JPS62242315A - Voltage nonlinear device - 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 applicable to voltage stabilization, abnormal type suppression, and matrix-driven liquid crystals.

It is used as a switching element in display devices such as KL.

Conventional technology 2 / The conventional voltage nonlinear element is made of zinc oxide (ZnO), bismuth oxide (Bi205) + cobalt oxide (co203).
), mangaf oxide (MnO2), antimony oxide (
By adding oxides such as Sb203),
There are various types such as ZnO varistors sintered at 50'C. Among them, the ZnO varistor has a voltage nonlinearity index α,
It is most commonly used because of its high surge resistance (see Japanese Patent Publication No. 19472/1983).

Problems to be Solved by the Invention In such conventional voltage nonlinear elements, such as ZnO varistors, there is a limit to reducing the element thickness (several tens of micrometers or less). 1
There is a limit to lowering the voltage (expressed as vBnA when mA is applied), and it cannot be used as a protection element for low voltage ICs or a voltage stabilizing element at low voltages.

However, as mentioned above, since a high temperature process of 1000'C or higher is required during firing, there is a problem in 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 provides an insulating substrate, one electrode provided on the insulating substrate, and an electrode provided on the one electrode. The lower layer side, which is the side, is hardened with an insulating binder, and the upper layer is hardened with the other electrode, which is a conductive paste. It is characterized in that it is composed of a semiconductor material.

Effect: According to this configuration, a large voltage nonlinearity index α can be obtained even in a low current range, and the varistor voltage can also be controlled by the amount of insulating binder, so the distance between the electrodes can be narrowed. (several tens of micrometers or less), and an element suitable for lower voltage can be obtained very easily. Furthermore, 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 by solidifying fine powder semiconductor material, there is point contact between the fine powders of each semiconductor material, and since the contact area is basically small, the parallel capacitance is small. This means that 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 based on examples.

FIG. 1 shows an example of the manufacturing process for obtaining the device of the present invention. First, fine particulate zinc oxide with a particle size of 0.06 to 1 μm is fired at 700 to 1300'C, and then the sintered ZnO is heated to a particle size of 0.5 to 50/Am (average particle size of 1 to 10 μm), 0.05 to 10 mol of manganese oxide was added to the ZnO fine powder, and 600 to 1
Heat treatment was performed at 350'C for 10 to 60 minutes to form an insulating film of 5 vanes of manganese oxide on the surface of the ZnO fine powder. At this time, it was observed that a thin MnO2 insulating film was formed on the surface of the finely powdered ZnO with a thickness of approximately several tens to several reentrants. Next, ZnO with the MnO2 insulating film created in this way attached to the surface
Since the fine powder group adhered to each other with weak force, it was loosened in a mortar or pot mill to form a fine powder. Next, low melting point glass powder and an organic binder were added to the finely powdered ZnO with the MnO2 insulating film formed on the surface obtained as described above as an insulating binder to bond the fine powders. , mixed. Here, as a binder, low melting point glass powder is used in an amount of 5 to 20 wt for fine powder ZnO.
%, and mixed it with an organic binder, for example, in equal weight to form a paint. here,
Ethyl cellulose is used as the organic inder,
The solid content was diluted to 10 wt % based on the solvent (for example, terpineol).

Next, the paint obtained as described above was applied by screen printing onto a glass substrate 2 provided with an ITO (indium, tin oxide) electrode 1 as shown in FIG. Heat treatment was performed at C for 10 to 30 minutes in air. Next, the other electrode 3 was formed by screen printing carbon paste to obtain an element of the present invention.

FIG. 2 is an enlarged sectional view of the voltage nonlinear element 4, and 5
6 is a ZnO fine powder, 6 is an MnO2 insulating coating applied to the surface of the ZnO fine powder 5, and 7 is an insulating binder that mechanically connects the ZnO fine powder 6 on the lower layer side, which is the ITO electrode 1 side. The fine powders 50 on the lower layer side are solidified together by the low melting point glass 7 as a binder.

Further, the ZnO%i powders 5 on the upper layer side are solidified with each other by electrodes 3 made of the above-mentioned carbon paste.

Next, the voltage-current relationship of the voltage nonlinear element produced as described above will be explained. Without further ado, FIG. 3 shows the voltage-current characteristics of the configuration of FIG. 2 in comparison with those of a conventional ZnO varistor. The device of the present invention is made by baking zinc oxide at 700'C and adding 0% MnO2 to it.
．． 7 ha with 5 mo1% added.

After heat treatment at 900'C for 60 minutes, the above organic binder was added to this ZnO fine powder with an average particle size of 5 to 10 μm and a low melting point glass fine powder (20 wt % based on the ZnO fine powder) manufactured by Jikei Pharmaceutical Co., Ltd. In a mixture of equal weights of
The characteristics are shown when the element area is thinned by 1 and the distance between 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=KVα Here, E is the current flowing through the element, ■ 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 is, the better the voltage nonlinearity is.

As shown in the characteristics in Figure 3, the conventional ZnO varistor shown in characteristic B has a voltage nonlinearity index α in the low current region.
is small, and cannot function as a good voltage nonlinear element at a current of 10'A or less. On the other hand, the voltage nonlinearity index α is large even in the low current range in the device of the present invention shown by the characteristic number, and even in the current range of about 1O-10A, -1
- It is shown that the function as a voltage nonlinear element can be exhibited in minutes. In addition, in order to express the varistor characteristics of a ZnO varistor, for example, it is necessary to
The voltage that appears between the electrodes when a current of A is passed is called the varistor voltage v1mA, and the varistor voltage v1□ and the voltage non-linearity index α are used. In the device of the present invention,
As mentioned above, even in the low current range, the voltage nonlinearity index α
is large, and the varistor voltage is, for example, v as shown in Figure 3.
, /IA.

