JPS61165909A - Refractory covered article - Google Patents

Abstract

An article of manufacture, for example an electrical conductor, as on the surface of a metal part an adherent, dense refractory keying layer and, on the keying layer a further electrically insulating refractory layer that has been formed by a faster deposition method. The keying layer is preferably formed by a vacuum deposition processing, e.g. sputtering evaporation, ionplating or chemical vapour deposition, and the further refractory layer is preferably formed by a sol-gel deposition method, plasma ashing method, a solution coating method or a plasma spraying method. The articles are particularly suitable for high temperature wires.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to articles formed from metals, such as copper or copper alloys, and in particular to such articles which may be exposed to high temperatures.

PRIOR ART One area in which the present invention is particularly applicable is electrical wires and cables. For example, the so-called "wires" used in electromagnetic windings of transformers, motors and other devices are exposed to severe temperature changes under overload conditions during use. Furthermore, in certain areas where cables are used, for example in military, underwater or offshore applications, it is desirable to use cables that can be exposed to fire and function for a period of time without damage. Previously proposed circuit and signal integrity cables have their respective conductors bonded together by mica tape or by large volumes of filler material or silicone, or by a combination thereof, to prevent short circuits in the event of exposure to fire. There is a principle that there must be a separation between
Traditional cables are quite heavy or large or heavy and large.

SUMMARY OF THE INVENTION The present invention is an article of manufacture having at least a portion formed of a metal, a dense refractory keying layer deposited on the surface of the portion, and a relatively fast deposition method on the keying layer. An article having another electrically insulating refractory layer formed by the present invention is provided.

The phrase "relatively fast deposition method" means that the deposition rate of the other refractory layer, measured, for example, in μm thickness per unit time, is greater than the deposition rate of the refractory keying layer. The properties of refractory coatings are known to depend significantly on the method by which they are formed or deposited on the substrate, and generally the method with the lowest deposition rate is fairly dense (i.e., non-porous). ) and form a refractory layer with high adhesion to metals. The refractory keying layer is formed by a vacuum deposition method, such as sputtering, evaporation, ion plating or chemical vapor deposition.
Other refractory layers have been formed by sol-gel deposition, plasma unwinding, solution coating, thermal spraying or other rapid vacuum deposition methods.

According to the invention, a refractory coating is provided that is fairly thin and has good electrical insulation properties, but also exhibits very good adhesion to the underlying metal, even when exposed to mechanical or thermal stress. It is possible to form an article having a

Preferably, the refractory keying layer is substantially free of impurities, ie, the refractory keying layer contains only the intended materials to satisfy the intended function and does not contain any materials produced during the manufacturing process. An important feature of a refractory keying layer is good control of the composition to optimize the high temperature performance of the article. The composition is entirely inorganic, as is the case with many mica-filled or glass-filled silicone resin systems, so that no conversion occurs when subjected to normal or emergency high temperature use. The composition is also improved by eliminating the use of a polymeric binder to support the inorganic material that is integrated by the combustion process to form the inorganic insulation. Similarly, articles in which the refractory coating is formed by electrochemical conversion of a metal layer, e.g. by electrodeposition of an aluminum layer, are not included in the invention; such layers are typically porous and Yes, ionic residues in the electrolyte,
For example, it is heavily contaminated with sulfates from the sulfuric acid electrodeposition process.

It is preferred that the metal from which part of the article is formed has a melting point of at least 800°C, more preferably at least 900°C, especially at least 1000°C. The invention is particularly advantageous for articles where the metal is copper or copper alloys, such as wires and cables that must be able to function at high temperatures for extended periods of time without damage, such as circuit and signal integrity cables and magnet wires. The invention will now be described with reference to wires and cables.

If the article comprises an electrical wire or cable, the conductor may be a single solid conductor, or have 7.19 or 37 strands, such that the underlying copper forms the conductor of the cable. It may also be a twisted conductor in which the individual strands are joined together to preferably form a bundle.

When twisting conductors, it is preferable to coat bundles rather than individual strands, i.e. the refractory coating is applied around the individual strands so that substantially only the outer surface of the outermost strand is coated. Preferably, it spreads around the bundle without any problems.

This form of conductor has the advantage that electrical contact between the strands is maintained, the bundle size is kept to a minimum (as the coating thickness is a significant proportion of the strand size in micro-dimension conductors), and the bulk The advantage is that the entire surface of the strands in the strand surface and in the central region of the conductor is not coated with a refractory coating, thereby helping to form a good electrical connection (eg, a crimp connection) to the conductor.

The advantage of forming circuit or signal integrity cables from twisted conductors according to the invention is that they are very flexible compared to other signal and circuit integrity cables, especially when using twisted conductors. The possibility of bending the wire in very tight bends (small bend radii) without deleterious effects depends in part on the fact that the integrity-providing layer is thinner than in other signal and circuit integrity cables. However, if the conductor is a stranded conductor, it can be bent in extremely tight bends without undue stress on the surface of the strands.

