JPS62193227A - 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 displays such as KL7i. It is used in switching elements of devices, etc.

Prior Art Conventional voltage nonlinear elements are made of zinc oxide (ZnO), bisyas oxide (BizOs), cobalt oxide (CO2), etc.
05), mango oxide (MnO2), antimony oxide (5b203), etc.
) to 1350°C, including ZnO varistors. Among them, what about ZnO barista? It is the most commonly used because it has a large E-pressure non-linearity index α and surge resistance. (Refer to Japanese Patent Publication No. 46-19472) Problems to be Solved by the Invention Conventional voltage non-linear elements such as these, including ZnO varistors, have limitations in making the element thickness thin (several tens of μm or less). Therefore, the varistor voltage (current 1 in the varistor)
There is a limit to how much mA can be passed and the current voltage (expressed as VillA) can be lowered, and it cannot 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
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.

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 1360°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. After that, a powder containing a plurality of fine powdered inorganic semiconductors or a powder containing the above fine powder and a fine powder of a metal or conductive metal oxide is added to an insulating powder. Prepare the organic adhesive or glass powder and organic binder, make it into a paint form, then print and spray the paint onto the insulating substrate on which the electrodes are arranged! It is characterized in that it is applied by coating or dipping and then hardened by heat treatment.

Effect: According to this method, a large voltage nonlinearity index α can be obtained even in a low current range, and by interposing a powdery conductive material, electrical connections between powdery semiconductor materials can be established. Because it is possible to obtain a stable device with less variation in characteristics, and also to control the varistor voltage depending on the amount of intervening conductive material, there is no need to be constrained by the distance between the electrodes, and the device can be extremely narrow as described above. (several tens of μ
Even if the device is not formed by using a dielectric film of less than m), an element suitable for lowering the voltage 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 powdery semiconductor material, the powdery conductive material is interposed between the powders of each semiconductor material, but there is point contact, and the contact area is basically small. Therefore, an element with small parallel capacitance can be obtained, and an element optimal as a switching element for devices such as liquid crystals can be provided.

Example Hereinafter, the present invention will be explained in detail based on examples.

@1 Figure shows an example 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/Zm is fired at 700 to 1300°C, and then the sintered ZnO is heated to a particle size of 0.5 to 601 tm (average particle size of 1 to 10 μm). ) and add cobalt oxide to the ZnO fine powder. , 06-10mo1% added, 6oo
Heat treated at ~135°C for 1° to 6°C,
An insulating film of cobalt oxide was formed on the surface of the fine powder. At this time, it was observed that a thin CO2O5 insulating film was formed on the surface of the finely powdered ZnO to a thickness of approximately several tens to several hundreds of layers. Next, the C o 2 created in this way
05 The ZnO fine powders with the insulating coating attached to their surfaces adhered to each other with weak force, so they were loosened in a mortar or bot mill to form a fine powder group in which a plurality 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, powdered ZnO on which the Co2O3 insulating film obtained as described above is formed is coated with silver powder as a powdered conductive material and an insulating binder (binder) for bonding between the powders. ) was added and mixed. Here, as a binder, the solid content of polyimide resin is S
wt%, and mix it in an equal weight to the total amount of ZnO powder and silver powder,
It was made into a paint form.

Next, as shown in FIG. 3, the vane obtained as described above is coated with ITO (indium tin oxide) on the glass substrate 3 provided with the pole 1 by screen printing, for example. Same as above (a glass substrate 4 provided with an ITO electrode 2 is placed and cured in the air at 280 to 400°C for 30 minutes, and a voltage nonlinear element 6 is installed between the electrodes 1 and 2. Figure 2 is an enlarged sectional view of the voltage nonlinear element 6, where e is a ZnO powder, 7 is a silver powder as a powdered conductive substance, and the ZnO powder 6 and the electrode 1.2 are 8 is an insulating binder that mechanically connects the powders 6 and 7, and the binder 8 solidifies the powders 6 and 7 together. 9 is Co applied to the surface of ZnO powder 6.
It is a 2O3 insulating film. Figure 4 shows ITO electrodes 11L, 1
Voltage nonlinear element 6 is placed on glass substrate 3a provided with
This shows the case where .

