Eutectic bonding of metal to ceramic
First Claim
1. A method for bonding a metal foil to a nonmetallic substrate, said foil being formed of a metal reactable to produce an oxide compound and further suitable for producing in combination with said oxide compound a low melting eutectic oxide composition, said method comprisingdepositing a thin film of said metal onto the substrate,oxidizing the metal film to form said metal oxide compound,arranging the metal foil and the substrate such that the foil lies in contact with the oxidized deposit,heating the arrangement at a temperature above the eutectic melting point and below the metal melting point, whereupon a liquid phase forms at the interface between the metal foil and the oxidized film,continuing to heat the arrangement at a temperature above the eutectic melting point for a time sufficient to dissolve the metal oxide compound into the liquid phase, whereupon the liquid phase wets the substrate, andcooling the arrangement, whereby the liquid phase solidifies and bonds the metal foil to the substrate.
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Accused Products
Abstract
An improved eutectic oxide bonding method is applied for bonding a metallic copper foil to a nonmetallic substrate by forming a liquid phase derived from a eutectic oxide composition. A metallic copper thin film is initially deposited onto the substrate and heated in a low oxygen atmosphere under suitable conditions to form a cuprous oxide film. A metallic copper foil is positioned on the substrate in contact with the cuprous oxide film. Preferably, the assembly is initially heated at a temperature below the eutectic melting point to soften the foil and promote intimate contact between the foil and the cuprous oxide film. Thereafter, the assembly is heated above the eutectic melting point to form a liquid phase at the interface of the foil and the cuprous oxide film, and maintained at the temperature for a time sufficient to dissolve the oxide film, whereupon the liquid phase wets the substrate. The assembly is cooled, and the liquid phase is solidified to bond the foil to the substrate. In addition to copper, the method may be adopted to bond foils of other metals, including chromium, iron, cobalt and nickel, using low melting eutectic oxides thereof.
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Citations
6 Claims
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1. A method for bonding a metal foil to a nonmetallic substrate, said foil being formed of a metal reactable to produce an oxide compound and further suitable for producing in combination with said oxide compound a low melting eutectic oxide composition, said method comprising
depositing a thin film of said metal onto the substrate, oxidizing the metal film to form said metal oxide compound, arranging the metal foil and the substrate such that the foil lies in contact with the oxidized deposit, heating the arrangement at a temperature above the eutectic melting point and below the metal melting point, whereupon a liquid phase forms at the interface between the metal foil and the oxidized film, continuing to heat the arrangement at a temperature above the eutectic melting point for a time sufficient to dissolve the metal oxide compound into the liquid phase, whereupon the liquid phase wets the substrate, and cooling the arrangement, whereby the liquid phase solidifies and bonds the metal foil to the substrate.
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3. A method for bonding a metallic copper foil to a nonmetallic substrate comprising
depositing a metallic copper thin film onto the substrate, oxidizing the copper film under conditions suitable for forming cuprous oxide compound, applying a metallic copper foil to the substrate to produce an arrangement comprising the foil in intimate contact with the oxidized copper film at an interface therebetween, heating the arrangement at a temperature above the melting point of a eutectic copper oxide composition composed of about 0.34 weight percent oxygen and the balance copper, but less than the copper metal melting point, whereupon during said heating the copper metal and the oxidized deposit combine to form a liquid phase at the interface, maintaining the arrangement at a temperature above the eutectic melting point and below the copper metal melting point for a time sufficient to dissolve the oxidized film into the liquid phase, whereupon the liquid phase wets the substrate, and cooling and solidifying the liquid phase to bond the copper foil to the substrate.
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4. A method for bonding a metallic copper foil to an alumina substrate comprising
vapor depositing a metallic copper thin film onto the substrate, heating the copper film in contact with a suitably low oxygen atmosphere to form a cuprous oxide film, applying a metallic copper foil directly onto the cuprous oxide film to form an assembly, heating the assembly to a temperature above the melting point of a eutectic copper oxide composition composed of about 0.34 weight percent oxygen and the balance copper, and below the copper metal melting point to form a liquid phase that comprises the cuprous oxide from said film and wets the substrate, and cooling the assembly to solidify the liquid phase and thereby bond the copper foil to the substrate.
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5. A method for bonding a metallic copper foil to an alumina substrate comprising
vapor depositing onto the substrate a metallic copper film having a thickness between about 200 Å - and 3000 Å
,heating the copper film to a temperature between 800°
C. and 1065°
C. while exposed to an atmosphere containing oxygen at a partial pressure less than 10-3 atmosphere to react the metallic copper form a cuprous oxide film,applying a metallic copper foil directly onto the cuprous oxide film to form an assembly, heating the assembly to a temperature less than 1065°
C. to soften the metallic copper foil to produce intimate contact between the foil and the cuprous oxide film,further heating the assembly to a temperature between about 1065°
C. and 1083°
C. to form a liquid phase derived from the cuprous oxide film in contact with the copper foil, which liquid phase wets the substrate, andcooling the assembly to solidify the liquid phase and thereby bond the copper foil to the substrate.
- and 3000 Å
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6. A method for bonding a metallic copper foil to an alumina substrate comprising
vapor depositing onto the substrate a metallic copper thin film having a thickness between about 500 Å - and 1000 Å
,heating the copper film to a temperature between 900°
C. and 1000°
C. while exposed to an atmosphere containing oxygen at a partial pressure between about 10-5 and 10-3 atmosphere to substantially react the metallic copper to form a cuprous oxide film,applying a metallic copper foil directly onto the cuprous oxide film to form an assembly, heating the assembly in an inert atmosphere to a temperature less than about 1065°
C. to soften the metallic copper foil to produce intimate contact at an interface between the copper foil and the cuprous oxide film,further heating the assembly in an inert atmosphere to a temperature between about 1065°
C. and 1070°
C. to form a eutectic liquid phase at the interface and to dissolve the cuprous oxide film into the liquid phase, whereupon the liquid phase wets the substrate, andcooling the assembly to solidify the liquid phase and thereby bond the copper foil to the substrate.
- and 1000 Å
Specification