JPS62193225A - Manufacture of 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 compensation changes depending on the applied voltage, and is useful for voltage stabilization, abnormal voltage control, and matrix-driven liquid crystal, EL, etc. It is used in switching elements of display devices, etc.

Conventional technology Conventional voltage nonlinear elements include zinc oxide (ZnO), bismuth oxide (Bi2O3, Co2O3, MnO203),
Cobalt oxide (Co 203 ), manganese oxide (Mn
There are various types of varistors, such as ZnO varistors which are sintered at 1000 to 1360°C with the addition of oxidizing moieties such as antimony oxide (Sb203) and antimony oxide (Sb203).

Among them, ZnO varistors are the most commonly used because they have a large voltage nonlinearity index α and 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 how low the voltage (expressed as 1 mA) can be when mA flows, and it cannot be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages.

Further, as mentioned above, since a high temperature process of 1QOo'C or more is required during 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 incorporates Bi2O3, Co2O3, MnO2o3. C.O.
After adding and mixing an inorganic or organic compound containing at least all of 30C03O31 and 5b203, heat treatment is performed at eoo~1360°C to form an inorganic insulating film on the surface of the inorganic semiconductor fine powder and improve its insulation properties. All or most of the above-mentioned fine powder inorganic semiconductors having a coating on the surface are brought into a state where a plurality of each are gathered, and then the above-mentioned fine powder is added to the powder or a part of the plurality of fine powder-like inorganic semiconductors gathered together. An insulating organic adhesive or a glass powder and an organic binder were added as a binder to the powder containing the powder to form a paint, and the paint was then applied by printing, spraying, or dipping onto an insulating substrate on which one electrode was arranged. After that, it is cured by heat treatment, and the other electrode is coated with conductive paint by printing, spraying, or dipping.

Effect: According to this method, 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 organic adhesive or glass powder. Reduce the distance between electrodes (several tens of μm)
(below)), and an element suitable for lowering the voltage can be obtained very easily. In addition, since it can be made by curing the applied paint at low temperatures, it is possible to form elements directly on the circuit board.
It can be expected to have a wide range of applications that cannot be imagined with ZnO varistors. Furthermore, since the obtained device is made of solidified powdered semiconductor material, there is point contact between the powders of each semiconductor material, and since the contact area is basically small, it is possible to obtain a device with a small parallel capacitance. This makes it 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 embodiment of the manufacturing process according to the manufacturing method of the present invention. First, fine particulate zinc oxide with a particle size of 0.06 to 1 μm is fired at 700 to 1300″C, and then the sintered ZnO is heated to 0.5 μm and a particle size of 5 to 60 μm (average particle size of 1 to 10 μm). The ZnO fine powder contains Bi2O3, Co2O3, MnO2o3.C020C0
The amount of a of 2O31,5b203 is 0.0S ~ 10mol
% and heat treated at 600 to 136 σC for 10 to eo minutes to form an insulating film of these oxides on the surface of the ZnO fine powder. At this time, it was observed that an insulating film of the above-mentioned oxide was formed on the surface of the finely powdered ZnO to a thickness of about several tens to several hundreds. Next, since the ZnO fine powders with the oxide insulating coating formed on their surfaces adhere to each other with weak force, they are loosened in a mortar or bot mill to form a fine mixture of a plurality of each of the above ZnO fine powders. It was made into a powder state (hereinafter, this state is referred to as a powder state).

At this time, there is no problem even if the ZnO fine powder is present alone in a part, and a state in which a part of the ZnO fine powder is included is also called powdery.

Next, low melting point glass powder and an organic binder were added as an insulating bonding agent to bond the powders to the powdered ZnO with the oxide insulating film formed on the surface obtained as described above. , mixed. Here, as a binder, the amount of low melting point glass powder is 6 to 20 wt% based on powdered ZnO.
This was mixed with an organic binder, for example, in equal weight to form a paint. Here, ethyl cellulose is used as the organic binder, and its solid content is 10w relative to the solvent (for example, terpineol).
t%.

Next, as shown in FIG. 2, the paint obtained as described above is applied onto a glass substrate 2 provided with ITO (indium tin oxide) [poles 1, for example, by screen printing, and 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.

