JPS62190819A - 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 non-linear element whose resistance value changes depending on an applied voltage, and is useful for voltage stabilization, abnormal voltage control, exposed matrix driven liquid crystal, EL, 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), and cobalt oxide (Oo2e5).
, manganese oxide (Mn02), antimony oxide (Sb2)
1000-1350℃ by adding oxides such as 05)
There are various types of varistors such as ZnO varistors sintered with Among them, ZnO varistors are most commonly used because of their large voltage nonlinearity index α and surge resistance. (Refer to Japanese Patent Publication No. 46-19472.) Problems to be Solved by the Invention In such conventional voltage nonlinear elements, including ZnO varistors, there is a limit to reducing the element thickness (less than a few micrometers). Therefore, the varistor voltage (current 1 to the varistor
There is a limit to lowering the voltage (expressed in V1111) when mA is applied, so it cannot be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages. Further, as described above, since a high temperature process of 100 C) or higher 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 includes a method in which an inorganic or organic compound containing at least all of Bi, Co, Mn, and Sb is added to and mixed with a fine powder of an inorganic semiconductor. rear,
Heat treatment is performed at 600 to 1,360°C to form an inorganic insulating film on the surface of the inorganic semiconductor fine powder, and all or most of the fine powdered inorganic semiconductors having the insulating film on the surface are collected in plural pieces. Then, an insulating organic adhesive or glass powder and an organic binder are added to the powder, which is a collection of multiple finely powdered inorganic semiconductors, or a powder containing some of the fine powders, to form a paint-like powder. The paint is then coated onto an insulating substrate on which electrodes are arranged by printing, spraying, dipping, etc., and then heat-treated to harden it.

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 (number +
μm or less), and an element suitable for lowering voltage can be obtained extremely 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 of solidified semiconductor material in the form of fine powder, there is no point contact between the fine powders of the respective semiconductor materials, and because the contact area is small, the parallel capacitance is small. As a result, 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 1300°C, and then the sintered ZnO is reduced to a particle size of 0.5 to 50 μm (average particle size of 1 to 10 μm). Pulverize and add Bi to the ZnO fine powder.
205, Co2o3, MnO2.

Add the total amount of 5b2o5 by 0.05 to 10mol1%i,
Heat treatment was performed at 600 to 1350° C. for 10 to 60 minutes to form an insulating film of these oxides on the surface of the ZnO fine powder. At this time, it was observed that a thin insulating film of the E oxide was formed on the surface of the finely powdered ZnO to a thickness of approximately several tens to several hundreds. Next, the ZnO fine powders with the oxide insulating coating on their surfaces adhered to each other with a weak force, so they are loosened in a mortar or pot mill to form fine ZnO powders that are made up of a plurality of individual 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 containing such ZnO fine powder in a part is also referred to as powder. next,
A binder (for bonding between the powders) is applied to the powdered ZnO on which the oxide insulating film obtained as described in E is formed.
A polyimide resin was added as a binder) and mixed.

Here, as a binder, the solid content of the polyimide resin is Swt relative to the solvent (for example, n-methyl-2-pyrrolidone) K.
%, and mixed with ZnO powder, for example, in an equal weight to form a paint. Next, the paint obtained as described above was applied to I as shown in FIG.
For example, it is coated on the glass substrate 3 on which the TO (indium tin oxide) electrode 1 is provided, and the h
K same (place the glass substrate 4 provided with the ITO electrode 2 and harden it in the air at 280 to 400°C for 30 minutes,
A voltage nonlinear element 5 was provided between the electrodes 1 and 2. FIG. 2 is an enlarged sectional view of the voltage nonlinear element 5, and is made of six ZnO
The powder, 7 is an oxide insulating coating applied to the surface of the ZnO powder 6, and 8 is a binder that mechanically binds the ZnO powders 6 together. solidified together. Figure 4 shows ITO electrode Ill,
A case is shown in which a voltage nonlinear element 5 is constructed on a glass substrate 3a provided with a voltage nonlinear element 1b.

Next, the voltage-current characteristics of the voltage nonlinear element created as follows 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. The device of the present invention is made by first firing zinc oxide at 700°C, then adding Bi2O3 and Co
2O3, MnO2, 5b203 each at 0.2110
1%, that is, 0.8 m o 1% in total, was heat-treated at 900°C for 60 minutes, and the average particle size was 6.
In a mixture of ~10 μm ZnO powder and binder in equal weight, the element area is 1-1 and the distance between electrodes is 30 μm.
The characteristics are shown when Now, as is well known, the voltage-current characteristics of a voltage nonlinear element are approximately expressed by the following equation.

1=KV" Here, ■ is the current flowing through the element, V is the voltage between the electrodes of the element, KI/'i is a constant corresponding to the specific resistance value, and α is the exponent of the voltage nonlinear characteristic described above, The larger the voltage nonlinearity index α is, the more excellent the voltage nonlinearity becomes.

