DE1952841B2 - VOLTAGE DEPENDENT CERAMIC RESISTANCE - Google Patents

Description

/ 1 =

in which V ₁ and V _{2 are} the voltages given by the currents I _{, and I 2.} The appropriate value for C depends on the type of application for which the _IS resistor is to be used. It is generally advantageous if the value η is as large as possible, because this exponent determines the extent to which the resistances deviate from the ohmic values.

With common varistors, which consist of germanium or silicon p-n area rectifiers, it is difficult to adjust the C-value for a wide range because of the voltage-dependent behavior these varistors not on the ceramic as such,

Stand according to Claim 1, characterized in that it is based on the p-n junction. on the other hand

that it also contains 0.05 to 8.0 mol percent bismuth oxide and 0.05 to 8.0 Μοΐμ percent of an oxide, selected from the group consisting of calcium oxide and cobalt oxide.

6. Voltage-dependent ceramic contradiction according to claim 2, characterized in that that it also contains 0.1 to 3.0 mol percent bismuth oxide and 0.1 to 3.0 mol percent of an oxide, selected from the group consisting of calcium oxide and cobalt oxide.

Summary:

It is essentially one made of zinc oxide and a ceramic resistor consisting of an additive made of lead oxide. Of the Voltage-dependent ceramic resistor made with lilei modified zinc oxide is used in its relation The tension has nonlinear properties Another addition of bismuth oxide. Calcium oxide and cobalt oxide improved.

The invention relates to a voltage-dependent ceramic resistor with non-ohmic resistance and in particular on such as a semiconductor resistor, which contains zinc oxide, with a non-ohmic resistance, which is applied to the ceramic isclbst is due.

Numerous voltage-dependent resistors, such as v .. B. silicon carbide varistors. Selenium rectifier and • germanium or silicon pn-electrolytic rectifier. have been used extensively to stabilize the voltage or current of electrical circuits. The electrical characteristics of such a voltage-dependent resistor are given by the equation

expresses, in which V is the voltage across the rejection of the silicon carbide varistors on voltage-dependent properties, which can be attributed to the contacts between the individual grains of silicon carbide, which are connected to one another by a ceramic binder, and the C value can be changed by changing a dimension in a direction in which the current flows through the varistors can be set. However, the silicon carbide varistors have a relatively low n-value and are

produced in such a way that a low C-value is educated.

U.S. Patent 2,887,632 teaches

Electronic parts suitable zinc oxide semiconductors and a method for their production described. the Zinc oxide semiconductor ceramics according to this patent is reduced to less than 900 "C under a reducible Atmosphere or, if organometallic compounds are added, under an inert atmosphere heated. These known zinc oxide semiconductors have ohmic properties and a low specific Resistance on.

The invention is now based on the object of a voltage-dependent ceramic resistor to create a high »i value and a adjustable C-value is excellent

This object is achieved according to the invention in that the voltage-dependent ceramic resistor consists essentially of zinc oxide and 0.05 to 10.0 mol per cent of lead oxide
The voltage-dependent ceramic resistor

<; <; according to the invention thus consists of a merged Body made of zinc oxide, in the specified proportions and. as indicated further below, optionally further additions of oxides. being the sintering at a temperature of 1000 to 1450 C in Air or, if the sintered body is to have a low electrical resistance, uuter an atmosphere other than air, e.g. B. a nitrogen or argon atmosphere is carried out. The sintered ceramic thus obtained has non-ohmic properties.

The drawing gives a partial cross section of the voltage-dependent ceramic according to the invention Resistance again.

9δ1 841

Before the proposed according to the invention "Pnnungsubhlinglgen ceramic resistors in are described individually, their structure will be explained with reference to the drawing, in which the number 10 denotes a voltage-dependent ceramic resistor as a whole, the contains as an effective element a sintered ceramic body with a pair of electrodes 2 and 3, attached to its opposite surfaces. The sintered body 1 is on a in the manner described below "lnd has some shape, 2, B. a circular, square or rectangular plate shape. Lead wires 5 and 6 are connected to the electrodes 2 and 3 conductively connected by a connecting means 4 such as solder or the like.

In the case of the voltage-dependent ceramic contradiction according to the invention, this is not ohmic Contrary °: .d to be traced back to the keyamic material itself. Therefore, the C value can be adjusted without affecting the value by changing the distance have been modified between the two mentioned opposing surfaces. The shorter distance leads to a lower C-value.

