CN102324290A - Copper electrode zinc oxide varistor and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of preparation method of copper electrode zinc oxide varistor; May further comprise the steps: make voltage-sensitive ceramic body, print copper electrode slurry, copper electrode oven dry, copper electrode burning infiltration; Wherein the copper electrode burning infiltration adopts chain-belt type tunnel electric furnace as production equipment, under the oxygen-free atmosphere environment, carries out.The present invention substitutes noble metal silver as electrode material with copper base metal, uses special electrode burning infiltration technology, produces the qualified copper electrode zinc oxide varistor of performance, has practiced thrift production cost greatly.The present invention has the following advantages: 1, this technology is fit to the production in enormous quantities of copper electrode zinc oxide varistor.2, the product of this technology production, each item electrical property (comprising voltage nonlinearity, leakage current, discharge capacity, energy tolerance etc.) all can reach the level suitable with the silver electrode product, meets customer need.3, product cost is more much lower than the silver electrode product of same size.

Description

Copper electrode zinc oxide varistor and preparation method thereof

technical field

The invention relates to the technical field of zinc oxide varistors with copper electrodes.

Background technique

Zinc oxide varistor is a semiconductor ceramic element made of zinc oxide as the main material, which is sintered at high temperature under normal atmospheric environment after semiconducting doping. Zinc oxide varistors widely used in the industry are still silver electrode components. The component has excellent voltage non-linear characteristics and the ability to withstand high-energy shocks. It is mainly used in household appliances, communications, industrial power supplies, lighting, automobiles and other fields, and plays the role of lightning protection and overvoltage protection. Since silver is a precious metal material, using it as an electrode material will inevitably increase the cost of the product, so consider other metal materials to replace silver as an electrode, such as copper. The electrode of the varistor is made of silver paste, and the atmosphere environment of the infiltration is the normal atmospheric environment, which is the same as the sintering environment of the varistor ceramic substrate. Therefore, the silver electrode infiltration process has little influence on the electrical properties of the varistor. However, copper paste is used to make the electrodes of varistors. The atmosphere environment of the infiltration cannot adopt the normal atmospheric environment. On the other hand, the control of infiltration temperature is also critical. If it is too high, the grain boundary potential of the varistor will be destroyed. barrier, resulting in serious degradation of the electrical performance of the varistor. The technology is in the research and development state at home and abroad, hoping to develop zinc oxide varistor technology that can replace silver electrodes.

The Chinese invention patent application with the application number 200310117432.2 and the title of the invention "copper electrode strontium titanate ring varistor and its preparation method" discloses a ring varistor and its preparation method. The ring-shaped varistor includes a ring-shaped resistor ceramic substrate and three or more electrodes, the substrate is made of strontium titanate, the electrodes are copper electrodes, and are located on the upper end surface, lower end surface or on the outside. The preparation method includes: manufacture of porcelain body, printing and drying of copper slurry, and reduction of copper electrodes. This application introduces the process of manufacturing copper electrode strontium titanate annular varistors. The copper paste is printed on the ceramic substrate and then dried to form copper electrodes. Electrodes are restored.

Contents of the invention

The object of the present invention is to provide a zinc oxide varistor with copper as an electrode and a preparation method thereof.

In order to achieve the above invention, the present invention adopts the following technical scheme: a method for preparing a copper electrode zinc oxide varistor, which is characterized in that it includes the following steps: making a pressure sensitive ceramic body, printing copper electrode paste, copper electrode baking Dry and copper electrode infiltration, in which the copper electrode infiltration adopts chain-belt tunnel electric furnace as the production equipment and is carried out in an oxygen-free atmosphere.

The oxygen-free atmosphere is realized by feeding high-purity nitrogen gas or high-purity nitrogen gas containing a very small amount of air into the furnace.

The entrance and exit of the chain-belt tunnel furnace are provided with dense air holes, and high-purity nitrogen gas is introduced into the air holes to form an air curtain to isolate the entry of external air.

The air flow rate of the air curtain is 10-200 L/min.

The hearth of the chain-belt tunnel electric furnace is sequentially provided with an inlet gas curtain area, several heating zones, a high temperature zone, a cooling zone and an outlet gas curtain zone. The proportion is controlled at 50-500ppm, and the higher the temperature is, the smaller the proportion of oxygen is.

The temperature of the high-temperature section is 500-600° C., and the constant temperature time is 1-10 minutes. The high-temperature section is fed with high-purity nitrogen with a purity of 99.999%, and the oxygen content is controlled at ≤ 20ppm.

