CN1629986A - Copper electrode strontium titanate ring varistor and preparation method thereof - Google Patents

Abstract

The invention discloses a ring piezoresistor and a preparation method thereof. The ring-shaped piezoresistor of the present invention comprises a ring-shaped resistor ceramic substrate and three or more than three electrodes, the substrate is made of strontium titanate, the electrodes are copper electrodes, and are located on the upper surface of the substrate , the lower end surface or the outer surface. The preparation method of the present invention comprises the following steps: manufacture of porcelain body, printing and drying of copper paste, reduction of copper electrode. The method of the invention only needs to be printed once, and the obtained product overcomes the phenomenon of "silver flinging" of the silver electrode annular piezoresistor, and has better welding resistance.

Description

Copper electrode strontium titanate ring varistor and preparation method thereof

technical field

The invention relates to a method for preparing a strontium titanate ring varistor and the product obtained, more specifically, the invention relates to a method for preparing a strontium titanate ring varistor with copper as an electrode and the product obtained.

technical background

Strontium titanate ring varistor is an electronic component mainly used in micro DC motors to absorb sparks and eliminate noise.

The existing strontium titanate ring varistor mainly uses silver as the electrode. The manufacturing process of this kind of varistor is: first use silk screen to print the first layer of silver paste, and bake it at a temperature of 100 ℃ ~ 200 ℃ Dry; then screen-print the second layer of silver paste and dry it at a temperature of 100°C to 200°C; finally reduce the first layer of silver paste and the second layer of silver paste at a temperature of 550°C to 650°C . The reason why silver paste needs to be printed twice is that silver paste is a kind of paste without ohmic characteristics. After the semiconductor printed with silver paste bears a certain high pulse voltage impact, it will show a large increase in resistance value. decline phenomenon. Therefore, before printing silver paste, it is necessary to print a layer of paste with ohmic characteristics (such as Ag-Zn paste); and this ohmic paste itself has almost no solderability, so it is necessary to print another layer of silver paste . It can be seen that when silver is used as an electrode, there are disadvantages of cumbersome preparation process, high cost and poor solderability.

Chinese patent application CN 02114902.x and Chinese patent CN 02225950.3 disclose a multi-electrode ring varistor, which includes a ring resistor and electrodes connected to the ring resistor. The electrodes include electrodes on both ends and side electrodes. Furthermore, the electrodes on both ends are connected to the side electrodes. CN 02114902.x and CN 02225950.3 simultaneously disclose that the annular resistor body is made of one or more doped and fired ZnO, SrTiO ₃ , TiO ₂ , SiC and SnO ₂ materials, and its electrodes are made of Ag, Cu, Au , Al, Ni, Pt, Sn, Zn, In-Ga, Pd and Cd, but it does not specifically specify the use of SrTiO ₃ as a ring resistor, nor does it specify that the ratio of Cu electrodes to Ag electrodes advantages, and there is no disclosure of the preparation method of the copper electrode strontium titanate ring varistor.

Contents of the invention

The object of the present invention is to provide a copper electrode strontium titanate annular varistor, which can avoid the "silver wave" phenomenon of the silver electrode annular varistor.

The ring-shaped piezoresistor of the present invention comprises a ring-shaped resistor ceramic substrate and three or more than three electrodes; the ring-shaped resistor ceramic substrate is made of strontium titanate, and the electrodes are copper electrodes, and the copper electrodes It is connected on the ceramic substrate of the ring resistor, and is located on the upper end surface, the lower end surface or the outer surface of the ceramic substrate of the ring resistor.

The advantage of adopting copper electrode in the present invention is: the electrode made of copper paste has good solderability, and copper paste itself is a kind of ohmic paste, the method for preparing copper electrode is relatively simple, if copper paste is used instead of silver Paste, only one layer can be printed.

In the above-mentioned ring varistor, the weight percentage of copper in the copper electrode is generally controlled between 70-95%.

In the present invention, the copper electrode may also contain 5-30% of one substance or a mixture of several substances selected from glass powder, silicate, quartz powder, boron oxide, lead oxide and bismuth oxide. The above-mentioned silicates are preferably selected from one or more substances selected from sodium silicate, potassium silicate, magnesium silicate and calcium silicate.

On the other hand, the present invention also provides a method for manufacturing a strontium titanate ring varistor, the method comprising the following steps:

(1) strontium titanate ceramic material to prepare the porcelain blank of strontium titanate ring varistor;

(2) debinding the porcelain body prepared in step (1) at high temperature;

(3) Carrying out reduction sintering in reducing atmosphere with the debinding porcelain body prepared in step (2), to make ceramic substrate;

(4) oxidizing the ceramic substrate prepared in step (3) at 800°C-1000°C;

(5) printing the copper paste onto the ceramic substrate obtained in step (4), and drying to form a copper electrode;

(6) Reducing the copper electrode obtained in step (5) in a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere at 700° C. to 900° C. to obtain a strontium titanate ring varistor.

In the above method, the high temperature debinding in step (2) is usually carried out at 500-800°C, preferably at 580-720°C.

In the present invention, the reducing atmosphere in step (3) is usually a hydrogen atmosphere or a nitrogen-hydrogen mixed atmosphere, and of course it can also be other suitable reducing atmospheres. The temperature of reduction sintering is generally 800-1500°C, preferably 1100-1450°C.

