JPS62282411A - Voltage-dependent nonlinear resistor - 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 3. Detailed Description of the Invention Industrial Application Field The present invention provides a capacitor with a laminated structure for protecting semiconductors and circuits from abnormal high voltage, noise, and static electricity generated in electrical equipment and electronic equipment. The present invention relates to voltage-dependent nonlinear resistors with varistor and varistor characteristics.

Conventional technology SiC varistors and ZnO having voltage-dependent nonlinear resistance characteristics have been used to absorb abnormally high voltages, remove noise, eliminate sparks, and counter static electricity in various electrical and electronic devices.
Thread ballista etc. were used. The voltage-current characteristics of such a varistor can be approximately expressed as in the following equation.

1=('l10)a Here, Δ is the current, V is the voltage, and C is a constant specific to the varistor, which is α multiplied by the voltage nonlinear index.

The α of SiC varistors is about 2 to 7, and the α of some ZnO yarn varistors is as high as 5o. Although such varistors have excellent performance in absorbing relatively high voltages, their low dielectric constant and small inherent capacitance make them difficult to absorb relatively low voltages below the varistor voltage. shows almost no effect, and the dielectric loss -δ is as large as 5 to 10%.

On the other hand, semiconductor capacitors with an apparent dielectric constant of about 5×10′ and −δ of about 1% are used to remove these low voltage noises. However, if a voltage or current exceeding a certain limit is applied to such a semiconductor capacitor due to a surge or the like, it may break down and no longer function as a capacitor.

Therefore, recently, a device has been developed that has 5rTiO as its main component and has both varistor and capacitor characteristics, but the varistor voltage is low, α is large,
It has not yet been possible to find a material that simultaneously satisfies the characteristics of high dielectric constant and high surge resistance.

Furthermore, as a conventional multilayer ceramic varistor, there is one disclosed in Japanese Patent Application Laid-Open No. 51-18849, which has a pair of varistor elements on the front and back sides of a varistor element 1 which has been sintered in advance, as shown in Fig. 4. Electrodes 2 are formed, and electrodes 3 and 4 are stacked so as to connect them in parallel, so that the electrodes 2 of the varistor are exposed to the outside even in areas other than the extraction portion. Furthermore, the surface is coated with an organic substance such as an adhesive or an exterior resin to protect this part and to adhere the varistor element 1. Therefore, due to the limitations of sintering temperature and thickness of the varistor element, v1! It is not suitable for reducing the value of n.

In addition, the one disclosed in Japanese Patent Publication No. 58-23921 is a multilayer varistor whose main component is ZnO thread and whose desired characteristics are a rise voltage of 4 V or more that can be adjusted arbitrarily.
It is effective as a small varistor due to its voltage nonlinearity, leakage current, power load characteristics, and surge resistance characteristics, but its low dielectric constant makes it almost ineffective in protecting semiconductors and circuits from noise and static electricity. Not shown.

Problems to be Solved by the Invention In order to protect semiconductors and circuits from noise, static electricity, etc., all characteristics such as low varistor voltage, large α, large dielectric constant, small −δ, and high surge resistance are all achieved at the same time. The aim is to make it possible to achieve high density packaging while being small and lightweight.

Means for Solving the Problems In the present invention, in order to solve the above problems, 5rxT
iO, (0,96; X < 1.0), (CayS
r+ ,)2Tie3(0,001≦y≦0.5,0.
95≦Z<1.00).

(Ba&sr, -&) bTio, (o, oo1≦a≦o
, 5゜0.95 ≦b < 1.00) , (Mg
cS r + −c ) 6 TiOs(0,001
≦O≦0.6, 0.95≦d<1.00), and a substance that can make the grain boundaries of this element high in resistance. has a plurality of laminated structures, electrodes are provided on the surface of the element body, and the parts other than the parts taken out to the outside are surrounded by the element body, and the internal electrodes and the characteristics of the capacitor and varistor are formed by sintering. It is characterized by a structure obtained by laminating elements having the following properties before sintering, integrating them, and then sintering them.

Effect of the present invention is to add 5rxTiO, (0, OO1≦) to the raw material powder.
x ≦0.5 ), (CaySr+-y)z'r
io, (QOOl ≦y≦0.5゜Q, 96≦z ＜
1.00), (BaaSr, -a,)bTiO
3 (0,001≦& ≦0.6, 0.96≦b<
1.00).

