JPS62190817A - 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 used for voltage stabilization, abnormal voltage control, and matrix-driven liquid crystals.

It is used in switching elements of display devices such as KL.

Conventional technology A conventional voltage nonlinear element consists of zinc oxide (ZnO), bismuth oxide (Bi203) + cobalt oxide ("203)"
+ Manganese oxide (MnO2), antimony oxide (Sb)
1000-1360 by adding oxides such as 203)
There are various types such as ZnO varistors sintered at °C.

Among them, ZnO varistors are the most commonly used because of their high voltage nonlinearity index α and high surge resistance.

(Refer to Japanese Patent Publication No. 46-19472) Problems to be Solved by the Invention Such conventional voltage nonlinear elements, including ZnO varistors, have limitations in making the element thickness thin (several tens of μm or less). Therefore, there is a limit to lowering the varistor voltage (expressed as the voltage v + mA when a current of 111 tm flows through the varistor), and it can be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages. It was something that didn't exist. In addition, as mentioned above, when firing
Since this method requires a high-temperature process of C or higher, 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, and causing problems.

Means to Solve the Problem In order to solve this problem, the present invention adds an inorganic or organic compound to a fine powder of an inorganic semiconductor, and after mixing,
Heat treatment is performed at 600-1350°C.

An inorganic insulating film is formed on the surface of the inorganic semiconductor fine powder, and all or most of the finely powdered inorganic semiconductors having the insulating film on the surface are gathered together, and then the fine powder is formed. An insulating organic adhesive or glass powder and an organic binder are added to a powder in which a plurality of inorganic semiconductors are assembled or a part of the powder contains the above-mentioned fine powder to form a paint, and then the above-mentioned paint is applied to an electrode. It is characterized in that it is applied onto an insulating substrate by printing, spraying, dipping, etc., and then heat-treated to harden it.

Effect: According to this method, a large voltage non-linearity index α can be obtained even in a low current range, and an element can be formed with a narrow distance between electrodes (several tens of μm or less), making it possible to reduce the voltage. A suitable element can be obtained very easily. Additionally, 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 or 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 since the contact area is small, a device with a 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.

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 0.06 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 μm (average particle size of 1 to 10 μm). 0.05 to 10 mo1% of cobalt oxide was added to the ZnO fine powder,
Heat treated at 136 o 0 C for 10 to 60 minutes, and
An insulating film of cobalt oxide was formed on the surface of the fine powder. At this time, it was observed that a thin CO□03 insulating film was formed on the surface of the finely powdered ZnO to a thickness of approximately several tens to several hundreds. Next, C'20! created in this way!
Since the ZnO fine powders with the insulating coating attached to their surfaces adhere to each other with weak force, they were loosened in a mortar or pot mill to form a fine powder group in which multiple pieces of each of the above ZnO fine powders were gathered (hereinafter, this (The state is called powder). 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 polyimide resin was added as a binder for bonding the powders to the powdered ZnO on which the CO□03 insulation film obtained as described above was formed and mixed. Here, the binder is a solid content of polyimide resin; it is diluted to Swt% with respect to the solvent (for example, n-methyl-2-pyrrolidone), and it is mixed with ZnO powder in an equal weight, for example. , in the form of paint. Next, the paint obtained as described above is applied, for example, by screen printing, onto a glass substrate 3 provided with an ITO (indium tin oxide) electrode 1, as shown in FIG.
On top of that is the same (glass substrate 4 provided with ITO electrode 2)
was placed and cured in the air at 28° to 40° C. for 30 minutes, and a voltage nonlinear element 5 was provided between the electrodes 1.2.

FIG. 2 is an enlarged sectional view of the voltage nonlinear element 5, and 6
7 is the ZnO powder, and 7 is the CO applied to the surface of the ZnO powder 6.
□0. The insulating coating 8 is a binder that mechanically binds the ZnO powders 6 together, and this binder 8
The O powders 6 are solidified together. Figure 4 shows ITO
A case is shown in which a voltage nonlinear element 6 is constructed on a glass substrate 3a provided with electrodes 1&, 1b.

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.

The device of the present invention is produced by first firing zinc oxide at 00°C,
To this, 0.5 mo1% of CO□03 was added and 9
After heat treatment at 00'C for 60 minutes, the average particle size was 5~
The graph shows the characteristics when the area of one element is set to 1-1 and the distance between the electrodes is 30 μm in a mixture of 1 μm ZnO powder and a binder in equal weights. Now, as is well known, the voltage τ current characteristic of a voltage nonlinear element is approximately expressed by the following equation.

