JPH0424547A - humidity sensor - Google Patents

Abstract

PURPOSE:To obtain a humidity sensor characterized by the long life of a sensor element and the quick response speed for temperature by coating a first electrode with orthophosphate, and thereafter depositing conducting paste or gold on a second electrode by vapor deposition. CONSTITUTION:Orthophosphate crystal 6 is deposited on a metal plate 8 made of steel material or the like by a high-frequency sputtering method. A lead wire 7 is soldered to the metal plate 7. The plate is made to be the first electrode. Conductive paste 5 such as carbon paste is printed in a comb shape as a counter electrode. Thus a humidity sensor S2 is obtained. The part of the conductive paste 5 can be formed by the vapor deposition of gold.

Description

[Detailed Description of the Invention] [Industrial Application Field] Humidity sensors (in a broad sense) that manage humidity, used as humidity sensors, moisture condensation sensors, raindrop sensors, etc., are useful in quality control and environmental management of industrial products. plays an important role.

Furthermore, humidity sensors are currently used in a wide range of applications, such as manufacturing processes in industries such as electronics, steel, textiles, food, and paper manufacturing, air conditioning management of buildings, and rainfall detection.

The present invention relates to an improvement of such a humidity sensor (in a broad sense).

[Prior Art] In conventional humidity sensors, ceramics, polymers, electrolytes, etc. are used as moisture-sensitive element materials for sensors, and most of them are described in, for example, Japanese Patent Publication No. 55-49705. The structure was such that a sensor element material film was formed on an insulating substrate, and electrodes were printed on it to produce a sensor element.

In addition, as a prior art of the present applicant which is an improvement over this conventional method, a method in which a chemical conversion film deposited on a metal electrode is brought into contact with a metal electrode serving as a counter electrode (Japanese Patent Application No. 63-1709
96) has also been proposed.

[Problems to be Solved by the Invention] However, the moisture-sensitive element materials for sensors in the prior art are extremely difficult to synthesize, have high manufacturing costs in terms of yield and production control, and have short lifespans for sensor elements. It had drawbacks such as slow response speed to humidity.

Also, the prior art has a second electrode to increase the electrode area.
This method increases the electrode area and improves performance by coating the surface of the chemical conversion film with carbon paste or conductive metal oxide to form the electrode. Since the phosphate film crystal has a large crystal grain size, there was a problem in that if an electrode was manufactured using the paste method, a short would occur between the two electrodes, making it impossible to obtain a humidity sensor element.

For this reason, although this type of humidity sensor has been theoretically developed for various uses, the reality is that it has not yet been widely used as a product.

SUMMARY OF THE INVENTION An object of the present invention is to provide a humidity sensor that solves the above-mentioned problems of the conventional humidity sensor.

[Means for Solving Problem U] The present invention provides a method for coating either the first electrode or the second electrode, which is a counter electrode, with an orthophosphate by a high-frequency spacing method, and then coating the second electrode or the first electrode with The present invention relates to a humidity sensor configured to be brought into contact with an electrode.

In this case, the humidity sensor is formed by coating the metal electrode, which is the first electrode, with orthophosphate by high-frequency sputtering, and then forming the second electrode, which is the counter electrode, by depositing conductive paste or gold in a comb shape. It can be done.

[Examples] The present invention will be specifically explained below using Examples, but before that, the basic concept of the present invention will be explained.

The present inventors have investigated the possibility of depositing films of various orthophosphates, which have traditionally been used as moisture-sensing agents, on metal materials. by the high frequency sputtering method used in

It has been discovered that a temperature sensor element with good characteristics can be obtained by depositing an orthophosphate film on the surface of a metal material and bringing it into contact with a second metal material that will serve as a counter electrode.

That is, it usually includes a zinc phosphate film that is deposited by taking advantage of the corrosion phenomenon of metals. Various orthophosphate films were deposited by high frequency sputtering method.

Figure 1 shows an example of the configuration of a rod-shaped humidity sensor. 1 is a metal wire made of steel material, on which the above-mentioned orthophosphate crystals are deposited by high-frequency sputtering, and a lead wire 3 is soldered to this wire. This will be used as the first electrode.

A humidity sensor element 81 as shown in FIG. 1 is fabricated using a copper wire, a gold-plated or nickel-plated stainless steel wire, or the like as the counter electrode 4.

In addition, the part 2 in FIG. 1 becomes a temperature sensing part.

FIG. 2 shows an example of the structure of a plate-shaped humidity sensor, in which 8 is a metal plate made of steel material, etc., and the above-mentioned orthophosphate crystal 63 is attached to this metal plate.
The lead wires 7 are deposited by high frequency sputtering and soldered to the metal plate 8.

This will be the first electrode.

A conductive paste 5 such as carbon paste is printed on this in the form of a comb as a pole, thereby obtaining a humidity sensor element S2 as shown in FIG. 2(b).

The film obtained by sputtering has a fine crystal grain size, so insulation between the two electrodes is maintained.

A humidity sensor element can be obtained.

Note that the conductive paste 5 portion may be formed by vapor deposition of gold.

Next, a specific embodiment of the present invention will be described.

