JPH01148954A - Resin coating method for moisture sensitive element - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a moisture sensitive film in coating a resin, by wetting a moisture sensitive element with an organic solvent before applying resin liquid on the moisture sensitive element. CONSTITUTION:Before application of resin liquid, a gas component which is adsorbed in ceramic particles in a moisture sensitive film is removed. In order to remove the gas component, the film is wetted with an organic agent. It is desirable to use a solvent which is used for diluting resin liquid. Namely, the moisture sensitive element is immersed into the suitable solvent for appropriate time before coating. The solvent can be sufficiently applied on the surface of the element by a suitable method such as spraying. Thereafter, the coat of resin is given as quickly as possible. The coating is performed by a method such as immersion and spraying. Thereafter, the resin is dried for a specified time. Thus the coating is finished. In this element, having the moisture sensitive film, which is coated in this way, the film is not broken during treating and high water resistance and an excellent moisture sensitive characteristic are provided. Therefore, the breakdown of the moisture sensitive film can be prevented.

Description

[Detailed Description of the Invention] The present invention relates to a moisture-sensitive element manufactured by forming a ceramic powder into a paste, forming an electrode in advance, coating it on a substrate, and then firing it. The present invention relates to a resin coating method for the purpose of improving. According to the present invention, a resin coating can be applied uniformly and uniformly without destroying the moisture-sensitive film, and with less deterioration of properties.
A moisture-sensitive element with excellent water resistance can be obtained.

In recent years, humidity sensors have been applied not only to the field of home appliances such as cooking equipment and air conditioning equipment, but also to all fields that require measurement equipment and humidity control, such as industry, agriculture, transportation, and medical fields. be. As a result, the environmental conditions in which humidity-sensitive elements are installed have diversified, and the elements may be exposed for long periods to atmospheres containing many substances other than moisture, such as salt, organic gas, cigarette smoke, and dust. It may also be installed near a humidifier that sprays water directly. In particular, direct adhesion of water droplets can greatly affect the aging of the moisture-sensitive element. As a countermeasure against these problems, it is necessary to install a heat cleaning circuit on the device, cover the surface of the device with resin or a glass-like melt containing highly moisture-sensitive Li ions, and then store the device in a case. The usual method is to do this. Although adding a heating circuit to the element is effective, it requires an extra circuit and the refreshing effect does not last long, so a non-heating type is preferable for small, highly sensitive humidity sensors. For this reason, a type that protects the moisture-sensitive element by using a multilayer structure of filters that allow moisture and water vapor to pass through well but prevents other specific harmful substances and direct water droplets from passing through has become mainstream.

■Resin coating also improves water resistance and durability for moisture-sensitive elements, which are manufactured by turning ceramic powder into a paste, forming electrodes in advance, coating it on a substrate, and then firing it. Effective for improvement. However, when an element having such a coating-type moisture-sensitive film is coated with a polymeric material such as a silicone resin or a fluororesin, problems such as a decrease in the responsiveness of the element and destruction of the moisture-sensitive film occur.

This problem cannot be improved by dipping the device directly in the resin or by spraying the device with resin. Conventionally, coating this type of device with a resin has been used to improve the durability of the device and to protect the film. It was a difficult process to balance deterioration.

The present invention was made to solve these problems and relates to a method for uniformly coating an element of this type with a resin without destroying the film.

Namely, the present invention relates to a resin coating for the purpose of improving the water resistance of a moisture-sensitive element manufactured by making a paste of ceramic powder, coating it on a substrate, and then firing it. A method for resin coating a moisture-sensitive element, characterized in that the moisture-sensitive element is pre-wetted with an organic solvent before applying the resin liquid to the moisture-sensitive element to prevent the moisture-sensitive film from being destroyed during resin coating. Regarding.

1. The moisture-sensitive element used in the present invention is manufactured by applying ceramic powder onto a substrate on which electrodes have been formed in advance, and then firing the powder. The powder is 5no2, Cry, F
e50. , ZrO, etc. are used. Also 2
A combination of more than one species is also possible.

The substrate used is AI, O, SiO□, ZrO, or the like. The electrodes are also screen printed with Au, Pt, ruthenium, etc.
It is formed by a method such as sputtering. Appropriate organic or inorganic solvents, resins, etc. are used to make the paste. The coating method can be screen printing or spraying. Appropriate auxiliary agents may be added during firing. Thereafter, firing, soldering, aging, and other treatments are performed to produce the moisture-sensitive element.

