JPH04110459A - Electrical insulating plate material - Google Patents

Abstract

PURPOSE:To produce the plate material without any film defect such as a pinhole and excellent in insulation performance by reducing the inclusion on the surface of a substrate at the time of dry-coating the stainless steel substrate with a ceramic insulating thin film. CONSTITUTION:The intrusion of oxygen, etc., into steel is controlled by vacuum refining, and the number of inclusions is reduced in the stainless steel sheet. The stainless steel sheet thus obtained is bright-annealed and then specularly polished to obtain a substrate. The substrate is dry-coated with a ceramic insulating film by sputtering, ion plating, etc., to obtain a stainless steel substrate insulating material excellent in insulation performance. Concretely, a leakage current is reduced to <=10<-10>A when the number of the inclusions >=1mum long on the stainless steel substrate surface is controlled to <=100 per square millimeter.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrically insulating plate-like material in which a ceramic thin film is formed on a metal substrate by a dry coating method.

BACKGROUND OF THE INVENTION Electrically insulating plate-like materials are used for IC substrates, solar cell substrates, etc., and are indispensable materials for the electrical and information industries. Furthermore, in elements such as capacitors and electrostatic actuators that require properties other than insulation, electrical insulation is one of the essential properties in addition to their inherent properties.

Conventionally, ceramic materials and organic materials have been used as this insulating material, but old ceramic materials lack strength or workability, and organic materials have drawbacks such as poor heat resistance. However, at present, no alternative material has been found.

An example of an insulating material is a metal material whose surface is coated with a ceramic thin film using a dry coating method to provide electrical insulation. This metal material has a certain degree of workability, excellent heat resistance and strength, and is inexpensive. However, from the standpoint of chemical resistance, strength, etc., it is best to use a stainless steel plate as the metal material for the substrate.

The dry coating method is a general term for a method of forming a thin film in a high vacuum, and is widely used as a method for forming an insulating film on a silicon wafer when manufacturing an LSI (7).

Problems to be Solved by the Invention When a stainless steel plate is used as a substrate, its surface is not smooth due to rolling defects, inclusions, unevenness, etc., and therefore the film formed thereon is not smooth. The film is not uniform, and there are many physical film defects such as pinholes, and many parts that are not physically defective but have weak electrical insulation.

For this reason, the material forming the ceramic thin film on the surface of the steer 1/S steel plate generally does not have good insulation properties, despite the presence of an insulating film on the surface. Therefore, in order to improve the insulation properties of the electrically insulating plate material used as the substrate on the stainless steel substrate, it is necessary to reduce film defects and electrical weak points as much as possible.

The object of the present invention is to provide an electrically insulating plate-like material using a steered steel plate as a substrate, which has very few film defects and electrical weak points.

Means and Effects for Solving the Problems Conventionally, as a method for reducing film defects in an insulating film, there are many documents in which attempts have been made to improve the evaporation equipment and evaporation conditions during film formation. However, there is no knowledge that film defects can be reduced by improving the substrate. As a result of repeated inspections of substrates, the present inventors have found that it is effective to reduce substrate surface defects. That is, the self-healing method (Werner Kern,
e Technology Mar, p35-42
(1974)), etc., are often located above substrate defects, and substrate surface defects play an important role in causing film defects.

(Mirror polishing method is considered as a method to reduce plate surface defects, and in fact, the insulation properties of the abrasive material are considerably better than those before polishing (stainless steel/bright annealed material).However,
The production cost of mirror polishing materials is very high - [2.Inclusions present in stainless steel are difficult to polish compared to Ifj materials and remain as protrusions, which become the starting point of insulation defects, so even if this material is used, The electrical insulation property does not reach the level of 1/bel that meets market requirements. Therefore, by reducing inclusions that become protrusions during polishing, a material with excellent electrical insulation properties can be obtained.

The gist of the present invention is as follows.

(1) In an electrically insulating plate-like material in which a ceramic thin film is formed on a stainless steel substrate by a dry coating method, the number of inclusions on the substrate is 1 g on the surface of the cold-rolled plate.
An electrically insulating plate-like material characterized in that the above-mentioned materials are made of a material having not more than 100 pieces per 1″f-side millimeter.

