JPS5932041B2 - thin film thermistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film thermistor, and more particularly to a thermometer thermistor configured to sense heat through mechanical contact with an object.

This type of thermometer is used, for example, to detect the temperature of food inside the cooking container or the temperature of oil vaporization in the vaporizer by coming into contact with the outer wall of the cooking container or the outer wall of the vaporizer of oil-burning equipment. It will be done.

This type of thermometer usually has a structure and usage as shown in FIG. That is, the temperature measuring body 1 contacts, for example, the outer wall 10 of the cooking container. Normally, the temperature measuring element 1 consists of a protection tube 2, a thermistor chip 3, and an adhesive layer 4 between the protection tube 2 and the thermistor chip 3, and the thermistor chip 3 is usually provided with an electrode on one surface of a flat insulating substrate 5. It is constructed by forming a film 6 and a temperature sensitive resistor film T. Actually, a lead wire 8 is further connected to the electrode film 6, and a temperature sensitive resistor T is connected through the lead wire 8.
Detects the resistance value, or temperature. As described above, this type of thermistor chip 3 has an electrode film 6 on one surface of a flat insulating substrate 5, such as ceramic such as alumina, beryllia, mullite, or borosilicate glass. , Au-Pd, Au, Ag, P
Thick film electrode such as t or Cr-Au3Cr-Cu3
Laminated thin film electrode such as Cr-Pt, temperature sensitive resistor film T, such as Ge, Si, SiC, or Fe-Cr-Co-
It is constructed by forming a thick film or thin film resistor made of a composite oxide such as Mn. However, in this case the thermistor chip 3
When bonding the protective tube 2 to a stainless steel tube, for example, the following drawbacks occurred. That is, when an organic adhesive such as an epoxy resin adhesive or a cyanoacrylate adhesive is used for the adhesive layer 4, stable adhesion can be easily obtained, but the heat resistance is only about 60 to 150°C. There was a drawback. When this type of thermometer is used in a cooker or a combustor, heat resistance of 300 to 600°C is usually required.

On the other hand, if an inorganic adhesive such as an alumina phosphate adhesive or a low melting point glass adhesive is used for the adhesive layer 4, it is possible to obtain adhesive properties with high heat resistance, but stable adhesive properties that are susceptible to thermal or mechanical shocks are obtained. There was a drawback that it was not possible to obtain Further, when connecting the lead wire 8 to the electrode film 6, such as the above-mentioned thick film or thin film electrode, the soldering method generally used for connecting electronic components uses a relatively thick lead wire, for example, 0.2 to 0.0 mm. 8
Although there is an advantage in that a wm0 copper or nickel wire can be directly connected to the electrode film 6, there is a disadvantage in that the heat resistance is only about 100 to 200°C.

On the other hand, the welding method can provide a connection with high heat resistance, but since the thickness of the electrode film 6 is at most 15 to 20 μm, thin wires with small heat capacity, such as 0.02 to 0.2 m0 gold wire, platinum wire, aluminum wire, etc. can be used. The wire was welded to the electrode film 6. However, in this case, the welding area inevitably becomes smaller, resulting in a disadvantage that the welding strength is usually on the order of several 7 to several 107. In order to compensate for this drawback, a structure is often used in which the welded part is covered with an electrically insulating cement, such as an alumina phosphate cement or a low melting point glass cement. However, in this case, there were drawbacks such as a complicated structure and increased cost. Furthermore, the thin wire cannot be practically used as the lead wire 8 because of its low mechanical strength, high price, and difficulty in handling. For this reason, it is necessary to separately prepare a thick lead wire, which usually poses no problem in practical use, and to use the thin wire and the thick lead wire by welding them together.

As a result, disadvantages such as a complicated structure and high cost arise.

The present invention is a thin film thermistor that eliminates these conventional drawbacks.
As shown in FIG. 22, the thin film thermistor chip 3 consists of an electrode film 6 and a temperature sensitive resistor film 7 formed on one surface of a flat insulating substrate 5. A molybdenum or tungsten metallized film is used at least for the electrode film 6, and the metallized coating film 9 is formed entirely on the other surface of the flat insulating substrate 5.

An embodiment of the present invention will be described below.

As mentioned above, the thin film thermistor chip 3 of the present invention has the molybdenum or tungsten metallized 5 coating film 9 formed entirely on the other surface of the flat insulating substrate 5. For example, the present thin film thermistor chip 3 can be bonded to a stainless steel pipe using a brazing material adhesive layer 4.

