JPH0276202A - Thin film thermistor - 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] Industrial Application Field The present invention relates to a thin film thermistor with high heat resistance.
This thin film thermistor is used as a temperature sensor for cooking appliances such as electric ovens and gas ovens with a thermal self-cleaning function.

Conventional technology thin film thermistors are described, for example, in the National Technical Report by Nagai et al.
Re-port) Vol, 29. (1983)
As shown in P. 145, it had a structure as shown in Fig. 3.

That is, it is composed of a thin film thermistor element 1 and an external lead wire 3 fixed to a ceramic fixing base 2 made of mullite or the like. The thin film thermistor element l includes a temperature sensitive resistor film 12 such as a silicon carbide (SiC) film formed on one surface of a flat alumina substrate 11 made of alumina, a pair of thick film electrode films 13, and this thick film electrode film 13. It is composed of a pair of thin metal wires 14, for example, a PL wire 14, connected to the wire. After forming the glass coating layer 4 on one surface of the flat alumina substrate 11 described above, the Pt wire 14 and the external lead wire 3 are connected to form a practical thin film thermistor.

Problems to be Solved by the Invention However, with such a structure, when the surface of the glass coating layer 4 of the thin film thermistor is covered with dew condensation water, the surface resistance of the glass coating layer 4 decreases, that is, the insulation property decreases. As a result, the resistance value between the thin metal wires 14 or the external lead wires 3 also becomes smaller than the resistance value of the temperature-sensitive resistor.

In order to eliminate insulation deterioration due to dew condensation, the periphery of the thin film thermistor element 1, ceramic fixing base 2, and external lead wire 3 may be coated with a Teflon-based paint film. Since the Teflon coating film is water-repellent, even if dew condensation adheres to its surface, they are independent and do not connect with each other, which improves insulation deterioration due to dew condensation. but,
The heat resistance of Teflon-based coatings is usually 300°C or less, and there is a problem in that it is difficult to use in open spaces with a thermal self-cleaning function that requires high temperatures of 500°C.

Although there is a glass glaze layer as a heat-resistant and water-repellent coating, the coefficient of thermal expansion of the thin film thermistor element 1 is approximately 70xl.
O-'/”c, the thermal expansion coefficient of the ceramic fixing base 2 is (4
0 to 70) It was difficult to form.

Therefore, the first object of the present invention is to prevent a decrease in resistance due to the adhesion of condensed water by providing a structure in which all parts that are prone to condensation can be insulated.

The second purpose is to maintain the reduction in resistance due to the adhesion of condensed water to a level that is not a problem in practice by increasing the insulation distance between the external lead wires.

The third purpose is to make sure that even if a large number of condensed waters adhere, the condensed waters are independent and do not connect with each other.

Means for Solving the Problems In order to achieve the above first object, the thin film thermistor of the present invention has a thin film thermistor element and an element support covered entirely with glass, and an insulating fixing base for fixing the element support. The heat-resistant external lead wire is fixed with an inorganic adhesive so that the tip is embedded in the end through-hole, and the thin-film thermistor element and the heat-resistant external lead wire are electrically connected at the exposed part of the heat-resistant external lead wire. This is the configuration to connect.

Furthermore, in order to achieve the second object, the present invention provides a central through hole provided in the insulating fixing base for fixing the element support and a central through hole provided in the insulating fixing base for fixing the heat-resistant external lead wire. A protrusion is provided around each of the end through holes.

Furthermore, in order to achieve the third object, the present invention provides a glass glaze layer on the surface of the insulating fixing base.

Operation The thin film thermistor of the present invention has the above structure, so that the surface of the flat element support on which the thin film thermistor element is arranged is completely coated with glass, and the thin film thermistor element is completely insulated from the glass coated surface. Even if dew condenses around the element, the thermistor resistance value will not be affected in any way. In addition, the heat-resistant external lead wire fixed to the insulating fixing base is also fixed so that its tip is embedded with an inorganic adhesive. Even if dew condensation water adheres to the surrounding surface, the insulation resistance value between the heat-resistant external lead wires remains high. In addition,
When a thin film thermistor is attached to a cooking appliance, the part of the thin film thermistor element is placed in contact with the atmosphere inside the cooking appliance, so the environment around the temperature sensitive resistor is prone to condensation. However, since the heat-resistant external lead wire is normally placed so as to be in contact with the atmosphere, there is almost no dew condensation around it. Therefore, reduction due to dew condensation on the heat-resistant external lead wire side is not practical.

