JPH02128412A - Diffusion agent for semiconductor ceramic capacitors and semiconductor ceramic capacitors using the same - Google Patents

Abstract

(57) [Abstract] 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 provides a diffusing agent for insulating grain boundaries of a polycrystalline semiconductor ceramic capacitor and improving electrical properties such as dielectric constant and insulation resistance, and a diffusion agent for this purpose. The present invention relates to a semiconductor ceramic capacitor having an insulating layer formed from a diffusing agent.

(Prior art and its problems) Semiconductor ceramic capacitors include barrier capacitance type, surface oxidation type, and grain boundary type. In the above-mentioned grain boundary type semiconductor ceramic capacitor, heat treatment is performed after applying a diffusing agent made of a metal compound such as a metal oxide to the surface of the semiconductor ceramic, so that the diffusing agent is diffused along the grain boundaries and Only the interface layer becomes an insulating layer, and the inside of the crystal grain remains a semiconductor structure. A grain boundary type semiconductor ceramic capacitor has a capacitor body with a much larger effective permittivity than a general ceramic dielectric.

Incidentally, in order to obtain a grain boundary insulated capacitor with a large capacity, it is said that it is desirable to grow crystal grains to a size of 20 to 30 μm or more. However, as the crystal grains become larger, the proportion of the grain boundary layer per unit area decreases, and the formation of an insulating layer is insufficient.Although the apparent dielectric constant increases, there are problems such as a decrease in insulation resistance. , it becomes necessary to devise measures for insulation treatment.

Semiconductor ceramic capacitors include strontium titanate (SrTi03) and barium titanate (BaTiOs).
), or a part of the above Sr is replaced with Ba, Mg or Ca
, some of the Ba was replaced with Sr, Mg, or Ca, and some of the Ti was replaced with Zr or Sn. Those insulated with an insulating layer are widely used.

Regarding the above-mentioned diffusing agent or insulating layer, many proposals have been made as described below.

In Japanese Patent Publication No. 60-20345, BiO3 and B2
An insulating layer made of at least one of O3, CuO, MnO, ZnO and pbo is disclosed.

In Japanese Patent Publication No. 62-49975, Cu, Bi,
An insulating layer made of at least one of Pb, B and St is described.

Furthermore, in Japanese Patent Publication No. 62-49976, Mn and
An insulating layer made of at least one of Bi, Cu, Pb, B and Si is described.

The semiconductor ceramic capacitors having an insulating layer described in these publications do not have sufficient insulation resistance, especially insulation resistance under high voltage, and are not suitable, for example, as a capacitor for removing noise near a power source.

(Technical Means for Solving the Problems) The present invention solves the above problems and provides a diffusion agent used in manufacturing semiconductor ceramic capacitors with high dielectric constant and insulation resistance, and low dielectric loss. Regarding.

According to the present invention, there is provided a diffusing agent for insulating grain boundaries of polycrystalline semiconductor ceramics, comprising 0.5 to 10% by weight of iron oxide and a total amount of 90 to 99.5% by weight of lead oxide and copper oxide. %, and a grain boundary insulated semiconductor ceramic capacitor having an insulating layer formed from this diffusing agent.

The polycrystalline semiconductor porcelain according to the present invention includes barium titanate (BaTi03), strontium titanate (
SrTi03) system, magnesium titanate (MgTi(
h) Systems that are known per se can be mentioned. Among these, polycrystalline semiconductor ceramics based on strontium titanate, those in which part of Sr is replaced with Ca, Ba, or Mg, and those in which part of Ti is replaced with Sn or Zr are preferable. .

When preparing the above-mentioned strontium titanate-based semiconductor ceramic, oxides of rare earth elements such as Y and Dy and Nb,
Semiconducting agents such as Ta, H oxides, additives commonly used in preparing semiconductor ceramic capacitors such as silicon oxide, manganese oxide, aluminum oxide, zirconium oxide, bismuth oxide, copper oxide, etc. can do.

The diffusing agent of the present invention comprises 0.5 to 10% by weight of iron oxide and 90 to 99.5% by weight of lead oxide and copper oxide.

Although there is no particular restriction on the ratio of lead oxide to copper oxide, the weight ratio of lead oxide/copper oxide is generally 0.2 to 50.

