JPS62190820A - 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 used for voltage stabilization, abnormal voltage control, and matrix-driven liquid crystal, E It is used in switching elements of display devices such as 'L'.

Conventional technology Conventional voltage nonlinear elements are made of zinc oxide (ZnO), bismuth oxide (B12O3), and cobalt oxide (CO203).
, 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. 48-19472) Problems to be Solved by the Invention Such a conventional voltage nonlinear element is a zn.

Since there is a limit to reducing the thickness of elements such as varistors (several tens of micrometers or less), there is a limit to reducing the varistor voltage (represented by the voltage V1mA when a current of 1111111 is passed through the varistor). , it could not be used as a protection element for low voltage ICs or as a voltage stabilizing element at low voltages. In addition, as mentioned above, when firing, 100
Since a high temperature process of 0'C or higher is required, 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 adds an inorganic or organic compound containing Mn to a fine powder of an inorganic semiconductor, mixes it, and then heat-treats it at 600 to 136°C. and
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 powder containing the above-mentioned fine powder is added to form a paint, and then the above-mentioned pane f electrode is arranged. It is characterized in that it is applied onto an insulated 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. 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 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 1700 to 13oO℃, and then the sintered ZnO is made into a particle size of 0.5 to 60 μm (average particle size of 1 to 10 μm). The ZnO fine powder was pulverized, and manganese oxide 'io, 05~10m01% was added to the ZnO fine powder.
After heat treatment at ~1350°C for 10-60 minutes, the ZnO
An insulating film of manganese oxide was formed on the surface of the 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 hundreds. Next, since the ZnO fine powders with the MnO2 insulating coating created in this way adhere to each other with weak force, they are loosened in a mortar or a bot mill to form fine powders in which a plurality of the above-mentioned ZnO fine powders are collected. 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 polyimide resin was added as a binder for bonding the powders to the ZnO powder on which the Mn□□ insulating film obtained as described above was formed and mixed. Here, as a binder, the solid content of the polyimide resin is s wt % relative to the solvent (for example, n-methyl-2-pyrrolidone).
It was diluted to give a paint-like composition, and mixed with ZnO powder in an equal weight, for example, to form a paint. Next, as shown in FIG. 3, the paint color obtained as described above is
It is coated on a glass substrate 3 on which an O (indium tin oxide) electrode 1 is provided, for example by screen printing, and the same glass substrate 4 on which an ITO electrode 2 is placed on top of it is heated at an angle of 280 to 400°. C. for 30 minutes in the atmosphere, 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 6, where 6 is Zn.
O powder 7 is MnO2 applied to the surface of ZnO powder 6
The insulating coating 8 is a binder that mechanically binds the ZnO powders 6 together, and the ZnO powders 6 are solidified together by the binder 8. Figure 4 shows ITO electrode 1
A case is shown in which a voltage nonlinear element 5 is constructed on a glass substrate 3a on which 1L and 1b 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 then MnO2 is added to it at 0.5%.
s mol % was heat-treated at 900°C for 160 minutes, and in this mixture of ZnO powder with an average particle size of 6 to 10 μm and a binder in equal weights, the element area was adjusted to 30 μm between the 1-9 electrodes. This shows the characteristics when Now, as is well known, the voltage-current characteristics of a voltage nonlinear element 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 that varies with 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 cannot function as a good voltage nonlinear element at a current of 10-'A or less. On the other hand, the device of the present invention shown in the characteristic curve has a large voltage nonlinearity index α even in a low current range, and can sufficiently function as a voltage nonlinear device even in a current range of about 10-105. 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 V.
jmA, and this varistor voltage v1mA and the voltage non-linearity index α 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, for example, v1 as shown in FIG.
It can be expressed in μA.

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 the bonding agent is insulating, so 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 the O powder is relatively large, 5 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 how the varistor voltage v1μA1 voltage nonlinear 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. 5.

As shown in FIG. 6, in the device of the present invention, the parallel capacitance is 1oO0 to 20,000 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. Furthermore, Table 1 shown below shows how the varistor voltage v1μA, voltage nonlinearity index α, and parallel capacitance C change when the amount of manganese oxide added and the heat treatment temperature are changed in the present invention. .

Table 1 As is clear from Table 1 and FIG. 6 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 1% smo. In addition, the heat treatment temperature depends on the amount of manganese oxide added, but
It showed good characteristics in the range of 1350'C. If the heat treatment temperature is outside the above-mentioned temperature range, for example below e o O'C, it may be difficult to form a sufficient insulating film.
At temperatures exceeding Ct-, 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. Similarly, the material constituting the insulating film is not limited to MnO2 alone;
i, Sr +'g.

Metal oxides such as Ni, Or, and Si or organometallic compounds of these metals can 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 particulate ZnO, which is an inorganic semiconductor, is heat-treated and pulverized to powder, and then Mn, which is an insulating inorganic compound, is
Although O2f 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 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 protection element for low-voltage ICs or as a voltage stabilizing element at low voltages, which could not be done with nO varistors. Furthermore, since the applied paint can be easily manufactured by curing at a low temperature, elements can be directly formed on circuit boards or glass substrates. 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 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 obtained by the method of the present invention and a conventional ZnO varistor. , FIG. 6 shows MnO in the device according to the method of the present invention.
2 is a diagram showing how the voltage non-linearity index α, the varistor voltage v1 μA, and the parallel capacitance C change when the amount of addition of No. 2 is changed. FIG. 1, 11L, 1m), 2-・-ITO electrode, 3
．． 3J4...Glass substrate, 5...Voltage nonlinear element, i,...ZnO powder, 7...
...MnO2 insulation coating, 8...Binder. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 4 Figure 5 Voltage (1')

Claims (1)

[Claims] After adding and mixing an inorganic or organic compound containing Mn to a fine powder of an inorganic semiconductor, heat treatment is performed at 600 to 1350°C to form an inorganic insulating film on the surface of the fine inorganic semiconductor powder. All or most of the above inorganic semiconductors in the form of fine powder on the surface are brought into a state where a plurality of pieces are gathered together, and then the above fine powder is applied to the powder or a part of the state in which a plurality of the inorganic semiconductors in the form of fine powder are gathered. An insulating organic adhesive or glass powder and an organic binder are added to the powder containing the 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, followed by heat treatment. A method for manufacturing a voltage nonlinear element, the method comprising curing the element.