JPS5871603A - Manufacturing method of 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 The present invention relates to a method for manufacturing a thin film thermistor in which a temperature sensitive resistor film and an electrode are formed on one surface of an insulating substrate. The purpose of heat treatment is to thermally stabilize the characteristics.

It is constructed by forming a temperature sensitive resistor film 2 and an electrode film 3 on one surface. The insulating substrate 1 is made of alumina.

Mullite, beryllia, quartz, borosilicate glass, etc. are used. As the temperature sensitive resistor film 2, a thin film of SiC is used.

The electrode film 3 may be a vapor-deposited electrode film of Mu, Cju, Ag, etc., undercoated with Or, Ni, Ni-Or, etc., or a vapor-deposited electrode film of Mu, Cju, Ag, etc., or Mu, Mu, Mu-Pd, or Pt.

A thick film electrode film such as mu-u-pt is used.

When this type of chip is subjected to thermal influences, the thermistor characteristics (resistance value and thermistor characteristics) change significantly. The following two points can be considered as the actual thermal influence on the thermistor characteristics. First, attaching leads after chip formation in the thermistor manufacturing process is a step. In this step, low-melting glass powder is baked onto the electrodes of the chip, and lead wires are connected through this. Baking this low melting point glass powder requires working conditions of 700° C. for 5 minutes, and therefore the thermistor characteristics are significantly affected by heat.

Second, since the thermistor is used for detecting the operating temperature in the practical process, the maximum operating temperature is 350°C intermittently.

The former is reflected in productivity such as the yield of thermistor manufacturing, and the latter is reflected in the life and reliability of the thermistor.

Conventionally, in order to thermally stabilize this type of chip, a method of pre-annealing the chip has been used. This annealing treatment is a method of heat treatment (aging in the atmosphere) using an electric furnace or the like after the chip is formed, and conditions are usually used at 700° C. for about 20 minutes to 3 hours (in the atmosphere). Among these, the conditions of 700° C. for 1 hour or more were used in actual production because there was no significant difference in the effect on stabilization and it was suitable for shortening the working time. However, according to the traditional annealing process.

Although it is possible to considerably suppress the thermal influence on thermistor characteristics, it has been difficult to reduce the range of variation. Therefore, it had some drawbacks in terms of thermistor manufacturing.

The present invention solves the above-mentioned conventional drawbacks in a chip in which a temperature-sensitive resistor film and an electrode film are formed on one surface of an insulating substrate by heat-treating at least the chip in a high vacuum. Hereinafter, one embodiment of the present invention will be described in detail.

The sample for the example experiment was an insulating substrate based on the chip configuration described above, and an amine substrate with a purity of 96 cm (L6.6 x 1.8 xt).
0.6%), a thick film sintered body of gold/platinum paste for the electrode film, and an 8iC Nubatta vapor-deposited film (2.6μ
m thickness) was selected. The initial characteristics of the thermistor of the chip created in this way are a resistance value (measured at 50°C) of approximately 18
0 Kg, the thermistor constant (value between 60° C. and 140”0) was approximately 2376°.

Next, for heat treatment in high vacuum, a general-purpose vacuum furnace (~×1
Φ-'Torr) was used. The heating temperature setting is 400.
500. Too and 900°C were selected, and each time was 50.60 minutes. The vacuum pressure is the ultimate vacuum pressure of 3 x 10'T.
orr, and the pressure was controlled to be 5×105 ToILr or less, including the reduction in the degree of vacuum due to heating. FIG. 2 shows the relationship between the resistance value change (measured at 60° C.) of the chip heat-treated in a high vacuum in this manner. In Figure 2, ((a) is treated at 400°C, ((b) is treated at 500'C', (c) is treated at 700°C, and) is 90°C.
It shows the resistance value characteristics over time during 0'C treatment, and it has been revealed that each exhibits a characteristic i-line. In the experiment ((a), (b).

