JPH05295518A - Method for producing insulating material coated with alumina film - Google Patents

Abstract

PURPOSE:To reduce insulation defects such as pinholes and to enhance insulating property. CONSTITUTION:Stainless steel is coated with an alumina film and heat-treated at >=600 deg.C in a nonoxidizing atmosphere of Ar, N2, etc. The number of pinholes can be reduced to <=1/10 and >=1MOMEGA electric resistance can be obtd. in the case of >=80% of production.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrically insulating material in which an alumina film is formed on a metal substrate by a dry coating method.

[0002]

2. Description of the Related Art Electrically insulating plate-shaped materials are used in electronic substrates such as IC substrates, sensor substrates, solar cell substrates, and electrode substrates.
It has become an indispensable material for the electric industry.

Ceramic materials, glass materials, organic materials, etc. have been conventionally used for this insulating material. However, ceramic / glass materials have the drawback of poor strength and workability, and organic materials have gas releasing and heat resistance properties. It has the drawback of being inferior in sex.

As the insulating material, there is a metal material which is provided with an electric insulating property by coating a ceramic thin film on a metal substrate using a dry coating method.

As the metal substrate, a stainless steel plate is used in terms of chemical resistance and strength.

When a substrate is coated with a metal oxide such as Al ₂ O ₃ by dry coating, in particular, when coating is performed by sputtering, insulation defects such as pinholes are likely to occur in the insulating film, which causes a decrease in insulation. Has become.

The pinhole portion lacks an insulating film locally, and its size is several μm or less.

As a method of repairing the pinhole portion, there is a method of reducing the number of remaining pinholes by repeating the coating treatment twice or more (so-called multilayer coating).

[0009] However, the multi-layer coating has a drawback that productivity is deteriorated because the coating process is repeated a plurality of times.

The dry coating method in the present invention is a general term for a method of forming a thin film in a vacuum using plasma as a medium, such as ion plating, sputtering and plasma-CVD.

[0011]

DISCLOSURE OF THE INVENTION In the present invention, in the production of a material coated with an alumina film using a stainless steel plate as a substrate, insulation defects such as pinholes generated in the coating process are eliminated after the coating process. By performing the above, it is intended to form an insulating film with a small number of insulating defects by a single coating process and improve the productivity of an insulating material having excellent insulating properties.

[0012]

According to the method of the present invention, an alumina film is dry-coated on a stainless steel substrate and subsequently heat-treated at a temperature of 600 ° C. or higher in a non-oxidizing atmosphere.

[0013]

The substrate of the present invention uses stainless steel. As for the surface properties of the substrate, in order to ensure the insulating property of the film more reliably, it is desirable that there be little unevenness such as intergranular corrosion due to pickling and grinding marks.

When a film is formed on the substrate by sputtering, for example, Al ₂ O ₃ as a target with Ar, a coating film in which the insulating film is partially missing due to a pinhole or the like is formed as described above. This film is inferior in insulating property to a film without pinholes.

The inventors of the present invention have studied the measures for improving the insulating property, and found that heat treatment at a temperature of 600 ° C. or higher in a non-oxidizing gas atmosphere eliminates pinholes and improves the insulating property. It was

The following experiments were carried out in order to determine the proper heat treatment conditions.

SUS430BA was used as a substrate, and an alumina film was formed on this by sputtering under the same conditions. All film thicknesses are 0.9 μm. These insulating materials were heat-treated in an Ar atmosphere as a non-oxidizing atmosphere.

The number of pinholes was electrolytically plated in a copper sulfate solution, and the number of Cu deposited was counted with a microscope.

The resistance value of the insulating material is that aluminum (10
(mm square × 0.2 μm) was used as an electrode for vapor deposition, and then a tester stylus was placed on the electrode to measure the electric resistance value at 50 locations.

The rate of showing an electric resistance value of 1 MΩ or more in the measurement was defined as the pass rate (%). The relationship between the heat treatment conditions and the number of pinholes is shown in FIG.

The number of pinholes is reduced by the heat treatment at 600 ° C. or higher, and can be reduced to 1/10 or less as compared with the coating process. FIG. 2 shows the relationship between the heat treatment conditions and the acceptance rate.

Non-heat-treated materials and heat-treated materials at 500 ° C. or lower are
Although the pass rate is 40% or less, the pass rate increases from 600 ° C or higher, and in the material heat-treated at 600 ° C x 1 hr, pinholes decrease, and the pass rate increases to 80% or more. It can be seen that the insulating property is improved due to the decrease in the number.

From the above results, the heat treatment atmosphere is, for example, A
A non-oxidizing atmosphere such as r or N ₂ may be used, and the heat treatment temperature may be 600 ° C. or higher.

When the heat treatment temperature is increased, the diffusion rate is increased and the time for reducing the pinholes is shortened, so that it is desirable to perform the heat treatment at a high temperature, but it is preferably 900 ° C. or lower in consideration of heat resistance of the substrate.

[0025]

[Example] As the substrate, SUS430BA and SUS304BA having smooth surfaces were used. Using an RF magnetron sputtering device, an alumina insulating film was formed under the same conditions by using Al ₂ O ₃ as a target.

The coating conditions are as shown in Table 1 and the film thicknesses are all 0.9 μm. This electrically insulating material was heat-treated at a temperature of 300 to 800 ° C. in a non-oxidizing atmosphere.

Table 2 shows the number of pinholes and the electric resistance value after the heat treatment of this material. The number of pinholes is reduced and the insulation is improved at the heat treatment temperature of 600 ° C. or higher.

When heat-treated in an air atmosphere containing oxygen, the pass rate was lowered at 750 ° C. or higher due to substrate oxidation in the pinhole portion.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

[Table 4]

[0033]

According to the present invention, an insulating material having an excellent electrical insulating property can be provided by performing a film forming process once by performing a film forming process and then performing a heat treatment at 600 ° C. or more in a non-oxidizing atmosphere. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between heat treatment conditions and the number of pinholes.

FIG. 2 is a diagram showing a relationship between heat treatment conditions and a pass rate.

Claims (1)

[Claims] 1. A stainless steel substrate is dry-coated with an alumina film, and subsequently at 600 ° C. in a non-oxidizing atmosphere.
A method of manufacturing an insulating material coated with an alumina film, characterized by performing heat treatment at the above temperature.