JPS60179619A - Thin film thermistor - Google Patents

Abstract

PURPOSE:To facilitate welding connection of lead wires because of a low melting point of an electrode film by forming a Ti or Zr film on the surface of a supporting vessel and adhering a ceramic insulating substrate and the supporting vessel to each other by soldering to make it possible to use the thick electrode film. CONSTITUTION:A Ti or Zr film 10 is formed on the surface of a supporting vessel 8 to adhere a ceramic insulating substrate 4 and the supporting vessel 8 to each other by soldering. Since no metallized films are used at all, a thick electrode film 5 can be used. Since the melting point of this electrode film 5 is lower than that of a metallized electrode film, welding connection of lead wires is easy, and the reliability of welding is high. The thick electrode film is formed by sintering in air at 600-1,000 deg.C. Thus, the electrode film is formed easily without special equipments to reduce the production cost.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermistor that detects temperature by mechanically contacting an object whose temperature is to be detected. This relates to a thermistor that detects the temperature of the food inside.

Conventional Structure and Problems Conventionally, this type of temperature detection has been carried out by mechanically contacting a thermocouple 2 with the bottom 1 of the pot, as shown in FIG. 1, and detecting the thermoelectromotive force of the thermocouple 2. was. At this time, the thermocouple 2 was fixed to the support container 3 in order to bring the thermocouple 2 into strong mechanical contact with the pot bottom 1i. However, the thermoelectromotive force usually has the drawback that only a small value can be obtained. For example, an alumel-chromel thermocouple is very thermal (500 to 10,000 C in air) and is inexpensive, but
Only an electromotive force of μV/'C is generated. Copper-constantan thermocouples and platinum-platinum/rhodium thermocouples also have thermoelectromotive force of 30 to 60 μV, which means that it is not possible to obtain CL.The former has shortcomings such as low heat resistance and the latter is expensive. In addition, when detecting a small thermoelectromotive force electrically as described above, a large electrical amplification is required, resulting in problems such as higher costs and the need for a complicated electrical circuit. be.

On the other hand, when temperature is detected using a thermistor instead of the above-mentioned thermocouple, the rate of change in resistance value with respect to temperature is 1 to 7%/
A large value of C can be obtained. Therefore, it has advantages such as not requiring a complicated electric circuit and being inexpensive.

In this case, the thermistor element is selected to be as small as possible and to have a small heat capacity in order to improve thermal response through miniaturization. Such small thermistor elements include bead-type thermistor elements that use composite oxide sintered bodies such as Fe, Ni, Co, and Mn as the temperature-sensitive resistor, or composite oxides such as those mentioned above, Ge, Si, SiC, etc. There are thin film thermistor elements that use the thin film of However, since bead-type thermistor elements usually have a complex shape similar to a sphere or a spheroid, the support container 3
It is difficult to reduce the thermal resistance at the contact point with
Even if the thermistor element itself has a small heat capacity, it has the disadvantage of slow thermal response.

On the other hand, since the thin film thermistor element can be bonded to the support container 3 by brazing as shown in FIG. 2, it has the advantage of providing high-speed response. However, in this case, the following drawbacks also occurred. That is, a typical thin film thermistor element usually has an electrode film 5 and the aforementioned thin film temperature sensitive resistor 6 formed on one surface of a flat insulating substrate 4 made of alumina or the like, and furthermore, a lead wire 7 is connected to the electrode film 5. It is configured by connecting,
If this continues, the thin film thermistor element will be attached to the support container 3 (usually
(composed of heat-resistant metal such as Fe-Cr alloy) cannot be soldered, so a metallized film 8 of W, Mo, etc. is formed on the other surface of the insulating substrate 4, and a metallized film 8 of W, Mo, etc. is formed on the other surface of the insulating substrate 4, and the brazing material is It was glued with solder. However, W, M o
Since metals such as metals have high melting points and are easily oxidized, the metallized film 8 is usually formed at a high temperature of 1400° C. or higher in a reducing atmosphere containing H2 or the like. For this reason, the manufacturing process is complicated and requires special equipment, as well as being expensive. Further, as the electrode film 5, a thick film electrode film with excellent heat resistance is often used, but a thick film electrode film easily deteriorates in a reducing atmosphere, and its heat resistance is 1000°C or less in air. Membrane electrode films are not compatible with the process of forming metallized films.

Conversely, the metallized film is also used in the process of forming a thick film electrode film (usually fired in air at a high temperature of 600 to 1000°C).
does not fit. Therefore, in the configuration shown in FIG. 2, a metallized film must also be used for the electrode film 5. This not only increases the price, but also has the drawback that when connecting the lead wire 7 to the electrode film 5, it is difficult to connect the lead wire 7 to the electrode film 5 by welding, which is commonly used, since the metallized film has a high melting point.

OBJECTS OF THE INVENTION The present invention eliminates these conventional drawbacks, and an object thereof is to provide a thin film thermistor with high-speed response and high reliability.

Structure of the Invention The thin film thermistor of the present invention comprises a flat ceramic insulating substrate, an electrode film and a temperature-sensitive resistor film formed on one surface of the insulating substrate, a brazing material layer, and a Ti film or Z on the surface.
The support container has an R film formed thereon, and the other surface of the insulating substrate and the support container are brazed and bonded using a brazing material layer.