In order to improve the water resistance of the moisture-sensitive element thus produced, a resin coating is applied. The resin used is silicone resin,
Resins with excellent water resistance such as fluororesin and phenol resin are used. This is diluted with a suitable organic solvent such as toluene, benzene, xylene, etc. These resins and solvents are 2
More than one species may be combined.

Conventionally, the moisture-sensitive element was applied directly by dipping it in a diluted resin solution or by spraying it, but in this case, part of the moisture-sensitive film was destroyed and cracked, and in severe cases, the moisture-sensing element was coated directly. Part of the film sometimes peeled off.

After intensive investigation into the cause of this, we found that bubbles are generated from the moisture-sensitive membrane the moment the moisture-sensitive membrane is covered with resin liquid, and these bubbles push up the moisture-sensitive membrane along with the resin film that has begun to harden, destroying it. I understand.

The reason for the generation of bubbles is thought to be that oxygen and nitrogen gas adsorbed on the surface of the ceramic particles that make up the moisture-sensitive membrane are desorbed by the resin liquid.

From these facts, we concluded that it is effective to prevent the destruction of the moisture-sensitive membrane by removing the gas components adsorbed to the ceramic particles of the moisture-sensitive membrane before applying the resin liquid. Obtained.

It has been found that moistening the membrane with an organic solvent is an extremely preferable method for removing gas components adsorbed on the moisture-sensitive membrane. More preferred is a method using a solvent used to dilute the resin liquid. This is because there is no adverse effect on subsequent resin application.

Before coating, the moisture sensitive element is immersed in these appropriate solvents for an appropriate period of time (mainly about several seconds to 10 seconds). These solvents may be evenly and sufficiently applied to the surface of the element by a suitable method such as spraying. After that, coating with the resin described above is performed as soon as possible. Coating methods include dipping, spraying, and direct application. Thereafter, the coating process is completed by drying for a certain period of time, for example, 4 to 8 hours.

A device having a coated moisture-sensitive film coated in this manner exhibits high water resistance and good moisture-sensing properties without the film being destroyed during processing.

Examples in which such coating treatment was performed will be described in detail below.

A1□0 in which electrodes were formed by making a paste of ZrO□ powder.
．． After coating on the substrate and baking it (see Figure 1), the temperature is 2.
It was immersed in toluene for 5 seconds in a clean room at 5°C and 50% humidity. Immediately after that, use 40C in advance.
It was immersed for 5 seconds in a silicone resin (dilution solvent: toluene) adjusted to the viscosity of Pi, and left in a clean room overnight. At this time, out of 96 devices tested, there were 0 devices whose moisture-sensitive film was destroyed by coating.
The destruction rate was 0%. Figure 2 (A) shows the response of this element.
Shown below. The response is relatively fast for a coated element. Regarding water resistance, it withstood being immersed in water for 10 minutes or more, showing sufficient water resistance for a normal type. There was no unevenness in the properties of the coated film even by visual inspection.

The same element was directly exposed to 40 ml without pretreatment by immersion in toluene.
Silicone resin with a viscosity of CPi (dilution solvent: toluene)
The sample was immersed in water for 5 seconds and left in a clean room overnight. At this time, out of 96 devices tested, 79 devices had their moisture-sensitive films destroyed by coating, for a destruction rate of 82%. The response of this element is shown in FIG. 2(B). The response is poorer than when pre-treatment with toluene is performed. Regarding water resistance, no significant difference was observed compared to when pretreatment with toluene was performed.

As described above, this invention improves the durability of the element by soaking a moisture-sensitive element having a coating-type moisture-sensitive film in a suitable solvent in advance and then coating it with a resin. At the same time, it is possible to prevent the accompanying destruction.

Furthermore, since the film can be applied thinly, the response speed becomes faster.

[Brief explanation of the drawing]

FIG. 1 shows an example of a moisture sensitive element, and FIG. 2 shows a response curve.

Claims (1)

[Claims] (1) In resin coating for the purpose of improving water resistance of moisture-sensitive elements manufactured by turning ceramic powder into a paste, coating it on a substrate, and firing it, before applying resin liquid to the moisture-sensing element. A method for resin coating a moisture sensitive element, characterized in that the moisture sensitive element is pre-wetted with an organic solvent to prevent the moisture sensitive film from being destroyed during resin coating.