Example 1 The target is the reagent phosphorous acid (Zn, (Po4)24
1120, IIopeiLe) was heated at 400″ for 0.60 minutes and pressed, 1 frequency 13.56MH.
5LJS30 under the conditions of output 3oow and pressure 1.2Pa
A sputtered film was formed on each diameter of the 4-wire rod.

By changing the sputtering time, the amount of film deposited could be adjusted to an appropriate value.

The film obtained after the heat treatment was determined to be anhydrous tertiary zinc phosphate (Znz(PO<)2) by X-ray diffraction.

The amount of Zn in the obtained film was measured using fluorescent X-rays, and the amount of film attached was calculated from this.

A gold-coated stainless wire of 80 μm was wound around the coated stainless steel wire, and the moisture sensitivity characteristics of the device were evaluated using a one-way humidity generator.

As can be seen from the measurement results in Figure 3, the sensor element fabricated from 1.2 g 7 m 2.3.5 g 7 m 2 with a small amount of film adhesion exhibits characteristics as an element capable of measuring humidity even in a low humidity region. On the other hand, the amount of film deposited is 8.6g/
In the case of m2, it was confirmed that the impedance value changes in the high humidity region.

The sensor element obtained in Example 1 was placed on the high humidity side (98%
Fig. 4 shows the results of a durability test carried out by shifting the temperature to the lower humidity (RH) and lower humidity side (53% RH). As can be seen from the figure, it was confirmed that the initial characteristics were maintained even after the 6-month cycle test.

Example 2: A sputtered film was formed on a 5US304 board in the same manner as in Example 1. A comb-shaped electrode as shown in FIG. 2 was printed on the obtained film to produce a device.

The measurement results in this case are that, as shown in Figure 5, the element fabricated with a coating weight of 1.1 g 7 m 2 has measurable characteristics in the low humidity region, 3.8 g 7 m ', 3.9 g 7 m 2
It was confirmed that the characteristics of the sensor element fabricated in '2000 changed only in the high humidity region.

In the case of this example as well, the impedance value showed a lower value as a whole compared to Example 1.

Example 3 A sputtered film was formed on a 5US304 board in the same manner as in Example 1. Gold was vapor-deposited on the obtained film using a vapor deposition apparatus. In this case, the thickness of the gold vapor-deposited film was set to 300 angstroms.

When the impedance value between the S'US substrate and the gold-deposited crotch was measured using the same measurement method as in Example 1, it was found that the device fabricated with a coating weight of 1.1 g/m2 had measurable characteristics in the low humidity region, and , 3.8g/m23.9g 7m
It was confirmed that the characteristics of the sensor element fabricated in Example 2 change only in the high temperature range.

Further, as shown in FIG. 6, the impedance values in this embodiment are lower overall than in the second embodiment.

Further, the results of the durability test are the same as those of Example 1 shown in FIG. 4, and therefore illustration thereof is omitted.

[Function] It is a well-known fact that the orthophosphate used in the humidity sensor of the present invention already has a function as a moisture-sensing agent for the humidity sensor, and the orthophosphate salt used in the humidity sensor of the present invention already has a function as a moisture-sensing agent. It is based on the functional principle that the electrical resistance value changes depending on the temperature and humidity measurement becomes possible.

As shown in Figures 1 and 2 (b), the humidity sensor element fabricated by sputtering has an electrode structure through a film, so the characteristics can be varied by controlling the amount of film deposited. Humidity sensor element can be easily obtained,
It is now possible to freely select the measurement humidity range.

In other words, this shows that the functions originally possessed by various orthophosphates as moisture sensitive agents were brought out by applying the device manufacturing method of the present invention.

In addition, in the case of the configuration shown in FIG. 2 (b), the electrode area is increased due to the present invention, so that the characteristics in the low impedance region are better than the temperature sensor element fabricated with the configuration shown in FIG. 1. What has been shown is also advantageous in terms of circuit design.

"Effects of the Invention" According to the humidity sensor configuration according to the present invention, the inherent characteristics of various orthophosphate films are fully utilized, and a humidity sensor that meets the demands for a wide range of humidity measurements and has excellent durability. Since the device can be obtained, its practicality is great.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 (B) are perspective views showing the humidity sensor elements of the first and second embodiments of the present invention, and FIG. 2 (A) is an exploded perspective view showing the structure of the second embodiment. It is. Further, FIGS. 3, 5, and 6 show the results of Example 1, respectively. FIG. 3 is an impedance-relative humidity characteristic diagram showing the effects of Example 2 and Example 3. Note that FIG. 4 is a characteristic diagram showing the durability test results of the humidity sensor element of Example 1. S2・Humidity sensor humidity sensing part

Claims (2)

[Claims] 1. A humidity sensor characterized in that either the first electrode or the second electrode, which is a counter electrode, is coated with orthophosphate by a high frequency sputtering method and then brought into contact with the second electrode or the first electrode. 2. The method is characterized in that after the metal electrode, which is the first electrode, is coated with orthophosphate by high-frequency sputtering, the second electrode, which is the counter electrode, is formed by depositing conductive paste or gold in a comb shape. Humidity sensor.