This is because the strands are arranged in regular hexagonal packing at the apex of the bend, so that the uncovered areas of the strands are exposed to the eye. Even if the uncoated conductor is exposed when the wire conductor is bent, no electrical contact will occur between adjacent stranded conductors. In this case, the shape of the stranded conductor is not cylindrical, but a hexagonal shape that rotates with the length of the conductor, and adjacent stranded conductors touch each other only at some points along their length, so , integrity is maintained. These points are usually provided by the outwardly directed portion of the strand surface in the outer layer of the conductor. It is at these contact points that a fire-resistant coating is always applied.

Preferably, the thickness of the further refractory layer is at least 0.5, more preferably at least 1, especially at least 2 μm, while at most 15, especially at most 610 μm, most preferably the thickness is determined by the specific operating conditions. About 5μ depending on
It is m. The exact thickness preferred depends on a number of factors, including the type of layer and the voltage rating of the wire; circuit protection cables typically require somewhat thicker jacketing than signal protection cables, and may be on the order of 15 μm or more. The lower limit of coating thickness is usually determined by the required voltage specification of the wire, while the upper limit is usually determined by the time and therefore cost of the coating operation.

The thickness of the refractory keying layer is typically less than the thickness of another refractory layer, preferably no greater than 0.5 μm;
Most preferably no greater than 0.3 μm. However, it is usually at least 0.1μ skin.

To maximize adhesion between a refractory keying layer and another refractory layer, it is preferred that they both have a similar designated chemical composition, ie, they both have a similar general chemical formula. However, as explained below, one or both of these layers may differ from the stoichiometry.

To further improve the high temperature properties of the article, particularly when the underlying metal is copper or a copper alloy, the article may include a metal interlayer located between the metal forming part of the article and the refractory keying layer. It is preferable to have. The metal forming the intermediate layer is one that forms a good bond between the underlying metal and the refractory keying layer, as described in European Patent Application No. 85304871.8 by the applicant. Preferably it is a metal that acts as a shield against the diffusion of oxygen and/or copper, or that acts to reduce stress on the refractory layer due to substrate distortion resulting from mechanical and thermal stress. Preferred metal interlayers include those formed from aluminum, titanium, tantalum, chromium, manganese, silicon or nickel, although other metals may be used. Examples of articles using them are described in European Patent Application No. 85304872.6 by the applicant.

In the case of electrical devices, the refractory layer may provide all the electrical insulation or one or more additional insulation layers may be provided thereon. The additional insulating layer may be inorganic or organic, or a mixed inorganic and organic layer may be provided.

For the wires of the present invention, the polymer insulation is used to provide additional insulation to the conductor during normal use conditions, as well as to provide desired dielectric and other properties (e.g., mechanical properties, abrasion resistance,
Color components are also provided to give wires a different color (e.g., potential). However, an important advantage of the present invention is that a significant proportion or all of the used insulation properties are provided by the fire-resistant coating;
The electrical properties of polymer insulation are less important than in other wire constructions where polymer insulation provides the only insulation between conductors. Among the known polymeric materials used for electrical insulation, polyethylene has the most suitable electrical properties, but is highly flammable and has poor mechanical properties. Attempts at flame-retardant polyethylene have either required halogenated flame retardants, which inherently generate corrosive and toxic hydrogen halides when exposed to fire, or have affected the electrical and mechanical properties of the polymer. They also require fairly large amounts of flame retardants without halogens, which also have harmful effects.

Accordingly, acceptable electrical wires are conventionally obtained only by a compromise between different properties, which is often resolved by using fairly thick-walled polymer insulation and/or two-wall constructions. Although such forms of polymeric insulation may be used in the wires of the present invention, the presence of the refractory layer solves these problems to a significant extent. This is because the polymers used for insulation are selected for their flammability and/or mechanical properties at the expense of their electrical properties. Examples of polymers that may be used to form the polymeric insulation include polyolefins such as homopolymers of ethylene and copolymers with alpha-olefins, halogenated polymers such as tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, and vinyl chloride homopolymers. or copolymers, polyamides, polyesters,
Mention may be made of polyimides, polyetherketones such as polyaryletherketones, aromatic polyetherimides and sulfones, silicones, alkene/vinyl acetate copolymers, and the like. The polymers may be used alone or in mixtures with each other and may include fillers such as silica, metal oxides, treated or untreated metal oxide flame retardants such as hydrated alumina and titania. The polymer may be used in a single-walled or striped-walled structure, for example a polyvinylidene fluoride layer may be placed over a polyethylene layer, for example. The polymer may not be crosslinked, but is preferably crosslinked, for example by chemical crosslinking agents or by electron or gamma irradiation, to improve mechanical properties and reduce flow upon heating. The polymer may contain other substances such as antioxidants, stabilizers, crosslinking promoters and processing aids. In short,
Polymer insulation is particularly effective with fillers such as hydrated alumina, hydrated titania, dawsonite and silica, so that the filler in the polymer insulation provides additional insulation when the wire or cable is exposed to fire. , comprising a filler having the same chemical composition as the refractory coating at least under pyrolysis conditions. Preferred types of polymeric insulation are those that become charcoal when exposed to fire, such as some of the aromatic polymers mentioned above, or those that become ash, such as silicone polymers, which when exposed to fire become charcoal or The ash provides the necessary insulation as well as the fireproof coating. polymer, composition,
Examples of its manufacture and wires using it are found in U.S. Patent No. 3,269,862.3,580,829.3,9
53,400.3°956.240.4,155,82
3.4,121°001 and 4,320,224,
British Patent Specification No. 1.473,972.1,603,2
05.2°068.347.2,035,333 and 1,604.405 and European Patent Specification No. 69.
No. 598. In some cases, for example when using certain aromatic polymers, it is suitable to form insulation on the conductor by plasma or thermal polymerization processes. Preferably, the wire is substantially halogen-free.

As mentioned above, preferred methods of forming the keying layer include evaporation, plasma assisted chemical vapor deposition and sputtering methods.

An advantage of using a relatively slow deposition method such as sputtering to form the keying layer is that it allows for more control over the chemical composition and mechanical properties of the keying layer. For example, it may be advantageous for the keying layer to be non-stoichiometric.

This improves the adhesion between the keying layer and the underlying layer and ensures that stresses occurring in the coating are not localized at the layer boundaries, e.g. due to differential thermal expansion, and that different parts of the layer have different properties. This is particularly the case when the stoichiometry of the keying layer varies over at least a portion of the thickness of the keying layer, as shown. For example, a significantly metal-rich portion of the keying layer will exhibit good adhesion to the conductor or intermediate layer, whereas a keying layer with the least amount of metal or metalloid will have the best electrical properties or good adhesion to another layer. Shows better adhesion.

If desired, the stoichiometry of the keying layer may vary continuously throughout the thickness of the coating, and may have one or more layers of fairly uniform stoichiometry. The keying layer may thus have an outer region of fairly uniform stoichiometry, preferably with a high content of oxygen or nitrogen, exhibiting optimal electrical properties or adhesion to another refractory layer. The relative thicknesses of the non-uniform and uniform layers may vary widely.

For example, a major portion of the keying layer may have a non-uniform stoichiometry, or a major portion of the keying layer may have a uniform stoichiometry. In the latter case, the non-uniform portion of the keying layer may be considered an interlayer that improves the adhesion of the remaining keying layer, especially at high temperatures. If the metal or metalloid-rich portion of the underlying keying layer is intended to improve the adhesion of the refractory coating, its specific composition may be
Depending on the composition of the underlying layer, in some cases the metal or metalloid-rich portion preferably consists essentially entirely of the metal or metalloid, with oxides or nitrides formed from the metal or metalloid. Gradually transform into something. This means that the system is
Particular preference is given to the inclusion of an underlying layer of a similar metal or metalloid.

The exact stoichiometry of the homogeneous top layer can be determined using wavelength-dispersive electron microblow analysis or by X-ray photoelectron spectroscopy (XP
It can be determined experimentally by using S). The composition of the coating, which changes from metallic to refractory throughout its depth, is evaluated using Auger electron spectroscopy (AES), where the film is successively sputtered away to expose new surfaces for compositional analysis. be able to.

Changes in stoichiometry are not limited to changes in metal or metalloid/oxygen or nitrogen proportions. In addition or in place of 2
The relative proportions of different metals or metalloids may vary, for example, such that there is a gradual change from one metal to an oxide or nitride of another metal making up the intermediate layer.

The outer region of the refractory keying layer contains at least 50% of the required stoichiometric oxygen or nitrogen molar content of the refractory insulating oxide or nitride, more preferably at least 6%.
Preference is given to having an oxygen or nitrogen molar content of 5%, especially at least 80%. Thus, the preferred oxide composition of the outer region has the formula: Ox [where X is at least 0.7 for aluminum]
5, preferably at least 11, especially at least 1.25
In the case of titanium or silicon it is at least 11, preferably at least 1.3, especially at least 1.5, and in the case of tantalum it is at least 1.25, preferably at least 1.6, especially at least 2. ] It can be shown as

The most preferred method of forming keying layers whose composition varies in thickness is sputtering.

In sputtering methods, primarily neutral atomic or molecular species may be formed from the material to be deposited and ejected from the target under bombardment of inert cations (eg, argon ions). The type of high energy released is
travel a considerable distance and enter a medium vacuum (e.g. 10-' to 1
The cations required for bombardment are generated in a glow discharge where the sputtering target acts as a cathode to the glow discharge system. The potential of is maintained in the case of an insulating target material by using radio frequency power applied to the cathode,
It keeps the target surface at a negative potential during processing.

If the target is a conductive material, DC power may be applied. The advantage of such techniques is that the control over the target material is greatly increased and the energy of the emitted species can be controlled, e.g.
Typically the evaporation method is 0. ! Compared to ~0.5eV, the sputtering method has I=lOeV, which is much higher than the evaporation method. Although considerable improvements in interfacial bonding are achieved, the deposition rate of the described sputtering method is lower than that of electron beam evaporation.

In magnetron sputtering, plasma is concentrated in front of a cathode (target) by a magnetic field.

The effect of magnetic fields on gas discharges is dramatic. In the discharge region, where a permanent magnet, usually placed behind the cathode, forms a sufficiently strong magnetic field perpendicular to the electric field, the secondary electrons resulting from the sputter bombardment process are deflected into a circular or helical path by the Lorentz force. . Thus, the electron density just before the cathode and the number of ionized argon atoms bombarding the cathode are substantially increased. There is an increase in plasma density and a significant increase in deposition rate. Bias sputtering (sputter ion plating) may be used as a variation of this technique. In this case, the wire conductor is
It is held at a negative potential with respect to the chamber and plasma. Bombardment of the wire conductor with argon ions produces a very clean surface. Sputtering of the target material onto the wire conductor in this process provides a simultaneous deposition/cleaning mechanism. This has the advantage that the interfacial bonding is considerably improved.

In a sputter ion plating system both the substrate and the wire conductor are held at a negative potential. In this case, the relative potentials are balanced to promote preferential sputtering of the target material. Target voltage is typically IKV depending on system design and target material
smaller. The wire substrate may be exposed to its own local plasma depending on its bias potential which is lower than that of the target. The exact voltage/power relationship achieved at the target or substrate depends on many variables and varies in detail from system to system.

Typical power density on target is lO~20W/cI
It is N'. The load on the substrate may be substantially lower;
It is frequently as low as 5% of the target load.

The preferred technique used to apply the oxide or nitride coating is reactive bias sputtering. In this method, a reactive gas is introduced into the chamber in addition to argon so that the oxide/nitride of the target material, which in this case is a metal or metalloid rather than an oxide/nitride, is deposited. Experimental results have shown that the level of reactive gas and its rate of introduction have a significant effect on the deposition rate. Control of reactive gas partial pressures and analysis of the sputtering atmosphere in a closed loop control system is highly desirable. Apart from the simultaneous deposition/cleaning benefits mentioned above, ion bombardment of the substrate increases the surface reaction between the reactive gas and the deposited species, so that a coating with the required stoichiometry is more fully formed. .

The partial pressure of the reactive gas is determined experimentally, but is usually between 2 and 2.
5% and sometimes up to 30%. The exact level depends on the stoichiometry of the coating and the rate of deposition.

Reactive sputtering is a preferred technique as it facilitates changing the stoichiometry of the coating. For example, an intermediate "layer" of pure metal used for the oxide/nitride coating can be deposited such that there are no sharp boundaries between the conductor metal, oxide/nitride metal, and oxide/nitride layers.

Various targets and ancillary equipment including microprocessor gas control units and vacuum chambers for use in these methods are commercially available. Although many variations in design are possible, most often use a "box" shaped chamber that can be pumped down to a high vacuum for use in any of the vacuum deposition methods described above. The system is typically, but not exclusively, subjected to one deposition method. One system that may be used to coat electrical wire uses an air-to-air transfer technique for passage of the electrical wire conductor through the deposition chamber, with one or more wire conductors on either side of the main deposition chamber. using an auxiliary vacuum chamber.

These auxiliary chambers extend from the deposition chamber to the atmosphere and are maintained at progressively higher pressures.

This reduces the load on individual vacuum seals. The described system has the advantage of continuously supplying wire conductors to batch process equipment. Preferably, the pressure in the vacuum deposition chamber is kept constant, typically between 10-4 and 10-t Torr.

The target used is a commercially available planar-magnetron sputtering source. These dimensions may vary widely, and targets over 21K in length may be used. There may be two to four such sources and they may be placed opposite each other so as to sputter the wire conductor passing through the chamber each time or from at least two sides.

The devices may be used in series to increase wire processing speed. As above, apply a negative bias to the magnetron to begin the sputtering process. The wires may be kept at a low negative bias as described above.

Improvements to the system may be made if necessary.

For example, by using an intermediate vacuum stencil between the atmosphere (population side) and the deposition chamber, an argon ion glow discharge is generated that cleans and heats the wire conductor surface by ion bombardment before entering the vacuum deposition chamber. let

Additionally, an intermediate chamber may be used between the clean chamber and the deposition chamber to deposit the intermediate layer.

Conditions may be controlled to produce the conductor coating without sharp boundaries between layers. For example, an intermediate "layer" of pure metal used for a refractory coating can be deposited such that there is no sharp boundary between the conductor metal, the intermediate layer, and the oxide or nitride coating. Similarly, an additional chamber may be installed between the deposition chamber and the atmosphere (outlet side) for depositing different metals, metal oxides or metal alloys onto the refractory coating for improved lubricity or wear resistance. May be used for.

In processes involving evaporation and activated evaporation and ion plating, other techniques are used for coating deposition.

Evaporation of the coating material takes place by heating the material so that its vapor pressure exceeds 10@-2 mbar. The evaporation temperature varies depending on the coating material (e.g. 1300-1800 DEG C. for refractory metal oxides) and the chamber pressure is usually 10@-4 to 10@-8 mbar. A similar wire transfer system as described is approximately 30 to 40 c+v above the source.
may be used to keep the substrate in place. Several heating methods exist, such as resistive, inductive, and electron beam impingement. However, the preferred method is high energy (
For example, an electron beam of fO, 000 eV) or an electron beam source impinging on a coating material in a water-cooled crucible. The use of a multi-pot melt or two source guns allows the deposition of multiple layers and stoichiometric gradient layers with the aid of electronic monitoring and control equipment.

The compound coating is made of the same compound (e.g., AL
O3) or by reactive evaporation (aluminum evaporated to a partial pressure of oxygen to give aluminum oxide). Variations in processing exist to promote reaction or deposition, for example activated reactive evaporation (ARE) can be used to increase the likelihood of reaction between the evaporate and the reactive gas.

In ion plating, a negative bias applied to the substrate in an inert gas promotes a simultaneous clean/deposit mechanism to optimize deposition as described for sputtering processes. A bias level of -2KV is typically used, but this can be reduced to suit wire substrates. Alternatively, high bias levels can be applied to a plate placed behind the traverse wire to achieve a similar effect.

The operating pressure is higher than ion plating techniques (e.g. 10
-3 to 1o-2 mbar), so that a more uniform coating is formed by gas scattering. To protect the filament, the ion plating electron beam gun is differentially pumped to maintain a vacuum higher than 10-'mbar.

In plasma assisted chemical vapor deposition (PACVD) methods, the substrate to be coated is exposed to low pressure (0,
1-10)-L) Exposure to plasma. This pressure is
Maintained by balancing the overall gas flow rate to the throughput of the pump system. The plasma is electrically activated and maintained by coupling energy from a power source through a matching network to the gaseous medium.

Thin films have been successfully deposited from high frequency plasmas into the direct current and microwave ranges. At high frequencies, energy may be coupled capacitively or inductively depending on chamber design and electrode geometry. Typically 0.1-10 W/cj in a capacitively coupled parallel plate reactor! A 3.56 MHz high frequency generator with a specification that allows power densities of 3.56 MHz may be used. The substrate can be set at temperatures up to 400° C., can be grounded, and can be floating or exposed to the required DC voltage bias. Typically, the deposition rate with this technique is
It is convenient to compare the deposition rates with those obtained by sputtering. Alumina deposition may be performed by exposing the substrate to a plasma containing oxygen and a volatile aluminum compound (eg, trimethylaluminum or aluminum butoxide) under appropriate processing conditions.

After forming the keying layer, another insulating refractory layer is applied. As mentioned above, another insulating refractory layer, such as a sol-gel derived coating, is formed over the vacuum deposited coating by any relatively fast technique.

The sol-gel process involves the hydrolysis and polycondensation of metal alkoxides, such as silicon teloraethoxide, titanium butoxide or aluminum butoxide, to produce inorganic oxide gels that are converted to inorganic oxide glasses by low temperature heat treatment. Metal alkoxides may be used as precursors for the production of inorganic glasses by the sol-gel route. Alumina gel can be made by adding an alkoxide of aluminum, such as aluminum 5ea-butoxide, to water that is heated to above 80°C and stirred at high speed. Approximately 2Q of water per mole of alkoxide is suitable. The solution is 0 per 11 moles of acid, e.g.
After adding 0.7 mol of hydrochloric acid, the mixture is kept at 90° C. for about 0.5 to 1 hour, and the sol particles coagulate. The sol is kept at the boiling point to allow excess butanol to evaporate, and reflux conditions are maintained until flocculation is complete. The volume of the sol is reduced by removing water, and a viscosity suitable for coating wires is obtained.

The wires may be provided with alumina gel for subsequent conversion to inorganic insulation by dipping or extrusion processing. In this process, as described above, the wire is drawn through a gel made to an appropriate viscosity so that a controlled thickness of gel adheres to the wire. Thickness is best controlled by wiping excess gel from the wire by using a cylindrical die. The gel coated wire is then suitably dried and burned to convert the coating to an inorganic oxide glass. The exact conditions regarding temperature and residence time during the various steps of the conversion depend on the gel composition produced and its tolerance to fairly rapid changes under the circumstances. The porosity and integrity of the coating are significantly affected by these steps. A suitable conversion process involves drawing the wire through a drying oven which is adjusted to a temperature of about 80<0>C and then through a staged heat treatment section that exposes the wire to a temperature of 300-500<0>C for several minutes. The required exposure time will depend on the initial thickness of the gel coating, but drying may be as slow as practical and the general guidelines above may be used. It is preferred to form the layers in a multiple pass process in which several thin layers are deposited in sequence.

Thermal spray (or plasma spray) methods involve injecting a powder of refractory compound into a high-temperature, high-velocity gas stream. This process occurs with a specially designed gun or torch, and the refractory compound is removed as a molten or semi-molten spray. This spray condenses to form a dense fire-resistant film when applied to a substrate. The hot gas stream is formed by controlled combustion of a flammable gas mixture, such as acetylene and oxygen, or by striking a low pressure, high current arc between metal electrodes in an inert gas.

Thermal spray torches are commercially available and include powder dispensers, gas flow controls, and shaping nozzles. Non-powder-dosed methods are used, including gravity and screw pumps. Gas temperatures can reach several thousand degrees Celsius. Plasma spraying is very similar to thermal spraying, but the heat source is provided by an electric arc.

In addition to gas regulation, a special DC power supply capable of supplying up to 100 OA at 100 V is required. The cathode may be made of thorium tungsten and the anode is typically water-cooled copper. A plasma jet emerges from the torch nozzle and refractory powder is injected into the jet. The temperature of the plasma jet may be higher than 10,000° C. and the gas velocity is up to 10,001/sec.

There are variations of the above methods, including detonation gun coating and low pressure spraying. In a detonation gun, pulsed powder is melted and accelerated by a controlled explosion of acetylene/oxygen in a water-cooled cylindrical chamber. This results in a fast gas flow (several thousand to seven seconds) and improved coating adhesion. Low pressure plasma spray
It is similar to conventional plasma spraying, except that the plasma jet (with molten powder) escapes into the vacuum, resulting in a denser, cleaner coating.

After depositing the keying layer and another refractory layer on the wire conductor, it is preferred to cover the oxide layer with a thin coating of polymeric resin or lacquer to provide shielding and mechanical protection against water or electrolytes during use. . Another polymeric insulation may then be extruded onto the coated conductor by methods known in the art.

To form a circuit or signal integrity cable, suitable electrical wires of the invention are simply gathered and enclosed within a jacket. If desired, the wires may be provided with a screen or anti-electromagnetic shield before applying the cable jacket.

The cable can be formed by braiding the wire bundle 1 and extruding the cable jacket thereon in a continuous process well known in the art. Any of the materials listed below for wire polymer insulation may be used, but the composition is free of halogens,
Preferred are, for example, the compositions described in GB Patent Specifications Nos. 1,603,205 and 2,068,347A. It is of course possible to use additional means to provide cable integrity, such as mica tape wrapping, but these are not necessary and are not preferred from the standpoint of increasing the size and weight of the cable.

The invention is also suitable for forming flat cables which cannot be wrapped with mica cheap. Thus, with the invention it is possible to form a flat cable that can function as a circuit and signal integrity cable.

Some embodiments of the present invention and methods for producing the same are shown below, but the present invention is not limited to these embodiments.

In FIG. 1, a 26 AWG stranded copper conductor formed from 19 copper strands I is coated with an aluminum oxide keying layer 0.5 μl thick by the sputter ion plating method described above and another 6 μm thick aluminum oxide keying layer by the sol-gel method described above. Covered with aluminum oxide refractory layer. Both of these layers are designated layer 2. The outer surface of the stranded conductor is coated with a 3 μm thick aluminum layer (not shown).
covered with. Trade name “ULTEM J”
The polyetherimide coating 3 commercially available as
Extruded on oxide coated conductor, average thickness 0.2IN
forming a polymer "insulating" layer.

Figure 2 shows that the seven wires shown in Figure 1 are bundled together and an anti-electromagnetic shield is placed around the bundle by braiding, as described in Example IA of British Patent Specification No. 2.068,347. 4 and extruding thereon a jacket 5 based on a halogen-free composition.

A cable so formed has a fairly small overall diameter relative to the volume of the copper conductor and is particularly lightweight.

FIG. 3 shows a flat conductor flat cable comprising a row of flat copper conductors 1 with 100 mil spacing. Each copper conductor 1 includes a 3 μm thick aluminum intermediate layer (not shown) as described above, a 0.5 μm thick alumina keying layer above it and another 6 μm thick alumina layer above it. is supplied.

Both alumina layers are designated layer 2. The coated conductor is embedded in a single polymeric insulation layer 3 formed, for example, from polyetherimide or polyetheretherketone or polyetherketone, commercially available under the tradename "Ut, TEM" J.

The apparatus used in batch processing to coat wire conductor substrates is shown in FIG. This device comprises a vacuum chamber in which the complete wire moving mechanism includes a wire draw-off reel 2 and a take-up reel 3, and is equipped with a wire support roll 10 and a tension roll 1. The mechanism drives a motor to control the passage of the electric wire 4 so that the electric wire 4 crosses the vertically installed target 5 many times. Adhesion is caused by the treatment described above. As before,
Changes can be made during setup. Additional targets on the other side of the wire to increase coating speed (not shown)
may be used and additional targets, e.g. target 6
can be used to deposit intermediate layers before and/or after depositing the primary oxide/nitride coating. Proper gas inlet sostem design that matches the particular geometry used facilitates the deposition of layers that do not have sharp boundaries, as described above. Batch length depends on chamber dimensions and transfer system design.

In such a batch processing operation, the wire 4 moves from one reel 2 to another reel 3 within the chamber. Depending on the path taken by the wire, it may pass in front of a small auxiliary target 6 in order to deposit an intermediate layer of any desired material. The power to this target combined with the number of passes before the target and the wire speed controls the interlayer deposition thickness. Next, wire 4 is a large main target.
Pass in front of Soto 5 and apply the main coating. Thickness depends on power, wire speed and number of passes. The ratio of intermediate layer to primary coating thickness is similarly controlled. Multiple layers can be formed by preferably reversing the mechanism so that the wires 4 pass through the targets 5.6 in the reverse order.

Thickness and composition may be varied in the reverse path as required. For example, the processes used in small magnetrons may be reactive in the reverse route to deposit metal compounds on the interlayers, such as Ti and TiNx. Layer deposition without a sharp boundary between the metal interlayer (or substrate) and the oxide/nitride coating results from an argon-rich atmosphere with a gradient of reactive gas content increasing as the wire moves down the target surface. This can be done by setting up a reactive gas gradient in front of the main target such that the deposition at is on the wire at the upper end of target 5. The gradient can be obtained by a baffle system (not shown) that gradually leaks oxygen introduced at the lower end of the target toward the upper end.

A simple way to form layers without sharp boundaries is to pass the wire back and forth through the system, with each pass increasing the level of reactive gas to the final level required to obtain the correct stoichiometry. This includes the use of multiple-pass treatments, which are increased in number. Thus, the stoichiometry of the interlayer increases as a series of small increasing steps from the metal to the required stoichiometry. Composite targets may also be used to form interlayers with stoichiometric gradients. In the case of separation articles, the article may alternatively be held in front of the target by a rotating sample holder.

FIG. 5 is a schematic cross-sectional view of a portion of an article of the invention showing a typical arrangement of layers that may be formed on a copper substrate. Layer thicknesses are enlarged for clarity.

The copper substrate 21 is provided with a thick (eg 1-3 μm) nickel layer 22, a metallic aluminum layer 23, a non-stoichiometric aluminum oxide A12xOx layer 24 and a stoichiometric aluminum oxide A12ffi03 layer 25.

Layers 23, 24 and 25 are formed by sputtering. Additional, fairly thick (e.g. approximately 5 thick
~15 μm) An aluminum oxide layer 26 is deposited on top of layer 25 by a sol-gel method.

Although the layers are clearly demarcated by lines in the drawings, such demarcations are preferred for copper/aluminum, aluminum/A1220X and AQl
OX/A (b It does not actually need to be formed especially between the 03 layers. In fact, aluminum, Al1.
0 and stoichiometric alumina layers may all be formed by similar sputtering methods, with the stoichiometry of the layer depending on the oxygen gradient used.

Examples are shown below.

Examples 1 and 2 A 3.3 μm thick aluminum intermediate layer was applied to a copper conductor by using a sputtering apparatus as schematically shown in FIG. The sputtering conditions are as follows. The wires were pre-cleaned by vapor degreasing in 1.1.1-trichloroethane prior to deposition. Cleaning was carried out by continuous passage through a vapor degreasing bath with a residence time of 3 minutes. As shown in FIG. 4, the electric wire 4 was placed in a vacuum chamber. Before starting the process, close the chamber.
A vacuum was applied to Xl0-'mbar. Argon was introduced at this stage to a pressure of 1.5 x lO-'' mbar. A high frequency (80 KHz) bias potential was then applied to the wire handling system, which was isolated from ground. Wire 4 from 2 to reel 3
A bias potential of -850 V was obtained for the moving moe. After completing the cleaning cycle, the pressure was reduced to 8xlO-3 mbar and the deposition process was started.

A DC power of 3 KV was applied to the aluminum target 5. The wire was coated as it moved from reel 2 to reel 3 and passed through target 5.

The residence time in this area was adjusted by wire speed to obtain the required thickness. The roll mechanism changed the wire surface exposed to the target as it passed through the target.

Wire samples of copper conductors coated with aluminum as described above were then coated with aluminum oxide in a similar manner. For this second coating, the aluminum oxide target was powered by an RF it source. The wire dwell time and target power were adjusted to obtain a constant thickness of aluminum oxide of approximately 0.2 μm.

During the deposition of both aluminum and aluminum oxide, the copper conductor was held at an appropriate bias potential with respect to the chamber to facilitate deposition.

Then a wire sample of copper conductor, in some cases 3°3 μm thick
Wire samples coated with aluminum and in some cases coated with additional aluminum oxide at a thickness of 0.2 μm as described above were coated with gel-derived aluminum oxide by the sol-gel process described above.

The samples were then tested for topcoat adhesion as follows. A certain length of electric wire was subjected to a tensile test, and the strain was continuously measured. During the test, the wire samples were observed using an optical microscope. Distortion was recorded when significant peeling of the coating was observed. The coating adhesion value was obtained from the recorded distortion value at this point. The composition of the samples and the results obtained are shown in Table 1.

Table 1 +1. The adhesion of the coating to bare copper was very poor and it was impossible to test the samples due to rapid peeling.

The results show a clear improvement in the adhesion of gel-induced alumina coatings with vacuum deposited aluminum oxide layers.

Examples 3 and 4 Pairs of similar wires are twisted (length 2, 2 twists per 5 ctx) to form a twisted pair cable and one end of the wires is connected to a 30V peak-to-peak I MHz square wave generator. The electrical performance of the wire manufactured in the same manner as in Example 2 was tested by observing the waveform passing through a 200 ohm load connected between the wires using an oscilloscope. The twisted pair cable was heated by a propane gas burner with a flat flame of width 8cjI. The flame temperature directly below the twisted pair was maintained at a specific temperature and the time until failure was recorded.

In Example 3, the sample did not fail in a 900°C flame for 70 seconds. In Example 4, the sample did not fail after being exposed to a flame for 72 minutes at 650°C. The substrate material to which the sol-gel derived aluminum oxide was deposited in Examples 3 and 4 had a dense 0.2 μm vacuum deposited aluminum oxide coating on its surface. Although this layer is insulating, it could not withstand 30V alone at room temperature.

Examples 5-7 22AW with sputtered aluminum and aluminum oxide layers using the method described in Examples 1 and 2.
Coated G19 strand steel wire conductor. The wire was then transferred to a pond vacuum chamber equipped with a 25KW electron beam gun.

The pressure in this chamber was pumped down to a base pressure of 5xl O-''5 mbar and another insulating refractory layer of aluminum oxide was deposited by electron beam evaporation. The electron beam power was approximately 6 KW (25 KV).

240 Scrap A), and the refractory was evaporated directly from highly sintered alumina pieces contained in a water-cooled copper crucible.

The rate of deposition of aluminum oxide by evaporation is approximately 3 μm/min, and the rate is 0.5 μm/min. It was much faster than the refractory keying layer deposition at 1 μM/min.

The samples produced as described above were tested for adhesion using the tensile method of Examples 1 and 2. The results are shown in Table 2. The results show that a thin refractory keying layer deposited by a relatively slow method improves the adhesion of another refractory layer deposited by a relatively fast method.

Table 2 Regarding the electric wire of Example 7, the same method as Example 3 (90
-0°C), but no damage was observed even after 4 hours. However, the wire of Example 5 suddenly peeled off when exposed to flame, so its electrical performance could not be tested.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the electric wire of the present invention, and FIG.
FIG. 3 is a cross-sectional view of a portion of a flat conductor flat cable; FIG. 4 is a schematic diagram of a portion of a speckling device showing the wire handling mechanism; FIG. The figure is a schematic cross-sectional view of a portion of the article of the present invention in the thickness direction. 1... Conductor (strand), 2, 22, 23, 24° 25.26... Layer, 3... Covering, 4... Shielding, 5
... Jacket, 21 ... Base material. Patent applicant: Raychem Limited, patent attorney: Aobai, Ao, and 2 other procedural amendments (
Voluntary) February 14, 1986

Claims (1)

Claims: 1. An article of manufacture having at least a portion formed of a metal, the portion having a dense refractory keying layer deposited on the surface thereof, and a highly dense refractory keying layer deposited on the keying layer by a relatively fast deposition method. An article having a separate electrically insulating refractory layer formed thereon. 2. The article of claim 1, wherein the thickness of the other refractory layer is greater than the thickness of the refractory keying layer. 3. The article according to claim 1 or 2, wherein the thickness of the further refractory layer is greater than 1 μm. 4. Article according to claim 3, wherein the thickness of the further refractory layer is greater than 2 μm. 5. The article according to any one of claims 1 to 4, wherein the thickness of the refractory keying layer is not greater than 0.5 μm. 6. An article according to any one of claims 1 to 5, wherein the refractory keying layer and the further refractory layer have similar indicated chemical compositions. 7. Article according to any of claims 1 to 6, wherein the refractory keying layer and/or the further refractory layer comprises a metal oxide. 8. The fire-resistant keying layer and/or another fire-resistant layer:
8. An article according to claim 7, comprising an oxide of aluminum, silicon, titanium or tantalum. 9. The article according to any one of claims 1 to 8, wherein the fire-resistant keying layer is formed by a vacuum deposition method. 10. The fire-resistant keying layer is formed by sputter ion plating,
10. The article of claim 9 formed by chemical vapor deposition or evaporation. 11. The article according to any one of claims 1 to 10, wherein the other fireproof layer is formed by a thermal spraying method, a sol-gel method, a plasma ashing method, or a solution coating method. 12. The article according to any one of claims 1 to 11, wherein the metal forming a part of the article comprises copper or a copper alloy. 13. An article according to any one of claims 1 to 12, comprising a metal intermediate layer located between the metal forming part of the article and the refractory keying layer. 14. The article of claim 13, wherein the intermediate layer has a thickness of at least 1 μm. 15. The article of claim 14, wherein the thickness of the intermediate layer is at least 2 μm. 16. The article according to any one of claims 13 to 15, wherein the intermediate layer is formed by a vacuum deposition method. 17. The article according to claim 16, wherein the intermediate layer is formed by sputter ion plating. 18. Claims 13 to 1, wherein the intermediate layer is formed by a metal rolling electroplating method or a melt coating method.
Articles described in any of Section 7. 19. The article according to any one of claims 13 to 18, wherein the intermediate layer is made of aluminum, silicon, titanium, tantalum, nickel, manganese, chromium, or an alloy thereof. 20. The refractory keying layer comprises an inorganic metal compound, and the intermediate layer comprises a metal similar to the metal present in the refractory keying layer. Goods. 21. The article according to any one of claims 13 to 20, wherein the intermediate layer is formed of a metal that forms an intermetallic compound with copper when heated. 22. The article according to any one of claims 13 to 21, wherein the intermediate layer comprises aluminum. 23. The stoichiometry of the refractory keying layer varies in at least a portion of its thickness such that the proportion of metal or metalloid in the layer decreases towards the outer surface of the layer Articles described in any of Item 22. 24. The stoichiometry of the refractory keying layer varies over at least a portion of its thickness such that no sharp boundary exists between the metal interlayer and the refractory keying layer. Articles listed in any of the paragraphs. 25. According to any one of claims 1 to 24, comprising one or more additional layers on top of another refractory layer or between a refractory keying layer and another refractory layer. goods. 26. The article according to any one of claims 1 to 25, which is in the form of an electric wire. 27. The article of claim 26, wherein additional outer polymeric insulation is provided. 28. The article of claim 27, wherein the polymeric insulation becomes charcoal when exposed to fire. 29. Claim 27 or 28, wherein the polymeric insulation is deposited by pyrolysis or plasma deposition.
Articles listed in section.