JPH0590010A - Thick-film thermistor - Google Patents

Abstract

PURPOSE:To solve a problem that moisture penetrates from the interface between a protective film and an insulating substrate such as alumina or the like and that moisture-proofness is deteriorated and to enhance the moisture- proofness of the title thermistor. CONSTITUTION:The title thermistor is provided with the following: an insulating substrate 1; an underglazed layer 2 which is formed on the insulating substrate and which is composed of glass; a thermistor layer 4 formed on the underglazed layer 2; and protective films 5, 6 which are formed on the thermistor layer and which are composed of glass. Since the underglazed layer is provided, the glass for the protective films 5, 6 comes into close contact with the glass for the underglazed layer 2, the airtightness of the thermistor layer 4 is kept and the thermistor has an effect to prevent moisture from penetration.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thick film thermistor.

[0002]

2. Description of the Related Art Conventionally, a thick film thermistor is formed by printing and firing a silver-palladium-based conductive paste on an insulating substrate such as alumina to form an electrode, and then printing and firing a thick film thermistor paste on the thermistor layer. Then, a protective film made of glass was formed on it.

[0003]

As described above, in the conventional thick film thermistor, the protective film made of glass is formed on the thermistor layer, but the protective film and the insulating substrate made of alumina or the like are subjected to the moisture resistance test for a long time. There is a problem that water permeates from the interface with and moisture resistance deteriorates.

The present invention has been made to solve the above problems, and an object of the present invention is to prevent water from penetrating into the thermistor layer and improve the moisture resistance.

[0005]

In order to achieve the above object, the present invention provides an insulating substrate, an underglaze layer made of glass provided on the insulating substrate, and an underglaze layer provided on the underglaze layer. The thermistor layer thus prepared and a protective film made of glass provided on the thermistor layer.

[0006]

According to the present invention, since the underglaze layer is provided, the glass of the protective film adheres to the glass of the underglaze layer, the airtightness of the thermistor layer is maintained, and the effect of preventing water penetration is obtained. is there.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thick film thermistor according to an embodiment of the present invention will be described below with reference to the drawings.

Example 1 As shown in FIGS. 1A and 1B, SiO ₂ and BaO were formed on an alumina substrate 1 having a purity of 96%.
The glass paste containing as a main component is printed and baked at 850 ° C. to form the underglaze layer 2. The softening point of this underglaze is about 780 ° C. Subsequently, a thick film silver palladium paste is printed on the underglaze layer 2 and baked at 850 ° C. to form the electrode 3. Next, Mn
A thick film thermistor paste containing O ₂ , CoO, and NiO as the main components is printed so as to connect between the pair of electrodes 3, and 850
The thermistor layer 4 is formed by baking at a temperature of ° C. After this, the same glass paste as the underglaze layer 2 is printed,
The first protective coat layer 5 is formed by baking at 0 ° C., borosilicate glass is printed on the first protective coat layer 5, and the second protective coat layer 6 is formed by baking at 600 ° C.

The B-constant of the thick film thermistor in this example thus constituted was 2640K, and the resistance value drift within 100 hours of the humidity resistance test (PCT) was within 1%.

COMPARATIVE EXAMPLE 1 Next, as a comparative example of the above example, as shown in FIGS. 2A and 2B, thick film silver palladium was formed on an alumina substrate having a purity of 96% as in Example 1. The paste is printed and baked at 850 ° C. to form the electrode 3.
Next, a thick film thermistor paste containing MnO ₂ , CoO, and NiO as main components is printed so as to connect between the pair of electrodes 3, and is baked at 850 ° C. to form the thermistor layer 4. After that, a glass paste containing SiO ₂ and BaO as main components is printed and baked at 850 ° C. to form the first protective coat layer 5, and subsequently, borosilicate glass is printed on the first protective coat layer 5.
The second protective coat layer 6 is formed by baking at 0 ° C.

The B constant of the thick film thermistor having no underglaze layer is 2560K, and the moisture resistance test 100
The resistance drift over time was about 10%.

It is considered that this is because water permeated from the interface between the alumina substrate 1 and the protective coat layers 5 and 6 and entered the thermistor layer 4.

That is, when the underglaze layer 2 is formed on the alumina substrate 1, the thermistor layer 4 is sealed in a dense glass because it adheres to the glass of the underglaze layer 2 when the glass of the protective coat layer 5 is baked. Therefore, it is presumed that it plays a role of preventing the permeation of water from the outside world.

The same effect was obtained even when the protective coat layer 5 was made of a glass different from that used for the underglaze layer.

[0015]

As is apparent from the above description, according to the present invention, by forming the underglaze layer on the insulating substrate, the airtightness of the thermistor layer can be maintained and the moisture resistance can be greatly improved. .

[Brief description of drawings]

FIG. 1A is a plan view of a thick film thermistor according to an embodiment of the present invention, and FIG. 1B is a sectional view taken along the line AA ′ of the thick film thermistor.

FIG. 2A is a plan view of a thick film thermistor of a comparative example, and FIG. 2B is a sectional view taken along the line BB ′ of the thick film thermistor.

[Explanation of symbols]

 1 Alumina Substrate 2 Underglaze Layer 3 Electrode 4 Thermistor Layer 5 First Protective Coating Layer 6 Second Protective Coating Layer

Claims (2)

[Claims] 1. An insulating substrate, an underglaze layer made of glass provided on the insulating substrate, a thermistor layer provided on the underglaze layer, and a glass provided on the thermistor layer. A thick film thermistor having a protective film made of. 2. The thick film thermistor according to claim 1, wherein the underglaze layer and the protective film are made of the same glass.