JPS6347125B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a voltage nonlinear resistor made of an oxide semiconductor. One of the circuit elements using semiconductors is a voltage nonlinear resistor. One of the circuit elements using semiconductors is a voltage nonlinear resistor, and a typical example is a varistor using a sintered body of ZnO with various oxides added. This type of varistor has non-linear voltage-current characteristics, and as the voltage increases, the resistance rapidly decreases and the current increases significantly, so it is useful for absorbing abnormal voltages and stabilizing voltages. has been made into By the way, the characteristics of a voltage nonlinear resistor are generally evaluated using the voltage-current characteristics expressed by the following approximate equation. I = (V/C) (where I is the current flowing through the varistor, V is the applied voltage, C is a constant, and α is a nonlinear coefficient) Therefore, the general characteristics of a varistor are expressed by two constants, C and α. and is usually expressed as a voltage V ₁ at 1 mA instead of C. The above ZnO varistors (voltage non-linear resistors) have many features such as the ability to adjust the voltage-current characteristics as desired. However, when using these ZnO varistors for pulses with short rise times, the following There was a drawback. In other words, conventional ZnO-based varistors have a drawback in that their ability to absorb overvoltage for pulses with a short rise time is significantly reduced, and they cannot perform the most important function as a nonlinear resistance element. This happens for the following reasons. Generally, when an overvoltage is applied to a varistor, it absorbs the overvoltage by flowing a current corresponding to the voltage. However, when a step voltage is applied to a conventional ZnO-based varistor, the response current (pulse response) shows a characteristic change over time. That is, a charging current due to the capacitance attached to the ZnO-based varistor first flows, and after reaching a peak, it decreases exponentially with respect to time. After that, the original current of the ZnO varistor decreases for several microseconds.
The current value gradually increases with a time constant of several tens of microseconds and converges to the current value expressed by the approximate expression of the voltage-current characteristic. In other words, the conventional ZnO-based varistor has a time region of several microseconds immediately after voltage application, in which the current is significantly limited. and,
In response to an overvoltage pulse with a short rise time, sufficient current does not flow through the varistor within the above time range, so the ability to absorb the overvoltage is significantly reduced. The object of the present invention is to improve the above-mentioned drawbacks and provide an oxide voltage nonlinear resistor that can be used even for pulses with short rise times. The present invention has ZnO as a main component, and as a subcomponent,
_{Al , _ _}
At least one selected from In and Ga, respectively.
Converted to Al ₂ O ₃ , In ₂ O ₃ , Ga ₂ O ₃ , 1×10 ^-4 ~3
A sintered body obtained by adding ² mol% of ×10 and a borosilicate lead glass containing Ag as a main component,
The present invention relates to an oxide voltage nonlinear resistor characterized in that an electrode containing 1 to 20% by weight of ZrO ₂ is formed at a temperature of 650 to 900° C. with respect to an electrode composition containing Bi ₂ O ₃ . The present invention will be explained below with reference to Example (1).
Basic composition in which Bi ₂ O ₃ , Co ₂ O ₃ , Sb ₂ O ₃ , MnO, and NiO are arranged in ZnO at 0.5 mol %, 0.5 mol %, 1 mol %, 0.5 mol %, 5 mol %, and 0.2 mol %, respectively. To,
Furthermore, at least one of Al ₂ O ₃ In ₂ O ₃ and Ga ₂ O ₃ is added in an amount of 1×10 ⁻⁴ to 3×10 ⁻² mol %, sufficiently wet mixed in a ball mill, and dried. A prepared powder was obtained. The prepared powder thus obtained was blended with polyvinyl alcohol as a binder and molded at a pressure of 1 ton/cm ³ to form a molded product with a diameter of 20.0 mm and a thickness of 2 mm, and then fired at a temperature of 1200°C. A sintered body was obtained. Thereafter, both sides of the sintered body are polished in parallel, and the polished surfaces are coated with Ag as the main component and borosilicate lead glass and Bi ₂ O ₃ as secondary components.
An electrode paste material containing 1 to 20% by weight of ZrO ₂ was applied by printing to an electrode composition containing
Baking at a temperature of 650-900℃, a voltage nonlinear resistor was obtained. Note that such electrode paste material is Ag
The main component is lead borosilicate glass as a subcomponent.
