JPH0496309A - Manufacture of surface reoxidation type semiconductor ceramic capacitor - Google Patents

Abstract

PURPOSE:To make it possible to mass produce large-capacity surface reoxide type semiconductor ceramic capacitors without causing a decrease in reliability by forming first and second nonreducing conductive paste layers so that an oxide layer occurs in a region in contact with a semiconductor ceramic substrate. CONSTITUTION:A carbon powder layer 2 containing metals is formed on one of the main surfaces of a semiconductor ceramic substrate 1. Next, nonreducing conductive paste is applied in such a manner as to cover the carbon powder layer 2 containing metals, forming a first conductive paste layer. This is dried, and a first electrode layer 3 is formed. Nonreducing conductive paste is applied on the other main surface of the semiconductor ceramic substrate 1, forming a second conductive paste layer. This is dried, and a second electrode layer 4 is formed. Next, a reoxidizing and baking operation is performed, forming a reoxide layer 5 and first and second electrode 4a, 5a. The reoxide layer 5 is formed during the heating operation. The surface of the semiconductor ceramic substrate 1 which is not covered with the first and second electrode layers 3, 4 is oxidized by oxygen in an oxidizing atmosphere.

Description

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

[Prior Art] When manufacturing a typical surface reoxidation type semiconductor ceramic capacitor, a molded body of ceramic material is sintered in the air (oxidizing atmosphere) and then reduced with N2 + H. A reduction treatment in an oxidizing atmosphere (a 2cc semiconductor substrate is obtained and then fired again in an oxidizing atmosphere to form a surface re-oxidation layer of about 10 to 20 μn on the surface of the semiconductor ceramic substrate), that is, a dielectric layer. A dielectric layer is formed 7, and a pair of metal electrodes are provided on the dielectric layer.

In this type of capacitor, the semiconductor ceramic part functions equivalently as an electrode, so 1. A first capacitance is obtained between one metal electrode and the semiconductor porcelain part, a second capacitance is obtained between the other metal electrode and the semiconductor porcelain part, and the first and second customers are connected in series. Connected. As a result, a significant increase in capacitance is not possible.

In order to solve the above-mentioned problems, a part of the surface re-oxidation layer is removed by polishing to expose the semiconductor porcelain part.
It has been proposed to provide one metal electrode here.

According to this, the thickness of the surface reoxidation layer is effectively reduced to 1/2, and a large capacity can be obtained.

Another method is to apply a paste of a non-reducing metal (e.g. silver) on top of the surface reoxidation layer to obtain one electrode, and a paste of a reducing metal (Z, etc.) to obtain the other electrode. There is a method of reducing the surface reoxidation layer under the reducible metal (base metal) by applying a paste of the base metal (base metal) and then baking it to achieve an electrode connection to the semiconductor porcelain part.

[Problems to be Solved by the Invention] Incidentally, the former method using polishing has a problem in that microcracks occur in the surface reoxidation layer and the semiconductor ceramic, resulting in a decrease in reliability. Of course, it is possible to perform polishing to prevent the occurrence of microcracks, but this will significantly reduce production efficiency and make mass production difficult.

If the latter method of coating and baking a reducing metal (base metal) is adopted, the reducing metal will come into contact with another element during mass production,
That part may be reduced and the insulation properties may be significantly reduced. Furthermore, reducing metals (base metals) are scattered in the baking furnace and adhere to themselves or other elements, causing insulation deterioration in that part and reducing reliability.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for mass-producing surface reoxidation type semiconductor ceramic capacitors with a large capacity without causing a decrease in reliability.

[Means for Solving the Problems] To achieve the above object, the present invention includes a step of forming a semiconductor ceramic substrate, and a layer of a mixture of carbon powder and metal powder on a specified region of the semiconductor ceramic substrate. and forming a first non-reducible conductive paste layer to cover this mixture layer; forming a second non-reducing conductive paste layer in the area where the mixture layer is formed, and an oxide layer is not formed in the area where the mixture layer is formed; manufacturing a surface reoxidation type semiconductor ceramic capacitor, comprising the step of heat-treating the first and second non-reducible conductive paste layers so that an oxidized layer is formed in the region in contact with the ceramic substrate; It is related to the method.

Note that it is desirable that the metal powder of the mixture layer has the same or good adhesion to the metal of the first non-reducible conductive paste layer.

