JPH04564B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for manufacturing a thick-film positive temperature coefficient semiconductor element that does not require a glass frit, among planar heating elements used for heat insulation and heating of equipment. be.

Conventional structure and its problems Elements made of BaTiO ₃ -based semiconductors have switching characteristics in which the resistance value increases rapidly above a certain temperature and self-heating characteristics after switching, and have fast temperature rise characteristics and self-temperature control functions. It is widely used because it does not require an external control circuit.

Conventional positive temperature coefficient thermistor heating elements have been obtained by press-molding BaTiO ₃ semiconductor powder and then firing it, but it is said to be difficult to obtain a practical thick film positive temperature coefficient thermistor heating element. Ta.

Conventionally, the following methods are known for processing BaTiO ₃ -based semiconductors into a film.

(1) After forming into a disk shape, the fired product is polished into thin pieces.

(2) Form a thin film on the substrate by vacuum evaporation.

(3) Conductive additives and glass frit are added to _BaTiO3 -based semiconductor powder to form a paste, which is then screen printed onto a substrate and then fired.

However, in the method (1) above, it is extremely difficult to polish the BaTiO ₃ -based semiconductor into a film because the crystal grain size of the semiconductor is large and brittle. Furthermore, the method (2) above is cumbersome to operate, and it is difficult to obtain a large amount of power suitable for the heating element. Furthermore, in method (3), the sheet resistance tends to increase and is difficult to control, making it unsuitable for heating elements, and requiring preparation and firing of the glass frit in advance, which is troublesome and difficult to control. Depending on BaTi ₃
It deteriorates the switching characteristics and self-heating characteristics of the semiconductor. Adding glass frit makes it vulnerable to thermal shock due to the difference in heat resistance and coefficient of thermal expansion between BaTiO ₃ -based semiconductors and glass frit, which impedes heat conduction. Furthermore, it is difficult to uniformly mix the conductive additive and the glass frit, which is one of the causes of variations in properties.

Purpose of the Invention Therefore, the present invention solves the manufacturing complexity that was a drawback of the prior art, and achieves excellent thermal shock resistance, thermal conductivity, and uniform characteristics by forming a thick film without using glass frit. It is an object of the present invention to provide a method for easily manufacturing a thick film type positive characteristic semiconductor element having the following characteristics.

Structure of the Invention The method for manufacturing a thick film type positive characteristic semiconductor element of the present invention includes adding at least one of Ta ₅ Si ₃ , Ta ₂ Si or TaSi ₂ to BaTiO ₃ -based semiconductor powder in an amount of 1 to 60% based on the total weight. % and a paste-like mixture is coated on a substrate to form a thick film and then fired to obtain a thick film type positive characteristic semiconductor element.

In the conventional method of using conductive additives and glass frits, conductive additives are required to electrically connect BaTiO ₃ -based semiconductor powders to each other, and glass frits are required to physically connect BaTiO ₃ -based powders to each other. It was hot.

However, according to the present invention, the material serves as both a conductive additive and a glass frit.
The feature is that Ta ₅ Si ₃ , Ta ₂ Si, and TaSi ₂ are used. These Ta ₅ Si ₃ , Ta ₂ Si, and TaSi ₂ are conductors at room temperature, but at temperatures above 1000 to 1100°C, a portion decomposes and SiO ₂ precipitates on the particle surface, but the inside of the particle remains intact. Decomposition is prevented by the SiO ₂ film on the surface. Therefore, when BaTiO ₃ -based semiconductor powder and Ta ₅ Si ₃ , Ta ₂ Si or TaSi ₂ powder are mixed and fired, the SiO ₂ precipitated on the surface of Ta ₅ Si ₃ , Ta ₂ Si or TaSi ₂ is the same as glass frit. Because the inside of the particle acts as a conductive additive,
By simply adding Ta ₅ Si ₃ , Ta ₂ Si or TaSi _{2 ,} a thick film type positive characteristic semiconductor device that does not require a glass frit can be obtained.

Furthermore, by adding a conductive metal, the thermal conductivity is improved compared to glass frit which has poor thermal conductivity, and the thermal shock resistance is also improved.

DESCRIPTION OF EMBODIMENTS Examples of the present invention will be specifically explained below with reference to FIG.

