 5, 1 is a substrate, 2 is an insulating film, 3 is a moisture sensitive film, 4
Is an electrode, and 5 is a fluorine-containing polymer film. The characteristics of this humidity sensor were similar to those of the humidity sensor manufactured in Example 2. After the humidity sensor was immersed in a saturated saline solution at 60 ° C. for 100 hours and then the characteristics were measured, it was the same as in FIG. 4 within the measurement error range. Therefore, it can be seen that this humidity sensor is extremely durable and highly reliable.

(Example 4) Si ₃ N ₄ was sputtered on a silicon substrate to form an insulating film. Pt was sputtered on this insulating film to form an electrode. The silicon substrate was spin-coated with the coating liquid for a moisture-sensitive film used in Example 1 and heat-treated at 700 ° C. for 1 hour to form a moisture-sensitive film on the electrode. Furthermore, on this moisture sensitive film, P
t was sputtered to form electrodes, and the humidity sensor shown in FIG. 6 was manufactured. In FIG. 6, 1 is a substrate, 2 is an insulating film, 3
Is a moisture sensitive film, and 4 is an electrode. FIG. 7 shows the humidity-sensitive characteristics of this humidity sensor.

Example 5 A through hole was opened in a silicon substrate, and this silicon substrate was heat-treated at 1100 ° C. for 4 hours to oxidize the surface and form a SiO ₂ insulating film. A comb-shaped electrode is provided on one surface of the silicon substrate, a terminal portion is provided on the opposite surface, and a conductive path is provided in the through hole.
It was formed by sputtering Au. The silicon substrate was roll-coated with the moisture-sensitive film coating solution used in Example 1 and heat-treated at 700 ° C. for 1 hour to form a moisture-sensitive film on the insulating film having the comb-shaped electrodes. A cross-sectional view of the humidity sensor thus manufactured is shown in FIG. In FIG. 8, 1 is a substrate, 2 is an insulating film, 3 is a moisture sensitive film, 4 is an electrode, 6 is a through hole, 7 is a conductive path, and 8 is.
Is a terminal part. FIG. 9 shows the humidity sensitivity characteristic of this humidity sensor.

Example 6 A SiO ₂ film was formed on a silicon substrate by CVD to form an insulating film. A comb-shaped electrode was formed on one surface of the silicon substrate, a terminal portion was formed on the opposite surface, and a conductive path was formed on the side surface by plating Au. The silicon substrate was spray-coated with the moisture-sensitive film coating solution used in Example 1, and the coating was performed at 700 ° C. for 1 hour.
By heat treatment for a time, a moisture sensitive film was formed on the insulating film on which the comb-shaped electrodes were formed. A cross-sectional view of the humidity sensor thus manufactured is shown in FIG. In FIG. 10, 1 is a substrate, 2 is an insulating film, 3 is a moisture sensitive film, 4 is an electrode, 7 is a conductive path, and 8 is a terminal portion. The humidity sensitivity characteristics of this humidity sensor were similar to those of the humidity sensor manufactured in Example 5.

Example 7 SiO ₂ was sputtered on a silicon substrate to form an insulating film. However, a part was masked so that the insulating film was not formed. By screen-printing Au paste on this insulating film,
A comb-shaped electrode was formed. One of the comb-shaped electrodes was provided with a terminal portion on the insulating film, and the other was connected to a portion where the insulating film was not formed. Then, another terminal portion was formed on the surface of the silicon substrate opposite to the comb-shaped electrode. This silicon substrate was spin-coated with the coating liquid for moisture-sensitive film used in Example 1 and heat-treated at 700 ° C. for 1 hour to form a moisture-sensitive film on the insulating film on which the comb-shaped electrodes were formed. A cross-sectional view of the humidity sensor thus manufactured is shown in FIG.
Shown in 1. In FIG. 11, 1 is a substrate, 2 is an insulating film, 3
Is a moisture sensitive film, 4 is an electrode, and 8 is a terminal portion. The humidity sensitivity characteristics of this humidity sensor were similar to those of the humidity sensor manufactured in Example 5.

Although the ceramic moisture sensitive film is used in this embodiment, a ceramic moisture sensitive film of another component or a polymer moisture sensitive film may be used. Further, in this embodiment, the humidity is detected by the resistance value, but it may be detected by the capacitance.

[0022]

As described above, in the humidity sensor of the present invention, since the insulating film is formed on the conductive substrate and the moisture sensitive film is formed on the insulating film, the thermal response becomes fast and
Large, cheap substrates can be used, mass productivity is improved, and the cost per unit is reduced. Also, at least one terminal portion,
When it is on the surface opposite to the moisture-sensitive film with respect to the conductive substrate, it has a good space factor, is inexpensive, and can be easily applied to small devices. Also, if silicon is used for the conductive substrate,
A highly reliable mass-produced humidity sensor can be obtained. further,
When the fluorine-containing polymer film is formed so that at least the portion of the moisture-sensitive film is covered, it is possible to obtain a highly reliable humidity sensor whose characteristics do not change even when immersed in an electrolyte solution. Therefore, in the fields that require humidity measurement and humidity control, especially those that require low price and high reliability,
It can be widely applied to mobile devices and the like.

[Brief description of drawings]

FIG. 1 is a sectional view of a humidity sensor of the present invention.

FIG. 2 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 3 is a sectional view of the humidity sensor of the present invention.

FIG. 4 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 5 is a sectional view of the humidity sensor of the present invention.

FIG. 6 is a sectional view of the humidity sensor of the present invention.

FIG. 7 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 8 is a sectional view of the humidity sensor of the present invention.

FIG. 9 is a humidity sensitive characteristic diagram of the humidity sensor of the present invention.

FIG. 10 is a sectional view of the humidity sensor of the present invention.

FIG. 11 is a sectional view of the humidity sensor of the present invention.

[Explanation of symbols]

 1 Substrate 2 Insulating film 3 Moisture sensitive film 4 Electrode 5 Fluorine-containing polymer film 6 Through hole 7 Conductive path 8 Terminal part

Claims (8)

[Claims] 1. A humidity sensor, comprising: an insulating film formed on a conductive substrate; and a moisture sensitive film formed on the insulating film. 2. A humidity sensor characterized in that an insulating film is formed on a conductive substrate, an electrode is formed on the insulating film, and a moisture sensitive film is formed on the insulating film on which the electrode is formed. . 3. An insulating film is formed on a conductive substrate, an electrode is formed on the insulating film, a moisture sensitive film is formed on the electrode, and an electrode is formed on the moisture sensitive film. A characteristic humidity sensor. 4. The humidity sensor according to claim 1, wherein at least one terminal portion is on a surface of the conductive substrate opposite to the moisture sensitive film. 5. The electrode on the surface of the conductive substrate on the moisture sensitive film side and the terminal portion on the surface of the conductive substrate opposite to the moisture sensitive film are formed on the side surface of the through hole or the side surface of the conductive substrate. The humidity sensor according to claim 4, wherein an insulating film is formed, and a conductive path is formed on the insulating film so as to be electrically connected. 6. The electrode on the surface of the conductive substrate facing the moisture sensitive film and the terminal portion on the surface of the conductive substrate opposite to the moisture sensitive film are electrically connected by utilizing the conductivity of the conductive substrate. The humidity sensor according to claim 4, wherein 7. The humidity sensor according to claim 1, wherein silicon is used as the conductive substrate. 8. The humidity sensor according to claim 1, wherein the fluorine-containing polymer film is formed so that at least the portion of the moisture sensitive film is covered.