JPH02159547A - Moisture sensor element - Google Patents

Abstract

PURPOSE:To enable accurate measurement of moisture in a wide range by establishing electrode width < space distance in a relationship between the electrode width of a comb-shaped electrode and the space distance to an electrode facing the electrode. CONSTITUTION:Chromium 7, nichrome 6 and gold 5a and 5b are laminated sequentially on an alumina substrate 23 by sputtering or evaporation and a photoetching is performed to form a comb-shaped electrode 1. At this point, L1< L2 is established in a relationship between the electrode width L1 of the comb-shaped electrode and a space distance L2 to an electrode facing the electrode. Then, ethanol and 0.02 N hydrochloric acid are added to tetraethoxy silane and after an agitation of the mixture, a fine powder silica, activated charcoal, carbon black and glycerin are added thereto. The substrate 23 is immersed into the solution thus obtained and further dried to bake. Thereafter, the substrate is attached to a protective film 8 to bake. This enables accurate measurement of moisture in a wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a humidity sensor element that utilizes the fact that the electrical resistance characteristics of the element change in response to the humidity in the outside world.

[Background Art] With the rapid progress of electronics, there is a demand for highly accurate and highly reliable sensors under various environments. Among these, there is a strong demand for humidity sensors, as there is no element that meets these demands.

Humidity sensors that detect humidity by changing the electrical characteristics of the element in response to external humidity include electrolyte-based, metal-based, polymer-based, and ceramic-based types, and each is currently being considered. Those that have been put into practical use are polymer-based and ceramic-based. All of these utilize the property that the electrical resistance or capacitance changes due to adsorption and desorption of water molecules to the element.

[Problems to be Solved by the Invention] However, conventional humidity sensors have problems in that they have poor accuracy at high and low humidity, and deteriorate when used for long periods at high temperatures. In particular, variable resistance types have abnormally high resistance at low humidity and poor accuracy at low humidity. In addition, polymer-based materials deteriorate due to swelling of the polymer membrane in high temperatures and have a short lifespan.

Therefore, the present invention is intended to solve these problems, and its purpose is to provide a highly accurate and reliable humidity sensor cord that can accurately measure humidity over a wide range and does not deteriorate even in harsh environments. It is in.

[Means for Solving the Problems] The humidity sensor element of the present invention is obtained by sequentially forming a thin film electrode, a moisture sensitive film, and a protective film on an insulating substrate. has a pair of comb-shaped electrodes, and is characterized in that the relationship between the electrode radius (L+) of the comb-shaped electrodes and the space distance (L2) to the opposing electrode is L + < L 2 .

The humidity sensor element of the present invention is a humidity sensor element in which a thin film electrode, a moisture sensitive film, and a protective film can be sequentially formed on an insulating substrate.
The moisture-sensitive membrane is characterized in that it is made of a porous silica membrane in which two types of carbon particles having different particle sizes are dispersed.

The humidity sensor element of the present invention is a humidity sensor element obtained by sequentially forming a thin film electrode, a moisture sensitive film, and a protective film on an insulating substrate, wherein the protective film is a porous silica film. shall be.

Specifically, since the moisture-sensitive membrane of the present invention is a porous silica membrane in which carbon particles are dispersed, its adhesion to metal electrodes is not very good. Alumina or glass is used as the substrate material, but since the porous wrinkle film of the present invention is fired at a low temperature, sufficient chemical bonding between the metal electrode and the porous silica film cannot be achieved, causing poor adhesion. . For this reason, silica (Si)
By efficiently increasing the area of the substrate that is likely to react with the side chains of , it is possible to improve the overall degree of adhesion.

[Example-1] Chromium (Cr) on alumina (A1203) substrate.

Gold (Au), nichrome (NiCr), and gold (Au) were sequentially laminated by sputtering or vapor deposition, and then photoetching was used to fabricate a comb-shaped electrode as shown in FIG. In Figure 1, 3 is an alumina substrate, 1 is a Cr electrode,
2 is a pad, and the Cr electrode 1 has a single layer structure, and the pad 2 has a four-layer structure. Further, the electrode radius L1 is 200 μm, and the space distance L2 between the opposing electrodes is 500 μm.