Hin higher value can be obtained when the ceramic sintered body of the invention consists essentially of 97.0 to 99.9 mole percent zinc oxide and 0.1 to 3.0 mole percent lead oxide.

According to the invention, the C value can be reduced without any change in size and without decreasing the value when the total ^; The inert ceramic body has a composition which corresponds essentially to 82.0 to 99.9 mole percent zinc oxide, 0.05 to 10.0 mole percent lead oxide and 0.05 to 8.0 mole percent bismuth oxide.

Line combination of a small C-value and a large «-value can be obtained, if the ceramic sintered body consisting essentially of 94.0 to 99.8 mole percent zinc oxide, 0.1 to 3.0 mole percent Lead oxide and 0.1 to 3.0 mole percent bismuth oxide is.

According to the invention, the resistance to the ambient temperature and the service life can be improved under electrical load if the sintered ceramic body is essentially made of 82.0 to 99.9 mole percent zinc oxide, 0.05 to 10.0 mole per / enl Lead oxide and 0.05 to 8.0 mole percent calcium oxide.

Furthermore, the resistance to the ambient temperature and the service life under clever load is greatly improved when the pesintered ceramic body consists essentially of 94.0 to 99.8 mole percent zinc oxide, 0.1 to 3.0 mole percent lead oxide and 0.1 to 3.0 mole percent lead. Calcium oxide consists.

According to the invention, the value is increased when the sintered ceramic body is substantially off 82.0 to 99.9 mole percent zinc oxide. 0.05 to 10.0 MoI percent Ordered lead oxide and 0.05 to 8.0 mole percent cobalt oxide.

The M value is also increased when the sintered Ceramic body has a composition that is essentially 94.0 to 99.8 mole percent zinc oxide, 0.1 to 3 * 0 mol percent lead oxide and 0.1 to 3.0 mol percent Corresponds to cobalt oxide.

According to the invention, a combination of a high / t value and a low C value can be used can be achieved when the sintered ceramic body has a composition that is substantially 74.0 to 99.85 mole percent zinc oxide, 0.Q5 to 10.0 mole percent Lead oxide, 0.05 to 8.0 mole percent cobalt oxide and 0.05 to 8.0 mole percent bismu oxide.

In addition, the C-value can be reduced and the »■ Value can be increased very much if the sintered ceramic body has a composition that essentially 91.0 to 99.7 mole percent zinc oxide,

ίο 0.1 to 3.0 mole percent lead oxide, 0.1 to 3.0 mole percent Cobalt oxide and 0.1 to 3.0 mole percent bismuth oxide.

According to the invention, a combination of high value, low C value and high loading

Stability can be achieved when the sintered ceramic body has a composition that is in essentially 74.0 to 99.85 mole percent zinc oxide, 0.05 to 10.0 mole percent lead oxide, 0.05 to 8.0 mole percent Bismuth oxide and 0.05 to 8.0 mole percent calcium oxide.

In addition, a combination of an extremely high at a low C and a great resistance can be obtained when the sintered Ceramic body has a composition that is essentially 91.0 to 99.7 mole percent Zinc oxide, 0.1 to 3.0 mole percent lead oxide, 0.1 to 3.0 mole percent bismuth oxide, and 0.1 to 3.0 mole percent Calcium oxide corresponds.

The sintered ceramic body 1 can according to a procedure known per se in the field of ceramics getting produced. The starting materials for the ceramic described above are in mixed in a wet mill to form homogeneous mixtures. The mixtures are dried

and compressed in a shape with a pressure of 100 to 1000 kg / cm ² into desired body shapes. The compressed bodies are sintered in air at a given temperature for 1 to 3 hours and then placed in the furnace

Room temperature (about 15 to about 30 C) cooled.

The suitable sintering temperature is determined from the point of view of the electrical resistivity, the Non-linearity and persistence are determined and, as stated above, ranges from 1000 to 1450 c.

The crushed ceramic bodies are when the electrical resistivity is decreased should be, preferably in a non-oxidizing atmosphere, such as. B. in nitrogen and argon, sintered.

For easier handling in the subsequent pressing process, the mixtures can initially be used at 700 Calcined to 1000 C and then powdered. That Mixture that is to be compressed can be mixed with a suitable binder, such as. B. with water, Polyvinyl alcohol, etc., are mixed.