(MgcSr, -.)dTie, (QOO1≦C≦0
．． 5. The main component is at least one of the following: 0.95≦d<1.00), an organic binder, a dispersant, and a plasticizer are added to create a raw sheet film, and the grain boundaries of the element are made to have high resistance. A material that can be used to create the sheet is coated on both sides of the raw sheet, internal electrodes are printed on it, stacked and pressed together, then cut into a predetermined size and sintered.

Therefore, during sintering, substances capable of increasing the resistance of the grain boundaries of the element body diffuse into the grain boundaries, selectively increasing the resistance of the grain boundaries, and forming energy barriers at the grain boundaries. Ballista characteristics are developed. Further, since the inside of the crystal grain has low resistance and the nine grain boundaries have high resistance, capacitor characteristics are exhibited.

Therefore, all of the internal electrodes, except for the part taken out to the outside, are enclosed in a varistor body with capacitor characteristics, and are surrounded only by the same sintered body with the electrodes integrated, so there are few voids. , there is little deterioration of electrode characteristics due to moisture intrusion or exterior resin, and it has excellent moisture resistance and high temperature load characteristics.

Example The present invention will be specifically explained below with reference to Examples.

First, the main raw materials were blended to have the composition shown in Table 1 below, mixed in a ball mill for 24 hours, dried, calcined at 850'C for 2 hours, crushed again, dried, and then , organic binder, dispersant.

Add a plasticizer and make into a slurry. A raw sheet having a predetermined thickness is made from this by a sheet forming method (for example, a doctor blade method).

On the other hand, substances that can make grain boundaries high in resistance (for example, Nl&20.NaF, L+i20.LiF
, N20゜KF, Ag2O,Cub, Cu2O,
An organic binder (for example, ethyl cellulose, etc.) is added to Tl2O, etc. to form a paste, which is applied to both sides of the green sheet and dried.

This raw sheet is cut into a predetermined size, and the internal electrode material (for example, gold) is formed by screen printing or the like.

Metals such as platinum, palladium, silver, molybdenum, and alloys thereof) are coated, a predetermined number of sheets are stacked, and raw sheets without electrodes are stacked on top and bottom and pressed.

Thereafter, it was cut into a predetermined size and fired at 1350° C. to 160° C. for 5 hours in a permeable atmosphere of N2:H2=9=1, and then fired at 900° C. to 1180° C. for 2 hours in air. Next, silver electrodes are applied to both end faces with exposed internal electrodes, and baked at 580'C.

As shown in FIGS. 1 to 3, the device obtained in this manner is enclosed in a varistor body having capacitor characteristics except for the portion where the internal battery 6 is taken out to the outside.
It has a structure in which the electrodes are surrounded only by the same laminated sintered body 6, and there are few voids and moisture does not easily enter, so there is little deterioration of the characteristics of the internal electrodes 6 due to the exterior resin. Further, in the figure, 7 and 8 are end face electrodes, and 9 is a layer of a substance that increases the resistance of grain boundaries.

Next, the characteristics of the device obtained as described above are shown in Table 2 below.

(Margin below) Note that the dielectric constant is a value calculated from the capacitance at IKIlz, and Surge! The withstand capacity is v4. after applying a pulse current of 8 x 20 μsec. The evaluation is based on the mark ttn current peak value when the change in n□ (voltage when +mm current is applied) is within ±10%.

In this embodiment, only the doctor blade method is shown as the sheet forming method, but any other film forming method may be used.

Moreover, the additives in the composition and the amounts added thereof may be of any type as long as they exhibit the characteristics of both a capacitor and a varistor. Furthermore, in this example, the raw materials were fired in a reducing atmosphere after being laminated, but the raw materials were fired in a reducing acid atmosphere in advance, and after pulverization, sheet forming, electrode printing, lamination, and cutting, they were fired in the air. It was confirmed that the same effect can be obtained even if the end face electrode is formed using the same method. Further, in this example, only palladium, silver-palladium, platinum-rhodium, platinum-iridium, platinum-molybdenum, and platinum-tungsten were shown as internal electrodes; Iridium, molybdenum, tungsten.

Any material may be used as long as the main component is one of nickel, iron, chromium, and copper, or an alloy of these metals.