In both the metallized coating film 9 and the protective tube 2, for example, a stainless steel tube 4, the brazing material not only flows smoothly and provides stable adhesion, but also has heat resistance that can be improved by appropriately selecting the brazing material. A temperature of about 300 to 600°C can be achieved. When this thin film thermistor chip 3 was soldered and bonded to the stainless steel protection tube 2 with silver solder (liquidus temperature ~700°C), the silver solder flowed smoothly and a tensile strength of 10 to 50 Kf/Cd was obtained. Ta.

Since the area of the metallized coating film 9 is usually 10 to 50 md, the actual tensile strength is about 1 to 25 Kf,
It has sufficient practicality. Also, around liquidus line ~780℃
When the stainless steel protective tube 2 and the thermistor chip 3 were bonded together using silver brazing material at ~930°C, nickel-based brazing material at ~930°C, or gold soldering material at ~1010°C, the same tensile strength as described above was obtained. .

In this way, the thin film thermistor chip 3 is connected to the stainless steel protection tube 2 by brazing in air at 300 to 600
Tensile strength remains almost unchanged even if a thermal cycle test is performed for 100 to 1000 cycles, where one cycle is 100 to 1000 hours of continuous standing at 300 to 600°C in air, followed by 15 minutes at room temperature. It never decreased. As described above, since the present thin film thermistor chip 3 can be brazed to the protective tube 2, not only can stable adhesion be easily obtained, but also the chip can
It is possible to obtain heat resistance of 00 to 600°C, and therefore, the conventional drawbacks can be overcome.

Moreover, since the present thin film thermistor chip 3 uses the metallized film for the electrode film 6, the metallized electrode film 6
A thick lead wire 8 can be brazed directly to the holder.

Therefore, like the soldering of the protective tube 2 and the present thin film thermistor chip 3 described above, not only can stable adhesiveness be easily obtained, but also heat resistance of 300 to 600°C can be obtained by appropriately selecting the brazing material. be able to.

In this way, the present thin film thermistor chip 3 has a simple structure and can realize highly heat-resistant lead wire extraction, thereby eliminating the drawbacks of the conventional structure. This thin film thermistor chip 3 is particularly useful when a SiC film is used for the temperature sensitive resistor film 7.

In other words, the SiC temperature-sensitive resistor film 7 can be used in a wide operating temperature range (3
0~400℃), and high heat resistance (300℃ in air).
~600°C). Therefore, as mentioned above, not only can stable adhesion be easily obtained, but also adhesive strength of 300 to 600
This thin film thermistor chip 3 provides heat-resistant adhesion at ℃
When the SiC temperature sensitive resistor film T is used, the characteristics of the SiC temperature sensitive resistor film 7 can be maximized. Furthermore, S
In order to impart high heat resistance to the iC temperature sensitive resistor film 7, it is usually necessary to perform an annealing treatment in air at 500 to 800° C. for 1 to 100 hrs.

This is because the initial characteristic change, mainly the resistance value change, of the SiC temperature-sensitive resistor film 7 is sufficiently progressed by the annealing treatment.
The purpose is to stabilize subsequent changes in thermal resistance. Such in-air annealing treatment oxidizes the metallized electrode film 6 or coating film 9, making it impossible to braze it.

However, in this case, the oxidation can be prevented by forming an oxidation prevention film, for example, a thick electrode film of Ag-Pd, Au-Pi, etc., on the metallized electrode film 6 or the coating film 9. Also, the metallized electrode film 6 or the coating film 9 is oxidized during brazing as described above. In this case, oxidation can be prevented by setting the atmosphere during brazing to a vacuum or inert gas atmosphere. Although the metallized coating film 9 has been described as being formed on the entire other surface of the flat insulating substrate 5, for example, as shown in FIG. A metallized coating film 9 is formed, a small hole is formed in the protection tube 2, the shape of the small hole is formed so as to overlap the pattern of the metallized coating film 9, and both are brazed together. Of course, it is also a good thing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional thin film thermistor, FIG. 2 is a sectional view of a thin film thermistor according to an embodiment of the present invention, and FIG. 3 is a sectional view of a thin film thermistor according to another embodiment. 3... Thermistor chip, 5... Flat insulating substrate, 6... Electrode film, 7...
Temperature-sensitive resistor membrane, 8...Lead wire, 9...
・Metallized coating film.

Claims (1)

[Scope of Claims] 1. A thin film thermistor chip comprising an electrode film and a temperature-sensitive resistor formed on one surface of a flat insulating substrate, wherein at least a molybdenum or tungsten metallized electrode film is used as the electrode film, and A thin film thermistor characterized in that the metallized coating film is formed entirely on the other surface of an insulating substrate. 2. The thin film thermistor according to claim 1, characterized in that a SiC film is used for at least the temperature sensitive resistor film.