JPH05251216A - Voltage dependent non-linear resistor ceramic element - Google Patents

Abstract

PURPOSE:To stabilize the electric characteristics even if a part of solder runs into the gap between a pin and an element within the title voltage dependent non-linear resistor ceramic element having the capacitor characteristics and varistor characteristics for protecting the semiconductor and circuits of equipment from the abnormal high voltage, noise, static electricity, etc., generated from an electric equipment. CONSTITUTION:Within the title voltage dependent non-linear resistor ceramic element, a semiconductor ceramics mainly comprising SrTiO3 having the voltage dependent resistance characteristics takes the shape having a cylindrical through hole in the central part of a cylinder wherein a doughnut type electrode with outer and inner periphery respectively smaller than the outer diameter of the cylinder and equal to the diameter of the through hole while another electrode is integrally arranged on the inner periphery of the through hole on both ends of the cylinder on the other hand, the other electrodes are arranged in the central part of outer peripheral sides of the cylinder at equidistance from both ends. Through these procedures, the distance between electrodes is not to be changed even if a part of solder 7 runs into the gap between a pin 6 and an element 5 thereby enabling the electric characteristics can be stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage-dependent non-linear resistance having capacitor characteristics and varistor characteristics for protecting semiconductors and circuits of equipment from abnormal high voltage, noise, static electricity, etc. generated in electric equipment and electronic equipment. Body porcelain element.

[0002]

2. Description of the Related Art Conventionally, SiC having a voltage-dependent non-linear resistance characteristic for absorbing abnormal high voltage, eliminating noise, eliminating sparks, and preventing static electricity in various electric and electronic devices.
Varistors and ZnO-based varistor are used.

The voltage-current characteristic of such a varistor can be approximately expressed by the following equation.

[0004]

[Equation 1]

Here, I is a current, V is a voltage, C is a constant unique to a varistor, and α is a voltage-current nonlinear index.

The α of SiC varistor is 2 to 7, and the α of some ZnO varistor reaches 50. Although such a varistor has excellent performance in absorbing a relatively high voltage, it has almost no effect in absorbing a relatively low voltage below the varistor voltage due to its low dielectric constant and small intrinsic capacitance. Is not shown, and the dielectric loss tan δ is as large as 5 to 10%.

On the other hand, in removing these low-voltage noises, the apparent dielectric constant is about 5 × 10 ⁴ , and tan δ is 1.
% Semiconductor capacitors are used. But,
When a voltage or current exceeding a certain limit is applied to such a semiconductor capacitor due to a surge or the like, the electrostatic capacity is reduced or destroyed, and the semiconductor capacitor does not function as a capacitor.

Therefore, recently, a material containing SrTiO ₃ as a main component and having both varistor characteristics and capacitor characteristics has been developed, and protection of semiconductor elements and circuits such as ICs and LSIs in electronic equipment such as computers and circuits and electronic It is used to remove noise that enters from cables and connectors that connect devices to each other.

A conventional voltage-dependent non-resistive porcelain element having the characteristics of both a varistor and a capacitor containing SrTiO ₃ as a main component will be described below.

As shown in FIG. 3, the voltage-dependent non-resistive porcelain element 10 used for removing noise penetrating from a connector is a semiconductor ceramic containing SrTiO ₃ as a main component and having voltage-dependent nonlinear resistance characteristics. An electrode 12 and an electrode 13 are arranged on the upper and lower surfaces of a cylindrical element 11 made of.

As shown in FIG. 4, when the voltage-dependent non-resistive ceramic element 10 is incorporated in the connector, the conductive adhesive 1
The pins 15 and the electrode 12 of the element 11 and the common terminal 14 and the electrode 13 of the element 11 are bonded with 6 and 17, respectively.
At this time, the conductive adhesive 1 is placed in the gap between the pin 15 and the element 11.
Part of 6 may flow in.

[0012]

As described above, in the conventional structure, the conductive adhesive 16 is provided in the gap between the pin 15 and the element 11.
There is a problem in that a part of the liquid crystal flows in, the apparent distance between the electrodes becomes small, the varistor voltage becomes low, the varistor voltage becomes polar, and the insulation resistance becomes low.

The present invention solves the above-mentioned conventional problems. Even if part of the solder flows into the gap between the pin and the element, the varistor voltage does not change, the varistor voltage does not have polarity, and the insulation resistance changes. It is an object of the present invention to provide a voltage-dependent nonlinear resistor porcelain element which is easy to form electrodes, has good solderability, and has good solder heat resistance.

