JPS62190821A - Manufacturing method of voltage nonlinear 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 voltage nonlinear element whose resistance value changes depending on an applied voltage, and is useful for voltage stabilization, abnormal voltage control, and matrix-driven liquid crystal, KL, etc. It is used in switching elements of display devices, etc.

Conventional technology Conventional voltage nonlinear elements are made of zinc oxide (ZnO), bismuth oxide (Bi20s), cobalt oxide (Ooze), etc.
3), manganese oxide (Mn02), antimony oxide (S
By adding oxides such as bzO3), 1oOo to 135
There are various types such as ZnO varistors sintered at 0°C. Among them, ZnO varistor has voltage non-linearity index α, length -
It is used most often because of its high resistance to heat.

(Refer to Japanese Patent Publication No. 4e-19472) Problems to be Solved by the Invention Conventional voltage non-linear elements such as these, including ZnO varistors, have limitations in reducing the element thickness (several tens of μm or less). Therefore, the varistor voltage (current 1 in the varistor)
There is a limit to lowering the voltage (expressed as V1mA when mA is applied), and it cannot be used as a protection element for low-voltage ICs or a voltage stabilization element at low voltages.

Further, as mentioned above, since a high temperature process of 1000° C. or higher is required for firing, there is a problem that a voltage nonlinear element cannot be directly formed on a glass substrate or a circuit board. Furthermore, conventional devices have a large parallel capacitance, making them unsuitable for use as switching elements for liquid crystals, for example.

Means for Solving the Problem In order to solve this problem, the present invention adds an inorganic or organic compound containing Bi to a fine powder of an inorganic semiconductor, and after mixing, performs heat treatment at 600 to 1360°C. , forming an inorganic insulating film on the surface of the inorganic semiconductor fine powder,
After that, an insulating organic adhesive or glass powder and organic binder are added to the semiconductor fine powder coated with the insulating coating to form a paint, and then the paint is printed, sprayed, or dipped onto the insulating substrate on which the electrodes are arranged. It is characterized in that it is applied by a method and then hardened by heat treatment.

Effect: According to this method, a large voltage nonlinearity index α can be obtained even in the low current range, and the distance between the electrodes can be narrowed (therefore, +
μm or less), and an element suitable for lowering voltage can be obtained extremely easily. However, since it can be made by curing the applied paint at a low temperature, it is possible to form elements directly on a circuit board, and it is expected to have a wide range of applications unimaginable for ZnO varistors and the like. Furthermore, since the obtained device is made of solidified semiconductor material in the form of fine powder, there is point contact between the fine powders of each semiconductor material, and the contact area is small, making it possible to obtain a device with a small parallel capacitance. , it is possible to provide an element that is optimal as a switching element for devices such as liquid crystals.

Example Hereinafter, the present invention will be explained in detail using examples.

FIG. 1 shows an embodiment of the manufacturing process according to the manufacturing method of the present invention. First, fine particulate zinc oxide with a particle size of 0.05 to 1 μm is fired at 700 to 130°C, and then the sintered ZnO is heated to O,S with a particle size of ~60 μm (average particle size of 1 to 10 μm). Bismuth oxide is added to the ZnO fine powder by 10 mo1% of O,OS, and 6oO to 1
A heat treatment was performed at 360° C. for 10 to 69 minutes to form an insulating film of bismuth oxide on the surface of the ZnO fine powder. At this time,
It was observed that a thin Bi2O3 insulating film was formed on the surface of the finely powdered ZnO to a thickness of approximately several tens to several hundreds of layers.

Next, since the ZnO fine powder group with the Bi2O3 insulating film formed on its surface adhered to each other with a weak force, it was loosened in a mortar or pot mill to form a fine powder. Next, Bi2 obtained as above
Finely powdered ZnO with an O5 insulating film formed on its surface,
A polyimide resin was added as a binder (bingu) to bond the fine powders and mixed. Here, as a binder, the solid content of polyimide resin is used as a solvent (for example, n-methyl-
2-pyrrolidone) K was weighed at 5WtX, and mixed with ZnO fine powder in an equal weight, for example, to form a paint. Next, the paint obtained as described above was coated with ITO (indium oxide) as shown in Figure 3.
Tin oxide] is coated on the glass substrate 3 provided with the electrode 1 by, for example, screen printing, and the same glass substrate 4 provided with the ITO electrode 2 is placed on top of it.
It was cured in the atmosphere at 0° C. for 30 minutes, and a voltage nonlinear element 5 was provided between the electrodes 1 and 2. FIG. 2 is an enlarged cross-sectional view of the voltage nonlinear element 5, and includes 6 pieces of ZnO & powder, 7 pieces of Zn
The Bi2O3 insulating coating applied to the surface of the O fine powder 6 is a binder that mechanically binds the ZnO fine powders 6 together. It is being

Figures If and a show a case where a voltage nonlinear element 5 is constructed on a glass substrate 31L on which TO electrodes 1a and lb are provided.