In addition, the range of the main raw material components of the element body was defined by x, z
When , b, and d are 1 or more, grain growth and semiconductor formation are promoted, and the surge resistance deteriorates because the varistor voltage is high and the intragranular resistance is high. Moreover, if it is less than 0.95, excess Ti will precipitate as a single crystal, resulting in an average -' structure, which will increase the varistor voltage and deteriorate the surge 1ilftt. Furthermore, y.

This is because if a and c are less than 0.001, no effect will be shown, and if they exceed O and S, grain growth will be suppressed, the varistor voltage will be high, the dielectric constant will be small, and the surge resistance will deteriorate.

In this example, only one type of substance capable of increasing the resistance of the main raw material component of the element body and the crystal grain boundaries of the element body is shown, but as the main raw material component of the element body, 5r
xTiOs (0,95≦x<1.00).

(Ca, Sr1.)2Tie, (o, oo1≦y
≦o, s, 0.95 ≦Z<1.00), (Ba,
Sr,-,)bTie, (0,001≦a≦0.6,
0.95≦b≦1. OO) + (' gcSr, -
c' (ITie, (0,001≦C≦0.5,
0.95 ≦ d < 1.00 (7) Among them, it is okay to add more than one at the same time, and substances that can make the crystal grain boundaries of the element high in resistance include Na O, Na
F, Li2O, LiF, K2O.

KF, Mg20. Multiple types of Cub, Cu2O, and Tl2O may be added at the same time.

When the device thus obtained was subjected to a mixed load test under conditions of 85°C, 190% RH, and a charge rate of 96, it was found that:
The rate of change in varistor voltage after 100 hours was +1.6 crabs, which was less than 2 compared to the conventional value, and the moisture resistance properties were significantly improved. It was also confirmed that the characteristics were improved in a high temperature load test at 125°C.

Effects of the Invention As described above, according to the present invention, characteristics such as a low varistor voltage, a relatively large α, a large dielectric constant, a small −δ, and a large surge resistance can be simultaneously satisfied.

Furthermore, compared to conventional laminated ceramic varistors, there are fewer voids, which prevents moisture from entering, improving moisture resistance, and because the internal electrodes do not come into direct contact with the exterior resin, high-temperature load characteristics are improved. Furthermore, the dielectric constant is 6 to 20 times greater than that of a ZnO yarn laminated varistor, making it extremely effective against steep-rising pulses such as noise and static electricity.

Therefore, according to the present invention, it is possible to obtain an element that is small, lightweight, can be mounted at high density, and can protect semiconductors and circuits from noise and static electricity, and its practical effects are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a voltage-dependent nonlinear resistor according to the present invention, FIG. 2 is a sectional view taken along the cutting line in FIG. 1 and viewed in the direction of the arrow, and FIG. Cutting line B-B' in Figure 1
FIG. 4 is a cross-sectional view taken along the arrow and viewed in the direction of the arrow, and FIG. 4 is a perspective view of a conventional voltage-dependent nonlinear resistor. 6... Sintered body, 6... Internal electrode, 7,
8... Edge electrode, 9... Layer of substance that makes the grain boundary high resistance. Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) Sr_xTiO_3 (0.95≦x<1.00)
, (Ca_ySr_1_-_y)_zTiO_3(0.
001≦y≦0.5, 0.95≦z<1.00), (B
a_aSr_1_-_a)_bTiO_3(0.001
≦a≦0.5, 0.96≦b<1.00), (Mg_c
Sr_1_-_c)_dTiO_3(0.001≦c≦
0.5, 0.95≦d<1.00) at least 1
A plurality of laminate structures are formed of an element whose main component is a type or more, and a substance capable of increasing the resistance of the crystal grain boundaries of this element, and the element except for the part taken out to the outside of the internal electrode is A voltage-dependent nonlinear resistor with capacitor characteristics surrounded by (2) Substances that can make the grain boundaries of the element high in resistance are Na_2O, Li_2O, LiF, K_2O, and KF.
, Ag_2O, CuO, and Tl_2O.
A voltage-dependent nonlinear resistor according to claim 1, comprising at least one type of voltage-dependent nonlinear resistor. (3) Internal electrodes include gold, silver, palladium, platinum, rhodium, iridium, molybdenum, tungsten, nickel,
Claim 1 whose main component is one of iron, chromium, and copper or an alloy of these metals.
Voltage-dependent non-linear resistor as described in section.