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 element of the present invention is produced by first firing zinc oxide at 700'C, then heat-treating the resultant to which 0.5 mo1% of Oo 205 is added at 900'C for 80 minutes, and then producing ZnO powder with an average particle size of 5 to 10 μm. and silver powder (average particle size 6 μm) (the total silver powder is 20F+).

In the case where an equal weight of the above-mentioned binder was added to h) and mixed, the characteristics are shown when the element area is 1-1 and the distance between the electrodes is 30 μm. Now, as is well known, the voltage-current characteristics of a voltage nonlinear element are approximately expressed by the following equation.

X=KV" 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 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 5, the conventional ZnO varistor shown in 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 10-4 A or less. On the other hand, in the device of the present invention shown by the characteristic curve, the voltage nonlinearity index α is large even in the low current range, and the device can sufficiently function as a voltage nonlinear device even in the current range of about 10-”A. In addition, 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 expressed as the varistor voltage v.
+mA, 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, v1μ as shown in FIG.
It can be represented by A.

In this way, in the present invention, the varistor voltage can be made low because the silver powder is dispersed within the element, which creates an electrical short circuit and substantially reduces the distance between the electrodes. This is because it has a so-called bridging effect (electrical bypass effect), which corresponds to shortening the length. 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, 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 the leakage current is small.

Figure 6 shows the varistor voltage v1μA1 when the amount of silver powder added as a powdery conductive substance is changed in the present invention.
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 much smaller than that of the conventional ZnO varistor, which is 1000 to 20,000 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 silver powder added, but this is thought to be because the electrical bypass changes depending on the amount of silver powder added, as described above.

Table 1 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 μA1 voltage nonlinear index α and parallel capacitance C change.

(The following is a blank space) As is clear from Table 1 and FIG. 6 above, each characteristic value is dependent on the amounts of cobalt oxide and silver 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 mo1%. The degree of heat treatment in t1 is 60, although it depends on the amount of cobalt oxide added.
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 this temperature, 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 Co2O3 (Bi, Bi, etc.).

Mn, Sb, Al, Ti, Sr0Mg, Mi
, Cr.

The material may be a metal oxide such as Sl or an organic metal oxide of these metals, and these may be used alone or in combination. Further, as the conductive substance, in addition to silver alone in this example, for example, xu
, Al, Zn, Ni, w.

Cu, Sn, In, Mn, Or,
fr, any metal or oxides 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, urea resins, and melamine resins.

Unsaturated polyester resins, diallyl phthalate resins, epoxy resins, polyurethane resins, silicone resins, etc. may also be used, and furthermore, glass powder and organic binders may be used in combination.

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, fine particle ZnO, which is an inorganic semiconductor, is heat-treated and pulverized to powder, and then Co, which is an insulating inorganic compound, is
Although 2O3 was added and then heat treatment was performed, 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.

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, by interposing a powdery conductive substance, the electrical connection between the powdery semiconductor substances can be stabilized, and an element with less variation in characteristics can be obtained. Since the advantage of being able to control the high IJ varistor voltage is obtained, 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.
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, the applied paint'
Because it can be easily manufactured by curing at low temperatures, 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 is a diagram showing how the voltage nonlinearity index α, the varistor voltage LztA, and the parallel capacitance C change when the amount of silver powder added is changed in the device according to the method of the present invention. 1.1&, 1b, 2...ITOTL pole, 3,3
turtle. 4... Glass substrate, 5... Voltage nonlinear element, 6... ZnO powder, 7... Silver powder, 8... Bonding agent, 9...CO2O3
Insulating coating. Name of agent: Patent attorney Toshio Nakao and 1 other person
](21 Figure 2 Figure 5 Figure 1 Voltage (1') 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 1350°C,
An inorganic insulating film is formed 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 gathered together, and then the fine powder is A powder in which a plurality of inorganic semiconductors are assembled together or a powder containing the above-mentioned fine powder and a metal or conductive metal oxide powder, an insulating organic adhesive, or a glass powder and an organic binder. A method for manufacturing a voltage non-linear element, which comprises: adding the paint to form a paint, applying the paint by printing, spraying or dipping onto an insulating substrate on which electrodes are arranged, and then heat-treating and curing the paint.