JPS61101004A - Manufacture of thick film type positive temperature coefficient semiconductor element - 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 Field of Industrial Application The present invention relates to a method for manufacturing a thick-film positive temperature coefficient semiconductor element that does not require glass frit, among planar heating elements used for heat insulation and heating of equipment, etc. It is.

Conventional structure and its problems 11a Elements made of TiO3-based semiconductors have switching characteristics in which the resistance value increases rapidly above a predetermined temperature and self-heating characteristics after switching, and have fast temperature rise characteristics and a self-temperature control function. However, it is widely used because it does not require an external control circuit.

Conventional positive temperature coefficient thermistor heating elements were obtained by press-molding BaT x O3 semiconductor powder and then firing it, but it was difficult to obtain a practical thick film positive temperature coefficient thermistor heating element. It had been.

Conventionally, the following methods are known for processing an f3a T *Oa semiconductor into a film.

■ After forming into a disk shape, the fired product is polished into thin pieces.

■ Form a thin film on the substrate by vacuum evaporation.

(2) Conductive additives and glass frit are added to BaTiO3-based semiconductor powder to form a paste, which is screen printed on a substrate and then fired.

However, in the method (2) above, it is extremely difficult to polish the BaT 103-based semiconductor into a film because the crystal grain size is large and brittle. In addition, the method (2) is cumbersome to operate, and it is difficult to obtain a large amount of power suitable for the heating element. Furthermore, method (2) tends to have a high sheet resistance and is difficult to control, is not suitable for heating elements, and requires preparing and firing the glass frit in advance, which is troublesome and Depending on the material of the glass frit, Ba T 103
It deteriorates the switching characteristics and self-heating characteristics of semiconductors. By adding glass frit, the glass frit becomes susceptible to thermal shock due to the difference in heat resistance and thermal expansion coefficient between the BaTiO3-based semiconductor and the glass frit, and heat conduction is hindered. Furthermore, it is difficult to uniformly mix conductive additives and glass frit, which is one of the causes of variations in properties.

Purpose of the Invention Therefore, the present invention solves the drawback of the prior art, which is the complexity of manufacturing, and creates a film with excellent thermal shock properties and thermal conductivity 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 is characterized in that Ba
HfB2 is added to SiO3-based semiconductor powder in a mixed amount of 1 to 60% by weight based on the total weight, and the paste-like mixture is applied onto a substrate to form a thick film, and then baked to form a thick film type. The purpose is to obtain a positive characteristic semiconductor device.

In the conventional method using conductive additives and glass frit, conductive additives are required for electrical connection between BaTiO3-based semiconductor powders, and glass frit is required to physically connect BaTiO3-based semiconductor powders. was necessary.

However, according to the present invention, HfB2 is used as a material that functions as both a conductive additive and a glass frit, which has a unique feature. This HfB2 is a conductor at room temperature, but at temperatures above 100 to 1100'C, a portion decomposes and B2O3 precipitates on the particle surface.
The inside of the particle remains intact and decomposition is prevented by the B2O3 film on the surface. Therefore, when B a T sO3-based semiconductor powder and HfB2 powder are mixed and fired, B2O3 precipitated on the surface of HfB2 plays the same role as glass frit,
Since the inside of the particles acts as a conductive additive, a thick film positive temperature coefficient semiconductor element that does not require a glass layer can be obtained simply by adding HfB2.

Furthermore, by adding a conductive metal, the thermal conductivity becomes better than that of glass frit, which has poor thermal conductivity, and the thermal shock resistance is also improved.

DESCRIPTION OF EMBODIMENTS Below, embodiments of the present invention will be specifically explained with reference to FIG.

Example 1 Adding 1.0 mol% Nb2O3 to BaT 103
After firing at 00° CT, it is pulverized to obtain a B a T 103 semiconductor powder. 2.5% by weight of HfB2 powder based on the total weight is added to the BaTiO3-based semiconductor powder and mixed uniformly, and a-terpineol is further added to form a paste mixture 1.

On the other hand, a pair of electrodes 3.4 made of a conductive material such as Aq are provided in advance on a substrate 2 made of Al2O3, etc., and the electrodes 3. Paste-like mixture 1 was applied by screen printing, etc., and heated to 1350°C at a heating rate of 10'% from room temperature.
The temperature was raised to 'C, 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 C was added to BaTiO3.
After adding eO2 and constituting at 1250°C, it is crushed to obtain Ba
A TiO3-based semiconductor powder is obtained. 33% by weight of HfB2 powder based on the total weight is added to the BaTio3-based semiconductor powder and mixed uniformly, and α-terpineol is further added to form paste mixture 1. Next, as in Example 1, the electrodes 3.4 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 3.4 remains. The temperature was raised from 1300'Q at a heating rate of 10'c/min, and 3
After holding for 0 minutes, allow to cool in the furnace. In this way, a thick film semiconductor element was obtained.

The sheet resistance at room temperature of the thick film semiconductor device thus obtained was s, 6KQ/crA in the case of Example 1, and 6KQ/crA in the case of Example 2.
In the case of 2°7Ω/crA, each temperature and resistance value 7.

The relationship was as shown in Figure 2. In FIG. 2, A shows the characteristics of the device obtained in Example 1, and B shows the characteristics in Example 2.

Effects of the Invention As described above, according to the manufacturing method of the present invention, HfB2 powder plays the role of both a conventional conductive additive and a glass frit, and has sufficient effects on electrical connection and physical connection.
A thick film positive characteristic semiconductor device cannot be obtained without a glass frit.

In addition, by using conductive metal 1 (fB2) with good heat conduction instead of glass frit, which has poor heat conduction, heat conduction is improved and thermal shock resistance is also improved.Furthermore,
Since it can be manufactured by screen printing, etc., it is easy to work with and mass production is possible.

In the present invention, any BaTiO3-based semiconductor powder may be used as long as it is made into a semiconductor by adding various additives to BaTiO33. In addition, the addition amount of HfB2 powder was specified to be 1 to 60% by weight based on the total weight, because if it was less than 1% by weight, the area resistance would be too large and it would be unsuitable for a heating element. On the other hand, if the weight coefficient exceeds 60, the sheet resistance becomes too small, and the self-control characteristics (PTC characteristics) become small, making it unsuitable for use as a heating element. Furthermore, BaTi
An organic solvent (alpha-terpineol in the example) was used to make the O3-based semiconductor powder and HfB2 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.
Its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing a thick film positive temperature coefficient 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] A thick film characterized by adding HfB_2 to BaTiO_3-based semiconductor powder in an amount of 1 to 60% by weight based on the total weight, applying the paste-like mixture on a substrate to form a thick film, and then firing it. A method for manufacturing a film type positive characteristic semiconductor device.