JPH061722B2 - Method for manufacturing thick film type positive temperature coefficient semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thick film type positive temperature coefficient semiconductor device which does not require glass frit among planar heating elements used for heat insulation and heating of equipment. Is.

Configuration of conventional example and its problems The element made of BaTiO ₃ based semiconductor has the switching characteristic that the resistance value rapidly increases at a predetermined temperature or more and the self-heating characteristic after switching. It is widely used because it does not require an external control circuit.

The conventional PTC thermistor heating element was obtained by pressure-molding BaTiO ₃ semiconductor powder and then firing it, but it is said that it is difficult to obtain a practical thick-film PTC thermistor heating element. It was

Conventionally, as a method of processing a BaTiO ₃ based semiconductor into a film,
The following are known.

After being formed into a disc shape, the fired product is ground into thin pieces.

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

A conductive additive and glass frit are added to BaTiO ₃ semiconductor powder to form a paste, which is screen-printed on a substrate and then baked.

However, since the crystal grain size of the BaTiO ₃ semiconductor is large and brittle in the above method, it is very difficult to polish it into a film. Also, the above method is troublesome to operate,
It is difficult to obtain high power suitable for the heating element. Furthermore, in the above method, the sheet resistance is likely to be high and the control is difficult, it is not suitable for the heating element, and the glass frit must be prepared and fired in advance, which is troublesome and depends on the material of the glass frit. Deteriorates the switching and self-heating properties of BaTiO ₃ semiconductors. Then, by adding glass frit, BaTiO ₃
Due to the difference in heat resistance and coefficient of thermal expansion between the system semiconductor and the glass frit, it is weak against thermal shock and prevents 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 characteristics.

SUMMARY OF THE INVENTION Therefore, the present invention solves the disadvantage of the above-mentioned prior art in manufacturing complexity, and by forming a thick film without using a glass frit, it has excellent thermal shock resistance and thermal conductivity, and has uniform characteristics. It is an object of the present invention to provide a method for easily manufacturing a thick film type positive temperature coefficient semiconductor device having

Method for producing a thick film type PTC semiconductor device having the structure This invention, BaTiO ₃
1.0 to 60.0% by weight of at least one kind of powder of Mo ₃ Si and Mo ₅ Si ₃ is added to the base semiconductor powder, and the paste-like mixture is applied onto the substrate to form a thick film and then baked. This is intended to obtain a thick film type positive temperature coefficient semiconductor device.

In the conventional method using the conductive additive and the glass frit,
A conductive additive was required for electrical connection between the BaTiO ₃ -based semiconductor powders, and a glass frit was required for physically connecting the BaTiO ₃ -based powders.

However, the present invention is characterized in that Mo ₃ Si and Mo ₅ Si ₃ are used because they serve as both the conductive additive and the glass frit.

These Mo ₃ Si and Mo ₅ Si ₃ are conductors at room temperature,
When the temperature reaches over 00 ℃, a part of it decomposes and Si is
Although O ₂ is deposited, the inside of the particle remains intact and the decomposition is prevented by the SiO ₂ film on the surface. Therefore, when BaTiO ₃ based semiconductor powder and Mo ₃ Si, Mo ₅ Si ₃ powder are mixed and fired, Mo ₃ Si, Mo
Since the SiO ₂ precipitated on the surface of the ₅ Si ₃ is the same role as the glass frit, the role of particle inside conductive additive, Mo ₃ S
Only by adding i, Mo ₅ Si ₃ , it is possible to obtain a thick film type positive temperature coefficient semiconductor device which does not require a glass frit.

Further, by adding a conductive metal, the thermal conductivity is poor and the thermal conductivity is improved as compared with the glass frit, and the thermal shock resistance is also improved.

Description of Embodiments An embodiment of the present invention will be specifically described below with reference to FIG.

Example 1 After adding 1.0 mol% of Nb ₂ O ₅ to BaTiO ₃ and baking at 1300 ° C.,
Grind to obtain BaTiO ₃ based semiconductor powder. 18.0 wt% of Mo ₃ Si powder is added to the BaTiO ₃ based semiconductor powder and mixed uniformly, and α-terpineol is further added to prepare a paste-like mixture 1.