[0014]

In order to achieve this object, the voltage-dependent nonlinear resistor porcelain element of the present invention comprises a cylindrical semiconductor ceramic having a cylindrical through hole at its center,
The outer periphery arranged on both end faces of the cylinder is smaller than the outer diameter of the cylinder, and the inner periphery is integrated with a donut-shaped electrode having the same diameter as the through hole and the electrode arranged on the inner peripheral face of the through hole, A structure in which different electrodes are arranged at equal distances from both end faces in the center of the outer peripheral side surface of the cylinder, and these electrodes are placed underneath the ohmic electrode and the upper layer of the non-ohmic electrode is overlaid. It is what

[0015]

In this structure, since one end face of the cylinder and the inner peripheral face of the through hole are integrated as one electrode, even if the conductive adhesive flows into the gap between the pin and the element when incorporated in the connector or the like. Since the distance between the electrodes does not change, the common terminals can be easily connected and the adhesive force can be increased.

[0016]

EXAMPLE An example of the present invention will be described below.

SrCO ₃ , CaCO ₃ , BaCO ₃ , Mg
CO ₃ and TiO ₂ are weighed at various composition ratios as shown in (Table 1) and mixed for 22 hours by a ball mill or the like.

[0018]

[Table 1]

Next, after drying, it is baked at 1120 ° C. for 4 hours, pulverized again for 22 hours by a ball mill or the like, and then dried to obtain the first component. Then, the first component, the second component, the third
The components were weighed so as to have the composition ratio shown in (Table 1), mixed for 22 hours with a ball mill or the like, dried, and granulated by adding 10% by weight of an organic binder such as polyvinyl alcohol, and 1 ( outer diameter of 4 mm at a pressing pressure of t / cm ² )
Formed into a cylindrical shape with φ, inner diameter 1.4 mmφ, and height 2.5 mm,
The binder is removed by firing in air at 1110 ° C. for 11 hours. Then, it is fired at 1420 ° C. for 5 hours in a reducing atmosphere such as a gas of N ₂ : H ₂ = 9: 1. After that, the element is formed by baking at 1050 ° C. for 5 hours in an oxidizing atmosphere such as air.

As shown in FIG. 1, on both end faces of the element 5 obtained as described above, ohmic A
Using a conductive paste such as g, a donut-shaped electrode whose outer circumference is smaller than the outer diameter of the cylinder and whose inner circumference is the same diameter as the through hole is provided by, for example, screen printing, and the inner surface of the through hole is ohmic. The conductive electrode is provided by, for example, a roller transfer method, and the base electrode 1 in which the donut-shaped electrode and the electrode on the inner peripheral surface of the through hole are integrated is formed. Also,
The underlying electrode 3 is formed by arranging ohmic electrodes on the outer peripheral side surface of the central portion of the cylinder at equal intervals from both end surfaces by a method such as roller transfer. Next, using the non-ohmic paste as the upper material, the upper electrode 2 and 4 are formed by the same method as that for forming the ohmic electrode on the ohmic electrode, and fired at 585 ° C. for 7 minutes. Then, the voltage-dependent resistor porcelain element 18 in which the base electrodes 1 and 3 and the top electrodes 2 and 4 are arranged on the element 5 is formed.

Next, as shown in FIG. 2, the pins 6 and the common terminal 9 are attached to the voltage-dependent resistor porcelain element 18 with the solders 7 and 8, and a resin such as butadiene rubber (not shown).
Fill and cure. The electrical characteristics of the voltage-dependent resistor porcelain element obtained as described above and after assembly of the connector are shown in (Table 2) and (Table 3), respectively.

[0022]

[Table 2]

[0023]

[Table 3]

V _{1mA in} (Table 2) and (Table 3) is 1 m
A voltage across the element when current flows in the A, the polarity of V _1mA is a value obtained by dividing the difference between the positive direction of V _1mA and the negative direction of the V _1mA in the positive direction of V _1mA, insulation The resistance is an insulation resistance value between the pin 6 and the common terminal 9 when the applied voltage is 12 VDC.

As is clear from (Table 2) and (Table 3), the voltage-dependent resistor porcelain element according to the present embodiment is V
An excellent effect is obtained compared to the conventional example in terms of _{1 mA} polarity and insulation resistance.

In addition, a part of Sr of the first component is Ca, Ba,
Although only a part of the ratio of substitution with Mg is shown in the examples, any ratio may be used as long as it is within the range of having both varistor characteristics and capacitor characteristics as the element characteristics. Furthermore, the second component and the third component are shown only for some combinations in the embodiments, but any component may be used as long as it has varistor characteristics and capacitor characteristics at the same time as element characteristics.

Further, as the ohmic electrode, there are Zn, Cu, Ni, etc. other than Ag, but any other electrode may be used as long as an ohmic connection can be made with the element. Also, the upper electrodes 2, 4
The type may be any non-ohmic electrode that can be soldered and has excellent solder heat resistance.