The second section is an enlarged cross-sectional view of the voltage non-linear element 4;
is a ZnO powder, 6 is an oxide insulating coating applied to the surface of the ZnO powder 5, and 7 is a low melting point glass as an insulating binder that mechanically connects the ZnO powders 6. The powders 6 are solidified together by a low melting point glass 7.

FIG. 3 shows a case where the amount of low melting point glass (binder) is small in the configuration of FIG. 2.

Next, the voltage-current characteristics of the voltage nonlinear element created as described above will be explained. First, Figure 4 shows the second
The voltage-current characteristics of the configuration shown in the figure are compared with those of a conventional ZnO varistor. The device of the present invention is made by first firing zinc oxide at 700°C, adding Bi2O3, C
o2O3, MnO2o3. Co2Q38MnO2,5b
203 each 0.2 mo1%, that is, the amount of a is 0.8
After heat treatment at 900°C for 160 minutes with 1% mo added, this ZnO powder with an average particle size of 6 to 10 μm and low melting point glass fine powder manufactured by Jitsukei Seiyaku ■ (2% for ZnO powder) were added.
0wt%) and the above organic binder in equal weight, the device area is 1-1 and the distance between the electrodes is 30 μm (this shows the characteristics of IC).Now, the voltage-current of the voltage nonlinear device As is well known, the characteristics are approximately expressed by the following equation.

I=KVa 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 a is the exponent of the voltage nonlinear characteristic mentioned above. The larger the voltage nonlinearity index α is, the greater the voltage nonlinearity is.

As shown in the characteristics in Figure 4, the conventional ZnO varistor shown by 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, in the device of the present invention shown by characteristic A, the voltage nonlinearity index α is large even in the low current range, and it can sufficiently function as a voltage nonlinear device even in the current range of about 10-10A. 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 1 mA is passed through the element is called the varistor voltage v.
Called 1mA, this varistor voltage v,! nA and the above-mentioned voltage nonlinearity index a are used. As mentioned above, in the device of the present invention, the voltage non-linearity index α is large even in the low current range, and the varistor voltage is changed to, for example, vl as shown in FIG.
It can be expressed in pA.

In this way, in the present invention, the varistor voltage can be reduced to a low level because firstly, the thickness of the voltage nonlinear element 4 can be made thin, and furthermore, as shown in FIG. This is because when the amount of the low melting point glass is small, the carbon electrode 3 penetrates into the voltage nonlinear element 4, thereby making it possible to form an element with a substantially narrower distance between the electrodes. Furthermore, although the reason why the voltage nonlinearity index a is large even in the low current range in the device of the present invention is not clear at present, This is thought to be due to the fact that since the semiconductor materials are solidified, there is point contact between the respective semiconductor materials, so the contact area is small, and the bonding agent is insulating, so the leakage current is small.

Here, the characteristics shown in Fig. 4 are as follows when the distance between the electrodes is 3
This is for an element with a thickness of 0 μm;
This is because the average particle size of the O powder is relatively large, 6 to 10 pm, so it is impossible to make the particle size any narrower. That is, the average particle diameter of the ZnO powder is 0.3~
If 31tm is used, it is possible to create an element with an inter-electrode distance of about 10μm or less.
The present inventors have confirmed through experiments that even in that case, good characteristics as shown in FIG. 4 can be obtained.

Figure 6 shows that Bi2O3, Co2O3, M
Varistor pressure when changing the total addition amount of nO2O3, Co2O3゜1VinO2, Sb2O3"IIIA %
It shows how the voltage non-linearity index α and the parallel capacitance fIkC change. Here, the firing of zinc oxide, etc.
Other conditions were the same as those in the case of FIG. 6th
As shown in the figure, in the device of the present invention, the parallel capacitance is 1,000 to 20,000 PF compared to the conventional ZnO varistor.
However, it is very small. The reason why this parallel capacitance JiC is small in the device of the present invention is as follows.
This is due to the small contact area between semiconductor materials as described above.

In addition, Table 1 shown below shows that in the present invention, Bi2O3,
Co2O3, MnO2Q3. Co2O31MnO2,S
It is a table showing how the varistor voltage v1 pA' voltage non-linearity index α and parallel capacitance C change when the total addition rate of b2O3 and the heat treatment temperature are changed.

