JPS6252924B2 - - Google Patents

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 is to thermally stabilize the properties by heat-treating the material in a high vacuum. The chip is constructed by forming a temperature-sensitive resistor film 2 and an electrode film 3 on one surface of an insulating substrate 1, as shown in FIG. The insulating substrate 1 includes 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 is a vapor-deposited electrode film of Au, Cu, Ag, etc. undercoated with Cr, Ni, Ni-Cr, etc., or Ag, Au, Ag-Pd, Pt, Au-Pt.
A thick film electrode film such as the following is used. When this type of chip is subjected to thermal influences, the thermistor characteristics (resistance value and thermistor constant) change significantly. The following two points can be considered as the actual thermal influence on the thermistor characteristics. The first is the lead attachment process after chip formation in the thermistor manufacturing process. In this process, low-melting glass powder is baked onto the electrodes of the chip, and lead wires are connected through this. Baking of this low melting point glass powder requires working conditions of 700°C for 5 minutes, so the thermistor characteristics are significantly affected by heat. The second factor is the temperature at which the thermistor is used in practical use. This type of thermistor is used to detect the internal temperature of a cooker, so at the maximum operating temperature,
It will be exposed to 350℃ 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 was used. This annealing process is a method of heating (aging in the atmosphere) in an electric furnace or the like after the chip has been formed.
The conditions of approximately 20 minutes to 3 hours (in the atmosphere) are used. In particular, under conditions of 700℃ x 1 hour or more, there is no significant difference in stabilization effect and it is suitable for shortening working time, so it is not recommended for actual manufacturing.
Conditions of 700°C x 1 hour were used. However, although the conventional annealing treatment can considerably suppress the thermal influence on the thermistor characteristics, it has been difficult to reduce the range of fluctuation thereof. Therefore, there have been disadvantages such as a decrease in the yield in manufacturing thermistors and large variations in reliability. The present invention solves the above-mentioned conventional drawbacks in a chip having a temperature-sensitive resistor film and an electrode film 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. Example For the experimental sample, an insulating substrate and an alumina substrate ( ^L 6.5 × ^W 1.8
× ^t 0.5m/m), a thick film sintered body of gold/platinum paste was selected for the electrode film, and a sputter-deposited SiC film (2.5 μm thick) was selected for the temperature-sensitive resistor film. The initial characteristics of the thermistor of the chip created in this way are a resistance value (measured at 50℃) of approximately 180KΩ, and a thermistor constant (50KΩ).
℃ and 140℃) was approximately 2375〓. Next, a general-purpose vacuum furnace (~×10 ^-6 Torr) was used for heat treatment in high vacuum. Setting the heating temperature
400, 500, 700, and 900°C were selected, and the holding time at each temperature was 10, 20, 30, 40, 50, and 60 minutes. The vacuum pressure was set to 3×10 ^-6 Torr.
The pressure is 5x including the decrease in the degree of vacuum due to heating.
Control was performed to keep it below 10 ^-3 Torr.
Figure 2 shows the relationship between the resistance value change (measured at 50°C) of the chip heat-treated in a high vacuum in this manner. In Figure 2, A shows the resistance value characteristics over time for 400°C treatment, B for 500°C treatment, C for 700°C treatment, and D for 900°C treatment, each of which shows a characteristic curve. It became clear. In the experiment, temperatures A, B, C, and D were selected, but for each temperature in between, characteristic curves similar to the temperature-dependent characteristic curves shown in Figure 2 can be obtained. can be easily inferred. Each sample prepared as described above was tested for thermal effects. The test conditions for thermal effects include 700℃ x 10
We chose to leave the sample at 400°C for 1000 hours (in the atmosphere) considering the practical use temperature. The 50°C resistance value before and after this test and the rate of change in the thermistor constant between 50°C and 140°C were examined to evaluate the effect of stabilizing the thermistor characteristics. In addition, in order to compare the effects of the present invention, we also compared chips annealed at 700°C for 60 minutes (in air), which is typical of conventional heat treatment, and vacuum conditions of 1 to 10 x 10 ^-2. The same thermal effect tests were conducted using chips heated at 700°C for 10 minutes in a controlled low vacuum region of the Torr range. 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, there was no significant difference in the stabilizing effect. Among these, the system which was heated and held for 10 minutes under conditions A to D shown in Fig. 2 is representative, and the table shows a comparison with conventional examples and those processed in a low vacuum region. The table shows the thermal effect test results after being left at 700℃ for 10 minutes (in the atmosphere), and the table below shows the results of thermal effects when left at 400℃ for 1000 hours (in the atmosphere). As is clear from the table, the thermistor characteristics of the chip heat-treated in a high vacuum according to the present invention [resistance value (at 50℃) change rate is ΔR', thermistor constant (between 50→←140℃ It can be seen that the rate of change of ) is shown as ΔB] exhibits a very stable effect against thermal influences. In addition, changes in thermistor characteristics in practical use include resistance values of ±6% and thermistor constants of ±2%.
% or less, but it can be seen that the rate of change in the thermistor characteristics of chips heat-treated in a high vacuum of at least 500° C. satisfies this requirement. Furthermore, no remarkable thermal stability of the thermistor characteristics could be obtained for chips heat-treated at 400°C in a high vacuum and chips heat-treated in a low vacuum region. However, if the above-mentioned use is intended to have a wide permissible range of change in the thermistor characteristics, it is clear that these heat treatments can be sufficiently effective. Therefore, 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
The maximum temperature is set at 900℃, because this temperature setting was made from the viewpoint of the heat resistance of the chip's electrode material, and it can be easily inferred that the temperature range changes depending on the composition of the electrode material.

【table】

【table】

[Table] As is clear from the above explanation, by heat-treating the chip of the present invention in a high vacuum, excellent thermal stability of thermistor characteristics can be achieved, and the yield and reliability of thermistor manufacturing can be improved. It is possible to obtain effects such as improvement of

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view schematically showing the thermistor element (chip) used in the experiment of the present invention, Figure 2
The figure shows the relationship between resistance value (at 50°C) and time when a chip is heat-treated in a high vacuum. 1... Insulating substrate, 2... Temperature sensitive resistor film, 3...
...electrode membrane.

Claims (1)

[Claims] 1. Manufacturing of a thin film thermistor by forming a temperature-sensitive resistor film and an electrode film on one surface of an insulating substrate to produce a thermistor element, and then heat-treating the thermistor element in a high vacuum. Method. 2. The method for manufacturing a thin film thermistor according to claim 1, wherein the vacuum pressure is at least 5×10 ^-3 Torr or less. 3. The method for manufacturing a thin film thermistor according to claim 1, wherein the heat treatment temperature is at least in the range of 500°C to 900°C.