JPH02201901A - Manufacture of laminated ceramic varister - 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 [Industrial Application Field] The present invention relates to a method for manufacturing a multilayer ceramic varistor using an improved lamination method.

[Prior Art and its Problems] Ceramisovarisk, whose main component is zinc oxide, has a resistance value that changes significantly depending on the applied voltage, and exhibits good current-voltage nonlinearity. For this reason, it has been widely used for surge absorption in various electronic devices and as a voltage stabilizing element.

In recent years, devices have become smaller and lower in voltage, and in response to this trend, multilayer ceramic varistors that are compact, have low varistor voltage, and high surge resistance have attracted attention, and various studies have been conducted.

However, as described in JP-A No. 54-106894, for example, conventional multilayer ceramic varistors are manufactured by cutting the sintered body after sintering and polishing it. Since a decrease in α is observed,
Its manufacture is carried out by the following method. That is, a calcined powder having a composition that exhibits voltage nonlinearity when sintered is made into a sheet by a doctor blade method,
Internal electrodes made of a high-melting point metal such as platinum or palladium are screen-printed on this raw sheet, which is then laminated, thermocompressed, and then cut into a predetermined shape. This is sintered in air, and external electrodes are baked on both ends of this sintered body to obtain a multilayer ceramic varistor.

In this way, in conventional laminated ceramic varistors, the internal electrodes are formed at the same time as the raw sheet is sintered, so the raw sheet contracts during sintering, creating strain between the raw sheet and the internal electrode, and delamination between the laminated sheets. However, the obtained device may not be able to achieve sufficient performance. In particular, in order to achieve a low varistor voltage, it is essential to form a thin film sheet, but shrinkage of this sheet form has been a problem. Furthermore, as the internal electrode material is baked at a high sintering temperature, it is necessary to use expensive high-melting point metals such as gold, platinum, and palladium as the main component, which significantly increases the manufacturing cost of multilayer ceramic varistors. This was a major problem in practical application.

[Means for solving problems]

The present inventors conducted extensive research to solve the problems of the prior art as described above, and as a result, they arrived at the present invention.

In the production of a multilayer ceramic varistor, the present invention involves adding an organic adhesive to a fine ceramic powder having varistor properties.
Alternatively, add glass powder and a solvent to make a paste, and apply this to an insulating substrate with electrodes formed on both the front and back sides.
The present invention relates to a method for manufacturing a laminated ceramic varistor, characterized in that the substrates are bonded together by heat treatment after lamination.

The fine ceramic powder having varistor properties used in the present invention is preferably produced by a method such as that described in JP-A-62-190801. That is, 700 to 1300 fine particles of zinc oxide
After baking at °C, sintered zinc oxide is added to 0.5-50μ
Zinc oxide fine powder is ground to a particle size of m, and additives such as manganese oxide are added to the zinc oxide fine powder in an amount of 0°0001 to 10IIlo1χ, calcined at 600 to 1400'C, and then crushed and classified. The particle size can be appropriately selected depending on the required varistor voltage, and a particle size of 1200° C. is preferably used.

The organic adhesive is not particularly limited, but suitable examples include polyimide resins, epoxy resins, gay resins, phenol resins, and the like.

The glass powder may have a glass composition that allows the electrode materials to adhere to each other, and specific examples include glass frit having a composition of bismuth oxide, silicon oxide, and boron oxide.

Further, the proportion of the ceramic fine powder having varistor properties, the organic adhesive, or the glass powder and the solvent used is not particularly limited, but is 10 parts by weight per 100 parts by weight of the ceramic fine powder.
~100 parts by weight are used.

Suitable examples of the insulating substrate include a glass substrate, an alumina substrate, an oxidized Beria substrate, and the like.

Further, various metals such as gold, platinum, palladium, silver, and aluminum can be used as the electrode material formed on the substrate, but an inexpensive metal such as silver is preferable from the viewpoint of manufacturing cost.