Further, it is possible to improve the noise elimination effect by connecting the voltage-dependent nonlinear resistor porcelain element with an inductance composed of, for example, a ferrite, a coil, a toroidal coil or the like.

As described above, according to this embodiment, the donut-shaped electrodes having the outer circumference smaller than the outer diameter of the cylinder and the inner circumference having the same diameter as the through hole are provided on both end surfaces of the cylinder, and the inner diameter of the through hole is increased. The electrode is provided on the peripheral surface, the donut-shaped electrode and the electrode on the inner peripheral surface of the through hole are integrated, and the electrode is provided in the central portion of the outer peripheral side surface of the cylinder at an equal distance from both end surfaces. Since one end surface and the inner peripheral surface of the through hole are integrated as one electrode, even if part of the solder flows into the gap between the pin 6 and the element 5, it is on the integrated upper electrode 2. , The apparent distance between the electrodes does not change. Therefore, the electrical characteristics are stable, the varistor voltage does not change, the varistor voltage does not have polarity, the insulation resistance does not change, and even if the voltage-dependent resistor porcelain element 18 is assembled into a connector, the characteristics change before and after assembly. Is extremely small and stable. Further, since the surface insulation distance between the electrodes can be widened, the reliability such as the electric charge life characteristic can be improved.

Further, the common terminal 9 is soldered to the upper electrode 4
When connecting with, it is possible to solder from both sides of the common terminal 9, so that the adhesive force between the common terminal 9 and the upper electrode 4 can be strengthened and the reliability can be improved. Although the length of the element is increased by making the element cylindrical, the size of the element can be reduced in the radial direction, so that the pin interval of the connector can be reduced and the size of the connector can be reduced. It is valid. Further, the height protruding from the common terminal 9 can be reduced by connecting the common terminal 9 to the electrode portion. Further, in order to sufficiently bring out the characteristics of the element, the underlying electrodes 1 and 3 are ohmic electrodes, and the upper electrodes 2 and 4 are non-ohmic electrodes. The characteristics of the element 5 can be sufficiently brought out without forming a barrier, soldering can be easily performed, and the solder heat resistance of the electrode can be improved. Furthermore, since the voltage-dependent nonlinear resistor porcelain element having such a structure has a symmetrical front-back and left-right structure, there is no directionality and it is not necessary to judge the front-back direction and left-right direction of the element at the time of assembly, and the number of assembly steps can be reduced. ..

[0031]

As is apparent from the above description of the embodiments, the present invention provides a cylindrical semiconductor ceramic having a cylindrical through hole at its center, and the outer circumferences arranged on both end faces of the cylinder are cylindrical. The donut-shaped electrode whose inner diameter is smaller than the outer diameter of the through hole and whose inner diameter is the same as the diameter of the through hole is integrated with the electrode arranged on the inner peripheral surface of the through hole, and the end surface of the cylindrical outer peripheral surface is more equal than both end surfaces. By arranging other electrodes with a space between them and by arranging these electrodes on top of the ohmic electrodes and overlaying the non-ohmic electrodes on top of each other, a part of the solder is placed between the pins and the element. Varistor voltage does not change even when flowing in, the varistor voltage does not have polarity and the insulation resistance does not change, electrodes are easily formed, solderability is good, and soldering heat resistance is excellent. It is possible to realize a resistor ceramic element.

[Brief description of drawings]

FIG. 1 is a sectional view of a voltage-dependent nonlinear resistor ceramic element according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the same voltage-dependent nonlinear resistor porcelain element connected to a connector.

FIG. 3 is a cross-sectional view of a conventional voltage-dependent nonlinear resistor ceramic element.

FIG. 4 is a schematic cross-sectional view of the same voltage-dependent nonlinear resistor porcelain element connected to a connector.

[Explanation of symbols]

 1 Base electrode 2 Top electrode 3 Base electrode 4 Top electrode 5 element

Claims (2)

[Claims] 1. A semiconductor ceramic having a cylindrical shape having a cylindrical through hole in the center thereof and having voltage-dependent nonlinear resistance characteristics containing SrTiO ₃ as a main component, and an outer periphery provided on both end faces of the cylinder. Is an electrode that is smaller than the outer diameter of the cylinder and has an inner periphery that is the same as the through-hole and has a donut-shaped electrode and an electrode that is disposed on the inner peripheral surface of the through-hole. Voltage dependence with separate electrodes in the center, spaced apart from both end faces, and non-ohmic electrodes on top of ohmic electrodes Non-linear resistor porcelain element. 2. A semiconductor ceramic having voltage-dependent nonlinear resistance characteristics, wherein a part of Sr of the main component SrTiO ₃ is replaced with at least one element of Ca, Ba and Mg. The voltage-dependent nonlinear resistor porcelain element described.