JPS62242304A - 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, EL, etc. It is used in switching elements of display devices, etc.

Conventional technology Conventional voltage nonlinear elements are made of zinc oxide (ZnO), hismuth oxide (B12o3), and cobalt oxide (C0203).
.

Manganese oxide (MnO2), antimony oxide (Sb2)
1000-1350' by adding oxides such as 03)
There are various risks such as Znω sintered with C.

Among them, ZnO varistors are the most commonly used because they have a large voltage nonlinearity index α and surge resistance (see Japanese Patent Publication No. 19472/1983).

Problems to be Solved by the Invention In such conventional voltage nonlinear elements, such as ZnO varistors, there is a limit to reducing the element thickness (several tens of micrometers or less). 1
There is a limit to lowering the voltage v1rrL (expressed in units of mA), and 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 to Solve the Problem In order to solve this problem, the present invention uses a plurality of finely powdered semiconductor substances having a thin insulating film mainly composed of B12O3 to form a single powder. A powdered semiconductor substance is solidified on an insulating substrate with one electrode, the lower layer side of which is the one electrode side is made of an insulating binder, and the upper layer side is made of an electrically conductive paste. It is characterized by being provided with

Effect: According to this configuration, a large voltage nonlinearity index α can be obtained even in a low current range, and the varistor voltage can also be controlled by the amount of insulating binder, so the distance between the electrodes can be narrowed. (several tens of micrometers or less), and an element suitable for lower voltage can be obtained very easily. Since it can be made by curing the applied paint at a low temperature, it is possible to form elements directly on circuit boards, and it is expected to have a wide range of applications unimaginable with ZnO varistors and the like. Furthermore, since the obtained device is made by solidifying powdered semiconductor material, there is point contact between the powders of each semiconductor material, and since the contact area is basically small, it is possible to obtain a device with a small parallel electrostatic capacitance. This makes 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 example of the manufacturing process for obtaining the device of the present invention. First, fine particulate lead oxide with a particle size of 0.05 to 1 μm is fired at 700 to 1300°C, and then the sintered ZnO is sintered with a particle size of 0.5 to 50 μm (average particle size of 1 to 10 μm). 1% of bismuth oxide was added to the ZnO fine powder, and 6oo~13% of bismuth oxide was added.
A heat treatment was performed at 50° C. for 10 to 60 minutes to form an insulating film of bismuth oxide on the surface of the ZnO fine powder. At this time, it was observed that a thin Bi206 insulating coating was formed on the surface of the finely powdered ZnO with a thickness of several tens to several hundreds.

Next, since the ZnO fine powders with the B12O3 insulating film attached to the surfaces created in this way are adhered to each other with a weak force, they are loosened in a mortar or pot mill to form a fine powder group in which each of the ZnO fine powders has a plurality of leap years. (hereinafter, this state will be referred to as 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, low melting point glass powder and an organic binder were added as an insulating binder to bond the powders to the powdered ZnO with the Bi2O3 insulating film formed on the surface obtained as described above, and the mixture was mixed. did. Here, as a binder, the amount of the low melting point glass powder is 5 to 20 wt% based on the powdered ZnO, and it is mixed with the organic binder in an equal weight, for example,
It was made into a paint form. Here, ethyl cellulose was used as the organic binder, and the solid content was diluted to 10 wt % with respect to the solvent (for example, terpineol).

Next, as shown in FIG. 2, the paint obtained as described above is applied onto a glass substrate 2 provided with an ITO (indium tin oxide) electrode 1 by, for example, screen printing. Heat treatment was performed in the air for 10 to 30 minutes. Next, the other electrode 3 was formed by screen printing carbon paste to obtain an element of the present invention.

FIG. 2 is an enlarged sectional view of the voltage nonlinear element 4, and 5
6 is the ZnO powder, and 6 is the Bi applied to the surface of the ZnO powder 5.
2O, an insulating coating, 7 is a low melting point glass as an insulating binder that mechanically bonds between the ZnO powder 5 on the lower layer side which is the side of the ITO electrode 1; As a result, the powders 5 on the lower layer side are solidified together. Furthermore, the ZnO powders 5 on the upper layer side are solidified with each other by electrodes 3 made of the carbon paste.

Next, the voltage-current characteristics of the voltage nonlinear element created as described above will be explained. First, Figure 3 shows the second
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 and adding 0.5 mo1% of B12O3 to it.
After heat treatment at 0°C for so minutes, this average particle size was 5 to 1.
01t711 ZnO powder and low N1 point glass fine powder manufactured by Okuno Seiko Kuwa ■ (20 wt% to ZnO powder) were mixed with the above organic binder in equal weight, and the element area was 1-2 and the distance between electrodes was 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.

I=KVa Here, ■ 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, 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 3, 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, the device of the present invention shown in the characteristics has a large voltage nonlinearity index α even in the low current range, and can sufficiently function as a voltage nonlinear device even in the current range of about 10'-10A. 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 1m is passed through the element is called the varistor voltage v17nA, and this varistor voltage v, 7WA and 2. A non-linear index α is 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 and aA as shown in FIG.

In this way, in the present invention, the varistor voltage can be made low because firstly, the element thickness of the voltage nonlinear element 4 can be made thin, and furthermore, as shown in FIG. Since the voltage non-linear element 4 on the lower layer side is hardened with the low melting point glass 7 and the voltage non-linear element 4 on the upper layer side is hardened with the carbon electrode 3, the distance between the electrodes can be substantially narrowed. This is because elements can be formed. At this time, if the amount of the low melting point glass 7 is small, the degree to which the carbon electrode 3 penetrates into the voltage nonlinear element 4 on the upper layer side increases, and the distance between the electrodes is more substantially narrowed to form an element. Because you can
This allows the varistor voltage to be lowered even further.

In addition, 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 in terms of color development, but the low melting point of the insulating binder is This is thought to be due to the fact that since it is solidified with glass, there is point contact between each semiconductor material, and the contact area is small, and the bonding agent is still insulating, so the leakage current is small.

Here, the characteristics shown in Fig. 3 are for an element with an inter-electrode distance of 30 μm as mentioned above, but this is
This is because the average particle size of the nO powder is relatively large, ie, 5 to 107 x 7711 degrees, so it cannot be made any narrower. In other words, if ZnO powder with an average particle diameter of 0.3 to 3 μm is used, it is possible to fabricate an element with an interelectrode distance of about 10 μm or less, and even in that case, as shown in Figure 3. The present inventors confirmed through experiments that good characteristics can be obtained.

FIG. 4 shows how the varistor voltage v1/jA' voltage non-linearity index α and parallel capacitance C change when the amount of bismuth oxide added is changed in the present invention. Here, other conditions such as the firing temperature table for zinc oxide were the same as those in the case of FIG. 3.

As shown in FIG. 4, in the device of the present invention, the parallel capacitance is 1000 to 20000 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.

In addition, Table 1 shown below shows the variance voltage v1 when the amount of bismuth oxide added and the heat treatment temperature are changed in the present invention.
1 is a table showing how the voltage non-linearity index α and the parallel capacitance C change over 1t person.

(Left below) 14.

As is clear from Table 1 and FIG. 4, each characteristic value is dependent on the amount of bismuth oxide added and the heat treatment temperature. Here, the amount of bismuth oxide added is O, OS
Particularly good characteristics were shown at ~3 mo1%. In addition, the heat treatment temperature is 600 to 1350, depending on the amount of bismuth oxide added.
It showed good characteristics in the 'C range. 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 explanation has been given using ZnO 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 Bi2O3 alone, but includes Al, Bi2O3 as the main component,
Metal oxides such as Ti, Sr, Mg, Ni, Or, and Si or organic metal oxides of these metals can be used alone or in combination.

Furthermore, the binder for solidifying the powdered 1'-conductor material may be an insulating organic adhesive made of a combination of glass powder and an organic binder, or a thermosetting resin such as polyimide resin or phenol resin. .

Furan resin, urea resin, melamine resin, unsaturated polyester resin, diallyl wotalate resin, epoxy resin,
Polyurethane resin, silicone resin, etc. may also be used.

Furthermore, although the above examples show cases in which glass powder alone is used as a binder, glass powder may also be used in combination with the above-mentioned insulating organic adhesive. After combining the powders,
The element can also be formed by printing the organic adhesive from above the element and filling it into the element.

Furthermore, although the elements and electrodes were formed by screen printing in the above embodiments, other coating methods such as spraying, dipping, etc. may also be used.

Furthermore, in the manufacturing process according to the above embodiment, first, fine particulate ZnO, which is an inorganic semiconductor, is heat-treated and pulverized to powder, and then Bi, 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 according to the present invention has a large voltage nonlinearity index α in the low current region, and an element with small parallel capacitance can be obtained.
It is possible to provide an element that is optimal as a switching element for a device such as a liquid crystal JL with low current consumption. In addition, since the device can be formed by narrowing the distance between the electrodes, a device with a low varistor voltage can be obtained, and the varistor voltage can also be controlled by the number of insulating organic adhesives or the amount of glass powder. Coupled with the large nonlinearity index α, it can be used as a film-holding element for low-voltage ICs or as a voltage stabilizing element at low voltages, which conventional ZnO varistors could not handle. 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. 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 DESCRIPTION OF THE DRAWINGS] FIG. 1 is a diagram showing an example of the manufacturing process of a voltage non-linear element according to the present invention, and FIG. 2 is an enlarged sectional view showing an example of the voltage non-linear element according to the present invention. , FIG. 3 is a diagram showing voltage-current characteristics of a device according to the present invention and a conventional ZnO varistor,
FIG. 4 shows the voltage non-linearity index α and the varistor voltage v1/ when the added amount of Bi2O3 is changed in the device according to the present invention.
, A and the parallel capacitance C change. 1...ITO electrode, 2...Glass substrate, 3
... Carbon electrode, 4 ... Voltage nonlinear element, 5 ... 187, ZnO powder, 6 ... Bi2O5 insulation coating, 7.
...Low melting point glass (binder). Name of agent Patent attorney Toshio Nakao and 1 other person Figure 3

Claims (1)

[Claims] A powdered semiconductor material, which is made up of a plurality of finely powdered semiconductor materials each having a thin insulating film mainly composed of Bi_2O_3, is placed on an insulating substrate provided with one electrode. 1. A voltage nonlinear element characterized in that a lower layer side, which is one electrode side, is hardened with an insulating binder, and an upper layer side is hardened with the other electrode made of a conductive paste.