(2) The electrically insulating plate material according to claim 1, wherein the dry coating method is sputtering, ion plating, or plasma CVD.

The present invention will be explained in detail below.

One way to reduce inclusions is to suppress the incorporation of oxygen, etc. into the steel by refining by vacuum melting.In fact, when electron beam refining, which is a type of vacuum melting method, is used, the oxygen in the steel is removed in a vacuum. It is possible to produce ultra-1+'4-clean steel with a very small number of inclusions, less than 10% of normal inclusions.

Using this, a stainless steel substrate insulating material with good insulation properties can be obtained by forming an insulating film on a substrate obtained by bright annealing and mirror polishing a material with a reduced number of inclusions. Specifically, as in Example 1, 1μ
The number of inclusions with a length of m or more is 10 per square millimeter.
When it becomes less than 0, the leakage current becomes less than 1O-10A,
Market demand reaches 1/bell.

The reason for using bright annealed materials is that other pickling materials have very large surface irregularities due to grain boundaries and grinding, making them unsuitable for use as mirror-polished substrates. Film formation processes include dry coating sputtering, ion plating, and plasma CVD.
etc. are used. Note that the insulating film is not limited to one layer, for example,
5in) (+ M 203 etc. can be made into a composite layer of 2 or more layers.Compared with a single layer film, the ceramic thin film made of a composite layer has the effect of filling the defects in the underlying film. Therefore, the insulation properties are improved.

Examples Example 1 Using 5US430 as a substrate, bright annealing and mirror polishing were performed using a material that was refined using an electron beam melting method to reduce inclusions, or a material that was normally refined using an electric furnace. Table 1 shows typical values of the components of the substrate and the number of inclusions. An M2O3 insulating film was formed on this under the same conditions. The coating conditions are as shown in Table 2, and all thicknesses are O, J.
It is pm.

The leakage current of each material thus prepared at a DC voltage of 50 V was measured. The measurement method is to use an A1 electrode (
In the measurement system, a stainless steel electrode with a diameter of 2φ was placed on a piece of material deposited with a 5+*m square x 0.17Lm) with a load of 50g. are being measured. Figure 1 shows the leakage current measurement results. As the number of inclusions decreases, the insulation improves, and I
The number of inclusions with a length of Bm or more is 1 per square millimeter.
If it is less than 00, the insulation (leakage current) is 1.0-10.
A or less, reaching the market demand of 1/bell. The length of the inclusions was in the range of IBm to 15m.

Example 2 As a substrate, the number of inclusions is determined by the length I on the surface of the rolled plate.
Two types of coating treatments were performed using 5O3430 bright annealed material with less than 100 particles per square millimeter of less than gm. j is M2O under the same conditions as Example 1.
3 films were coated with 0.8 gm, and the other was coated with 0.4 gm of Ag2O3 under the same conditions, and then 5iO) (0.4 gm) was coated using plasma CVD under the conditions shown in Table 2.
μm coated. The second IN is the leakage power value at a DC voltage of 50V. AQ7 even with the same film thickness
It can be seen that the 03 +5 iox two-layer film has better insulation properties.

(Hereinafter, blank spaces) Effects of the Invention According to the present invention, it is possible to provide a plate-like material having excellent electrical insulation properties using a stainless steel plate as a substrate.

[Brief explanation of drawings]

Figure 1 shows the insulation properties (leakage current) of an insulating material made of stainless steel refined using electron beam melting and a material formed in an ordinary electric furnace, and Figure 2 shows the insulation properties (leakage current) of the same stainless steel. M2O3 single layer film and 5iO)(+/I
2032 is a diagram showing the difference in insulation properties (leakage current) of the insulating materials coated with the JJ2032 layer film. FIG.

Claims (2)

[Claims] (1) In an electrically insulating plate-like material in which a ceramic thin film is formed on a stainless steel substrate by a dry coating method, the number of inclusions on the substrate is 1 μm in length on the surface of the cold-rolled plate.
An electrically insulating plate-like material characterized by being made of a material having 100 or less of the above elements per square millimeter. (2) The electrically insulating plate material according to claim 1, wherein the dry coating method is sputtering, ion plating, or plasma CVD.