JPH03280411A - Manufacture of surface reoxidized type semiconductor ceramic capacitor - Google Patents

Abstract

PURPOSE:To improve reliability of the title capacitor having excellent practical electric insulation resistance value and dielectric breakdown voltage by a method wherein the reoxidizing heat treatment is conducted on a semiconductor ceramic in the atmosphere of partial pressure of oxygen higher than that of atmospheric air. CONSTITUTION:The raw material of a semiconductor ceramic is mainly composed of barium titanate (BaTiO3) and one or two or more kinds selected from titanate oxide (TiO2), neodymium oxide (Nd2C3), lanthanium oxide (La2O3), manganese oxide (MnO2) and the like are added to the above-mentioned material. The adding quantity should be 0.1 to 10 mol or thereabout in total quantity against barium titanate of 100. The semiconductor ceramic is formed using the semiconductor ceramic manufacturing method which is conventionally used, and the partial pressure of oxygen when a reoxidation heat treatment is conducted on the semiconductor ceramic should be oxygen gas ratio of 25 to 100vol.% in the oxydizing atmosphere consisting of oxygen gas and nitrogen gas, namely, in the partial pressure of oxygen of about 0.25 to 1.0 which is higher than the partial pressure of oxygen in atmospheric air, and the heat treatment temperature in the partial pressure of oxygen should be 900 to 1050 deg.C or thereabout.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a surface reoxidation type semiconductor ceramic capacitor.

(Prior Art) Conventionally, as a manufacturing method of this type of surface reoxidation type semiconductor ceramic capacitor, barium titanate (BaTiO
2) as the main component, with a small amount of neodymium oxide, lanthanum oxide, etc. added to the molded body, which is then fired at high temperature in the air and then heat-treated in a neutral or reducing atmosphere to form a semiconductor. The converted semiconductor porcelain is heated again in the atmosphere at a temperature of 9.
A method of performing reoxidation heat treatment at 00 to 1100°C is known.

Surface reoxidation type semiconductor ceramic capacitors manufactured in this manner have a dielectric layer formed on the surface, and are relatively compact and have a large area capacitance, and are therefore widely used in electronic circuits.

(Problem to be Solved by the Invention) However, in the above manufacturing method, the dielectric layer formed on the surface by reoxidation heat treatment has problems with the rate of oxygen diffusion from the atmosphere into the surface layer portion of the semiconductor ceramic and the rate of oxygen diffusion inside the semiconductor ceramic. Because it depends on the diffusion rate, for example, if the reoxidation heat treatment temperature for semiconductor ceramics is performed at a high temperature such as 1100°C, oxygen diffusion will proceed inside the semiconductor ceramics, so the dielectric layer on the surface of the resulting ceramic capacitor will be thick. Although the electrical insulation resistance value and dielectric breakdown voltage are improved due to this formation, there is a problem that the area capacitance is reduced.Also, if the reoxidation heat treatment temperature for semiconductor porcelain is performed at a low temperature such as 900°C, the inside of the semiconductor porcelain Not only oxygen diffusion is suppressed, but also oxygen diffusion on the ceramic surface is suppressed, so the resulting dielectric layer on the surface of the ceramic capacitor is formed with a thin and non-uniform thickness, resulting in a large area and volume. There is a problem in that the insulation resistance value and dielectric breakdown voltage decrease, and a ceramic capacitor having sufficient areal capacitance, electrical insulation resistance value, and dielectric breakdown voltage cannot be obtained.

The present invention solves the above-mentioned problems and is a method for manufacturing a surface reoxidation type semiconductor ceramic capacitor that has excellent electrical insulation resistance and dielectric breakdown voltage when the areal capacitance is the same, and is highly reliable for practical use as a capacitor. The purpose is to provide

(Means for Solving the Problems) A method for manufacturing a surface reoxidation type semiconductor ceramic capacitor of the present invention is a method for manufacturing a surface reoxidation type semiconductor ceramic capacitor by subjecting semiconductor ceramic to reoxidation heat treatment. The reoxidation heat treatment is carried out at an oxygen partial pressure higher than the oxygen partial pressure in the atmosphere.

The raw material for the semiconductor porcelain used in the present invention includes, for example, barium titanate (BaTi0=) as the main component, and titanium oxide (Ti02) and neodymium oxide (Nd20).
3), lanthanum oxide (La203), manganese oxide (
Examples include those to which one or more types of oxides such as MnO□) are added. The amount of these oxides added is as follows:
Generally, the total amount is α, 1 per 100 moles of barium titanate.
The amount should be about 10 moles.

In order to create semiconductor porcelain from the raw material for semiconductor porcelain, a conventional semiconductor porcelain manufacturing method may be used.

In addition, the oxygen partial pressure when performing reoxidation heat treatment on semiconductor porcelain is, for example, the oxygen gas ratio in an oxidizing atmosphere consisting of oxygen gas and nitrogen gas, or about 25 to 100 to 96, that is, the oxygen partial pressure in the atmosphere. 0 higher than oxygen partial pressure (0,20)
．． 25 to about 1.0, and the heat treatment temperature in the oxygen partial pressure is about 900 to 1050°C.