More specifically, it can be manufactured by the following method. First, ceramic fine powder with varistor properties is prepared, an organic adhesive or glass powder and a solvent are added to it to form a paste, and this is printed by screen printing on an insulating substrate with electrodes formed on both the front and back sides. Coating by method, spray method, dipping method, etc., then laminating, 35
By performing heat treatment at a temperature of about 0 to 600°C, the substrates are bonded together to obtain a laminate. Next, an external electrode material such as silver paste is applied to the end face of the laminate, and an angle of 500 to 600°
A multilayer ceramic varistor can be easily manufactured by heat treatment at a temperature of approximately C.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the manufacturing method of the laminated ceramic varistor of this invention will be explained in detail using one Example shown in FIGS. 1-3 which are attached drawings.

In the figure, 1 is an insulating substrate, and 2 is an internal electrode formed on both end surfaces of the insulating substrate. 3 is a ceramic varistor layer obtained by adding an organic adhesive or glass powder and a solvent to ceramic fine powder having varistor properties, making it into a paste, and then heat-treating the mixture. Reference numeral 4 denotes an external electrode that is connected to one end of the internal electrode 2 when stacked.

Example 1 After molding zinc oxide powder with a particle size of 0.05 to 1 μm into pellets, it was fired at 1200°C for 2 hours, and then crushed and classified. Particles of Jm were obtained.

0.0001 to 10 molX of each of bismuth oxide, manganese oxide, cobalt oxide, antimony oxide, and aluminum oxide are added and mixed to this zinc oxide powder, and after baking this at 800 to 1400°C, it is lightly pulverized.
The particles were classified to have a particle size of 2 to 20 μm to obtain a ceramic fine powder having varistor properties.

To 100 parts by weight of this fine ceramic powder, 50 parts by weight of glass frit, 5 parts by weight of ethyl cellulose, and 40 parts by weight of butyl calpitol were added and mixed to form a paste.

On the other hand, silver paste was applied to both the front and back sides of the glass substrate by screen printing, and then baked at 500°C to impart the above-mentioned paste-like varistor properties onto the glass substrate 1 on which the internal electrodes 2 as shown in Fig. 1 were formed. Ceramic fine powder was applied by screen printing, and the required number of sheets were stacked on top of each other as shown in FIG.

Next, the stacked laminate was heat-treated at a temperature of 350 to 600°C, and then, as shown in FIG. 3, a silver paste was applied to the end face of the laminate to form external electrodes 4. Then, this was heat-treated in the atmosphere at a temperature of 500°C to obtain a multilayer ceramic varistor having three layers. The thickness of one layer of this ceramic fine powder was 20 μm.

The varistor voltage (voltage value at which a current of 1 mA flows, VlmA) of the multilayer ceramic varistor manufactured in this manner was IOV, and the nonlinear coefficient at this time was 20.

Example 2 The number of laminated sheets was 3 in the same manner as in Example 1 except that a paste was used in which 50 parts by weight of polyimide resin was added to 100 parts by weight of ceramic fine powder having varistor properties.
A multilayer ceramic varistor was manufactured.

The varistor voltage of this multilayer ceramic varistor is 10V.
, and the nonlinear coefficient at this time was 20.

〔Effect of the invention〕

According to the present invention, a ceramic fine powder exhibiting varistor properties is used to manufacture a laminated ceramic varistor at a low heat treatment temperature, so distortion occurs due to simultaneous firing of internal electrodes and raw sheets as in conventional manufacturing methods. Therefore, it is possible to obtain a device with sufficient performance, and in particular, it is possible to suitably manufacture a laminated ceramic varisque having a low varistor voltage as in the case of a thin film sheet. Furthermore, a low melting point material such as silver can be used as the internal electrode material, which can greatly contribute to cost reduction.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an insulating substrate according to the present invention coated with internal electrodes, Fig. 2 is a cross-sectional view of the insulating substrate, and Fig. 3 is a lamination of the insulating substrate and ceramic fine powder having varistor properties. , is a cross-sectional view of a multilayer ceramic varistor with external electrodes coated on its end face. 1: Insulating substrate, 2: Internal electrode, 3: Fine ceramic powder with varistor properties, 4: External electrode Patent applicant Ube Industries, Ltd. Figure 2

Claims (1)

[Claims] In manufacturing multilayer ceramic varistors, an organic adhesive or glass powder and a solvent are added to ceramic fine powder with varistor properties to form a paste, and this is applied onto an insulating substrate with electrodes formed on both the front and back sides. A method for manufacturing a laminated ceramic varistor, characterized in that the substrates are bonded together by heat treatment after lamination.