JPH04293203A - Thin film thermistor and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film thermistor having a structure that allows easy connection of lead wires, and a method for manufacturing the same.

0002

[Prior Art] Conventionally, this type of thin film thermistor is shown in FIG.
As shown in FIG. 1, a pair of thin film thermistor elements are formed by forming a temperature sensitive resistor film 22 such as silicon carbide (SiC) and a pair of electrode films 23 and 23' on one surface of a flat alumina substrate 11. A pair of internal lead wires 24 such as Pt thin wires (about 0.1 mm in diameter) are attached to the thick film electrode films 23 and 23'.
, 24' are connected, and a glass coating layer 25 is further formed. However, this pair of internal lead wires 24, 24
' is a thin wire, so it has weak mechanical strength and is not practical. For this reason, this thin film thermistor element has been put into practical use by being connected to an external lead terminal with strong mechanical strength. The external lead terminal is connected to the electrically insulating support 6 with a thick stainless steel wire (
A pair of external lead wires 27, 27, such as
A pair of internal lead wires 24, 24' of a thin film thermistor element were connected to a pair of external lead wires 27, 27' of an external lead terminal, respectively. (For example, Japanese Patent Publication No. Hei 2-14761)

000
3]

In such a conventional structure, a pair of internal lead wires 24, 24' such as Pt wires are connected to a pair of electrode films 23, 23'. SiC thin film thermistors have excellent heat resistance and resistance temperature characteristics suitable for detecting a wide temperature range, so
It is used in ovens, etc. as a temperature sensor used in the temperature range of . Therefore, the pair of internal lead wires 24,
As the wire 24', a Pt wire or a Ni wire having excellent heat resistance is used, and the pair of internal lead wires 24, 24' are usually connected to the pair of electrode films 23, 23' by welding, respectively. is used. Furthermore, welding is usually used to connect the pair of internal lead wires 24, 24' and the pair of external lead wires 27, 27'. This is because welded connections have excellent heat resistance. However, since these welding operations require a lot of working time, there has been a problem that the cost is high. In addition, the insulation distance between the pair of internal lead wires 24, 24' or between the pair of external lead wires 7, 7' is determined by the creepage of the flat alumina substrate 21 between the pair of internal lead wires 24, 24'. This insulation distance is determined by the distance or the creeping distance of the glass coating layer 25, and is as short as 5 to 10 mm. When such a thin film thermistor is used as a temperature sensor in a cooking appliance such as an electric oven, the thin film thermistor is placed inside the cooking cabinet. A large amount of water vapor is generated in the cooking cabinet when food is heated, resulting in a supersaturated state of water vapor. As a result, a lot of condensed water adheres to the surface of the thin film thermistor element, that is, the outer surface of the flat alumina substrate 21 and the outer surface of the glass coating layer 25, so that the pair of internal lead wires 2
If the insulation distance between 4 and 24' was short, there was a problem that leakage occurred between them.

The present invention solves this problem by eliminating the pair of internal lead wires 24, 24' and directly connecting the external lead wires to the electrode films 3, 3', thereby eliminating the need for welding work. The purpose of this is to increase the insulation distance and prevent leakage.

[0005]

[Means for Solving the Problems] In order to solve the above problems, a thin film thermistor of the present invention is composed of a thin film thermistor element and a pair of plate-shaped metal lead wires, and the thin film thermistor element has a flat alumina substrate and a pair of plate-shaped metal lead wires. , electrically connecting a pair of through holes provided in the flat alumina substrate and one surface and the other surface of the flat alumina substrate,
a pair of conductive members disposed through the through hole;
The flat alumina substrate is mainly composed of a pair of electrode films disposed including the through hole on the one surface thereof, and a temperature sensitive resistor film laminated on the pair of electrode films, and the other , the pair of plate metal lead wires are arranged on the other surface of the flat alumina substrate of the thin film thermistor element to face the pair of through holes, and the pair of conductive members and the pair of plates The thin-film thermistor element is covered with a glass sintered body, including the pair of plate-shaped metal lead wires, each connected by a pair of conductive adhesives, and surrounding the thin film thermistor element.

[0006]

[Operation] With this configuration, a pair of conductive members and a pair of conductive fixing materials are formed by firing the conductive paste for the through hole and the conductive paste for the connection instead of the conventional pair of internal lead wires. Therefore, conventional welding work is no longer necessary.