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 A, 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 shown in the characteristic curve, the voltage nonlinearity index α is large even in the low current range, and it can sufficiently function as a voltage nonlinearity device even in the current range of about 105. 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 mm is passed through the element is called the varistor voltage V1.
This varistor voltage V1mA and the above-mentioned voltage non-linearity index α are used.

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

In this way, in the present invention, the varistor voltage can be made low because the element can be formed by narrowing the 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 not clear at present, but it is because the powdered semiconductor material (ZnO) is hardened with a binder. 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 that the bonding agent is insulating, so that the leakage current is small.

Here, the characteristics shown in FIG. 5 are obtained by changing the distance between the electrodes by 3
This is for an element with a thickness of 0 μm;
This is because the average particle diameter of O powder is relatively large, 6 to 10 μm, and cannot be made any narrower. That is, the average particle diameter of the ZnO powder is 0.3 to 3
The inventors have found that if a micrometer electrode 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 FIG. 5 can be obtained. Confirmed by experiment.

FIG. 6 shows that in the present invention, Bi2O5t”205tMn
Varistor voltage v1.02.8 when the total addition amount of b203 is changed. ．． It shows how the voltage non-linearity index α and the parallel capacitance C change. Here, other conditions such as the firing temperature of zinc oxide were the same as those in the case of FIG. 5. As shown in FIG. 6, in the device of the present invention, the parallel capacitance is conventional (D Z n O/(risk 100
It is very small compared to the 0 to 2oooOPF. 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 Bi2O3,00205, MnO
2.

It is a table showing how the varistor voltage v1□0 voltage nonlinear failure α and parallel capacitance C change when the total addition stoichiometric amount of 5b2o5 and the heat treatment temperature are changed.

(Hereinafter, blank spaces) As is clear from Table 1 and FIG. 6, each characteristic value is dependent on the total stoichiometric amount of the oxide and the heat treatment temperature. Here, the total stoichiometric amount of oxides trio, os~
Particularly good characteristics were shown at 3mo1%. In addition, the heat treatment temperature depends on the total stoichiometric amount of oxides added, but is between 600 and 1350.
T? : It showed good characteristics in the range of . If this heat treatment temperature is outside the above temperature range, for example below 600°C, it will 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. Good characteristics cannot be obtained.

In addition, in the above embodiment, the semiconductor material is
Although the description has been made using znO as an example, it goes without saying that other semiconductor materials may be used. Similarly, the material constituting the insulating film is Bi2O3,00
203, MnO2, 5b203, but all of Bi, Co, Mn, and Sb can be used as main components. T: L, Sr, Mg, Ni.

Metal oxides such as Or and Si or these organic metal compounds can be used alone or in combination.

Furthermore, as a binder for solidifying powdered semiconductor materials,
Insulating organic adhesives other than polyimide resins may be used, and thermosetting resins such as phenol resins, furan resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, epoxy resins, polyurethane resins, silicon resins, etc. may also be used. 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 above examples, 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 powder, and then Bi, which is an insulating inorganic compound, is
2O3,00203,MnO2.

5b2o5 was added and then heat-treated, but it is possible to directly apply the inorganic compound to the inorganic semiconductor fine 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 element 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. It is possible to provide an element that is optimal as a switching element for devices such as liquid crystal, KL, etc., which has 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 low-voltage Xa protection element 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 a low temperature and easily manufactured, elements can be directly formed on circuit boards or glass substrates. Therefore, the voltage non-linear element of the present invention having various features can be expected to have a wide range of applications unimaginable for conventional ZnO <IJ stars, etc., and its industrial potential is great.

[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. 6 is a diagram showing the voltage-current characteristics of the device obtained 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.
O3゜00203, voltage nonlinear index α when changing the total addition stoichiometric amount of MnO2, 5b203, varistor voltage v11
1k and a diagram showing how the parallel capacitance C changes. FIG. 1.1&, 1b, 2...-4TO electrode, 3,31L
. 4...Glass substrate, 6...Voltage nonlinear element, e...ZnO powder, 7...
Oxide insulating film with additives, 8...Binder. Fig. 1 Fig. 2 Fig. 4 Electrician Unagi Pair Parallel Miyun Shoulder Rabbit 5 Fig. 5 One Power Voltage (1')

Claims (1)

[Claims] After adding and mixing an inorganic or organic compound containing at least all of Bi, Co, Mn, and Sb to a fine powder of an inorganic semiconductor, heat treatment is performed at 600 to 1350 ° C.
An insulating film is formed on the surface of the inorganic semiconductor fine powder, and all or most of the fine powder inorganic semiconductors having the insulating film on the surface are gathered together, and then the fine powder is An insulating organic adhesive or a glass powder and an organic binder are added to a powder containing a plurality of inorganic semiconductors or a powder containing the above-mentioned fine powder to form a paint, and then the paint is applied to an insulating film with electrodes arranged. A method for manufacturing a voltage nonlinear element, which comprises applying the coating onto a substrate by printing, spraying, dipping, etc., and then heat-treating and curing the coating.