I=KVa 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 is, the better the voltage nonlinearity is.

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
If the voltage is small and the current is less than +10 A, it cannot function as a good voltage nonlinear element. On the other hand, the voltage nonlinearity index α of the device of the present invention shown by the characteristics is large even in the low current range, indicating that it can sufficiently function as a voltage nonlinearity device even in the current range of about 1o. ing. Furthermore, 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 m is applied to the element is expressed as the varistor voltage v1. !
This varistor voltage v, IIIA and the voltage non-linearity index α are used. As mentioned 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 is changed to v, for example, as shown in FIG.
It can be expressed in 1 mm.

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. Because of this, there is a point contact between each semiconductor material, and the area of contact is small, and because the bonding agent is insulating.

This is thought to be due to the decrease in leakage current.

Here, the characteristics shown in FIG. 6 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 diameter of the O powder is relatively large, 5 to 10 μm, and cannot be made any narrower. That is, the average particle diameter of ZnO powder is 0.3
The inventors have 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 approximately 10 μm or less, and even in that case, good characteristics as shown in FIG. 6 can be obtained. was confirmed by experiment.

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

As shown in FIG. 6, in the device of the present invention, the parallel capacitance of the conventional ZnO varistor is 100° to 20,000°.
Although it is a PF, it is very small.

The reason why this parallel capacitance 1C is small in the device of the present invention is that the contact area between the semiconductor materials is small, as described above.

Table 1 below shows the varistor voltage 7 when the amount of cobalt oxide added and the heat treatment temperature are changed in the present invention.
18 is a table showing how the voltage non-linearity index α and the parallel capacitance C change.

(Hereinafter referred to as gold and white) As is clear from Table 1 and FIG. 6 above.

It can be seen that each characteristic value depends on the amount of cobalt oxide added and the heat treatment temperature. Here, particularly good characteristics were exhibited when the amount of cobalt oxide added was O,OS~3m01%. In addition, the heat treatment temperature depends on the amount of cobalt oxide added, but
It showed good characteristics in the range of 0 to 1350'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;
At temperatures exceeding C, good characteristics cannot be obtained because the voltage nonlinearity index α becomes less than the required value.

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. Also,
Similarly, the material constituting the insulating film is Co20
．． but not limited to Mu/, Ti.

Metal oxides such as Sr, Mg, Ni, Cr, and Si or organometallic compounds of these metals may be used, and these may be used alone or in combination.

Furthermore, as a binder for solidifying powdered semiconductor materials,
Insulating organic adhesives other than polyimide resins may also be used, such as thermosetting resins such as phenolic resins, furan resins, area resins, and melamine resins.

Unsaturated polyester resins, diallyl phthalate resins, epoxy resins, polyurethane resins, silicone resins, and the like may also be used, and furthermore, a combination of glass powder and an organic binder may be used.

Further, in the above embodiments, the elements were formed by the double IJ+ printing method, but other coating methods such as spraying, dipping, etc. may be used.

Furthermore, in the manufacturing method according to the above embodiment.

First, fine-particle ZnO, which is an inorganic semiconductor, was heat-treated and pulverized to form a powder. Co20s, an insulating inorganic compound, was then added and then heat-treated. It is possible to add an inorganic compound 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 also has a small parallel capacitance. It is possible to provide an element that is most suitable as a switching element for devices such as , small-sized liquid crystal, ICI, etc. with small current consumption. In addition, since the device can be formed with a narrow distance between the electrodes, a low varistor voltage can be obtained, which, combined with the large voltage nonlinearity index α mentioned above, cannot be achieved with conventional ZnO varistors. It can be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages. 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 has great industrial potential.

[Brief explanation of drawings]

FIG. 1 shows 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. 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 Co2 in the device according to the method of the present invention.
FIG. 6 is a diagram showing how the voltage non-linearity index α, the varistor voltage v111, and the parallel capacitance C change when the amount of O3 added is changed. 1.1&, 1t), 2-...-ITO electrode, 3.31
゜4...Glass substrate, 6...Voltage nonlinear element, 6...ZnO powder, 7...
Co20. Insulating coating, 8...Binding agent. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 5

Claims (1)

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