JPH06118045A - Humidity sensor - Google Patents

Abstract

PURPOSE:To provide a humidity sensor with good mass productivity and high reliability in which the process is simplified and a process suitable for mass production can be used. CONSTITUTION:A moisture sensitive film 1 is formed on a silicon base 3 by screen printing, and SiO2 is spattered around the moisture sensitive film 1 to form an insulating film 4. Cr, Au are evaporated on the insulating film 4 to cover at least the whole moisture sensitive film 1, whereby an electrode 2 is formed to form a humidity sensor. The silicon base 2 is used as a part of the electrode 2.

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, since most of the moisture-sensitive films of conventional humidity sensors are polymer type and ceramic type, they are poor in acid resistance, alkali resistance, water resistance, etc.
The process after forming the moisture sensitive film was limited. There is also a problem in the reliability of the moisture sensitive film.

In addition, the conventional humidity sensor has a problem that the process is complicated and the cost is increased when the electrode is formed. Further, when an insulator is used as the substrate, the thermal conductivity becomes smaller than that when a conductor is used, so there is a problem that the heat response of the humidity sensor becomes slow.

Therefore, the present invention solves such a problem, and an object of the present invention is to provide a humidity sensor having good mass productivity, good heat resistance, and high reliability.

[0008]

The humidity sensor of the present invention comprises:
A moisture sensitive film is formed on a conductive substrate, an insulating film is formed on a part or all of the periphery of the moisture sensitive film on the conductive substrate, and the moisture sensitive film is covered on the moisture sensitive film and the insulating film. At least 1
One electrode is formed, and the conductive substrate is used as a part of the electrode.

The conductive substrate may be a metal plate such as stainless steel, copper or aluminum, or conductive ceramics. The surface of the insulating substrate may be coated with a conductive substance. 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.

When the gold electrode is formed so as to cover at least the moisture sensitive film, it is possible to obtain a highly reliable humidity sensor whose characteristics do not change even when immersed in an electrolyte solution. If a fluorine-containing polymer film is formed so that at least the electrode portion on the moisture sensitive film is entirely covered therewith, a more reliable humidity sensor can be obtained.

[0011]

【Example】

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

This coating solution was screen-printed on a silicon substrate and heat-treated at 700 ° C. for 1 hour to form a moisture sensitive film. Sputter SiO ₂ around this moisture sensitive film,
An insulating film was formed. On the moisture-sensitive film and the insulating film, Cr,
Au was vapor-deposited to form an electrode. A cross-sectional view of the humidity sensor thus produced is shown in FIG. 1, and a plan view thereof is shown in FIG. 1 and 2, 1 is a moisture sensitive film, 2 is an electrode, 3 is a substrate,
Reference numeral 4 is an insulating film. The insulating film may cover a part of the moisture sensitive film as shown in FIG.

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 to stand in a constant temperature and humidity chamber at 60 ° C. and 90% for 1000 hours, and the characteristics were measured. The results were the same as those in FIG. 4 within the measurement error range. 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 2 The humidity sensor prepared in Example 1 is covered with a solution (7% by weight) of a solvent-soluble fluorine-containing polymer dissolved in a perfluoro solvent, at least all electrodes on the moisture-sensitive film are covered. Screen-print, 180
It heat-processed at 1 degreeC for 1 hour, and formed the fluorine-containing polymer film. A cross-sectional view of the humidity sensor thus produced is shown in FIG. In FIG. 5, 1 is a moisture sensitive film, 2 is an electrode, 3 is a substrate,
Reference numeral 4 is an insulating film, and 5 is a fluorine-containing polymer film. The characteristics of this humidity sensor were similar to those of the humidity sensor created in Example 1. 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. Therefore, it can be seen that this humidity sensor is extremely durable and highly reliable.

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.

[0016]

As described above, in the humidity sensor of the present invention, the humidity sensitive film and the insulating film are formed on the conductive substrate, and the electrodes are formed so as to cover all the moisture sensitive film, so that the manufacturing process is simplified. The thermal response becomes faster. Moreover, when silicon is used for the conductive substrate, a humidity sensor having high mass productivity and high reliability can be obtained.

[Brief description of drawings]

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

FIG. 2 is a plan view 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.

[Explanation of symbols]

 1 moisture sensitive film 2 electrode 3 substrate 4 insulating film 5 fluoropolymer film

Claims (4)

[Claims] 1. A moisture sensitive film is formed on a conductive substrate, an insulating film is formed on a part or all of the periphery of the moisture sensitive film on the conductive substrate, and the moisture sensitive film is formed on the moisture sensitive film and the insulating film. A humidity sensor, wherein at least one electrode is formed so as to cover the film, and a conductive substrate is used as a part of the electrode. 2. The humidity sensor according to claim 1, wherein silicon is used as the conductive substrate. 3. The humidity sensor according to claim 1, wherein gold is used as the electrode. 4. The humidity sensor according to claim 1, wherein the fluorine-containing polymer film is formed so that at least the electrode portion on the moisture-sensitive film is entirely covered.