It can be easily obtained by adding a predetermined amount of ZrO ₂ to an electrode paste material containing Bi ₂ O ₃ and thoroughly mixing it in a mechanical agate mortar. The pulse response of the voltage nonlinear resistor obtained in this way is expressed as the voltage V _0.1 A when a pulse voltage with different rise times is applied and a current of 0.1 A flows through the element. It is shown in Figure 1. In FIG. 1, curve 1 is according to the present invention,
Al ₂ O ₃ contained in the sintered body is 1×10 ^-3 mol%, lead borosilicate glass, Bi ₂ O ₃ and ZrO ₂ contained in the electrode are 1% by weight, 1% by weight and 5% by weight, respectively. The baking temperature is 800℃. Curve 2 shows, under the conditions of curve 1, that among the electrode components,
Curve 3 shows a reference example when ZrO ₂ is not added, and curve 3 shows a case when Al ₂ O ₃ among the sintered body components is not added under the conditions of curve 1. Curve 4 is the condition of curve 1, and the electrode component
This is a conventional example in which ZrO ₂ and Al ₂ O ₃ among the components of the sintered body are not added. As is clear from FIG. 1, according to the present invention,
It can be seen that the pulse response is significantly improved even for pulses with short rise times. FIG. 2 shows the relationship between the amount of Al ₂ O ₃ added and the pulse response. Here, the pulse response is the voltage when a pulse with a rise time of 5 × 10 ^-8 seconds is applied.
It was expressed as the ratio R of V _0.1A (5×10 ⁻⁸ ) and the voltage V _0.1A (1×10 ⁻⁵ ) when a pulse with a rise time of 1×10 ⁻⁵ seconds was applied. R = V _0.1A (5 × 10 ^-8 ) / V _0.1A (1 × 10 ^-5 ) Here, R represents the voltage rise ratio due to the difference in the rise time of the applied pulse, and the closer to 1, the better the response. show. The curve shown by the solid line in FIG. 2 is the curve shown in this example.
Bi ₂ O and ZrO ₂ are 1% by weight, 1% by weight, and 5% by weight, respectively.
Weight% and electrode baking temperature are at 800°C. As is clear from FIG. 2, when the amount of Al ₂ O ₃ added is 1×10 ⁻⁴ mol % or more, the response is significantly improved. Furthermore, nonlinearity is also shown in FIG. Nonlinearity was expressed as the ratio V _1A /V _1nA of the voltage V _1A to V _1nA when a current of 1A was passed through the element. From the curve shown by the broken line in FIG. 2, it can be seen that nonlinearity is also improved by adding Al ₂ O ₃ . Figure 3 shows the relationship between electrode baking temperature and pulse response. As in the case of FIG. 2, the pulse responsiveness was expressed as the voltage rise ratio R. The curve shown in Figure 3 is obtained by adding 1×10 ^-3 mol% of Al ₂ O ₃ to the basic composition.
The lead borosilicate glass, Bi ₂ O ₃ and ZrO ₂ contained in the electrode are 1% by weight, 1% by weight and 5% by weight, respectively. It can be seen that the pulse response is significantly improved when the electrode baking conditions are 650 to 900°C. FIG. 4 similarly shows the relationship between the amounts of In ₂ O ₃ and Ga ₂ O ₃ added and the pulse response. In Figure 4, curve 5 is In ₂ O ₃
Curve 6 is the case of addition of Ga ₂ O ₃ and is shown by a solid line. In addition, the state of change in voltage nonlinearity V _1A /V _1nA is shown by a broken line. FIG. 5 similarly shows the relationship between the amount of the mixture of Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ added and the pulse response and voltage nonlinearity. Curve 7 shows the mixture of Al ₂ O ₃ and Ga ₂ O ₃ in their respective proportions, and curve 8 shows the mixture of Al 2 O 3 and Ga ₂ O ₃ .