It is advantageous if the sintered ceramic body on the opposite surfaces with Abrasive powder, such as B. with silicon carbide with a particle size of 300 to 1500 mesh, ground or is polished.

The sintered ceramic bodies are traced with electrodes on their opposite surfaces

generally applicable and appropriate procedures, e.g. after electroplating, vacuum evaporation3-, metallization9-, sputtering * or after the silver painting process.

? 84

The voltage dependence of the ceramic resistor according to the invention becomes practical - not by the type of electrodes used, but by the thickness of the sintered ceramic body pbo

influenced. In particular, the C value changes to 5 (Molpro / entt

speaking of the thickness of the sintered ceramic body,

while the value is almost independent of the thickness O

is. This clearly shows that the chip "\

voltage dependency is due to the ceramic itself and not to the electrodes. 10 ^ ·

Conductor wires can be 0.5

Way using a usual I.

Solder with a low melting point must be attached. It is convenient to use a conductive adhesive, containing silver powder and resin in an organic solvent for connecting the lead wires to use with the electrodes.

The voltage-dependent ceramic resistors according to the invention have a high resistance to temperature and to a long-term load test which is carried out at 70 ^Λ for an operating time of 500 hours. The η value and the C value do not change noticeably after the heating effects and the endurance test. It is advantageous to achieve a high resistance to moisture if the voltage-dependent ceramic resistors obtained in a moisture-proof resin, such as. B. epoxy resin and phenolic resin /. be embedded in a manner known per se.

Currently preferred embodiments of the invention are explained below.

Table I.

C.
ici I mA) (I. PbO
(MoI-
percentage) C.
(at I mA) η 1010 3.2 2 870 5.0 900 4.7 3 920 4.8 840 5.1 5 1030 3.5 800 5.5 8th 1100 3.2 835 5.3 10 1200 3.0

example 1

A mixture of zinc oxide and lead oxide having a composition corresponding to Table 1 is mixed in a wet mill for 3 hours. The mixture is dried and then calcined at 70 ° C. for 1 hour. The calcined mixture is pulverized by means of a motor-driven ceramic body for 30 minutes and then pressed in a mold with a pressure of 500 kg / cm ² into a body shape with a diameter of 17.5 mm and a thickness of 2.5 mm.

The pressed body is sintered in air at 1350 ° C. for 1 hour and then cooled in the furnace to room temperature (to about 15 to about 30 ^° C.). The sintered disk is ground on the opposite surfaces with the aid of silicon carbide with a particle size of 600 mesh. The resulting sintered disk has a size of 14 mm in diameter and 1.5 mm in thickness. The commercially available electrodes made of silver paint are applied to the opposite surfaces of the sintered disk with the aid of a paint. Then the lead wires are connected to the silver electrodes by soldering. The electrical properties of the resistors obtained are shown in Table 1. It can be seen that the sintered body of zinc oxide containing lead oxide in an amount of 0.05 to 10.0 mole percent is suitable for a variable voltage resistor. In particular, the addition of lead oxide in an amount of 0.1 to 3.0 mol percent leads to an even more pronounced nonlinear behavior in terms of stress.

At game 1 2

Starting materials consisting of 99.5 mol percent zinc oxide and 0.5 mol percent lead oxide are used in the in the manner described in Example 1 mixed.

dried, calcined and powdered. The pulverized mixture is pressed in a mold into a shape of 17.5 mm in diameter and 5 mm in thickness with a pressure of 500 kg / cm ^2.
The pressed body is sintered in air at 135O ° C. for 1 hour and then cooled to room temperature in the furnace. The sintered disk is ground on the opposite surfaces to a thickness shown in Table 2 using silicon carbide having a particle size of 600 mesh.

The ground disc is with the electrodes and the lead wires on the opposite surfaces provided according to the ArI and manner given in Example 1. The electrical values of the obtained Resistances are given in table 2

give; the C-value changes approximately proportionally to the thickness of the sintered disk, while the n-value is practically independent of the thickness. It's easy to see that in terms of tension, that isn't linear behavior of the resistors to the sintered

Body is self-attributable.