In addition, the non-reducible conductive paste layer is made of powder of noble metal (non-reducible metal) such as silver and glass frit (metal oxide and/or
or a non-metallic oxide) and a vehicle.

[Function] The carbon powder used in the present invention has the function of inhibiting the formation of an oxidized layer. The metal powder mixed with the carbon powder contributes to the connection between the semiconductor ceramic substrate and the electrode based on the first non-reducible conductive paste layer. The first non-reducible conductive paste layer prevents the reducing mixture containing carbon from unnecessary adhesion to other capacitor elements and from scattering into the heating furnace.

[Example] Next, a method for manufacturing a surface reoxidation type semiconductor ceramic capacitor according to an example of the present invention will be described with reference to FIGS. 1 to 4.

First, high purity (over 99.5%) barium titanate (
94.5 mol% of BaTi03) and neodymium oxide (N
d203) 5 mol% and 0.5 mol% of manganese oxide (MnO) as a mineralizer were weighed and wet-mixed using a resin pot containing alumina balls.

Next, this mixture was dehydrated and dried, and then an organic binder was added thereto, and the mixture was molded into a disk having a diameter of 10 mm and a thickness of 0.5+ am under a pressure of 800 to 1000 kg/c12.

Next, this molded body was heated (in an oxidizing atmosphere) to 13
After obtaining a sintered body by firing at 00"C for 12 hours, it was cooled by -degree, and then the sintered body was subjected to a reduction treatment at 1000°C for 2 hours in a reducing atmosphere of 90% N + 10% H2.
A disk-shaped conductor ceramic substrate 1 shown in FIG. 1 was obtained.

Next, on one main surface L of the semiconductor ceramic substrate 1-, a conductive material made of organic binder and a vehicle is placed on a mixture of 1% by weight of non-reducible metal powder (Ag powder) and 99% by weight of carbon powder. paste (mixture a content: 50% normal temperature)
) was coated by a printing method (7) and dried to form a mixture layer, that is, a metal-containing carbon powder layer 2 as shown in FIG.

Next, add silver powder and glass frit (e.g. pb).

B C) A silver paste, that is, a non-reducible conductive, electrically conductive paste consisting of --8tO2 or a substance containing CaOlMgO or Na20 in place of this pbo) and a vehicle is coated with a metal-containing carbon powder layer as shown in FIG. Apply by printing method to cover 1. A first conductive paste layer 1-1 was formed, and this was dried to form a first electrode layer 3. Further, a silver paste (paste consisting of silver powder, glass frit, and vehicle), which is a non-reducible conductive paste, is applied on the other main surface of the semiconductor ceramic substrate 1 by a printing method (1). A second conductive paste layer was formed l-5; by drying this, a second electrode layer 4 was formed.

Next, the material shown in FIG. 3 was subjected to a reoxidation treatment and baking treatment at 800 DEG C. for 2 hours to form a reoxidation layer 5 and first and second electrodes 4a==53. During the second heat treatment, the carbon powder forms an oxidized layer on the surface of the semiconductor ceramic substrate 1.
7. On the other hand, the first and second electrode layers 3.4 based on non-reducible conductive paste contain glass frit, which prevents liquid phase diffusion or oxygen The re-oxidized layer 5 is formed by the diffusion of the oxidized material. Note that the surface of the semiconductor ceramic substrate 1 that is not covered with the first and first electrode layers 3.4 is oxidized based on oxygen in the oxidizing atmosphere.

Most of the carbon powder (reaction initiation temperature in the atmosphere: 500'C) in the metal-containing carbon powder layer 2 is oxidized and burned away, or the metal powder (silver) remains and becomes the electrode 2a, forming the semiconductor ceramic substrate. 1 and the first electrode 3a. The electrode phase 2a made of silver adheres well to the first electrode 3a (- made of silver mirror). Since it is covered with a first electrode layer 3 made of silver paste, it does not adhere to other capacitor elements.

When we measured the electrical characteristics of this capacitor at 20°C, we found that the capacitance was 673 nF/cm2, the tan δ was 2.8%, the insulation resistance (IR) was more than 1010 Ω, and the breakdown voltage was 0.9 kV DC. there were.

In addition to varying the amount of metal powder to carbon powder,
A capacitor was made using the same method as described above, and its electrical characteristics were similarly measured.The results were as follows.

(1) If the metal powder is 0% and the carbon powder paste is used as an irises, the first silver mirror is multilayered! 3 a-1' The conductor and the ceramic base 1 are in an open state, and a capacitor cannot be obtained.