Normally, the ceramic insulating substrate and the brazing material do not wet each other, and there is almost no chemical bonding force between them, so it is difficult to bond the ceramic insulating substrate with brazing. Since the T1 film or Zr film is formed on the surface of the container, when the brazing material is placed between the insulating substrate and the support container and heated, Ti atoms are adsorbed and diffused on the surface of the insulating substrate, resulting in the insulation The substrate is brazed and bonded to the support container.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention is shown in FIG. An alumina substrate 4 is used as a flat ceramic insulating substrate.
An Au--Pt thick film electrode film 5 and a SiC temperature-sensitive resistor sputtered film 6 were formed on one surface of the substrate.

On the other hand, a support container 3' made of Fe-Cr alloy is prepared, and a Ti film 10 (or Zr film 1
0) was formed. The T1 film 10 is easily formed by vacuum evaporation or sputtering.

Thereafter, a eutectic silver solder foil was placed between the other surface of the alumina substrate 4 and the support container 3, and heated to about 820° C. in vacuum.
Connected with solder. After soldering and adhesion, analysis of the vicinity of the soldered surface of the alumina substrate 4 revealed that Ag, C
Ti atoms were also detected along with u and Al atoms. Therefore, during the heating in vacuum mentioned above, the Ti atoms (Ti film 10) that were initially present on the surface of the support container 3 move to the alumina substrate 4, where they are adsorbed and diffused, and as a result, the alumina substrate 4 and the support It is considered that the container 3 was bonded to the container 3 by brazing using the brazing material layer 9.

As is clear from the above explanation, the Au-Pt thick film electrode film 5 and the SiC temperature-sensitive resistor sputtered film 6 are only heated to about 820° C. in vacuum during brazing bonding, so these films are will not deteriorate. Therefore, the electrode film 5
As such, a thick film can be used.

The 90% thermal response time of the thin film thermistor thus formed was measured. This time is defined as the time required for the temperature of the membrane thermistor to reach TI+0.9(T2-T1)'C when the temperature at the bottom of the pot, which was initially maintained at T1°C, suddenly changes to T2°C. Ru. T1=room temperature, T2
: Under the condition of 100℃, 90% thermal response time is 3~
Fast thermal response was obtained in 5 seconds. Also, alumina substrate 4
The adhesive strength to the support container 3 is 100 to 500 g/m
m2, and showed sufficient strength for practical use.

The material of the support container 3 is Fe-Ni-Co alloy, Fe-C
It is preferable to use one selected from the group consisting of r alloy, Fe-Ni alloy, and Ti. This is because the thermal expansion coefficient of the alumina substrate 4 is approximately 80 x 10-7/°C, so in order to minimize the residual thermal distortion after soldering and bonding, the thermal expansion coefficient of the support container 3 is (50 to 110). This is because it is desirable that X 10-7/'C.

Further, the solder material is preferably silver-copper eutectic silver solder.

This is because this eutectic silver solder is easy to process into a foil shape and is often used industrially in a foil shape.

A foil-like silver solder is placed between the other surface of the alumina substrate 4 and the support container 3, and the two are easily soldered and bonded by heating in vacuum.

Further, it is desirable that the temperature sensitive resistor film is a SiC sputtered film. This is because the SiC sputtered film has excellent heat resistance and a wide temperature range (30 to 300°C) required for various types of cooking.
) by having characteristics suitable for temperature detection over

Note that similar results can be obtained even if a Zr film is used instead of the Ti film 10.

Effects of the Invention According to the thin film thermistor of the present invention, the following effects can be obtained while maintaining high-speed response comparable to that of the conventional one.

By forming a Ti film or a Zr film on the surface of the support container, the ceramic insulating substrate and the support container are bonded by brazing.In other words, no metallized film is used, so a thick electrode film can be used. . Since this thick electrode film has a lower melting point than a metallized electrode film, lead wires can be easily welded and welded with high reliability. In addition, metallized electrode films are formed by firing at temperatures of 1400°C or higher in a reducing atmosphere, whereas thick electrode films are formed by firing at temperatures of 60°C or higher in air.
It is formed by firing at 0 to 1000°C.

Therefore, the electrode film can be easily formed without using special equipment, and the manufacturing cost can be reduced.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views showing the conventional structure, and FIG. 3 is a cross-sectional view showing the structure of a thin film thermistor according to an embodiment of the present invention. 3... Support container, 4... Flat ceramic insulating substrate, 5... Electrode film, 6... Temperature sensitive resistor film, 7... - Lead wire, 9... Brazing material layer, 10... Ti film or Zr film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3

Claims (1)

[Claims] (1) A flat ceramic insulating substrate, an electrode film and a temperature-sensitive resistor film formed on one surface of the insulating substrate, a wax film, and a titanium film or zirconium film formed on the surface. and a support container which is bonded to the other surface of the insulating substrate and the support container by a soldering layer. ('2J) Claim 1 states that the layer of the support container is a type selected from 11'I of iron-nickel-cobalt alloy, chromium alloy, iron-nisogal alloy, and titanium alloy. (3) The thin film thermistor according to claim 1, wherein the temperature sensitive resistor film is a silicon carbide sputtered film.