The printing of the copper paste in step (5) can use a screen or other utensils capable of printing. The mesh size of the screen should be selected according to the properties of the slurry so that the slurry can be evenly printed on the surface of the ceramic substrate. It is preferable to use a screen of 180 to 300 meshes. The copper paste used in printing has a copper content of 60%-90%, preferably 70%-85%, and the copper paste may also contain other components that enable copper electrodes to be printed on the ceramic substrate. For example, 9%-20% glass frit and 1%-10% solvent may be contained. The drying method in this step is natural drying, blowing drying or drying drying, and the drying temperature is generally 70-220°C, and the preferred temperature range is 100-200°C.

In step (6), the copper electrode should be fully reduced, and the reduction time is not particularly limited, but preferably within several minutes to several hours, more preferably within 10-30 minutes.

The copper electrode strontium titanate annular varistor of the present invention overcomes the silver layer consumption phenomenon of the silver electrode annular varistor due to the increase in welding temperature or welding times, that is, the so-called "silver swinging". At the same time, the copper electrode strontium titanate ring varistor has better soldering resistance than the silver electrode ring varistor, and can withstand welding with a 480°C soldering iron for more than 10 seconds.

Description of drawings

Figure 1 is a strontium titanate ring varistor with copper electrodes located on the upper surface.

Figure 2 is a strontium titanate ring varistor with copper electrodes located on the side faces.

In the figure, l------upper copper electrode (shaded part)

2------Side copper electrode (shaded part)

3------Toroidal varistor body

Detailed ways

Example 1

The special ceramic material for strontium titanate ring varistor is made by extrusion molding method to make ring green sheet, and after debinding at 650°C, it is sintered at 1350°C in an atmosphere furnace containing nitrogen and hydrogen mixture After the semiconductor ceramic is produced, it is oxidized at 900°C to obtain a strontium titanate ring varistor ceramic substrate. The copper paste that is 80% (weight percentage composition) with Cu content, glass powder content is 15%, solvent content is 5%, is printed on this substrate by 200 mesh screens, (and dry at 150 ℃) ; and after being reduced in an atmosphere furnace containing nitrogen-hydrogen mixed gas at a temperature of 800 ° C, a copper electrode strontium titanate ring varistor is obtained. The weldability of the ring strontium titanate is better through measurement.

Example 2

The special ceramic material for strontium titanate ring-shaped varistors is made of ring-shaped blanks by extrusion molding, and after debinding at a temperature of 600 ° C, the semiconductor ceramics are sintered at a temperature of 1200 ° C in a hydrogen atmosphere furnace. , Oxidized at 800 ° C to obtain strontium titanate ring varistor ceramic substrate. It is 70% to contain Cu, the glass powder content is 20%, and the copper paste that solvent content is 10% is printed on this substrate by 180 mesh screens, (and dry at the temperature of 100 ℃); After being reduced in a nitrogen atmosphere furnace at 700°C, a copper electrode strontium titanate annular varistor was obtained, and it was measured that the weldability of the annular strontium titanate was better.

Example 3

The special ceramic material for strontium titanate ring-shaped varistors is made of ring-shaped blanks by dry pressing, and after debinding at a temperature of 750 ° C, the semiconductor ceramics are sintered at a temperature of 1400 ° C in a hydrogen atmosphere furnace. , the strontium titanate annular varistor ceramic substrate was obtained by oxidation at 1000°C. Be 85% with Cu content, glass frit content is 9%, the copper paste that solvent content is 6%, is printed on this substrate by 300 mesh screens, (and dry at the temperature of 200 ℃); After being reduced in a nitrogen atmosphere furnace at 900°C, a copper electrode strontium titanate annular varistor is obtained. According to measurements, the solderability of the annular strontium titanate is better.

Claims (10)

1. An annular varistor comprising an annular resistor ceramic substrate and three or more electrodes, characterized in that the annular resistor ceramic substrate is made of strontium titanate , the electrodes are copper electrodes; the electrodes are connected to the ceramic substrate of the ring resistor, and are located on the upper end surface, the lower end surface or the outer surface of the ceramic substrate of the ring resistor. 2. The ring varistor according to claim 1, characterized in that the weight percentage of copper in the copper electrode is 60-95%. 3. The ring-shaped varistor according to claim 2, characterized in that, said copper electrode contains 5-30% of glass powder, silicate, quartz powder, boron oxide, lead oxide One substance or a mixture of several substances in bismuth oxide. 4. The annular varistor according to claim 2, wherein the silicate is a substance selected from sodium silicate, potassium silicate, magnesium silicate and calcium silicate or Several substances. 5. A method for manufacturing a strontium titanate ring varistor, characterized in that the method comprises the following steps: (1) preparing a ceramic blank of a strontium titanate ring varistor from a strontium titanate ceramic material; (2) debinding the porcelain body prepared in step (1) at high temperature; (3) Carrying out reduction sintering in reducing atmosphere with the debinding porcelain body prepared in step (2), to make ceramic substrate; (4) oxidizing the ceramic substrate prepared in step (3) at 800°C-1000°C; (5) printing the copper paste onto the ceramic substrate obtained in step (4), and drying to form a copper electrode; (6) Reducing the copper electrode obtained in step (5) in a nitrogen atmosphere or a nitrogen-hydrogen mixed atmosphere at 700° C. to 900° C. to obtain a strontium titanate ring varistor. 6. The method according to claim 5, characterized in that the high temperature debinding in step (2) is carried out at 500-800°C. 7. The method according to claim 5, characterized in that the reducing atmosphere in step (3) is a hydrogen atmosphere or a nitrogen-hydrogen mixed atmosphere. 8. The method according to claim 5, characterized in that the copper paste printing in step (5) is screen printing. 9. The method according to claim 5, characterized in that the Cu content of the copper paste used in step (5) is 60%-90%. 10. The method according to claim 5, characterized in that the drying method in step (5) is natural drying, air drying or oven drying at 70-220°C.

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