In addition, the element support on which the glass coating layer is formed passes through the central through-hole and is fixed to an insulating fixing base with an inorganic adhesive in the middle, and the heat-resistant external lead wire also has its tip inside the end through-hole. are fixed to the insulating fixing base using an inorganic adhesive, but these inorganic adhesives may connect with each other. Inorganic adhesives are porous, so they easily absorb moisture.
Connected dew condensation water is likely to be generated, and therefore the insulation resistance between the heat-resistant external lead wires is likely to decrease. In such cases, by using a fixing base with protrusions around the central through-hole and the end through-holes, and arranging the inorganic adhesive only inside these protrusions, it is possible to The insulation distance between the external lead wires can be increased. Therefore, even if dew condensation water adheres, the insulation resistance between the heat-resistant external lead wires is maintained at a practically sufficient level.

Furthermore, by providing a glass glaze layer on the surface of the insulating fixing base, even if multiple pieces of condensed water adhere to each other, each condensed water will be independent and will not connect with each other.
A decrease in insulation resistance can be prevented. Since the glass glaze layer only needs to be formed on the surface of the insulating fixing base, it can be easily formed.

Embodiment Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. FIG. 1 is an exploded perspective view showing the structure of the thin film thermistor of the present invention. The thin film thermistor element process consists of a pair of thick film electrode films 1 formed on one surface of a flat alumina substrate 11.
2, a pair of metal wires 4 connected to a temperature sensitive resistor film 13 and a pair of thick film electrodes 12. As the thin metal wire 14, a Pt wire, Ni wire, or the like having a diameter of 50 to 200 μm is used. The connection between the two is made by welding, conductive adhesive, or the like.

On the other hand, a flat element support 5 consisting of an insulating flat plate 52 made of alumina or the like on which a pair of thick conductive films 51 were formed was prepared. A thin film thermistor element 1 is arranged at one end of a flat element support 5, and a pair of thin metal wires 14 are connected to a pair of thick film conductive films 5.
1, and a pair of other thin metal wires 6 were connected to the other ends of the pair of thick conductive films 51. In this way, the glass coating layer 4 was formed on the surface of the element support 5 to which the thin film thermistor element 1 and the other pair of thin metal wires 6 were connected.

In FIG. 1, the glass coating layer 4 is shown with its cross sections 41, 42 removed for clarity.

Next, an insulating fixing base 7 having a central through-hole lower 1 placed in the center and a pair of end-through lowers 2 placed on the left and right sides of the central through-hole lower 1 and a pair of heat-resistant external lead wires 3 were prepared. The element support 5 on which the glass coating layer 4 is formed and the pair of heat-resistant external lead wires 3 are assembled as shown in FIG. 2 to complete the thin film thermistor of the present invention. That is, the element support 5 on which the glass coating layer 4 was formed was passed through the central through-hole lower 1 and fixed to the insulating fixing base 7 with an inorganic adhesive 8 at the intermediate portion thereof. Next, the tip 3 of the heat-resistant external lead wire 3
The heat-resistant external lead wire 3 was fixed to the insulating fixing base 7 so that the lead wire 1 was embedded in the end-penetrating lower part 2 with an inorganic adhesive 8. Thereafter, another pair of thin metal wires 6 were connected to the pair of heat-resistant external lead wires 3 by welding or conductive adhesive to complete a thermistor.

In order to evaluate the stability of the thin film thermistor of the present invention against dew condensation, the periphery of the thin film thermistor element kept at room temperature was exposed to a flow of supersaturated water vapor to force the periphery of the element into a state of condensation, thereby reducing the thermistor resistance value. We investigated the fluctuations. Supersaturated water vapor flow was generated using an ultrasonic humidifier. The thin film thermistor of the present invention did not show any decrease in resistance due to dew condensation even after this exposure was continued for more than 100 hours. On the other hand, when a conventional thin film thermistor (FIG. 3) was evaluated under the same conditions, a decrease in resistance due to dew condensation was observed within 30 minutes. Furthermore, even if the area around the thermistor element of a conventional thin-film thermistor was coated with a Teflon-based paint film to increase the insulation against dew condensation and evaluated under the same conditions, a decrease in resistance due to condensation was observed within 50 hours. It was done. In this way, the T of the present invention
It is clear that the i1M thermistor has excellent stability against condensation.

In this way, in the thin film thermistor of the present invention, the surface of the flat element support 5 on which the thin film thermistor element 1 is arranged is completely covered with the glass coating film 4, and the thin film thermistor element 1 is completely covered with the glass coating film 4. Since the thin film thermistor element 1 is insulated, even if dew condenses around the thin film thermistor element 1, the thermistor resistance value is not affected in any way.

Also, a heat-resistant external lead wire 3 fixed to an insulating fixing base 7
Since the tip 31 of the heat-resistant external lead wire 3 is fixed so as to be embedded in the inorganic adhesive 8, and the tip 31 of the heat-resistant external lead wire 3 does not come into direct contact with condensed water, condensed water adheres to the surface around the inorganic adhesive 8. However, the insulation resistance between the heat-resistant external lead wires 3 is maintained high.