The cooling zone is fed with high-purity nitrogen with a purity of 99.999%, the oxygen content is controlled at ≤ 20ppm, and water-cooling equipment is used for cooling, and the temperature of the product out of the furnace is lower than 60°C.

The printed copper electrode paste uses 200-250 mesh nylon screen printing electrodes to obtain a copper electrode layer with a film thickness of 5-10 μm.

The drying of the copper electrodes is carried out in an ordinary atmospheric environment, the drying temperature is 100-200° C., and the time period is 5-15 minutes.

A copper electrode zinc oxide varistor prepared according to the above preparation method.

The present invention uses base metal copper instead of noble metal silver as the electrode material, and uses a special electrode burning-infiltration process to produce qualified copper electrode zinc oxide piezoresistors, which greatly saves production costs. The invention has the following advantages: 1. The technology is suitable for mass production of copper electrode zinc oxide piezoresistors. 2. The electrical properties of the products produced by this process technology (including voltage nonlinear coefficient, leakage current, flow capacity, energy tolerance, etc.) can reach a level equivalent to that of silver electrode products to meet customer needs. 2. The product cost is much lower than that of silver electrode products with the same specifications.

Description of drawings

Fig. 1 is a structural schematic diagram of a copper electrode varistor ceramic body.

Among them, 1 pressure sensitive ceramic body, 2 copper electrodes

Detailed ways

Example 1

This example is the production process of 20K821 copper electrode zinc oxide varistor with a diameter of φ20mm. The steps are as follows:

First make the pressure-sensitive ceramic body according to the traditional varistor sintering process, and then use a 200 mesh screen to print on the pressure-sensitive ceramic body with a copper content of 70%-75% and a firing temperature of 520-600°C on the pressure-sensitive ceramic body with a thickness of 8-10 μm. Low-temperature copper paste for zinc oxide varistors (can be purchased from the market), and then use a general chain-belt drying furnace. Minute process for drying. Then, after installing it with a screen, put it into a chain-type nitrogen atmosphere protection tunnel electric furnace dedicated to zinc oxide varistors, such as a tunnel furnace with a model BHTDL-100 designed by Xinbaohua Electronic Equipment Company. Copper electrodes. The process parameters of the infiltration process are shown in Table 1 below:

Table 1

The entire infiltration process must be carried out in an almost oxygen-free atmosphere. Through the dense air holes at the entrance and exit of the tunnel furnace, high-purity nitrogen is sprayed to form an air curtain, which isolates the entry of external air and creates an oxygen-free atmosphere for the furnace. The size of the air curtain is controlled using a flow meter. In the furnace, pipes are used to deliver high-purity nitrogen gas or mixed gas containing a very small amount of air to each temperature zone. In the heating zone with a temperature of 200-450°C, in order to more advantageously remove organic matter such as solvents and binders in the copper paste, the high-purity nitrogen introduced is mixed with a small amount of air, and the mixing ratio of oxygen is controlled at 50-50°C. 500ppm, the higher the temperature range, the smaller the proportion of oxygen. For the high-temperature zone, the highest copper electrode infiltration temperature of the zinc oxide varistor is 500-600°C, and the constant temperature time is 1-10 minutes. This temperature zone must be fed with high-purity nitrogen with a purity of 99.999%, and the oxygen content is controlled at ≤ 20ppm. The setting of temperature and time differs depending on the size of the piezoresistor. The cooling zone is fed with high-purity nitrogen with a purity of 99.999%, and the oxygen content is controlled at ≤20ppm. Water cooling is used near the outlet to ensure that the temperature of the baked product is lower than 60°C. After being released from the oven, the product should be sealed and stored in an environment with a room temperature of 20-30°C and a humidity of ≤60%.

The 20K821 copper electrode zinc oxide varistor produced by the above process has a varistor voltage of 740~900v, a nonlinear coefficient α≥50, a leakage current ≤3μA, good solderability of the electrode, and a flow capacity of 8/20μs. And 2ms energy tolerance performance reaches the level of the silver electrode varistor with the same specification, and the production cost is saved by more than 50%.