(2) If the metal powder is 0.1 weight 96, the capacitance is 703 nF /c++12, t, an δ is 12.
5%, the insulation resistance was 1[-]10Ω or more, and the breakdown voltage was 0.1kV.

(3) If the metal powder is 10% by weight, the capacitance is 6
It was 75nF/cm2, tan δ was 2.4%, insulation resistance was 10”Ω or more, and breakdown voltage was 1.0kV.

(4) If the metal powder is 50% by weight, the capacitance is 6
It was 72nF/cI112, tan δ was 2.3%, insulation resistance was 1010Ω or more, and breakdown voltage was 0.9kV.

(5) If the metal powder is 90% by weight, the capacitance is 6
The resistance was 70nF/em2, tan δ was 2.4%, insulation resistance was 1010Ω or more, and breakdown voltage was 0.9kV.

(6) When the metal powder is 100% by weight (carbon powder is 0% by weight), the capacitance is 358nF/cs2, tanδ is 2.0%, insulation resistance is 1010Ω or more, and breakdown voltage is 1.2kV. Ta.

As a comparative example, a reoxidation layer is formed on the surface of the semiconductor ceramic substrate 1 shown in FIG. ) and a silver paste layer (
A capacitor was obtained by forming a non-reducing paste layer (non-reducing paste layer) and performing these baking treatments, and its characteristics were measured in the same manner as in the example. The capacitance was 690 nF/cIm2, tan δ was 3.9%, and insulation was high. The resistance was 107Ω and the breakdown voltage was 0.11kV.

As is clear from the above Examples and Comparative Examples, when the metal powder is in the range of 1 to 90% by weight, better electrical characteristics can be obtained than when the metal powder is 100% by weight or when Zn is used.

[Modifications] The present invention is not limited to the above-described embodiments, and, for example, the following modifications are possible.

(1) The metal powder to be mixed with the carbon powder is preferably silver, which is the same as the metal of the first electrode 3a, but it is a metal that has good adhesion to the first electrode 3a and has a melting point that does not melt at the baking temperature. It can be anything.

(2) It is also applicable to manufacturing cylindrical capacitors.

(3) The temperature of each heat treatment can be varied depending on the type of ceramic material and electrode material. For example, the temperature of the oxidation firing can be set to any temperature in the range of 1100 to 1400°C, the temperature of the reduction treatment can be set to any temperature in the range of 800 to 1200°C, and the temperature of the reoxidation treatment can be set to any temperature in the range of 700 to 1100°C.

[Effect of the invention] As is clear from the above, the present invention has the following effects.

(b) Since the reducing layer made of a mixture of carbon powder and metal powder is covered with a non-reducing metal layer and baked, reducing substances (carbon) are removed from unnecessary parts of the product itself or other products during the baking process. It will not adhere to the surface and cause characteristic deterioration.

(b) Since the metal powder is mixed into the carbon powder, good electrical connection can be achieved after the carbon is oxidized (burned).

[Brief explanation of the drawing]

1, 2, 3, and 4 are cross-sectional views showing the surface reoxidation type semiconductor ceramic capacitor according to the embodiment of the present invention in the order of manufacturing steps. DESCRIPTION OF SYMBOLS 1... Semiconductor ceramic base, 2... Metal-containing carbon powder layer, 3... First electrode layer, 4... Second electrode layer,
5... Oxidized layer. Agent Norihiro Takano Written amendment to the next procedure 0. Eh, procedural amendment 0. . 2. Name of the invention 2. Name of the invention Surface reoxidation type semiconductor (k. Connection with the porcelain 11-denza manufacturing method incident)

Claims (1)

[Scope of Claims] [1] A step of forming a semiconductor ceramic substrate, and forming a mixture layer of carbon powder and metal powder on a specified region of the semiconductor ceramic substrate, and forming a second layer so as to cover the mixture layer. forming a second non-reducible conductive paste layer on a specified region of the semiconductor ceramic substrate simultaneously with, before or after forming the first non-reducible conductive paste layer; forming a layer; an oxide layer is not formed in the region where the mixture layer is formed, but an oxide layer is formed in the region where the first and second non-reducible conductive paste layers are in contact with the semiconductor ceramic substrate; A method of manufacturing a surface reoxidation type semiconductor ceramic capacitor, comprising the step of heat-treating the first and second non-reducible conductive paste layers so that the first and second non-reducible conductive paste layers are formed.