(Example) Next, specific examples of the present invention will be described together with comparative examples.

First, 100 moles of barium titanate (BaTi03), 0.2 moles of titanium oxide (Ti02), 1 mole of neodymium oxide (Nd203), and lanthanum oxide (La20) were added.
3) Semiconductor porcelain raw material powders to which 0.5 mol and 0.1 mol of manganese oxide (Mn02) were added were prepared.

Next, this raw material powder was mixed for 20 hours using a ball mill using urethane-coated cobblestones. After dehydrating this mixture and drying it at a temperature of 150°C for 3 hours, 4 parts by weight of methyl cellulose and 5 parts by weight of glycerin were added to this as a binder.
Parts by weight were added, and an appropriate amount of water was further added and kneaded. The kneaded material was molded using a mold with an outer diameter of 1.8 mm, an inner diameter of 1.0 mm, and a length of 4 mm.
It was molded into a 5-inch cylindrical molded body.

The molded body was fired in the air at a temperature of 1,350°C for 2 hours, and then heat treated at a temperature of 1,100°C for 2 hours in a reducing atmosphere containing 3% by volume of hydrogen gas and 97% by volume of nitrogen gas to create semiconductor porcelain. did.

Subsequently, the semiconductor porcelain was subjected to an oxygen partial pressure (oxygen gas volume ratio in 100 volumes of oxygen gas and nitrogen gas) of 0.20 (atmosphere), 0.25.0, 30.0.40. ．． 0.60°, 0.80, and 1.00, respectively, and the heat treatment temperature was changed to 96°C.
Surface reoxidation type semiconductor ceramic capacitors were fabricated by performing reoxidation heat treatment for 2 hours under various conditions of 0°C, 985°C, 1000°C, and 1015°C.

Silver paste was applied to the cylindrical outer and inner surfaces of the prepared surface reoxidation type semiconductor ceramic capacitor, and the temperature was raised to 800°C.
The electrodes were formed by baking at ℃.

For each surface reoxidation type semiconductor ceramic capacitor (hereinafter referred to as a sample) created in this way, the areal capacitance,
The electrical insulation resistance value and dielectric breakdown strength were investigated, and the results are shown in the table.

In addition, the areal capacity is determined by measuring the frequency I using a digital LCR meter.
It was determined from the capacitance (C) measured at KHz and a voltage of 1 V and the electrode area of the sample.

Further, the electrical insulation resistance value was the value measured for the sample after applying a DC voltage of 50 V to the sample for 30 seconds.

Further, the dielectric breakdown voltage was defined as the voltage value applied when the current flowing through the sample reached 111+A while increasing the DC voltage applied to the sample.

As is clear from the table, Examples 1, 2. It was confirmed that when the area capacity was the same as in Comparative Example 1 in which the heat treatment was performed in the air, the electrical insulation resistance value and dielectric breakdown voltage were improved.

Furthermore, it can be seen that by increasing the oxygen partial pressure, a ceramic capacitor with a high electrical insulation resistance value and high insulation resistance voltage can be obtained when the reoxidation heat treatment temperature is the same. Furthermore, it can be seen that the higher the oxygen partial pressure is, the higher the electrical insulation resistance value and dielectric breakdown voltage are when the areal capacitance is the same.

Therefore, when subjecting semiconductor ceramics to reoxidation heat treatment, by adjusting the oxygen partial pressure and heat treatment temperature, it is possible to manufacture surface reoxidation type semiconductor ceramic capacitors with different areal capacitances in accordance with applications.

Note that the atmosphere during the reoxidation heat treatment is not limited to a mixed gas of oxygen gas and nitrogen gas, and instead of some or all of the nitrogen gas mixed with oxygen gas, He%Ar,
One of the inert gases such as Ne, Kr, Xe, Rn, etc.
A species or two or more species can be used.

(Effects of the Invention) As described above, according to the present invention, since the reoxidation heat treatment on semiconductor ceramics is performed in an oxygen partial pressure higher than that of the atmosphere, the oxygen partial pressure of the reoxidation heat treatment can be reduced. By increasing the heat treatment temperature, the heat treatment temperature can be lowered, suppressing oxygen diffusion inside the semiconductor porcelain and forming a thin and uniform dielectric layer on the surface of the semiconductor porcelain.If the areal capacitance is the same, the electric Since the insulation resistance value and dielectric breakdown voltage can be improved, it is possible to easily manufacture highly reliable surface reoxidation type semiconductor ceramic capacitors with excellent electrical insulation resistance value and dielectric breakdown voltage for practical capacitors. Applicant: Taiyo Yuden Co., Ltd. Agent: Kin Kitamura −.

3 other people

Claims (1)

[Claims] A method for manufacturing a surface reoxidation type semiconductor ceramic capacitor by subjecting semiconductor porcelain to reoxidation heat treatment, characterized in that the reoxidation heat treatment to the semiconductor porcelain is performed in an oxygen partial pressure higher than the oxygen partial pressure in the atmosphere. A method for manufacturing a surface reoxidation type semiconductor ceramic capacitor.