Table 2

Thickness (mm) C (at I mA) π initially (4.0) 2100 5.5 3.5 1850 5.4 3.0 1600 5.6 2.5 1330 5.5 2.0 1050 5.5 1.5 800 5.5 1.0 530 5.4

Example 3

Made of zinc oxide with a content of lead oxide and bismuth oxide corresponding to one in the table The specified proportion are voltage-dependent resistances according to the one described in Example 1 Procedure established. The properties achieved by the resistors are given in Table 3 It can easily be seen that the combination of lead oxide and bismuth oxide as an additive is too low C values without the η value being converted into a changes accordingly strongly.

7th
Table 3

PbO (Mole percent)

0.05

0.05

0.05

0.5

0.5
10
10
10

0.1

0.1

0.1

0.5

0.5

0.5

Bi ₂ O, (mole percent)

0.05

0.5

0.05

0.05

0.5

0.1

0.5

0, i

0.1

0.5

0.5

C. ft (at I mAI 3.3 700 3.1 205 3.1 690 5.4 530 5.4 540 3.2 800 3.1 240 3.0 810 4.8 450 4.7 445 4.8 460 5.4 530 5.5 535 4.9 600 4.9 180 4.6 460 5.5 160

Example 4

From zinc oxide with a content of lead oxide and calcium oxide in a proportion specified in Table 4, voltage-dependent resistors are produced according to the process route specified in Example 1. The resistances obtained are tested according to the methods used for electronic parts. The endurance test is carried out at an ambient temperature of 70 ° C. and at 0.5 watt over a period of 500 hours. The heating repeating test is performed by five times repeating a sequence in which said resistors at 85 ° C ambient temperature, held for 30 minutes, then quickly cooled to -20 ⁰ C and held for 30 minutes at this temperature. Table 4 shows a difference for the C-value and the n-value? On the resistances before and after the endurance test. It is easy to see that the combination of lead oxide and calcium oxide as an additive affects the electrical durability and the resistance to the environment.

Table 4

PbO CaO Endurance test I ii (/ ο I (Mol- (MoI- -8.8 Samples I) percentage) I C (%) -6.5 0.05 0.05 -9.0 -7.5 0.05 0.5 -6.9 -5.9 0.05 8th -7.4 -6.0 0.5 0.05 -5.8 -8.1 0.5 8th -6.2 -7.4 10 0.05 -8.2 -9.0 10 0.5 -7.1 -4.8 10 8th -9.4 0.1 0.1 -4.8

Periodic heating test

IC (Vo) i WM °.

7.9 -8.3 6.0 -6.7. 7.1 -7.1 6.8 -6.9 6.7 -6.7 7.2 -7.5 5.9 -6.3 8.0 -8.1 4.0 -4.2

PbO Ca O (MoI- (MoI- pro / ent) percentage 0.1 0.5 0.1 3 0.5 0.1 0.5 3 3 0.1 3 0.5 3 3 0.5 0.5

Load duration read IC ("Al Ih (%)

-3.0
-4.7
-5.3
-4.9
-3.8
-2.6
-3.7
1.3

-3.4
-5.0
-5.0
-4.8
-3.7
-2.5
-3.8
-2.0

test with mung more periodic -2.8 Heat -3.5 2.9 -3.5 3.2 -3.2 3.0 -3.1 3.4 -1.9 3.4 -2.2 2.0 -1.5 2.9 1.5

Example 5

Zinc oxide, which contains the additives given in Table 5, becomes voltage-dependent resistors according to the procedures described in Example 1 manufactured. The n values of the resistances obtained are given in Table 5. It it is easy to see that the combination of lead oxide and cobalt oxide as an additive in pronounced! Way leads to an extremely strong non-linear behavior with regard to the voltage.

Table 5

PbO CoO (Mole percent) (Mole percent] 0.05 0.05 0.05 0.5 0.05 8th 0.5 0.05 0.5 8th 10 0.05 10 0.5 10 8th 0.1 0.1 0.1 0.5 0.1 3 0.5 0.1 0.5 3 3 0.1 3 0.5 3 3 0.5 0.5

(at 1 mA)

1030

990

1000

800

790

1150

1140

1160

910

900

890

800

.780

900

910

900

790

4.8
9.5
4.9
8.0
7.5
4.5
9.0
4.6
9.5

14th
9.4
8.0
7.8
7.0

14th
9.5

16

Example 6

Made of zinc oxide, which is the one given in Table 6

Contains additives are according to the example

Procedure described depends on the voltage

Resistors made. The electrical properties of the resistances obtained are shown in the table specified. It is easy to see that the combination of lead oxide, cobalt oxide and bismuth oxide as additions in a pronounced way to an excellent η value and at the same time to a g «

leads to a lower C-value.

