JPS62122103A - Manufacture of laminated chip varistor - 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 Field of Industrial Application The present invention relates to a method for manufacturing a multilayer chip varistor whose main component is zinc oxide (ZnO).

Conventional technology Conventionally, the resistance of multilayer chip varistors whose main component is zinc oxide (ZnO) changes significantly depending on the applied voltage9.
．． The voltage-current characteristics show significant nonlinearity. For this reason,
It has been widely used to stabilize voltages in electronic equipment and as a circuit protection element against surge currents.

Recently, equipment has become smaller and lower voltage, and in response to this trend, we have applied ceramic sheet lamination technology to create a zinc oxide-based laminated chip that is small, low-impact, has high risk voltage, and high surge resistance. Baristas are attracting attention.

The manufacturing method for laminated chip Balinuta is to comb a ceramic green sheet made of ceramic powder mainly composed of zinc oxide and an organic material with a noble metal paste such as platinum, palladium, silver, etc. that is stable at high temperatures, alternating with ceramic sheet layers. Print the structure and then cut it into a predetermined shape to create a green chip. This was fired in the atmosphere to obtain a sintered body, and a silver-palladium alloy was baked on both ends of this sintered body to form external electrodes, thereby manufacturing a multilayer chip varistor.

Problems to be Solved by the Invention In such a conventional configuration, if the terminal electrodes of the laminated ceramic body are formed only of silver, migration due to silver will occur and solderability will be poor. In order to achieve this, a silver-palladium alloy to which around 20% palladium is added is used. However, palladium is expensive, with a market price of 700 to 900 yen per gram, and adding palladium increases the cost of the stain electrode by three to five times.

Furthermore, instead of adding palladium, for example Nati o
nal, Technical, Rep'i1M, V
o 131, A3, p. 145, "High permittivity dielectric material for multilayer ceramic capacitors" is a method of plating on silver electrodes, but ZnO
The multilayer chip varistor has many internal pores in the ceramic, and the adhesion between the terminal electrode and the chip varistor is poor.

As a result, the acidic plating solution penetrates into the interior, reducing the varistor voltage.

There was a problem in that electrical properties such as withstand capacity deteriorated, making it impossible to obtain products with good properties.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention embeds a sintered body of a multilayer chip varistor in a mixed powder of zirconia powder and glass powder and heat-treats it to remove the glass component. Diffusion is performed to form a glass component layer on the surface of the element body, and then a silver electroplating layer and a metal plating layer are formed.

Effect By using such a method, the glass component compensates for the internal pores and defects in the multilayer chip varistor, densifies the element, and further improves the adhesion between the element and the terminal electrodes. By improving the adhesive strength and preventing the acidic plating solution from penetrating into the laminate, this prevents the electrical properties from deteriorating after plating.

Example The present invention will be explained below based on examples.

Ceramic powder mainly composed of zinc oxide, organic binder,
Add an organic solvent to make a slurry, and use a doctor blade to create a green sheet approximately 50 layers thick. This was cut into a predetermined size, platinum paste was printed on it, green sheets were laminated to form a comb-shaped structure alternating with single-layer sheets, and the paste was printed to obtain a 10-layer structure. Thereafter, it is cut into a desired shape to create green chips.

After degreasing the organic matter from this green chip, it becomes 1200 to 1
A multilayer chip varistor was manufactured by sintering at 300°C. The size of this sintered chip is 1.5 x 3 x O
, 55 Cmm).

The sintered body of this multilayer chip varistor was embedded in a mixed powder obtained by mixing zirconia oxide powder 1001 with glass powder as shown in Table 1, and heat-treated at 800°C in this state. Silver electrode paste was applied to both ends of the thus obtained chip varistor and baked. On top of the silver electrode, apply 1~2μ of Ni plating, and
Terminals were formed by forming 4 to 6 μm of solder plating. FIG. 1 shows a multilayer chip varistor obtained by the manufacturing method of the present invention. In FIG. 1, (1) is a zinc oxide ceramic body, (2) is a platinum electrode pupil, (3) is a glass powder diffusion layer, 4) is silver coated, (5) is Ni plated, and (6) is solder plated.

Table 1 shows one conventional manufacturing method in which silver-palladium was used for the terminal electrode, and another conventional method in which a silver electrode was formed and the silver electrode was plated without diffusion of glass powder into the chip. 1 shows the electrical properties of the varistor voltage surge withstand capacity of V and mA of the multilayer chip varistor based on the manufacturing method of the present invention; and the physical properties of the bending strength and tensile strength of the element body.

As is clear from Table 1 above, the multilayer chip varistor of the present invention shows no deterioration in electrical characteristics (especially surge resistance) after plating compared to conventional methods, and It was observed that the bending strength and tensile strength were significantly improved, and good results were obtained. In addition, Brzo
A good range of addition amount of 3°B203-5i02 type glass powder was 5 to 20%. In other words, if the coefficient is less than 5, the effect of diffusion of the glass component will not be sufficiently exhibited, and if it exceeds 20, on the other hand, the glass component will be too large, causing a compositional deviation, which will cause a deviation in the varistor voltage and surge resistance. It is.

In addition, in the above example, Bib, Br203.5i
Although 02 series glass powder is used, any glass-containing powder can be used as long as it does not deteriorate the electrical and physical characteristics of the multilayer chip varistor.

As mentioned above, the multilayer chip varistor of the present invention has very strong electrical characteristics after being plated with Ni and solder, which prevents cranking when soldering directly to a printed circuit board. In addition, the present invention contributes to greatly reducing electrode costs, and the effects of the present invention are significant.

FIG. 3 is a cross-sectional view of a laminated chip parinuta.

(1) -----Zinc monoxide-based lamic body (2) --
--- One platinum electrode (31 --- Glass powder diffusion layer (4) --- One silver (51 --- Ni plating [61 --- Solder plating

Claims (1)

[Claims] A laminated sintered body in which ceramic body layers and metal electrode layers containing zinc oxide as a main component are alternately laminated is embedded in a mixed powder of zirconia powder and glass powder, and then heat treated to produce the above-mentioned sintered body. A multilayer chip varistor is characterized in that a multilayer chip varistor element body is formed by diffusing the above-mentioned glass component inside, and silver electrodes are coated on both ends of the element body, and a metal plating process is performed. Production method.