JPS62193217A - 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 value changes depending on an applied voltage, and is useful for voltage stabilization, abnormal voltage control, and matrix-driven liquid crystal, KL, 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 (BizO5), and cobalt oxide (Oo2eS).
, mancan oxide (Mn02), 77thimony oxide (Sb2)
1000-1350' by adding oxides such as
There are various types such as ZnO varistors sintered with carbon.

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. 4θ-19472) Problems to be Solved by the Invention In such conventional voltage nonlinear elements, including ZnO varistors, there is a limit to how thin the element can be (less than several tens of μm). Therefore, the varistor voltage (current 1 to the varistor
There is a limit to lowering the voltage (expressed as V+InA when mA is applied), and it cannot be used as a protection element for low-voltage ICs or a voltage stabilizing element for low iEE. It's a moat, as mentioned above, when firing at 1000℃
Since the above-mentioned high-temperature process 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 to a fine powder of an inorganic semiconductor, and after mixing,
Heat treatment is performed at 600 to 1350'C to form an inorganic insulating film on the surface of the inorganic semiconductor fine powder, and then the semiconductor fine powder with the insulating film and graphite or amorphous carbon fine powder as a conductive substance are added. An insulating organic adhesive or glass powder and an organic binder are added to the mixture 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. The t% mark is determined by curing by performing the following steps.

Effect: According to this method, a large voltage non-linearity index α can be obtained even in a low current range, and by interposing a finely powdered conductive material, the electrical conductivity between finely powdered semiconductor materials can be improved. It is possible to obtain a device with stable connections and less variation in characteristics, and it is also possible to control the varistor voltage depending on the amount of intervening conductive material, so it is not limited by the distance between the electrodes, and it is possible to Even if the device is not formed with a very small diameter (several tens of μm or less), an device suitable for lowering the voltage can be obtained very easily. Also,
Since it can be made by curing the applied paint at low temperatures, it is possible to form elements directly on circuit boards, and it is 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 the respective semiconductor materials, although there is a conductive material in the form of fine powder, and the contact area is basically the same. Since it is small in size, it is possible to obtain a device with a small parallel capacitance, making 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 0.05 to 1 μm is fired at Too~1300'C, and then the sintered ZnO is sintered with a particle size of 0.6 to 50/1 m (average particle size of 1 to 0.05~10m01% of cobalt oxide was added to the ZnO fine powder, and 6oO
After heat treatment at ~1360°C for 1°~6Q minutes, the ZnO
An insulating film of cobalt oxide was formed on the surface of the fine powder. At this time, it was observed that a Co,.05 insulating film was formed thinly on the surface of the finely powdered ZnO to a thickness of approximately several tens to several hundreds of layers. Next, the Co2O created in this way
3. Since the ZnO fine powders with the insulating coating on their surfaces adhered to each other with weak force, they were all loosened in a mortar or pot mill to form fine powders.

Next, fine graphite powder as a fine powder conductive material and an insulating layer for bonding between the fine powders are applied to the fine powder ZnO on which the Co2O5 insulating film obtained as described above is formed. A polyimide resin was added as a binder and mixed.

Here, as a binder, the solid content of polyimide resin is 5wt relative to the solvent (for example, n-methyl-2-pyrrolidone).
%, and mixed it in an equal weight to the total amount of fine ZnO powder and silver powder to form a paint.

Next, as shown in FIG. 3, the paint e obtained as described above is applied onto a glass substrate 3 provided with an ITO (indium tin oxide) electrode 1 by, for example, screen printing, and the same ( The entire glass substrate 4 provided with the ITO electrode 2 was mounted and cured in the atmosphere at 280 to 400°C for 30 minutes, and a voltage nonlinear element 6 was provided between the electrodes 1.2. It is an enlarged cross-sectional view of the voltage nonlinear element 5, in which 6 is ZnO fine powder, 7 is graphite fine powder as a fine powder conductive substance, and 6 questions about ZnO fine powder and the ZnO fine powder 6 and electrode 1. Good electrical connection is made between 2 and 8. 8 is made of these fine powders.

An insulating binder mechanically connects the fine powders 6 and 7, and the fine powders 6 and 7 are solidified with this binder 8. 9 is a Co2O3 insulating film applied to the surface of the ZnO fine powder 6. FIG. 4 shows a case where a voltage nonlinear element 5 is constructed on a glass substrate 32L provided with ITO electrodes 1a, 1k).

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 first fired with zinc oxide at a temperature of 700'C2, and then heated with CO20s.
'Fr0.5 mo1% added 1900'C18
After heat treatment for 0 minutes, this Zn with an average particle size of 3 to 5 pm
O fine powder and graphite fine powder (average particle size 31 km)
) and the above-mentioned binder of equal weight is added to the total valve (graph 1ite fine powder is 20Wt) and mixed, and the characteristics are shown when the element area is 1-1 and the distance between the electrodes is 301 km. ing. Now, as is well known, the voltage-current characteristics of a voltage nonlinear element are approximately expressed by the following equation.

I=KV" Here, Δ is the current flowing through the element, and ■ is the current between the electrodes of the element.
is the pressure, K is a constant corresponding to the resistance value of the specific resistance, and α is the exponent of the voltage nonlinearity described above. The larger the voltage nonlinearity index α is, the better the voltage nonlinearity is. Become.