Furthermore, since the thin film thermistor element including the pair of plate metal lead wires is covered with a glass sintered body, the insulation distance between the pair of plate metal lead wires depends on the shape of the thin film thermistor element. Therefore, the insulation distance can be substantially increased.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIGS. 1(a) and 1(b) show the structure of a thin film thermistor according to an embodiment of the present invention. As shown in the figure, a pair of through holes 8 and 8' were provided at opposing positions on the flat alumina substrate 1. The flat alumina substrate 1 has a width of 2 mm, a length of 6 mm, a thickness of 0.5 mm, and a pair of through holes 8 and 8'.
The diameter was 0.4 mm. After printing a conductive paste for electrodes on one surface of the flat alumina substrate 1 to cover the pair of through holes 8 and 8', it is dried and fired to form a pair of Au-P.
Thick film electrode films 3 and 3' were formed. Thereafter, a conductive paste for through holes was applied onto the inner surfaces or spaces of the through holes 8, 8', and then dried and fired to form conductive members 9, 9'. The pair of thick film electrode films 3, 3' and the pair of conductive members 9, 9' are a pair of conductive members 9, 9' so as to electrically connect one surface and the other surface of the flat alumina substrate 1. The ends of the sexual members 9, 9' are electrically connected. Examples of conductive paste for electrodes and conductive paste for through holes include Ag paste, Ag-Pd paste, and Au-Pt.
Paste etc. are used.

[0010] After that, silicon carbide (S
iC) A temperature sensitive resistor film 2 was formed on one surface of a flat alumina substrate 1 to constitute a thin film thermistor element. At this time, it is desirable that the firing temperature of the conductive paste for the electrode film and the firing temperature of the conductive paste for the through hole be the same. After printing and drying the conductive paste for the electrode film and printing and drying the conductive paste for the through hole, both can be fired simultaneously to form the electrode films 3, 3' and the conductive members 9, 9' at the same time. It is from.

However, when heat resistance up to 500° C. is required, an Au-Pt thick film electrode film (firing temperature 900-1000° C.) is excellent as the electrode films 3, 3'. Therefore, although the conductive members 9 and 9' may be formed using Au-Pt paste as the conductive paste for the through-hole,
Pt paste is not preferred because it is expensive. In this case, as the through-hole paste, A
g-Pd paste is preferred. Since this Ag-Pd paste is used in large quantities industrially, it is not only low-priced, but also has a firing temperature lower than that of Au-Pt paste, so after firing the Au-Pt paste, Ag-Pd paste is
- There is also the advantage that the Au--Pt electrode film does not thermally aggregate when firing the Pd paste.

After forming the thin film thermistor element in this manner, a pair of conductive members 9, 9' formed in the pair of through holes 8, 8' are formed on the other surface of the flat alumina substrate 1. A conductive paste for connection was applied. After this,
After a pair of plate-shaped metal lead wires 10 and 10' are closely attached to the conductive paste for connection, the conductive adhesive material 11 is dried and fired.
, 11' were formed. As this conductive paste for connection, a paste of the same type as the conductive paste for electrode film is used. At this time, as shown in FIG. 2, a pair of auxiliary electrode films 12, 12' are formed on the other surface of the flat alumina substrate 1, covering the pair of through holes 8, 8'.
12' is preferably connected to the conductive members 9, 9'. The auxiliary electrode films 12, 12' can be formed with a larger area of 1-2 mm square than the area of the through holes 8, 8' (about 0.5 mm in diameter), and are conductive. Since the members 9 and 9' are connected, it becomes easy to apply the conductive paste for connection.

After this, a pair of plate metal lead wires 10, 1
0' and the surroundings of the flat alumina substrate 1 were covered with glass paste, and then dried and fired to form a glass sintered body 13. At this time, it is desirable that the firing temperature of the electrically conductive paste for connection and the firing temperature of the glass paste be the same. A pair of plate-shaped metal lead wires 10, 10' are adhered to a conductive paste for connection and then dried, and then coated with glass paste and dried, and both are fired simultaneously to form an adhesive conductive sintered body 11, 1
1' and the glass sintered body 13 can be formed simultaneously. In particular, it is desirable that the firing temperature for both is 700°C or lower. If the firing temperature is lower than this, the change in the resistance value of the SiC temperature-sensitive resistor film 2 due to the firing process can be suppressed to ±(1-2)% or less.

The pair of plate metal lead wires 10, 10' are as follows:
A Fe-Cr alloy plate with a width of about 1.2 mm and a thickness of about 0.3 mm is used in place of the conventional external lead wire. This alloy not only has excellent heat resistance, but also has a small coefficient of thermal expansion.
Even when covered with a glass sintered body 12 having a coefficient of thermal expansion comparable to that of the alumina substrate 1, no cracks occur.

In the thin film thermistor of the present invention constructed in this way, the conventional pair of internal lead wires 24, 24'
Instead, a pair of conductive members 9, 9' and a conductive fixing material 1
1, 11' are used. Therefore, the thin film thermistor of the present invention does not require any welding work. A pair of conductive adhesive materials 11, 11' connecting a pair of conductive members 9, 9' and a pair of plate-shaped metal lead wires 10, 10' are used to improve productivity such as coating process, adhesion process, drying process, baking process, etc. Since it is formed using an excellent process, the time required for connection can be reduced to 1/2 to 1/3 compared to conventional welding work.