Next, the voltage-current characteristics of the voltage nonlinear element created as described above will be explained. First, Figure 6 shows the 3rd
The voltage-current characteristics of the configuration shown in the figure are compared with those of a conventional ZnO varistor. In the device of the present invention, zinc oxide is first fired at 700°C, and B12O3 is added to it at a temperature of 0.
After heat-treating the ZnO fine powder with an average particle size of 6 to 10 μm and the binder in equal weights, the element area was reduced to 1%.
-1 The characteristics are shown when the distance between the electrodes is 30 μm. Now, as is well known, the voltage-current characteristics of a voltage nonlinear element are approximately expressed by the following equation.

I=KV'' Here, E is the current flowing through the element, V is the voltage between the electrodes of the element, K is a constant corresponding to the resistance value of the specific resistance, and α is the exponent of the voltage nonlinear characteristic mentioned above. The larger the voltage nonlinearity index α, the better the voltage nonlinearity.

As shown in the characteristics in Figure 6, the conventional ZnO varistor shown in characteristic B has a voltage nonlinearity index α in the low current range
is small, and if the current is less than 10 Å, it will not function as a good voltage nonlinear element and will not last long. On the other hand, in the device of the present invention as shown by the characteristics, the voltage nonlinearity index α is large even in the low current range, and it is possible to sufficiently exhibit the function as a voltage nonlinearity device even in the current range of about 10%. It shows. In addition, normally, in order to express the varistor characteristics of a ZnO varistor, for example, the voltage that appears between the electrodes when a current of 1m is passed through the element is called the varistor voltage Vi.
mA, and this varistor voltage V1mA and the voltage non-linearity index α are used.

In the device of the present invention, as described above, the voltage nonlinearity index α is large even in the low current range, and the varistor voltage can be expressed, for example, by vi/jA as shown in FIG.

In this way, in the present invention, the varistor voltage can be lowered, and the element can be formed with a narrower distance between the electrodes.

Furthermore, the reason why the voltage nonlinearity index α is large even in the low current range in the device of the present invention is that the fine powder semiconductor material (ZnO) is hardened with a binder, although the reason is not clear at present. This is thought to be due to the fact that there is a point contact between the respective semiconductor materials, and the contact area is small, and the bonding agent is insulating, so the leakage current is small.

Here, the characteristics shown in Fig. 6 are obtained by changing the distance between the electrodes by 3 as mentioned above.
This is for an element with a thickness of 0 μm;
This is because the average particle size of the O fine powder is relatively large, 6 to 10 μm, and cannot be made any narrower. That is, the average particle diameter of the ZnO fine powder is 0.3
The present inventor has found that if a material with a diameter of ~3 μm is used, it is possible to create an element with an interelectrode distance of about 10 μm or less, and even in that case, good characteristics as shown in Figure 5 can be obtained. This was confirmed through experiments.

FIG. 6 shows how the varistor voltage v1fim, the voltage nonlinearity index α, and the parallel capacitance C change when the amount of bismuth oxide added is changed in the present invention. Here, other conditions such as the firing temperature of zinc oxide were the same as those in the case of FIG. 6.

As shown in FIG. 6, in the device of the present invention, the parallel capacitance is 1000 to 20000 compared to that of the conventional ZnO varistor.
Although it is a PF, it is very small.

The reason why this parallel capacitance C is small in the device of the present invention is that the contact area between the semiconductor materials is small, as described above.

In addition, Table 1 shown below shows the varistor voltage v1 when the amount of bismuth oxide added and the heat treatment temperature are changed in the present invention.
11A1 is a table showing how the voltage nonlinearity factor α and the parallel capacitance C change.