Next, tetraethoxysilane (Si (OC2H5)4
) 50 ml and 25 ml of ethanol. 0. Add 4ml of 02N hydrochloric acid and stir, then add 13.5g of fine powder silica, 5.4g of activated carbon, 2.7g of carbon black, 1g of glycerin.
The electrode-attached alumina substrate prepared above was immersed in the solution to which 0 ml was added, dried after immersion, and then fired at 430°C. Thereafter, a protective film containing a mixture of tetraethoxysilane, ethanol, and 0.02N hydrochloric acid to which fine powder wrinkle strength was added was deposited and fired. A cross-sectional structural diagram of the humidity sensor element thus produced is shown in FIG. 4 is a moisture sensitive film, 5a,
5b is gold, 6 is nichrome, 7 is chromium, 8 is a protective film,
23 is an alumina substrate. When the humidity characteristics of this humidity sensor were evaluated, it was found to have good linearity as shown in FIG. After this, 100
After leaving it in a dry state at °C for 1000 hours and checking the adhesion, there was no problem, and when we evaluated the humidity characteristics again,
Overall, the resistance was shifted to the high resistance side by only about 3%, which was good.

[Example-2] An electrode was produced on an alumina substrate in the same manner as in Example-1.

The material of the electrode at this time was gold, and the electrode radius (LI) and the space distance (L2) to the opposing electrode were determined as shown below.

Table 1 (L=μm) As shown in Table 1 above, by setting L 1 <L2, the adhesion was good and the reliability was excellent.

[Example 31 A humidity sensor element was produced in the same manner as in Examples 1 and 2. The electrode materials at this time were molybdenum, titanium, tantalum, tungsten, and niobium, respectively. This result was also good as shown in Example 1.2.

■ -----1 High O・---------1 No practical problems [Effects of the invention] As described above, according to the invention, in the thin film electrode of the humidity sensor, the electrode radius of the comb-shaped electrode ( By setting the relationship between L1) and the space distance (L2) to the opposing electrode to be LI<L2, even a silica film with a low firing temperature can be bonded by increasing the substrate area, making it a highly reliable humidity sensor. The element is obtained.

Further, the electrical resistance of the electrode is almost negligible compared to the resistance value of the moisture-sensitive film, so there is no problem in practical use.

In addition, in the examples, specific numbers for the electrode radius L+ and space distance L2 are described, but of course, if the relationship is Ll<L2, the numbers are not defined and combinations are free. It is.

FIG. 1 is a diagram showing an example of the electrode pattern of the humidity sensor element of the present invention.

FIG. 2 is a cross-sectional structural diagram of a humidity sensor element in Example-1 of the present invention.

FIG. 3 is a humidity characteristic diagram of the humidity sensor element obtained in this example.

■, 7・・ 2・・・・・ 3, 23・ ４　・　・・・ 5a, 5b 6 ・ ・ ・ ・ 8・・・・・ chrome electrode pad alumina substrate moisture sensitive membrane Money Nichrome Protective film that's all Applicant: Seiko Epson Corporation Representative Patent Attorney Kizobe Suzuki (1 person)

[Brief explanation of the drawing]

Figure 2

Claims (3)

[Claims] (1) In a humidity sensor element obtained by sequentially forming a thin film electrode, a moisture sensitive film, and a protective film on an insulating substrate,
The thin film electrodes have a pair of comb-shaped electrodes, and the electrode radius (L_1) of the comb-shaped electrodes and the space distance (L_1) to the opposing electrode
A humidity sensor element characterized in that the relationship _2) is L_1<L_2. (2) In a humidity sensor element obtained by sequentially forming a thin film electrode, a moisture sensitive film, and a protective film on an insulating substrate,
2. The humidity sensor element according to claim 1, wherein the humidity sensitive film is made of a porous silica film in which two types of carbon particles having different particle sizes are dispersed. (3) In a humidity sensor element obtained by sequentially forming a thin film electrode, a moisture sensitive film, and a protective film on an insulating substrate,
The humidity sensor element according to claim 1, wherein the protective film is a porous silica film.