As is clear from Table 1 and Figure 5 above, each characteristic 1
It can be seen that the resistance depends on the total amount of the oxides added and the heat treatment temperature. Here, the total amount of these oxides added is 0.
Particularly good characteristics were shown at 05 to 3 mo1%. In addition, the degree of heat treatment is 600 to 135 depending on the total amount of oxide added.
It showed good characteristics in the 0°C range. 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 1360'C, the voltage non-linearity index α will fall below the required value. Therefore, 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, as a material constituting the insulating film, B 1203.
It is not limited to CO2031MnQ2,5b203, but includes all of Bi, Co, Mn, and Sb as main components, as well as AI, Ti, Sr, Mg, Ni, and Cr.

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

Furthermore, as a binder for solidifying powdered semiconductor materials,
An insulating organic adhesive may be used on the outside of the cedar board, which is a combination of glass powder and an organic binder, and thermosetting resins, such as polyimide resins, phenol resins, furan resins, urea resins, melamine resins, unsaturated polyester resins, and Digril 7.
Tallate resin, epoxy resin, polyurethane resin, silicone resin, etc. may also be used.

Furthermore, although the above example shows the case where glass powder alone is used as the binder, glass powder may also be used in combination with the above insulating organic adhesive. For example, glass powder may be used in combination with ZnO After combining the powders,
The element can also be formed by printing the above organic adhesive from the top of the element and filling it into the resistor.

Further, in the above embodiments, the elements and electrodes were formed by gold screen printing, but other coating methods such as spraying, dipping, etc. 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 powder, and then Bi, which is an insulating inorganic compound, is
2O3, Co2O3, MnO2o3. Co2O3,'M
nO2゜5b203 was added and then heat treatment was performed, but it is possible to add the inorganic compound directly to the inorganic semiconductor powder and omit the processing steps of firing and pulverizing the inorganic semiconductor fine particles. be.

Effects of the Invention As is clear from the above explanation, the voltage nonlinear device obtained by the method of the present invention has a large voltage nonlinearity index α in the low current region, and also has a small parallel capacitance. Therefore, 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.
Moreover, the varistor voltage can be controlled by the amount of insulating organic adhesive or the amount of glass powder, and in combination with the large voltage nonlinearity index α mentioned above, protection of low voltage ICs that could not be achieved with conventional ZnO varistors is possible. It can be used as an element or a voltage stabilizing element at low voltage. Furthermore, since the applied adhesive can be easily manufactured by curing the adhesive at a low temperature, the element can be directly formed on a circuit board or a glass substrate. The voltage nonlinear 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 has great industrial potential.

[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 stabilizing element obtained by the method of the present invention, and FIG. is a cross-sectional view showing another example in which the device of the present invention is provided on a glass substrate, FIG. 4 is a diagram showing voltage-current characteristics of the device obtained by the method of the present invention and a conventional ZnO varistor, and FIG. is the method K of the present invention,! : Element K Oite, Bi2O3,
Voltage non-linearity index α, varistor voltage ■1 when changing the total amount of C02o3°MnO2,5b203 added FIG. 3 is a diagram showing how aA and parallel capacitance tC change. 1...ITO electrode, 2...Glass substrate, 3...Carbon electrode, 4...Voltage nonlinear element, 6... ZnO powder, 6...
- Oxide insulating film with additives, 7...Low melting point glass (binder). Name of agent: Patent attorney Toshio Nakao and 1 other person
2 Mouth 4 Figure Ichiriki tmi (1') Figure 5

Claims (1)

[Claims] Bi_2O_3, Co_2O in fine powder of inorganic semiconductor
After adding and mixing an inorganic or organic compound containing at least all of _3, MnO_2 and Sb_2O_3, heat treatment is performed at 600 to 1360°C to form an inorganic insulating film on the surface of the inorganic semiconductor fine powder, and
All or most of the finely powdered inorganic semiconductors having the insulating coating on the surface are brought together in a plurality of pieces, and then the finely powdered inorganic semiconductors are made into powder or a part of the finely powdered inorganic semiconductors. An insulating organic adhesive or glass powder and an organic binder are added as a binder to the powder containing the fine powder to form a paint, and then the paint is printed, sprayed, or dipped onto an insulating substrate on which one electrode is arranged. 1. A method for manufacturing a voltage nonlinear element, characterized in that the electrode is coated with a conductive paint, the electrode is cured by heat treatment, and the other electrode is coated with a conductive paint by printing, spraying, dipping, or the like.