Example 1 1.0 mol % of La ₂ O ₃ is added to BaTiO ₃ and fired at 1300°C, followed by pulverization to obtain BaTiO ₃ -based semiconductor powder. Based on the total weight of the BaTiO ₃ -based semiconductor powder
4.0% by weight of Ta ² Si powder is added and mixed uniformly, and α-terpineol is further added to form paste mixture 1.

On the other hand, on a substrate 2 made of Al ₂ O ₃ etc., a pair of electrodes 3 made of a conductive material such as Ag,
4, and apply the paste mixture 1 by screen printing or the like so that a portion of the electrodes 3 and 4 remain on the electrodes 3 and 4, and then heat the mixture from room temperature to
The temperature was raised to 1350°C at a heating rate of 10°C/min, held for 1 hour, and then allowed to cool in the furnace. In this way, a thick film type positive characteristic semiconductor device was obtained.

Example 2 In the same manner as in Example 1, 3.0 mol% of BaTiO ₃ was added.
Add La ₂ O ₃ and bake at 1250℃, then crush.
Obtain BaTiO ₃ based semiconductor powder. 50.0% by weight of TaSi ₂ powder based on the total weight is added to the BaTiO ₃ -based semiconductor powder and mixed uniformly, and α-terpineol is further added to form paste mixture 1. Then,
As in Example 1, the electrodes 3 and 4 are provided on the substrate 2 in advance, and the paste mixture 1 is applied by screen printing or the like so that a portion of the electrodes 3 and 4 remains, and the mixture is heated for 10 minutes from room temperature. The temperature was raised to 1300°C at a heating rate of °C/min, held for 30 minutes, and then allowed to cool in the furnace. In this way, a thick film semiconductor device was obtained.

The sheet resistance at room temperature of the thick film semiconductor device thus obtained was 5.8KΩ/cm ² in Example 1 and 0.3KΩ/cm ² in Example 2, and the relationship between temperature and resistance value for each is as follows: It was as shown in Figure 2. Second
In the figure, A indicates the characteristics of the device obtained in Example 1, and B
is the characteristic in the case of Example 2.

Effects of the Invention As described above, according to the manufacturing method of the present invention,
Ta ₅ Si ₃ , Ta ₂ Si or TaSi ₂ powder acts as both the traditional conductive additive and the glass frit,
This has a sufficient effect on electrical connection and physical connection, and a thick film positive characteristic semiconductor element can be obtained without glass frit.

In addition, instead of glass frit, which has poor thermal conductivity, Ta ₅ Si ₃ , which is a conductive metal with good thermal conductivity, is used.
By using Ta ₂ Si or TaSi ₂ , heat conduction is improved and thermal shock resistance is also improved. Furthermore, since it can be manufactured by screen printing or the like, the work is easy and mass production is possible.

In the present invention, any BaTiO ₃ -based semiconductor powder may be used as long as it is made into a semiconductor by adding various additives to BaTiO ₃ . Also, Ta ₅ Si ₃ ,
The amount of Ta ₂ Si, TaSi ₂ powder added to the total weight is 1
The reason why it is specified as ~60% by weight is that if it is less than 1% by weight, the sheet resistance becomes too large and is not suitable for a heating element.
It is also impossible to physically fix BaTiO ₃ powders together;
If it exceeds 60% by weight, the sheet resistance becomes too small,
This is because the self-control characteristic (PTC characteristic) becomes small, making it unsuitable for a heating element.

Further, in the examples, only the case where one type of conductive metal was added was shown, but it was confirmed that the same effect could be obtained if multiple types were added in a total amount within the specified amount. Furthermore, BaTiO ₃ -based semiconductor powder and Ta ₅ Si ₃ ,
An organic solvent (α-terpineol in the example) was used to make the Ta ₂ Si, TaSi ₂ powder into a paste, but any solvent may be used as long as it can be made into a paste.

As described above, according to the present invention, it is possible to easily manufacture a thick film type positive characteristic semiconductor device that does not require a glass frit, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing a thick film type positive characteristic semiconductor device obtained by the method of the present invention, and FIG. 2 is a diagram showing the relationship between temperature and resistance value of the device according to an embodiment of the present invention. 1...Paste mixture, 2...Substrate, 3, 4
……electrode.

Claims (1)

[Claims] 1 _{Ta 5 Si 3} , Ta ₂ Si,
A thick film characterized by adding at least one type of TaSi ₂ in an amount of 1 to 60% by weight based on the total weight, applying a paste-like mixture onto a substrate to form a thick film, and then firing the mixture. A method for manufacturing a type positive characteristic semiconductor device.