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, 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 10-10 A. It shows. In addition, normally in a ZnO varistor, for example, 1 mA is applied to the element to express the varistor characteristics.
The voltage that appears between the electrodes when a current of
As mentioned above, even in the low current range, the voltage nonlinearity index α
is large, and the risk voltage can be expressed, for example, in v1μ as shown in FIG.

In this way, in the present invention, the varistor voltage can be made low because the fine graphite powder is dispersed in all the elements, which creates an electrical short circuit and substantially reduces the distance between the electrodes. This is because it shows a so-called bridging effect (electrical bypass effect), which corresponds to a shortening of the current. Therefore, by adding an appropriate amount of a conductive substance, an element can be formed without being restricted by the distance between the electrodes, for example, without making the distance between the electrodes extremely narrow. 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 fine powder semiconductor material (ZnO)
is hardened with an insulating binder, so there is a point contact between each semiconductor material, and the contact area is small. Also, since the binder is insulating, the leakage current is small. considered to be a thing.

Figure 6 shows the varistor voltage V, μA1 voltage nonlinear index α, and parallel capacitance C when the amount of graphite fine powder added as a fine powder conductive substance is changed in the present invention.
It shows how things change.

Here, other conditions such as the firing temperature of zinc oxide are determined by the sixth
The conditions were the same as in the case shown in the figure. As shown in FIG. 6, in the device of the present invention, the parallel capacitance is much smaller than that of the conventional ZnO varistor, which is 100° to 2000°PF. 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, from FIG. 6, it can be seen that the varistor voltage changes depending on the amount of fine graphite powder added, but this is thought to be because the electrical bypass changes depending on the amount of fine graphite powder added, as described above.

In addition, Table 1 shown below shows the varistor voltage v1 when the amount of cobalt oxide added and the heat treatment temperature are changed in the present invention.
It is a table showing how μA, voltage nonlinearity index α, and parallel electrostatic field Ju C change.

(Left below) As is clear from Table 1 and FIG. 6 above, each characteristic value is dependent on the amount of cobalt oxide and fine graphite powder added and the heat treatment temperature. Here, especially good characteristics were exhibited when the amount of cobalt oxide added was 0.05 to 3 mol %. Further, although the heat treatment temperature varied depending on the amount of cobalt oxide added, good characteristics were exhibited within the range of eoo to 1350°C. This heat treatment temperature is outside the above temperature range, for example 60
Good characteristics cannot be obtained because it is difficult to form a sufficient insulating film at 0°C (unyellow), and at temperatures exceeding 1350' (E), the voltage nonlinearity index α becomes less than the required value. It is.

In addition, in the above example, the semiconductor material is
Although the explanation has been made using Znofz as an example, it is of course possible to use other semiconductor materials. Similarly, the material constituting the insulating film is not limited to Co2O3, but also Bi.

Mn, Sb, Al, Ti, Sr,
Mg, Ni, Or.

Metal oxides such as No. 31 or organic gold monooxides of these metals may also be used, and these may be used alone or in combination.

In addition, conductive substances other than the graphite used in this embodiment (C amorphous carbon, such as channel plastic, furnace black, and acetylene blank) may be used.

Thermal plaques, rambulbs, etc. may also be used, and they can be used alone or in combination.

Furthermore, the binder for solidifying the finely powdered bioconductor material may be an insulating organic adhesive other than polyimide resin.
Thermosetting resins, such as phenolic resins, furan resins,
Urea resin, melamine resin.

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.

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 form a fine powder, and then Co2O5, which is an insulating inorganic compound, is added, and then the heat treatment is carried out. However, it is also 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, ELfi, etc., with low current consumption. Also, a fine powder conductive substance? By intervening the conductive material, it is possible to stabilize the electrical connection between the fine powder semiconductor materials and obtain an element with less variation in characteristics, and the varistor voltage can be controlled by the amount of intervening conductive material. Because of this advantage, a low varistor voltage can be obtained without being restricted by the distance between the electrodes, for example, without making the distance between the electrodes extremely narrow. It can be used as a low-voltage rC protection element and a voltage stabilizing element at low voltages, which cannot be handled by a varistor. 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 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 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. , Figure 6 shows the voltage nonlinearity index α when the amount of graphite fine powder added is changed in the device according to the method of the present invention.
, is a diagram showing how the varistor voltage v1 μA and the parallel capacitance ZC change. 1.1a, 1b, 2...-4TO electrode, 3,311
゜4...Glass substrate, 6...Voltage nonlinear element, 6...ZnO fine powder, 7...
・Graphite fine powder, 8...Binder, 9...
...Co2O3 insulation coating. Name of agent: Patent attorney Toshio Nakao Haga 1st person
1 (21 Figure 2 Figure 4 Figure 5 Electric FcCV) Figure 6

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 1360°C,
An inorganic insulating film is formed on the surface of an inorganic semiconductor fine powder, and then an insulating organic adhesive is added to the semiconductor fine powder on which the insulating film is applied and graphite or amorphous carbon fine powder is added as a conductive substance. Alternatively, a voltage non-linear method is characterized in that glass powder and an organic binder are added to form a paint, and then the paint is applied by printing, spraying, dipping, etc. onto an insulating substrate on which electrodes are arranged, and then heat treatment is performed to harden the paint. Method of manufacturing a sexual element.