The inorganic adhesive 8 is formed by applying a fluid slurry to a predetermined location and then firing it at 400 to 500°C.

Due to this fluidity, during application, the slurries applied to the center through-hole portion and the end through-hole portions may not be separated but may be connected to each other, and the inorganic adhesive 8 may be connected. Since the inorganic adhesive 8 after firing is porous, it easily absorbs moisture and generates condensed water, so such a connection of the inorganic adhesive 8 must be avoided. In such a case, it is desirable to provide protrusions around each of the center penetration lower 1 and the end penetration lower 2 of the insulating fixing base 7. This prevents the slurry, which is easy to flow, from flowing in this protrusion, and therefore the inorganic adhesive 8 is disposed only within this protrusion, thereby preventing the inorganic adhesive 8 from bonding. Furthermore, since the protrusion increases the insulation distance between the heat-resistant external lead wires 3, it is possible to prevent the insulation from decreasing due to dew condensation.

Furthermore, it is desirable to provide a glass glaze layer on the surface of the insulating fixing table 7. Since the glass glaze layer has water repellency, even if a large number of condensed water particles adhere to its surface, each of the condensed water particles becomes independent and does not connect with each other. Therefore, reduction in insulation resistance due to dew condensation can be prevented. Note that it is sufficient to form the glass glaze layer only on the surface of the insulating fixing base 7, so it can be easily formed.

Effects of the Invention As described above, in the thin film thermistor of the present invention, the surface of the flat element support on which the thin film thermistor element is arranged is completely coated with glass, and the thin film thermistor element is completely insulated from the glass coated surface. Even if dew condenses around the thin film thermistor element, the thermistor resistance value is not affected in any way. In addition, the heat-resistant external lead wire fixed to the insulating fixing base is also fixed so that its tip is embedded in an inorganic adhesive, so that the tip of the heat-resistant external lead wire does not come into direct contact with condensed water.
Even if condensed water adheres to the surface around the inorganic adhesive, the insulation resistance value between the heat-resistant external lead wires remains high (maintained).

In addition, by providing protrusions around the central and end through-holes of the insulating fixing base, the inorganic adhesive can be placed only inside these protrusions, thereby preventing the connection between the inorganic adhesives. This can be prevented and the insulation distance between the heat-resistant external lead wires can be increased.

Furthermore, by providing a glass glaze layer on the surface of the insulating fixing base, even if a large number of condensed water adhere to each other, each condensed water becomes independent and does not connect with each other.
A decrease in insulation resistance can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a thin film thermistor showing an embodiment of the present invention, FIG. 2 is an assembled perspective view of the same, and FIG. 3 is a sectional view of a conventional example. DESCRIPTION OF SYMBOLS 1... Thin film thermistor element, 3... Heat resistant external lead wire, 4... Glass coating layer, 5...
...Element support, 6...Pair of other thin metal wires, 7...Insulating fixing base, 8...Inorganic adhesive, 11...・・Flat alumina substrate, 12
...Pair of thick film electrode films, 13 ... Temperature-sensitive resistor film, 14 ... Pair of thin metal wires, 41.4
2...Cut surface of glass coating layer, 51...
Pair of thick conductive films, 52... Insulating flat plate, 71
...Center through-hole, 72... End through-hole. Name of agent: Patent attorney Shigetaka Awano Haka1 / -;l
Membrane Boomisug Kiko Figure 2

Claims (3)

[Claims] (1) A thin film thermistor element consisting of a pair of thick film electrode films and a temperature sensitive resistor film formed on one surface of a flat alumina substrate, and a pair of thin metal wires connected to the pair of thick film electrode films, A pair of thick film conductive films is disposed at one end on the surface of a flat element support on which a pair of thick film conductive films are formed, and the pair of thin metal wires are connected to one end of the pair of thick film conductive films, and the pair of thick film conductive films an element support having a pair of thin metal wires connected to the other end; and a glass coating layer covering the surface of the flat element support on which the thin film thermistor element and the pair of thick film conductive films are formed. , an insulating fixing base having a central through-hole disposed in the center and a pair of end through-holes disposed on the left and right sides of the central through-hole, and a distal end portion embedded in the pair of end through-holes; a pair of heat-resistant external lead wires fixed to the insulating fixing base with an inorganic adhesive; a thin film thermistor which is fixed to a fixed base and which connects the pair of other thin metal wires and the pair of heat-resistant external lead wires; (2) The thin film thermistor according to claim (1), wherein the thin film thermistor is an insulating fixing base having projections provided around the end through-hole and the center through-hole. (3) The thin film thermistor according to claim (1), which is an insulating fixing base having a glass glaze layer formed on its surface.