Example 2

This example is the production process of 10K471 copper electrode zinc oxide varistor with a diameter of φ10mm, including the following steps:

First make the pressure-sensitive ceramic body according to the traditional varistor sintering process, and then use a 200 mesh screen to print on the pressure-sensitive ceramic body with a copper content of 70%-75% and a firing temperature of 520-600°C on the pressure-sensitive ceramic body with a thickness of 8-10 μm. Low-temperature copper paste for zinc oxide varistors (can be purchased from the market), and then use a general chain-belt drying furnace. Minute process for drying. Then, after installing it with a screen, put it into a chain belt type nitrogen atmosphere protection tunnel electric furnace dedicated to zinc oxide varistors and burn infiltrated copper electrodes. The process parameters of the infiltration process are as follows:

The entire infiltration process is carried out in an almost oxygen-free atmosphere. The same atmospheric environment as in Example 1 can be used.

The 10K471 copper electrode zinc oxide varistor produced by the above process has a varistor voltage of 430-5100v, a nonlinear coefficient α≥50, a leakage current ≤3μA, good solderability of the electrode, and a flow capacity of 8/20μs. And 2ms energy tolerance performance reaches the level of the silver electrode varistor with the same specification, and the production cost is saved by more than 50%.

Example 3

This example is the production process of 7K271 copper electrode zinc oxide varistor with a diameter of φ7mm, including the following steps:

First make the pressure-sensitive ceramic body according to the traditional varistor sintering process, and then use a 200 mesh screen to print on the pressure-sensitive ceramic body with a copper content of 70%-75% and a firing temperature of 520-600°C on the pressure-sensitive ceramic body with a thickness of 8-10 μm. Low-temperature copper paste for zinc oxide varistors (can be purchased from the market), and then use a general chain-belt drying furnace. Minute process for drying. Then, after installing it with a screen, put it into a chain belt type nitrogen atmosphere protection tunnel electric furnace dedicated to zinc oxide varistors and burn infiltrated copper electrodes. The process parameters of the infiltration process are as follows:

The entire infiltration process is carried out in an almost oxygen-free atmosphere. The same atmospheric environment as in Example 1 can be used.

The 7K271 copper electrode zinc oxide varistor produced by the above process has a varistor voltage of 243-297v, a nonlinear coefficient α≥48, a leakage current ≤3μA, good electrode solderability, and a flow capacity of 8/20μs. And 2ms energy tolerance performance reaches the level of the silver electrode varistor with the same specification, and the production cost is saved by more than 50%.

Claims (10)

1. the preparation method of a copper electrode zinc oxide varistor; It is characterized in that may further comprise the steps: make voltage-sensitive ceramic body, print copper electrode slurry, copper electrode oven dry, copper electrode burning infiltration; Wherein the copper electrode burning infiltration adopts chain-belt type tunnel electric furnace as production equipment, under the oxygen-free atmosphere environment, carries out.

2. preparation method according to claim 1 is characterized in that: said oxygen-free atmosphere is to realize through the high pure nitrogen that feeds high pure nitrogen to burner hearth or contain the denier air.

3. preparation method according to claim 2 is characterized in that: the import of said chain-belt type continuous tunnel furnace is provided with densely covered pore with outlet, feeds high pure nitrogen to said pore, forms gas curtain, the entering of isolated extraneous air.

4. preparation method according to claim 3 is characterized in that: the throughput of said gas curtain is 10～200L/min.

5. preparation method according to claim 1; It is characterized in that: the burner hearth of said chain-belt type tunnel electric furnace is disposed with import gas curtain district, plurality of sections heating zone, high-temperature region, cooling area and outlet gas curtain district; In heating zone, feed the high-purity nitrogen that is mixed with micro-air; Wherein the mixed proportion of oxygen is controlled at 50～500ppm, the interval that temperature is high more, and the ratio of oxygen is more little.

6. preparation method according to claim 5 is characterized in that: the temperature of said high temperature section is 500～600 ℃, and constant temperature time is 1～10 minute, and this high-temperature region feeds the high purity nitrogen of 99.999% purity, and Control for Oxygen Content is at≤20ppm.

7. preparation method according to claim 5 is characterized in that: said cooling area feeds the high purity nitrogen of 99.999% purity, and Control for Oxygen Content is at≤20ppm, and adopts water cooling equipment to lower the temperature, and the temperature of the product of coming out of the stove is lower than 60 ℃.

8. preparation method according to claim 1 is characterized in that: said print copper electrode slurry is to adopt 200～250 purpose nylon mesh to print electrode, and obtaining thickness is the copper electrode layer of 5-10 μ m.

9. preparation method according to claim 1 is characterized in that: said copper electrode oven dry is carried out under the normal atmospheric environment, and the temperature of oven dry is 100-200 ℃, and the time cycle is 5～15 minutes.

10. copper electrode zinc oxide varistor that makes according to the described preparation method of claim 1～9.

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