When a thin film thermistor is used as a temperature sensor for a cooking appliance, a large amount of water vapor is generated in the cooking chamber when food is heated, resulting in a supersaturated state of water vapor. As a result,
A lot of condensed water adheres to the outer surface of the thin film thermistor. However, in the thin film thermistor of the present invention, since the glass sintered body 13 is formed covering the pair of plate-shaped metal lead wires 10, 10', compared to the conventional thin film thermistor, the pair of plate-shaped lead wires 10, 10' The insulation distance between the two can be increased. Therefore, the influence of dew condensation that occurs during food heating can be reduced.

[0017]

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, the following effects can be obtained.

(1) Since a pair of conductive members and a pair of conductive fixing materials are used in place of the conventional pair of internal lead wires, no welding work is required.

(2) Since the pair of conductive members and the conductive adhesive are formed only through highly productive processes such as coating, adhesion, drying, and firing, the time required for connection is shorter than that of conventional methods. Compared to welding work, the time can be reduced to 1/2 to 1/3.

(3) Since the glass sintered body is formed to cover the pair of plate-shaped metal lead wires, the insulation distance between the pair of plate-shaped lead wires can be increased compared to conventional thin film thermistors. Therefore, it is possible to reduce insulation deterioration due to dew condensation that occurs during food heating.

[Brief explanation of drawings]

FIG. 1(a) is a partially cutaway exploded perspective view of a thin film thermistor according to a first embodiment of the present invention; FIG. 1(b) is a sectional view of the same;

FIG. 2 is a cross-sectional view of a thin film thermistor according to another embodiment of the present invention.

[Figure 3] Cross-sectional view of a conventional thin film thermistor

[Explanation of symbols]

1 Alumina substrate 3, 3’ Electrode film 8, 8' through hole 9, 9' Conductive member 11, 11' Adhesive conductive sintered body 12 Auxiliary electrode film 13 Glass sintered body

Claims (8)

[Claims] 1. A thin-film thermistor element and a pair of plate-shaped metal lead wires, the thin-film thermistor element including a flat alumina substrate, a pair of through holes provided in the flat alumina substrate, and a pair of plate-shaped metal lead wires. a pair of conductive members that are electrically conductive from one surface of the substrate to the other surface and are disposed through the through hole; and the through hole is provided on the one surface of the flat alumina substrate. and a temperature-sensitive resistor film disposed in a layered manner on the pair of electrode films, and the pair of plate-shaped metal lead wires are connected to the flat plate of the thin film thermistor element. The pair of conductive members and the pair of plate-shaped metal lead wires are connected to each other by a pair of conductive adhesives, and the pair of conductive members and the pair of plate-shaped metal lead wires are respectively connected to A thin film thermistor comprising a plate-shaped metal lead wire and a sintered glass body surrounding the thin film thermistor element. 2. A pair of auxiliary electrode films including a pair of through holes are disposed on the other surface of the flat alumina substrate, and the pair of auxiliary electrode films and the pair of conductive members are connected. thin film thermistor. 3. The thin film thermistor according to claim 1, wherein the pair of plate-shaped metal lead wires are made of an iron-chromium alloy. 4. A step of printing a pair of conductive paste for electrodes including a pair of through holes on one surface of a flat alumina substrate, and then drying and baking to form a pair of electrode films; A step of applying a pair of conductive paste for the through holes on the inner surface of the mouth or the space between the pair of through holes, and then drying and firing it to form a pair of conductive members, and a process of forming a silicon carbide film by sputtering. a step of applying a pair of connecting conductive pastes in contact with the pair of conductive members formed in the pair of through holes on the other surface of the flat alumina substrate; forming an adhesive conductive sintered body by adhering the shaped metal lead wires to the pair of connection conductive pastes and then drying and firing them; and the flat alumina substrate including the pair of plate-shaped metal lead wires. A method for producing a thin film thermistor, which mainly includes the steps of coating the periphery of the glass paste with glass paste, drying and firing it to form a glass sintered body. 5. The firing temperature of the conductive paste for electrodes and the conductive paste for through holes are the same, and after applying and drying the conductive paste for electrodes and applying and drying the paste for through holes, 5. The method of manufacturing a thin film thermistor according to claim 4, wherein the conductive paste for the through hole and the paste for the through hole are simultaneously fired to form the electrode film and the conductive member at the same time. 6. The method for manufacturing a thin film thermistor according to claim 4, wherein the firing temperature of the conductive paste for electrodes is higher than the firing temperature of the conductive paste for through holes. 7. The firing temperature of the conductive paste for connection is the same as the firing temperature of the glass paste, and the pair of plate-shaped metal lead wires are closely attached to the pair of conductive paste for connection and then dried, and the glass paste is coated. 5. The method of manufacturing a thin film thermistor according to claim 4, wherein after drying, the conductive fixing material and the glass sintered body are simultaneously formed by firing both. 8. The method for manufacturing a thin film thermistor according to claim 7, wherein the firing temperature of the conductive fixing material and the firing temperature of the glass sintered body are 700° C. or less.