When In ₂ O ₃ are mixed in equimolar proportions,
Curve 9 is obtained when Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ are mixed in equimolar proportions. Fourth
The conditions for forming the electrodes in FIGS. 5 and 5 are exactly the same as in FIG. 2. As is clear from Figures 2, 4, and 5, when Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ are added to the basic composition, or when they are added in combination, , the pulse response is significantly improved, and the nonlinearity is also improved. In the present invention, the reason for limiting the range of addition amounts of Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ is that these additives or a combination of these additives are
At less than 10 ^-4 mol%, the improvement in pulse response is 3×
This is because if the amount exceeds 10 ^-2 mol %, satisfactory nonlinearity cannot be obtained. FIG. 6 similarly shows the relationship between the amount of ZrO ₂ added among the electrode components and the pulse response. Figure 6 shows that among the sintered body components, the amount of Al ₂ O ₃ added is 1 × 10 ^-3 wt%, and among the electrode components, borosilicate lead glass and Bi ₂ O ₃ are 1% by weight and 1% by weight, respectively. This is when the electrode baking temperature is 800℃. As is clear from FIG. 6, by containing 1% by weight or more of ZrO ₂ in the electrode component, the pulse response is significantly improved. In addition
If the ZrO ₂ content exceeds 20%, nonlinearity and solderability of the electrode will deteriorate, making it impossible to obtain a product sufficient for practical use. Next, to explain Example (2), ZnO
0.05 to 2 mol%, 0.05 to 2 mol%, 0.05 to 2 mol% of Bi ₂ O ₃ , Co ₂ O ₃ , and MnO, respectively, and 0.1 to 3 mol of Sb ₂ O ₃ , MgO, and NiO each as necessary. ,
To the basic composition of 0.1 to 15 mol and 0.05 to 2 mol %, at least one of Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ is added in 1 x 10 ^-3 mol %, and fired. The composition after baking of the sintered body obtained by
An electrode material containing lead borosilicate glass, Bi ₂ O ₃ , and ZrO ₂ as subcomponents of 1% by weight, 1% by weight, and 5% by weight, respectively, was applied by printing and baked in air at a temperature of 800°C. Example (1) An experiment was conducted under the same conditions as in the case of , and the characteristic data of the voltage nonlinear resistor as shown in Table 1, including the reference example, was obtained.

【table】

[Table] As is clear from Table 1, in Example (2), the pulse response expressed by the voltage rise ratio R and V _1A /
It can be seen that the nonlinearity represented by V _1n exhibits the same effect as the results of Example (1) shown in FIGS. 1 to 5, as already explained. According to the present invention, the basic composition is ZnO as the main component.
Bi ₂ O ₃ , Co ₂ O ₃ , MnO each 0.05 to 2 mol%,
Even when it changes from 0.05 to 2 mol%, Bi ₂ O ₃ ,
At least one of In ₂ O ₃ and Ga ₂ O ₃ is added and blended, and the resulting sintered body has an electrode composition containing Ag as the main component and borosilicate lead glass and Bi ₂ O ₃ as secondary components. ,
By forming an electrode containing 1 to 20% by weight of ZrO ₂ at a temperature of 650 to 900°C, the effects of the present invention can always be expected. The basic composition includes Sb ₂ O ₃ ,
It is clear from Examples (1) and (2) that even if additives such as MgO and MiO are added as necessary, the effects of the present invention are always exhibited. To supplement and explain the principle of the present invention, the main point of the present invention is to demonstrate voltage-current nonlinearity.
Al ₂ O ₃ , In ₂ O ₃ , Ga ₂ O ₃ , etc. are added to the ZnO sintered body, and an electrode containing ZrO ₂ is added to the obtained sintered body at 650 to
It is baked at a temperature of 900℃. Al ₂ O ₃ ,
When In ₂ O ₃ and Ga ₂ O ₃ are added, they form a solid solution within the ZnO particles.
Forms a large amount of donors. Furthermore, baking the electrode in the above temperature range corresponds to forming the electrode and reheating the sintered body at the same time. Such reheating is nothing but a transition of the crystal structure of the Bi ₂ O ₃ layer sandwiched between ZnO particles from α or β type to γ type. Based on these facts, the inventors conducted extensive experiments and analyzes and found that the pulse response characteristics of the voltage nonlinear resistor are closely related to these facts. In other words, the pulse response depends on the electronic state of ZnO grains and the grain boundary phase.
