JPH04366B2 - - 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 pressurizing BaTiO ₃ -based semiconductors into a film.

After being formed into a disk shape, it is fired and polished into thin pieces.

A thin film is formed on the substrate by vacuum evaporation.

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

However, in the above method, it is extremely difficult to polish the BaTiO ₃ -based semiconductor into a film because the crystal grain size of the BaTiO 3 -based semiconductor is large and brittle. Furthermore, the above method is cumbersome to operate, and it is difficult to obtain a large amount of power suitable for the heating element. Furthermore, the above-mentioned method tends to increase 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 depends on the material of the glass frit. teeth
Deteriorates the switching characteristics and self-heating characteristics of BaTiO ₃ semiconductors. 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 is based on the method _of manufacturing a thick film _{type positive} characteristic semiconductor element of the present invention.
A thick film type can be created by applying a paste-like mixture of one or more types of La ₅ Si ₃ powder to a paste of 1 to 60% by weight based on the total weight, forming a thick film on a substrate, and then firing it. The purpose is to obtain a positive characteristic semiconductor device.

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, LaSi is used as a conductive additive and as a glass frit.
It is characterized by the use of LaSi ₂ or La ₅ Si ₃ . This LaSi, LaSi ₂ , La ₅ Si ₃ is a conductor at room temperature, but when the temperature reaches 1000-1100℃ or higher, a part of it decomposes and SiO ₂ precipitates on the particle surface, but the inside of the particle remains intact and the surface The SiO ₂ film prevents decomposition. Therefore, BaTiO ₃ -based semiconductor powder and
When LaSi, LaSi ₂ or La ₅ Si ₃ powders are mixed and fired, the SiO ₂ precipitated on the surface of LaSi, LaSi ₂ or La ₅ Si ₃ plays the same role as glass frit, and the inside of the particles acts as a conductive additive. To do this, LaSi,
By simply adding LaSi ₂ or La ₅ Si ₃ powder, it is possible to obtain a thick film type positive temperature semiconductor device that does not require a glass frit.

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 SrO is added to BaTiO ₃ and fired at 1300°C, followed by pulverization to obtain BaTiO ₃ -based semiconductor powder.
20% by weight of LaSi powder based on the total weight was added to the BaTiO ₃ semiconductor powder, mixed uniformly, and further α
- Add terpineol to make pasty 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 part of the electrodes 3 and 4 remain on the electrodes 3 and 4, and heat the mixture at a heating rate of 10°C/min from room temperature. Raise the temperature to 1350℃, 1
After holding for a period of time, it is 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.
After adding SrO and firing at 1250℃, crush
Obtain BaTiO ₃ based semiconductor powder. 35% by weight of La ₅ Si ₃ 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. Next, 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. After increasing the temperature from 1300℃ at a rate of 10℃/min and holding it for 30 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 0.80KΩ/cm ² in Example 1 and 0.25KΩ/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.

Here, in place of the LaSi, La ₅ Si ₃ powder, LaSi ₂
Even when powder was used, the same characteristics as in the above example could be obtained. In addition, these LaSi,
It was confirmed that equivalent characteristics could be obtained when two or more types of LaSi ₂ and La ₅ Si ₃ powders were mixed and added. When one or more of these LaSi, LaSi ₂ or La ₅ Si ₃ powders are added to BaTiO ₃ semiconductor powder in an amount of 1 to 60% by weight based on the total weight, a thickness with good properties can be obtained. A film type positive characteristic semiconductor device was obtained.

Effects of the Invention As described above, according to the manufacturing method of the present invention,
LaSi, LaSi ₂ , La ₅ Si ₃ powders act as both conventional conductive additives and glass frits, and have sufficient effects for electrical and physical connections, creating thick film positive properties without glass frits. A semiconductor element will be obtained.

In addition, instead of glass frit, which has poor thermal conductivity, we are using LaSi, a conductive metal with good thermal conductivity.
By using LaSi ₂ and La ₅ Si ₃ , 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, LaSi,
The amount of LaSi ₂ , La ₅ Si ₃ powder added is 1 to the total weight.
If it is outside the range of ~60% by weight, if it is less than 1% by weight, the area resistance becomes too large and is not suitable for a heating element, and the BaTiO ₃ powder cannot be physically fixed together.
On the other hand, if it exceeds 60% by weight, the sheet resistance becomes too small and the self-control characteristic (PTC characteristic) becomes small, making it unsuitable for a heating element. moreover,
Although an organic solvent (alpha-terpineol in the example) was used to make the BaTiO ₃ -based semiconductor powder and the LaSi, LaSi ₂ , La ₅ Si ₃ powder into a paste, 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 element that does not require glass frit, and its practical effects are great.

[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] 1 BaTiO ₃ based semiconductor powder with LaSi, LaSi ₂ ,
It is characterized by adding one or more types of La ₅ Si ₃ powder in an amount of 1 to 60% by weight based on the total weight, applying the paste-like mixture onto a substrate to form a thick film, and then firing it. A method for manufacturing a thick film type positive characteristic semiconductor device.