109587/3

Table 6

PbO CoO Bi ₂ O, C. ff (Mole percent) (Mole percent) (Mole percent) (at I mAi 0.05 0.05 0.05 700 4.7 0.05 0.05 8th 680 4.5 0.05 8th 0.05 720 4.9 0.05 8th 8th 750 5.0 10 0.05 0.05 700 4.4 10 0.05 8th 720 4.6 10 8th 0.05 790 4.6 10 8th 8th 800 4.5 0.1 0.1 0.1 450 9.5 0.1 0.1 3 440 9.3 0.1 3 0.1 440 9.4 0.1 3 3 420 8.8 3 0.1 0.1 450 7.0 3 0.1 460 7.0 3 3 0.1 455 9.5

PbO
(Mole percent) CoO
(Mole percent) Bi ₂ O ₃
(Mole percent) C.
(at I mA) 11th 5 3
0.5 3
0.5 3
0.5 450
160 9.5
16

Example 7

ίο Made of zinc oxide, which is specified in table 7 Contains additives, are voltage-dependent according to the procedure described in Example 1 Resistors made. The resistances obtained are under the same conditions as in that

f5 example 4 tested. Table 7 gives the initial C value and the difference in the C value and the η value resulting from the values before and after Endurance test result, again. It can be easily seen that when using the combination from lead oxide, bismuth oxide and calcium oxide as an addition to the initial C value of the resistor is reduced and that at the same time the durability in the electrical and environmental endurance tests is excellent.

Table 7

PbO Bi ₂ O ₃ CaO (Mole percent) (Mole percent) (Mole percent) 0.05 0.05 0.05 0.05 0.05 8th 0.05 8th 0.05 0.05 8th 8th 10 0.05 0.05 10 0.05 8th 10 8th 0.05 10 8th 8th 0.1 0.1 0.1 0.1 0.1 3 0.1 3 0.1 0.1 3 3 3 0.1 0.1 3 0.1 3 3 3 0.1 3 3 3 0.5 0.5 0.5

(at 1 mA)

650 190 670 500 515 750 225 800 450 420 400 490 510 560 165 420 135

load
(%) duration test
ln ("/ ol firmly with periodis
ICfVoI rather warming
ln (%) 8.4 -9.2 -7.9 -8.5 6.0 -8.6 -7.2 -6.4 7.2 -7.2 -78 -7.3 6.9 -6.9 -6.9 -6.8 5.9 -8.3 -7.3 -5.9 7.3 -7.7 -6.9 -7.8 6.8 -8.0 -7.4 -7.7 7.9 -9.3 -8.5 -8.3 4.0 -5.0 -5.0 -4.2 4.2 -4.7 -4.8 -4.4 3.9 -4.8 -5.0 -4.3 4.9 -3.8 -4.1 -3.9 3.2 -4.2 -3.9 -4.1 3.4 -5.0 -5.0 -4.5 4.1 -4.8 -4.7 -3.0 5.0 -4.9 -4.5 -3.4 0.8 • -1.2 -1.3 -0.9

1 sheet of drawings

0 AO

Claims (5)

are 1 95T841 claims: 1. Voltage-dependent ceramic resistor, characterized in that it consists essentially of zinc oxide and 0.05 to 10.0 mole percent lead oxide. 2. Voltage-dependent ceramic resistor according to claim 1, characterized in that that it consists essentially of zinc oxide and 0.1 to 3.0 mole percent lead oxide. 3. Voltage-dependent ceramic resistor according to claim 1, characterized in that that it also contains 0.05 to 8.0 mole percent of an oxide selected from that of bismuth oxide, calcium oxide and cobalt oxide existing group. 4. Voltage-dependent ceramic resistor according to claim 2, characterized in that that it also contains 0.1 to 3.0 mole percent of an oxide. that made up of bismuth oxide, calcium oxide and cobalt oxide existing group. 5. Voltage-dependent ceramic resistance, / the current flowing through the resistor, C is a constant that corresponds to the voltage at a given current, and the exponent η is a numerical value greater than 1. The value Wr η is calculated according to the following equation: