JPH0636622A - Insulated wire - Google Patents

Abstract

PURPOSE:To eliminate the deterioration under high temperature and improve the flexibility by covering a copper conductor material with a tantalum layer and an oxidation-resistant metal layer, and further covering the material with a ceramic layer formed via the heat treatment of ceramic precursor solution. CONSTITUTION:A tantalum layer 2 is provided in such a way as covering a conductor material of copper or copper alloy, and an oxidation-resistant metal layer 3 such as Ni and Cr is formed to cover the layer 2. Furthermore, an insulation ceramic layer 4 is formed in such a way as covering the layer 3 through the heat treatment of ceramic precursor solution, thereby forming an insulated wire. Also, ceramic particulates are dispersed in the ceramic precursor solution. Sol formed via the sol-gel method, the organic acid salt of metal, polysilazane, polycarbosilazane or the like is available as a ceramic precursor. This insulated wire has no glass absorption source.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulated electric wire used as an electric wire for wiring, an electric wire for winding, etc. in high vacuum equipment, equipment used at high temperature and the like.

[0002]

2. Description of the Related Art Insulated wires are sometimes used in equipment such as heating equipment and fire alarms that require safety under high temperatures. The insulated wire is also used in an environment where the vehicle is heated to a high temperature. As such an insulated wire, an insulated wire in which a conductor is coated with a heat-resistant organic resin such as polyimide or fluororesin has been conventionally known.

When used in an application where high heat resistance is required or in an environment where a high degree of vacuum is required, organic coating alone is not sufficient in terms of heat resistance and gas releasing property. Therefore, the conductor is passed through an insulated wire of the type in which the conductor is passed through a ceramic insulator tube or a tube made of a heat-resistant alloy made of stainless alloy or the like, and metal oxide fine particles such as magnesium oxide are filled between them for insulation. A type of MI cable (Mineral Insulated Cable) has been used for such an application.

As an insulated wire used for applications requiring heat resistance and flexibility, there is a glass braided insulated wire in which glass fiber is woven and used as an insulating member.

Further, as an insulated wire used for applications requiring heat resistance, Japanese Patent Laid-Open No. 55-043746 and Fujikura Technique (April 1989, No. 76, 51-51)
There is a ceramized electric wire disclosed on page 56). This is because an insulating layer made of a mixture of silicon resin and ceramic powder is formed on a wire made of nickel-plated copper, platinum, silver, or stainless steel, and even if the silicon resin is heated above a temperature at which it can be thermally decomposed, It is a ceramized electric wire that retains insulation by remaining ceramic powder after decomposition.

[0006]

In the insulated wire coated with the organic resin as described above, the maximum temperature at which the insulating property can be maintained is about 300 ° C. at most. Therefore, 30
Such an organic insulation-coated electric wire cannot be used in an application where guarantee of insulation is required at a high temperature of 0 ° C or higher.

[0007] Further, the insulated wire whose heat resistance is enhanced by using a ceramic insulator tube has drawbacks such as poor flexibility. Since the MI cable is composed of a heat resistant alloy tube and a conductor, the outer diameter of the cable becomes large. Therefore, the MI cable has a relatively large cross section with respect to the allowable power amount. Also, MI
The outer layer of the cable has good flexibility because it is made of a heat-resistant alloy tube, but in order to use it as a wire for winding that is wound into a coil on a bobbin, it is made of a heat-resistant alloy. It is necessary to bend the tube with a predetermined curvature. At this time, it is difficult to bend the heat-resistant alloy tube. Further, when the MI cable is wound into a coil, it is difficult to improve the winding density because the tube of the outer layer is thicker than the conductor.

Further, when a glass braided insulated wire having flexibility and heat resistance is used, when the glass braided insulated wire is arranged in a predetermined shape according to the application, there is a problem that dust proof of glass occurs from the glass fiber. This glass dustproof can be a source of adsorption of glass. Therefore, when the glass braided insulated wire is used in an environment where a high degree of vacuum is required, it is impossible to maintain a high degree of vacuum due to the glass adsorption source provided by the glass dustproof.

On the other hand, conventionally, as an insulated wire having good heat resistance, electric insulation and heat dissipation, there is a so-called alumite wire obtained by anodizing an aluminum or aluminum alloy wire.

In this alumite wire, the wire material is limited to one kind of aluminum. In consideration of heat resistance, the melting point of aluminum is 660 ° C, so the upper limit of heat resistance is specified by itself, and mechanical strength decreases even at temperatures lower than 660 ° C, and the limit of use is about 500 ° C. ing.

Further, in the ceramized electric wire, the coating after the resin is pyrolyzed is in the form of particles and is liable to generate dust, and cannot be used in a vacuum.

From the viewpoint of high electrical conductivity, ease of soldering, strength and cost as the conductor, copper or copper alloy is most suitable. However, copper has a low resistance to an oxidant, and is oxidized even at room temperature in the atmosphere, or turns into a basic carbonate patina. Furthermore, in a high-temperature environment, oxidation progresses, making it impossible to use as a conductor. In order to overcome this problem, a nickel-plated copper wire having a copper surface plated with nickel has been conventionally used. However, although the nickel-plated copper wire has no particular problem when used at about 400 ° C., at higher temperatures, the diffusion and alloying of copper and nickel proceed, and the conductivity of the conductor decreases.
For example, after 2000 hours at 600 ° C., the conductivity of the conductor decreases by about 20% IACS.

An object of the present invention is to solve the above-mentioned conventional problems and to provide an insulated wire having the following characteristics.

(A) No alteration in a high temperature environment (b) Excellent flexibility (c) No glass adsorption source

[0015]

An insulated wire according to the present invention comprises a core material made of copper or a copper alloy, a tantalum layer provided so as to cover the core material, and an oxidation resistant metal provided so as to cover the tantalum layer. And an insulating ceramic layer formed so as to cover the oxidation resistant metal layer by heat treatment of a ceramic precursor solution.

As the oxidation resistant metal layer, nickel, chromium, aluminum, platinum, silver, nickel alloy, chromium alloy, aluminum alloy, platinum alloy, silver alloy or stainless steel can be used.

As the insulating ceramic layer, silica,
Alumina, zirconia, silicon nitride, silicon carbide, aluminum nitride, partially stabilized zirconia, and the like can be used.

Examples of the ceramic precursor for forming the insulating ceramic layer include a sol formed by a sol-gel method, a metal organic acid salt, polysilazane, polycarbosilane, and polyborosiloxane.

When a thick insulating ceramic layer is required, fine ceramic particles may be dispersed in the ceramic precursor solution.

Further, for applications requiring a high degree of flexibility, a high degree of adhesion is required so that the insulating ceramic layer does not fall off even during severe bending. In order to form such an insulating ceramics layer, it is preferable to form a chromium oxide containing layer by electrolytic plating on the surface of the oxidation resistant metal layer, for example. When the oxidation resistant metal layer is aluminum or an aluminum alloy, it is preferable to anodize the surface.

FIG. 1 is a sectional view showing an embodiment according to the present invention. Referring to FIG. 1, a tantalum layer 2 is provided around a copper wire core material 1. An oxidation resistant metal layer 3 is provided around the tantalum layer 2, and an insulating ceramic layer 4 is provided around the oxidation resistant metal layer 3.

[0022]

In the present invention, the substance which comes into direct contact with the core material made of copper or copper alloy is tantalum. Tantalum diffuses very slowly into copper and copper alloys, even at high temperatures, so that little alloying occurs. Further, it also effectively acts as a barrier to prevent the diffusion of other substances into copper. Although tantalum is excellent in such an effect, it does not have large resistance to oxidation at high temperatures. In the present invention, since the surface of such a tantalum layer which is easily oxidized is covered with an oxidation resistant metal layer such as nickel, the tantalum layer is prevented from being oxidized.

Further, since the insulating ceramic layer provided so as to cover the oxidation resistant metal layer in the present invention is formed by heating the ceramic precursor solution, it is a smooth thin film and is flexible. It has excellent properties and does not have gas adsorption. According to the present invention, in order to form the insulating ceramics layer, for example, a step of applying a ceramics precursor solution and heating it can be repeated a plurality of times. As the insulating ceramics, various materials can be selected according to the application.

In the present invention, the insulating ceramic layer can be obtained by applying a ceramic precursor solution and subjecting it to heat treatment.

As the ceramics precursor, a sol prepared by the sol-gel method can be used. A metal organic polymer having an alkoxide group, a hydroxy group, a metaxane bond, and the like, which is prepared by a hydrolysis reaction and a dehydration condensation reaction of a compound having a hydrolyzable organic group such as a metal alkoxide, is obtained. The body. As the metal alkoxide, those containing an organic group such as ethoxide, procoxide and butoxide are used.

The solution containing the ceramics precursor also includes a solution prepared by mixing and dissolving a metal organic compound (Metal-organic Compounds) in an appropriate organic solvent. Since what is used in this invention is one that thermally decomposes this metal organic compound to form a metal oxide film, it is limited to those whose thermal decomposition temperature at atmospheric pressure is lower than the boiling point of the metal organic compound. It For example, SiO ₂ , Al ₂ O ₃ , Z
Examples include rO ₂ , TiO ₂ , and MgO. As the organic acid salt, metal salts with naphthenic acid, caprylic acid, stearic acid, and octylic acid are preferable.

The oxide insulating layer formed by the thermal decomposition method of the organic acid salt is a ceramicized oxide. This oxide may be formed by heat treatment in an atmosphere of an oxygen stream in the heat treatment of the precursor solution of the metal oxide.

Examples of the nitride and carbide insulating ceramic layers include silicon carbide, silicon nitride, and aluminum nitride.

When silicon nitride is formed, it is preferable to use polysilazane as a ceramic precursor, and when aluminum nitride is formed, it is preferable to use a polymer of alkylaminoaluminum.

The reason for this is that it has been found that when the ceramics are transformed into ceramics by heating, the shrinkage rate is small, and thus it is difficult for defects such as cracks to occur in the ceramics film produced.

The carbide insulating layer is formed by a thermal decomposition method of polycarbosilane or polyborosiloxane. The heat treatment of polycarbosilane and polyborosiloxane may be performed under an inert atmosphere in an argon or nitrogen stream. The insulating layer obtained by such heat treatment is a ceramicized carbide. When heating is performed in the atmosphere, a part or most of the carbide may be oxidized to form a mixture of oxide and oxide.

In this way, the ceramicized carbide insulating layer exhibits excellent heat insulating properties even at high temperatures of 1000 ° C. or higher.

Furthermore, for applications requiring a high degree of flexibility, strong adhesion is required so that the insulating ceramic layer does not fall off even during severe bending. In such a case, it is preferable to form the chromium oxide containing layer around the oxidation resistant metal layer by electroplating. Also,
When the oxidation resistant metal layer is aluminum or an aluminum alloy, it is preferable to anodize this surface.

When the chromium oxide-containing layer is formed by the electroplating method, an aqueous solution of chromic acid to which a small amount of organic acid is added is used. Generally, as an electrolytic bath used when performing chrome plating, a Sargent bath mainly containing chromic acid and sulfuric acid is known, but it is different from this bath in the following points.

That is, it has a function of dissolving the mineral acid mixed in the electrolytic bath and the chromium oxide produced on the plating surface during electrolytic plating. Therefore, a glossy metallic chrome layer is plated. In the present invention, this chromium oxide is preferentially plated. Further, a thin film of insulating ceramics is formed on the outer surface of the layer mainly containing chromium oxide by heat treatment of a precursor solution of metal nitride. In order to increase the adhesion of this thin film, it is preferable that the surface of the layer mainly containing chromium oxide is rough. Therefore, the current density and the like are different from those of the bright plating that is generally performed.

In bright plating, depending on the processing temperature, 1
A current density of 0-60 A / dm ² is used, but in the present invention, a current density of 100-200 A / dm ² is used to obtain a rough surface.

Since the method of using a solution is used for forming the insulating layer, the linear substrate can be coated at high speed with simple equipment.

[0038]

【Example】

Example 1 A wire having a structure in which a tantalum layer was provided around a core material of oxygen-free copper and a nickel layer was provided outside the core material was prepared by a pipe fitting method. The wire diameter is 0.5 mm and the nickel layer is 25
The thickness of the tantalum layer was 10 μm. The initial conductivity was 79% IACS.

Under a nitrogen stream, 1,1,1,3,3,3-
Hexamethyldisilazane 40g and trichlorosilane 1
5 g were mixed and stirred at 70 ° C. for 5 hours. Furthermore, 16
Distillation was performed at 0 ° C. to remove by-products by distillation. Next, by-products were completely removed by vacuum distillation at 120 ° C. and 5 mmHg to obtain 5 g of polysilazane. The by-products mentioned here are mainly trimethylchlorosilane and oligosilazane. Polysilazane was diluted 5 times with toluene to obtain a coating solution containing a ceramics precursor.

The wire rod manufactured by the above fitting method was immersed in this coating solution. The wire rod was taken out and heated in a nitrogen atmosphere at a temperature of 700 ° C. for 10 minutes to dry the coating solution to grow a ceramic film on the surface. The steps of applying the solution and heating were repeated 10 times to form an insulating ceramic layer.

A 30 cm-long sample was taken from the insulated electric wire thus obtained. A platinum foil with a thickness of 0.02 mm was closely wound around each of four points of this sample with a length of 10 mm at intervals of about 50 mm. When an alternating voltage of 60 Hz was applied between the conductor and the metal foil, dielectric breakdown occurred at 500V. Further, when the insulated electric wire was bent, the insulating property was maintained even when bent to a diameter of 10 mm.

Further, this insulated wire is heated at 600 ° C. for 200 times.
After heating for 0 hour, a 30 cm long sample was taken. Similarly to the above, a platinum foil with a thickness of 0.02 mm was applied to the four locations of the sample at intervals of about 50 mm.
Wound 0 mm length, 60H between conductor and metal foil
When an alternating voltage of z was applied, dielectric breakdown occurred at 500V. Furthermore, as a result of measuring the electric conductivity, 79% IAGS was maintained.

Example 2 Polyborodiphenylsilo
_{xane) (-SiPh 2 -O-BO} 2 -) _n-dissolved in toluene and 40 wt% of the solution. Furthermore, 3 g of silicon carbide powder (nominal particle size 0.50 μm) was mixed to obtain a coating solution. A wire produced by the same fitting method as in Example 1 was
It was immersed in this coating solution. The temperature is 50
Heated at 0 ° C. for 10 minutes. The steps of dip coating and heating were repeated 5 times to form an insulating ceramic layer.

A sample having a length of 30 cm was taken from the obtained insulated wire. About 0.05mm thick platinum foil
The sample was tightly wound at four positions with a length of about 10 mm at intervals of 0 mm. 800 when AC voltage of 60Hz is applied between conductor and metal foil
Dielectric breakdown with V. Further, when the insulated electric wire was bent, the insulating property was maintained even when bent to a diameter of 50 mm.

Furthermore, this insulated wire is heated at 600 ° C. for 200 hours.
After heating for 0 hour, a 30 cm long sample was taken. Platinum foil with a thickness of 0.02 mm is placed at about 50 mm intervals at four locations on this sample, each with a thickness of about 10 mm.
Wrapped closely in the length of. 60 between conductor and metal foil
When an alternating voltage of Hz was applied, dielectric breakdown occurred at 800V. Furthermore, as a result of measuring the conductivity, 79% IACS
Maintained.

Example 3 A wire having a structure in which a tantalum layer was formed around an oxygen-free copper core material, and a copper layer was further formed around the tantalum layer,
It was prepared by the fitting method. This was wire-drawn and reduced in diameter, and then the outermost copper was dissolved and removed with nitric acid. This wire was plated with chromium in a thickness of 3 μm using a Sargent bath. As a result, a wire having a wire diameter of 0.45 mm and a tantalum layer thickness of 10 μm was obtained. The initial conductivity of this wire was 91% IACS.

A chromium oxide containing layer was formed as follows so as to cover this wire. An electroplating solution having a concentration of chromic acid 200 g / l, ammonium metavanadate 20 g / l and acetic acid 6.5 g / l was used.
The plating conditions were such that the conductor was used as a cathode, the bath temperature was 50 ° C., the current density was 150 A / dm ² , and the treatment time was 2 minutes, and chrome plating was performed. In this way, a chromium oxide-containing layer was formed on the outer surface with a thickness of about 1 μm.

To an n-butanol solution of 10 mol% zirconium butoxide and 20 mol% ethanolamine, 2.1 times mol of water was added to the zirconium alkoxide by diluting diethylene glycol monomethyl ethanol, and the mixture was stirred at 110 ° C. for 2 hours. Then, a coating solution was prepared.

The wire having the chromium oxide-containing layer formed thereon was dipped in this coating solution. Pull this wire up to 1 at 800 ° C
Heat for 0 minutes. 10 steps of this dip coating and heating
The insulating ceramics layer was formed by repeating the process.

A 30 cm-long sample was taken from the obtained insulated wire. About 0.05mm thick platinum foil
The sample was wound around four places with a length of about 10 mm at intervals of 0 mm. 6 between conductor and metal foil
When an AC voltage of 0 Hz was applied, dielectric breakdown occurred at 1000V. When the insulated wire is bent, the diameter is 20m.
The insulation was maintained even when bent to a diameter of m.

Further, this insulated wire is heated at 600 ° C. for 200 times.
After heating for 0 hour, a 30 cm long sample was taken. A platinum foil having a thickness of 0.02 mm was wound around four points of the sample at intervals of about 50 mm and each having a length of about 10 mm. When an alternating voltage of 60 Hz was applied between the conductor and the metal foil, dielectric breakdown occurred at 1000V.
Furthermore, as a result of measuring the electric conductivity, 91% IACS was maintained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1 core material 2 tantalum layer 3 oxidation resistant metal layer 4 insulating ceramic layer

Claims (4)

[Claims] 1. A core material made of copper or a copper alloy, a tantalum layer provided so as to cover the core material, an oxidation resistant metal layer provided so as to cover the tantalum layer, and a ceramic precursor solution. An insulated wire, comprising: an insulating ceramic layer formed so as to cover the oxidation resistant metal layer by heat treatment. 2. The insulated wire according to claim 1, wherein ceramics fine particles are dispersed in the ceramics precursor solution. 3. The insulated wire according to claim 1, wherein a chromium oxide-containing layer is formed on the surface of the oxidation resistant metal layer by electrolytic plating. 4. The insulated wire according to claim 1, wherein when the oxidation resistant metal layer is aluminum or an aluminum alloy, the surface is anodized.