(Hereinafter, blank space) As is clear from Table 1 and FIG. 6 above, each characteristic value is dependent on the amount of bismuth oxide added and the heat treatment temperature. Here, the amount of bismuth oxide added is O, OS
Particularly good characteristics were shown at ~3 mo1%. In addition, the heat treatment temperature varies depending on the amount of bismuth oxide added, but is 600 to 13
Good characteristics were shown in the 501C range. If the heat treatment temperature is outside the above temperature range, for example below 800'C, it may be difficult to form a sufficient insulating film, and if the temperature exceeds 1350'C, the voltage non-linearity index σ will be below the required value. This is the reason why good characteristics cannot be obtained.

In addition, in the above embodiment, the semiconductor material is
Although ZnO has been described as an example, it goes without saying that other semiconductor materials may be used. Similarly, the material constituting the insulating film is not limited to Bi2O3 alone, but may include Bi2O5 as the main component.
．． Ti, Sr, Mg, Ni.

Metal oxides such as Or and Si or these carbon-containing organometallic compounds can be used alone or in combination.

Furthermore, the binder for solidifying the fine powder semiconductor material may be an insulating organic adhesive other than polyimide resin.
Thermosetting resins, such as phenolic resins, furan resins,
urea resin, melamine resin, unsaturated polyester resin,
Diaryl phthalate resin, epoxy resin, polyurethane resin, silicone resin, etc. may be used, and furthermore, a combination of glass powder and an organic binder may be used.

In addition, although the elements were formed by screen printing in the example described in Kitagi, other coating methods such as spraying,
A method such as immersion may also be used.

Furthermore, in the manufacturing method according to the above embodiment, first, ZnO in the form of fine particles, which is an inorganic semiconductor, is heat-treated and pulverized to form a fine powder, and then B, which is an insulating inorganic compound, is
Although i2O5 was added and then heat treatment was performed, it is possible to add the inorganic compound directly to the inorganic semiconductor fine powder and omit the processing steps of firing and pulverizing the inorganic semiconductor fine particles. .

Effects of the Invention As is clear from the above explanation, the voltage nonlinear element obtained by the method of the present invention has a large voltage nonlinearity index α in the low current region, and is characterized by a small parallel capacitance. , it is possible to provide an element that is optimal as a switching element for devices such as liquid crystals and EL devices with low current consumption. In addition, since the device can be formed with a narrower distance between the electrodes, a device with a lower varistor voltage can be obtained.
Combined with the large voltage nonlinearity index α mentioned above, the conventional Z
It can be used as a protection element for low-voltage XC and a voltage stabilization element at low voltages, which could not be supported by nO varistors. Furthermore, since the applied paint can be cured at low temperatures and easily manufactured, elements can be directly formed on circuit boards or glass substrates. The voltage non-linear element of the present invention having such various characteristics can be expected to have a wide range of applications unimaginable for conventional ZnO varistors and the like, and its industrial applicability is excellent.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the steps of a method for manufacturing a voltage nonlinear element according to the method of the present invention, FIG. 2 is an enlarged sectional view showing an example of a voltage nonlinear element obtained by the method of the present invention, and FIG. 4 and 4 are cross-sectional views showing examples in which the device of the present invention is provided on a glass substrate, respectively, and FIG. 5 is a diagram showing the voltage-current characteristics of the device manufactured by the method of the present invention and a conventional ZnO varistor. , FIG. 6 shows Bi2 in the device according to the method of the present invention.
FIG. 3 is a diagram showing how the voltage non-linearity index α, the varistor voltage v1μ, and the parallel capacitance C change when the amount of O5 added is changed. 1.1, 1b, 2・---・ITO electrode, 3.3&,
4...Glass substrate, 5...Voltage nonlinear element, 6...ZnO fine powder, 7...
Bi2O3 insulation coating, 8...Binder. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 5 (Voltage 0') Figure 6

Claims (1)

[Claims] After adding and mixing an inorganic or organic compound containing Bi to a fine powder of an inorganic semiconductor, heat treatment is performed at 600 to 1350°C to form an inorganic insulation film on the surface of the fine inorganic semiconductor powder, and then the insulation film is An insulating organic adhesive or glass powder and an organic binder are added to the applied semiconductor fine powder to form a paint, and the paint is then applied by printing, spraying, or dipping onto an insulating substrate on which electrodes are arranged. A method for manufacturing a voltage nonlinear element, which comprises curing by heat treatment.