This is determined by the electronic states of Bi ₂ O ₃ , and only when these electronic states simultaneously become favorable for pulse responsiveness can a significant improvement in pulse responsiveness be achieved. Therefore, in the present invention, the addition of Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ changes the electronic state of ZnO particles and changes the electrode temperature between 650°C and 900°C.
Baking corresponds to making the electronic states of the _three Bi ₂ O phases favorable for pulse responsiveness, and according to the present invention, these favorable states are simultaneously satisfied. Furthermore, in the present invention,
If we refer to the effect of ZrO ₂ included in the electrode,
In general, for electrode compositions mainly composed of Ag, lead borosilicate glass, which has a relatively low softening point, is used to strengthen the bond between the electrode and the sintered body, which further improves the solderability of the electrode. Therefore, Bi ₂ O ₃ is contained as a frit component in an amount of about several percent by weight. When this type of electrode is used, these frit components diffuse into the interior of the sintered body during electrode baking, and have an adverse effect on the electronic state favorable for responsiveness, making it impossible to achieve the object of the present invention. In order to solve these problems, it is conceivable to bake an electrode made only of Ag, which does not contain a frit component, in the above temperature range, for example. Table 2 compares the pulse response and electrode performance obtained by the above method with that of the present invention.
2 is an electrode made only of Ag, 2 is an electrode mainly composed of Ag and contains 1% by weight of lead borosilicate glass and Bi ₂ O ₃ , and 3 is an electrode under the same conditions as Example (1) of the present invention. It is baked at 800℃. The sintered body used in Example (1) was the one in which 1×10 ⁻³ mol % of Al ₂ O ₃ was added.

[Table] As is clear from Table 2, electrodes made of Ag only have insufficient electrode performance, while electrodes containing lead borosilicate glass and Bi ₂ O ₃ do not have sufficient pulse response. do not have. Adding ZrO ₂ to an electrode containing Ag as a main component, lead borosilicate glass, and Bi ₂ O ₃ significantly suppresses the diffusion of frit components into the sintered body in the electrode baking temperature range.
This provides an electrode with excellent adhesive strength and solderability without impairing the excellent pulse response of the sintered body itself. As explained above, according to the present invention, there is provided an oxide voltage nonlinear resistor that has excellent pulse responsiveness that can be used for pulses with short rise times and also has excellent nonlinearity. It is.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the pulse rise time and voltage of the conventional example, the reference example, and the oxide voltage nonlinear resistor according to the present invention. FIG. ₂ is a curve diagram showing the pulse rise time and voltage of the oxide voltage nonlinear resistor according to the present invention. A curve diagram showing the amount of O ₃ added, voltage increase ratio, and nonlinearity. Figure 3 is a curve diagram showing the reheating temperature and voltage increase ratio. Figure 4 is a curve diagram showing the addition of In ₂ O ₃ and Ga ₂ O ₃ . Figure 5 is a curve diagram showing the amount, voltage rise ratio, and nonlinearity of Al ₂ O ₃ ,
A curve diagram showing the amount of a mixture of In ₂ O ₃ and Ga ₂ O ₃ added, voltage increase ratio, and nonlinearity. FIG. 6 is a curve diagram showing the content of ZrO ₂ contained in the electrode, voltage increase ratio, and nonlinearity.

Claims (1)

[Claims] 1 ZnO as the main component and at least as a subcomponent
For raw materials containing 0.05 to 2 mol%, 0.05 to 2 mol%, and 0.05 to 2 mol% of Bi, Co, and Mn in terms of Bi ₂ O ₃ , Co ₂ O ₃ , and MnO, respectively,
At least one selected from Al, In, and Ga is converted into Al ₂ O ₃ , In ₂ O ₃ , and Ga ₂ O ₃ and is 1×10 ^-4
A sintered body obtained by adding ~3 × 10 ^-2 mol% and an electrode composition containing Ag as a main component and borosilicate lead glass and Bi ₂ O ₃ as subcomponents in the sintered body, Electrode containing 1-20% by weight of ZrO ₂ at 650-900℃
An oxide voltage nonlinear resistor characterized by being formed at a temperature of .