(C) and (2) were selected, but for each temperature in between, it is unlikely that characteristic curves similar to (L) with temperature dependence shown in Figure 2 can be obtained. It is easy to draw an analogy.

Each sample prepared as described above was tested for thermal effects. The test conditions for thermal effects include 700°C x 10 minutes (in the atmosphere), which takes into account the above-mentioned thermistor manufacturing temperature, and 400'C x 1, which takes into account the practical use temperature.
The experiment was carried out by selecting a 61'-' exposure position for 000 hours (in the atmosphere). The 60°C resistance value before and after this test and the rate of change in the thermistor constant between 60°C and 140°C were examined to evaluate the effect of stabilizing the thermistor characteristics.

However, in order to compare the effects of the present invention, we conducted a comparison of chips annealed at 700°C for 60 minutes (in the atmosphere), which is typical of conventional heat treatment, and vacuum conditions.
The same thermal effect test was conducted using a chip that had been heat treated at 700° C. for 10 minutes in a controlled low vacuum range of 10×10 −2 TOrr.

As a result, it was found that the thermistor characteristics of the chip heat-treated in a high vacuum according to the present invention were extremely stabilized thermally. In particular, when looking at the temperature holding time of heat treatment as a parameter, no significant difference was observed in the stabilizing effect.

Among these, those in U) to (B) shown in FIG. 2 that were heated and held for 10 minutes are representative, and comparisons with conventional examples and those processed in a low vacuum region are shown in the table. Table 1 shows the temperature at Too°C for 10 minutes (in the atmosphere).

Table 1 shows the results of a test on thermal effects caused by standing at 400°C for 1600 hours (in the atmosphere).

As is clear from Tables 1 and 11, the thermistor characteristics [resistance value (6
0'C) The rate of change is △R', the thermistor princess number (6o→
140° C.) whose rate of change is indicated by ΔB] shows a very stable effect against thermal influences. In addition, changes in thermistor characteristics in practical use require a resistance value within ±6 inches and a thermistor constant within ±2 degrees, but changes in the thermistor characteristics of chips heat-treated in a high vacuum of at least 500'C or higher are necessary. It can be seen that the rate of change satisfies this requirement. Furthermore, in the chips heat-treated at 400° C. in a high vacuum and the chips heat-treated in a low vacuum region, remarkable thermal stability of the thermistor characteristics could not be obtained. However, if the above-mentioned use is intended to have a wide permissible range of change in the thermistor characteristics, it is clear that such heat treatment will not be effective enough.
There is/obey.

As a result, it has become possible to manufacture thin film thermistors with excellent compatibility, resulting in improved yields. Furthermore, as a result of improved thermal stability, stable reliability can be obtained.

In addition, in this experiment, the heat treatment temperature was set to 900°C.
This is because this temperature setting was made from the viewpoint of the heat resistance of the electrode material of the chip, and it can be easily inferred that the temperature range changes depending on the configuration of the electrode material.

As is clear from the above explanation, by heat-treating the chip of the present invention in a high vacuum, excellent thermal stability of the thermistor characteristics can be achieved, and the yield of thermistor manufacturing can be improved.
Effects such as reliability and improvement can be obtained.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view schematically showing the thermistor element (chip) used in experiments in the present invention, and Figure 2 shows the resistance value (at 60°C) and time when the chip was heat-treated in a high vacuum. FIG. 1... Insulating substrate, 2... Temperature sensitive resistor film, 3... Electrode film. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 TIME trni*)→

Claims (3)

[Claims] (1) A method for manufacturing a thin film thermistor, in which a therminuta element is formed by forming a temperature-sensitive resistor film and an electrode film on one surface of an insulating substrate, and then the therminuta element is heat-treated in a high vacuum. (2) The method for manufacturing a thin film therminuta according to claim 1, wherein the vacuum pressure is at least 6×10 Torr or less. (3) The method of voicing a thin film thermistor according to claim 1, wherein the heat treatment temperature is at least in the range of SOO°C to 900°C.