On the other hand, a pair of A is previously formed on the substrate 2 made of Al ₂ O ₃ or the like.
The electrodes 3 and 4 made of a conductive substance such as g are provided in advance,
The paste mixture 1 is applied onto the electrodes 3 and 4 by screen printing so that a part of the electrodes 3 and 4 remains, and the temperature is raised from room temperature to 1350 ° C. at a heating rate of 10 ° C./min. After holding for 1 hour, the furnace is allowed to cool. Thus, a thick film type positive temperature coefficient semiconductor device was obtained.

After firing at Similarly to BaTiO ₃ and 3.0 mol% of Y ₂ O ₃ was added 1250 ° C. as in Example 1, to obtain a BaTiO ₃ based semiconductor powder by grinding. The BaTiO ₃ based semiconductor powder has a total weight of 39.5
Weight% Mo ₅ Si ₃ powder is added and mixed uniformly, and α-terpineol is further added to form a paste-like mixture 1. Then, the electrodes 3 and 4 are provided in advance on the substrate 2 in the same manner as in Example 1, and the paste mixture 1 is applied by screen printing or the like so that a part of the electrodes 3 and 4 remains, and the temperature is kept at room temperature. To 1300 at a heating rate of 10 ° C / min
The temperature is raised to 0 ° C., held for 30 minutes, and then allowed to cool in the furnace. Thus, a thick film type semiconductor device was obtained.

The sheet resistance of the thick film type semiconductor device thus obtained at room temperature is 2.7 KΩ / cm ² in the case of Example 1 and 1.6 K in the case of Example 2.
It was KΩ / cm ² , and the relationship between each temperature and resistance value was as shown in FIG. In FIG. 2, A is the characteristic of the device obtained in Example 1, and B is the characteristic in the case of Example 2.

Here, even if Mo ₃ Si and Mo ₅ Si ₃ are added at the same time, the same effect as that of the above-described embodiment can be obtained.

As described above, according to the production method of the present invention, the powder serves as both the conventional conductive additive and the glass frit,
It has a sufficient effect on electrical connection and physical connection, and a thick film positive-characteristic semiconductor device can be obtained without glass frit.

Further, by using the conductive metals Mo ₃ Si and Mo ₅ Si ₃ having good thermal conductivity instead of the glass frit having poor thermal conductivity, thermal conductivity is improved and thermal shock resistance is also improved. further,
Since it can be manufactured by screen printing, the work is easy and mass production is possible.

In the present invention, BaTi ₃ -based semiconductor powder is BaTi
Any material may be used as long as it is made into a semiconductor by adding various additives to O ₃ . Further, the addition amount of Mo ₃ Si, Mo ₅ Si ₃ powder is defined to be 1 to 60% by weight based on the total weight. If it is less than 1% by weight, the sheet resistance becomes too large and it is unsuitable for a heating element.
This is because it is impossible to physically fix the BaTiO ₃ powders to each other, and if it exceeds 60% by weight, the sheet resistance becomes too small, and the self-controlling characteristic (PTC characteristic) becomes small, making it unsuitable for a heating element. Furthermore, the organic solvent (α-terpineol in the example) was used to make the BaTiO ₃ based semiconductor powder and the Mo ₃ Si, Mo ₅ Si ₃ powder into a paste, but any material that can be made into a paste may be used.

Further, BaTiO ₃ based semiconductor powder to which Mo ₃ Si is added has a sheet resistance of 2.7 KΩ / cm ² , and also Mo ₃
In the case where Mo ₅ Si ₃ was added instead of Si, the sheet resistance was 1.6 KΩ / cm ² , and in both cases, the sheet resistance was larger than the sheet resistance of 1.2 KΩ / cm ^{2 in} which MoSi ₂ was added. Is strong against inrush current and has an effect that it can be used for low temperature heat generation.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a thick film type positive temperature coefficient semiconductor device obtained by the method of the present invention, and FIG. 2 is a view showing a relation 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. At least one kind of powder of Mo ₃ Si and Mo ₅ Si ₃ is added to BaTiO ₃ based semiconductor powder in an amount of 1.0 to 60.0% by weight, and a paste-like mixture is applied onto a substrate to form a thick film. A method for manufacturing a thick film type positive temperature coefficient semiconductor device, comprising: