JPH0412005B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a thick film varistor.

(Conventional technology) Conventionally, 2
Thick film varistors are known as terminal elements that are mainly used to suppress impact voltage, absorb noise, compensate for temperature, and the like.

This thick film varistor is made by laminating a varistor layer in which ZnO as semiconductor crystal grains and glass frit as a binder for the semiconductor crystal grains are fired in air on an electrode made of silver or the like fired on an insulating substrate. It has a structure in which silver electrodes and the like are fired on top of the varistor layer, and the varistor layer is sandwiched in a sandwich pattern.

(Problems to be Solved by the Invention) By the way, when the above-mentioned thick film varistor is used as a spark extinguishing element for a motor, sparks
For example, if there are too many sparks, noise will increase, while if there are too few, oxides will accumulate on the commutator, making it difficult to rectify the current. Therefore, in the past, the film thickness of the thick film varistor was changed or expensive metal oxides such as Bi ₂ O ₃ , Co ₂ O ₃ , MnO, TiO ₂ , Sb ₂ O ₃ ,
10mA by adding Cu ₂ O ₃ etc. during molding
The varistor characteristics expressed by the voltage value E ₁₀ when flowing, the voltage nonlinearity index α value, etc. were characterized in order to generate the desired spark, but controlling it by film thickness has many accuracy problems. When metal oxides are added, there is a problem in that they are expensive as mentioned above, resulting in increased manufacturing costs.

An object of the present invention is to provide a thick film varistor whose varistor characteristics can be easily controlled without changing the film thickness or adding expensive metal oxides.

(Means for Solving the Problems) In order to achieve the above object, the thick film varistor of the present invention has either an N-type semiconductor oxide or a P-type semiconductor oxide as a main component, and the other semiconductor oxide. It is characterized by being made by blending small amounts of substances.

(Function) According to the present invention, the other semiconductor oxide blended with either the N-type semiconductor oxide or the P-type semiconductor oxide serving as the main component works to change the varistor characteristics, and It also works to easily obtain desired varistor characteristics.

(Example) Examples of the present invention will be described below.

First, in order to obtain powder particles of N-type semiconductor oxide, ZnO solids were milled using a ball mill or the like with a diameter of 1 mm to 5 mm.
Then dry at 1100-1400℃ for 0.5-10
Bake for an hour. This sintered body is then pulverized to 400 mesh or less using a crusher, and then sieved to only the required particle size of around 10 μm.

On the other hand, the glass frit powder as a glass component is composed of well-known glass components, that is, in this example, ZnO, BaO, B ₂ O ₃ , Bi ₂ O ₃ , and Co ₂ O ₃ , and the composition ratio is ZnO 32 weight %, BaO27
wt%, _B2O3 32wt%, _{Bi2O3 4.5wt} % _,
Co ₂ O ₃ Weighed and mixed to 4.5% by weight, 1100
After being melted at a high temperature above ℃, it is rapidly cooled in water,
It is produced by finely pulverizing it to the required particle size.

The N-type semiconductor oxide thus produced
1.6% by weight of Cu ₂ O, which is a P-type semiconductor oxide, which is a characteristic part of the present invention, is added to 53.4% by weight of ZnO powder particles and 45% by weight of glass frit powder particles, and mixed.
Ethylene cellulose and BCA as a solvent are added to the obtained solid molecules and thoroughly kneaded to form a paste, which is then used as a barista paste.

Meanwhile, as shown in FIG. 1, in parallel with the above procedure, Ag, Au, Pt, etc.
A conductive paste consisting of the above is printed by screen printing, fired and laminated as the lower electrode 2.

Then, the above-mentioned Pallister paste is printed on the lower electrode 2 by screen printing method, and after drying,
It is fired at 1000°C and laminated as the varistor layer 3.

After that, the varistor layer 3 is
An upper electrode 4 is laminated thereon.

As a comparative sample, P
Comparative Example 1 was prepared by molding a conventional thick film varistor without adding Cu ₂ O, which is an N-type semiconductor oxide, and which was made of ZnO, which is an N-type semiconductor oxide, and glass frit.

By the way, the voltage value of 1mA flowing through the varistor is
It is known that the voltage non-linearity index α is expressed as α=1/[log(E ₁₀ /E ₁ )], where E ₁ is the voltage value when ₁₀ mA flows.

Therefore, the present inventor has developed the above-mentioned Example 1 and Comparative Example 1.
In contrast, when E ₁ and E ₁₀ were measured respectively and the α value was calculated, the α value of Example 1 was α = 3
Therefore, the α value of Comparative Example 1 was α=6.1, which demonstrated that the α value was significantly reduced compared to the conventional thick film varistor. Since the smaller the α value, the more easily sparks are produced, the thick film varistor of Example 1 is particularly effective in producing a large amount of sparks. Incidentally, E _10, which is one of the varistor characteristic display values.
The value was 26V in Example 1 and 6V in Comparative Example 1.

In addition to the above Example 1, in which 3 parts of Cu ₂ O, which is a P-type semiconductor oxide, was added to 100 parts of ZnO, which is an N-type semiconductor oxide, 8 parts of Cu ₂ O was added to 100 parts of ZnO. Added Example 2 to Example 1
When molded using the same method as above and measuring the _E10 value, _E10 = 100V.In addition, various amounts of P-type semiconductor oxide were added and thick film varistors were molded using the same method as described above. , E ₁₀ values were measured, and it was found that the varistor characteristics, that is, the E ₁₀ values, could vary in a quadratic curve depending on the amount of P-type semiconductor oxide added, as shown in FIG.

In this way, in a thick film varistor whose main component is an N-type semiconductor oxide, by adding a small amount of a P-type semiconductor oxide during molding, the varistor characteristics can be changed.

By the way, in the above embodiment, ZnO is used as the N-type semiconductor oxide constituting the thick-film varistor, but the N-type semiconductor oxide is not limited to ZnO, and may also be TiO ₂ , CdO, etc. Similarly, a small amount of P-type semiconductor oxide is added.
The material is not limited to Cu ₂ O, but may be VO, MnO, CoO, NiO, etc. as long as it is a P-type semiconductor oxide.

In addition, in the above embodiment, N which forms the main component
Although one type of semiconductor oxide is used, two or more types of N-type semiconductor oxides are mixed and sintered to generate an electrically conductive oxide, and a P-type semiconductor oxide is added to the electrically conductive oxide. A small amount may be added and mixed and sintered to form a thick film varistor.

Contrary to the above, P-type semiconductor oxides, such as Cu ₂ O used in the above examples, VO,
ZnO, mainly composed of MnO, CoO, NiO, etc.
It is also possible to add a small amount of N-type semiconductor oxide, such as TiO ₂ or CdO, and sinter the mixture to form a thick film varistor. The same effect as in the above embodiment in which a small amount of P-type semiconductor oxide is added as the main component is exhibited. However, the P-type semiconductor oxide cannot exhibit its properties when sintered in air. That is, since it changes to an N-type semiconductor oxide, it is necessary to sinter it in an inert gas, such as nitrogen or argon.

The thick film varistor of the above embodiment is of the Sanderch type as shown in FIG. 1, but it goes without saying that it can also be applied to a planer type.

(Effects of the Invention) As described above, according to the present invention, bistor characteristics can be improved by using either an N-type semiconductor oxide or a P-type semiconductor oxide as a main component and blending a small amount of the other semiconductor oxide. Since the varistor characteristics can be controlled, there is no need to change the film thickness or add expensive metal oxides, making it possible to easily control the varistor characteristics at low cost.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of a thick film varistor showing an embodiment of the present invention, and Fig. 2 is for explaining the _E10 value which changes depending on the ratio of the amount of P-type semiconductor oxide added to the N-type semiconductor oxide. This is a diagram. 5...Thick film varistor.

Claims (1)

[Claims] 1. A thick film varistor comprising a conductive component of an N-type semiconductor oxide or a P-type semiconductor oxide and a glass component for bonding the same, the main component being either one of the semiconductor oxides, A thick film varistor made by blending a small amount of the other semiconductor oxide.