When the proportion of iron oxide is less than 0.5% by weight, the insulation resistance of the semiconductor ceramic capacitor is not significantly improved, and on the other hand, when the proportion exceeds 10% by weight, the dielectric constant of the semiconductor ceramic capacitor deteriorates.

In addition to those consisting of iron oxide, lead oxide, and copper oxide, the diffusing agent of the present invention includes compounds that are converted into these oxides by firing in an oxidizing atmosphere as described below, such as carbonates of iron, lead, or copper, and organic acids. Also included are salts, nitrates, and chlorides.

In addition to the above-mentioned components, the diffusing agent of the present invention includes Bi,
Mn, Zn, V, Cr, TI, Co,, Ni
, As, Sb, and other oxides.

The diffusing agent of the present invention is applied to the surface of semiconductor ceramics by coating or dipping in accordance with a method known per se.
The diffusing agent can be diffused into the grain boundaries by firing in an oxidizing atmosphere at a temperature of about 1,000 to 1,400"C. The diffusing agent may be directly applied to the surface of the semiconductor porcelain. It may be heat treated or melted at a temperature of about 1,000''C, pulverized, and applied to the surface of semiconductor porcelain together with a suitable binder and diluent.

(Example) Examples of the present invention are shown below.

Example l For a mixture of 5rC(h 43 mol%, CaC0+ 7 mol% and Ti(h 50 mol%), Y, Oj
．． After adding 04% and 20.15% by weight of 5in and pulverizing and mixing, the mixture was pre-calcined at 1,150''C for 2 hours.

Polyvinyl alcohol was added to the calcined powder and the mixture was pressure-molded into a disk shape. After degreasing the compact, it was heated in a reducing atmosphere consisting of 3.5% by volume of hydrogen and 96.5% by volume of nitrogen.
It was baked at 400-1.450°C for 3 hours.

4 parts by weight of Metrose and 30 parts by volume of terpineol were mixed with 100 parts by weight of the mixed powder of the dispersing agent shown in Table 1 to form a paste, which was diluted by adding an appropriate amount of butyl calpitol.

The semiconductor porcelain is immersed in the above suspension, and the semiconductor porcelain 1 is
A diffusing agent was applied at a ratio of 15 to 30 cm per B, and then heat treated in air at 1,100 to 1,250°C for 1 hour to form an insulating layer at the grain boundaries of the semiconductor ceramic.

Furthermore, silver paste was applied to both sides of the semiconductor porcelain, and 80%
A semiconductor ceramic capacitor was produced by baking at 0°C for 30 minutes.

Regarding this semiconductor ceramic capacitor, the apparent dielectric constant (ε
), dielectric loss (tan δ) and insulation resistance (IR) were measured. The results are shown in Table 1. Note that ε and tan δ were measured under the condition of frequency IKIIz, and insulation resistance was measured by applying a DC voltage of 70 V/mm.

Table 1 1 0.5 B9.5 10.0 30,000
0.302 1.0 89.0 10.0 2B, 0
00 0.303 2.0 88.0 10.0 2
6,500 0.354 5.0 85.0 10.
0 25,500 0.505 10.0 Bo, 0
10.0 15.000 0.706 0.2 8
9.8 10.0 34,000 0.20? 25
．． 0 65.0 10.0 8,000 1.508
5.0 90.0 5.0 27,500 0.
309 5.0 45.0 50.0 25,000
0.4010 5.0 20.0 75.0 19
．． 500 0.70 In Table 1, Nos. 016 and 7 are comparative examples.

(Effects of the Invention) As can be seen from Table 1, the semiconductor ceramic capacitor obtained using the diffusing agent of the present invention has an effective dielectric constant of 15,
000 or more, tan δ is 0.7% or less, and insulation resistance is 70. It has excellent electrical characteristics of 3 x 10"0 cm or more when OV/mm is applied.

Claims (2)

[Claims] (1) A diffusing agent for grain boundary insulation of polycrystalline semiconductor ceramics, which mainly contains 0.5 to 10% by weight of iron oxide and 90 to 99.5% by weight of lead oxide and copper oxide. A diffusing agent for semiconductor ceramic capacitors, which is characterized by: (2) A grain boundary insulated semiconductor ceramic capacitor characterized by having an insulating layer formed of the diffusing agent according to claim 1.