In this way, in the present invention, the varistor voltage can be made low because firstly, the element thickness of the voltage nonlinear element 4 can be made thin, and furthermore, as shown in FIG. Since the voltage non-linear element 4 on the lower layer side is hardened with the low melting point glass 7 and the voltage non-linear element 4 on the upper layer side is hardened with the carbon electrode 3, the distance between the electrodes can be substantially narrowed. This is because elements can be formed. At this time, if the amount of the low melting point glass 9 vane 7 is small, the degree of penetration of the carbon electrode 3 into the voltage nonlinear element 4 on the upper layer side is large, and the distance between the electrodes is narrowed more substantially. Therefore, the varistor voltage can be further lowered. Furthermore, although the reason why the voltage nonlinearity index α is large even in the low current range in the device of the present invention is not clear at present, the low melting point of the insulating binder is This is thought to be due to the fact that since it is solidified with glass, there is point contact between the respective semiconductor materials, and the contact area is small, and the leakage current is small because the bonding agent is insulating.

Here, the characteristics shown in Fig. 3 are obtained by changing the distance between the electrodes by 3 as described above.
This is for an element with a thickness of 0 μm;
This is because the average particle diameter of O fine powder is relatively large, 5 to 10 μm, and cannot be made any narrower. That is, the average particle diameter of the ZnO fine powder is 0.3
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 than 10 μm, and even in that case, good characteristics as shown in Figure 3 can be obtained. The present inventors confirmed this through experiments.

FIG. 4 shows how the varistor voltage v+, aA, voltage nonlinearity index α, and parallel capacitance C change when the amount of manganese 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. 3.

As shown in FIG. 4, 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 manganese oxide added and the heat treatment temperature are changed in the present invention.
7 is a table showing changes in a kite, a voltage nonlinear index α, and a parallel capacitance C;

11 Page 13 Beno As is clear from Table 1 and FIG. 4 above, each characteristic value is dependent on the amount of manganese oxide added and the heat treatment temperature. Here, the amount of manganese oxide added is 0.05
Particularly good characteristics were shown at ~3 mo1%. In addition, the heat treatment temperature varies from 600 to 13
It showed good characteristics in a temperature range of 50°C. If the heat treatment temperature is outside the above temperature range, for example below 600'C, it may be difficult to form a sufficient insulating film, and if the temperature exceeds 1350'C, the voltage non-linearity index α will fall 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 MnO2 alone, but with MnO as the main component, kl,
Ti, Sr, Mg, Ni.

Metal oxides such as cr and sl or organometallic oxides of these metals can be used alone or in combination.

Go to 14-5 Furthermore, the binder for solidifying the fine powder semiconductor material may be an insulating organic adhesive made of a combination of glass powder and an organic binder, or a thermosetting resin such as a polyimide resin, Phenolic resin, furan resin, urea resin, melamine resin.

Unsaturated polyester resins, diallyl phthalate resins, epoxy resins, polyurethane resins, silicone resins, etc. may also be used.

Furthermore, although the above example shows the case where glass powder alone is used as a binder, it is also possible to use a combination of glass powder and the above-mentioned insulating organic adhesive. After heat-treating and bonding the fine powders, the device can be formed by printing the organic adhesive from above the device and filling it into the device.

Furthermore, although the elements and electrodes were formed by screen printing in the above embodiments, other coating methods such as spraying, dipping, etc. may also be used.

Furthermore, in the manufacturing process according to the above embodiment, 15. First, fine particulate ZnO, which is an inorganic semiconductor, is heat-treated and pulverized to form a fine powder, and then MnO2, which is an insulating inorganic compound, is added. After that, heat treatment was performed, but it is possible to directly add the inorganic compound 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 according to the present invention has a large voltage nonlinearity index α in the low current region, and an element with small parallel capacitance can be obtained.
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 by narrowing the distance between the electrodes, a device with a low varistor voltage can be obtained, and the varistor voltage can also be controlled by the amount of insulating organic adhesive or the amount of glass powder. Coupled with the large nonlinearity index α, it can be used as a protection element for low-voltage ICs or as a voltage stabilization element at low voltages, which conventional ZnO varistors could not handle. Furthermore, since the applied paint can be cured at a low temperature to make it easier to manufacture, 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 an example of the manufacturing process of a voltage non-linear element according to the present invention, FIG. 2 is an enlarged sectional view showing an embodiment of the voltage non-linear element according to the present invention, and FIG. 3 is a diagram showing an example of the manufacturing process of a voltage non-linear element according to the present invention. Figure 4 shows the voltage-current characteristics of the device and the conventional ZnO varistor. Figure 4 shows the changes in the voltage nonlinearity index α, varistor voltage v+pk, and parallel capacitance C when the amount of MnO2 added is changed in the device according to the present invention. FIG. 1...ITO electrode, 2...Glass substrate, 3
...Carbon electrode, 4...Voltage nonlinear element, 5...17, -ZnO fine powder, 6...MnO2 insulation coating, 7.
...Low melting point glass (binder). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 4 Power Voltage (V)

Claims (1)

[Claims] An insulating substrate, one electrode provided on the insulating substrate, a lower layer side provided on the one electrode side, which is the one electrode side, is hardened with an insulating bonding agent, and an upper layer side is solidified with an insulating bonding agent. 1. A voltage nonlinear element comprising a fine powder semiconductor material coated with a thin insulating film mainly composed of MnO_2 and solidified by the other electrode made of conductive paste.