Direct bonding of metals to ceramics and metals

A method of bonding a metal to a substrate comprising the steps of:

• selecting a substrate from the group consisting of ceramics and metals;
• selecting a metal which will form a direct bond with said substrate;
• selecting a bonding agent compatible with said substrate, said bonding agent being one which forms a eutectic alloy with said metal, said eutectic alloy consisting predominately of said metal and having a eutectic temperature lower than the melting point of said metal;
• reacting said metal with a small amount of said bonding agent;
• positioning said metal on said substrate;
• heating said metal and said substrate in an inert atmosphere to a temperature between said eutectic temperature and said melting point for at least a few seconds to form a melt at the interface between said metal and said substrate, wherein said steps of reacting and heating are controlled so that the melt is hypoeutectic;
• and
• cooling said metal and said substrate to form a bond.

A method of bonding a metal to a substrate comprising the steps of:

• selecting a substrate from the group consisting of ceramics and metals;
• selecting a metal which will form a direct bond with said substrate, where said metal contains a quantity of a bonding agent which is compatible with said substrate and forms a eutectic alloy with said metal, said eutectic alloy consisting predominately of said metal and having a eutectic temperature lower than the melting point of said metal, said quantity of bonding agent being in the range of about 100 to 2,000 parts per million parts of said metal;
• positioning said metal on said substrate;
• heating said metal and said substrate in an inert atmosphere to a temperature between said eutectic temperature and said melting point for at least a few seconds to form a melt between said metal and said substrate;
• and
• cooling said metal and said substrate to form a bond.

A method of bonding copper to a substrate comprising the steps of:

• selecting a substrate from the group consisting of ceramics and metals;
• oxidizing at least one surface of a sheet of copper to a thickness in the range of about 200 Angstroms to about 5,000 Angstroms;
• positioning said copper on said substrate;
• and
• heating said copper and said substrate in an inert atmosphere to a temperature between 1065.degree. and 1083.degree. Celsius for a time sufficient to form a hypoeutectic melt at the interface between said copper and said substrate;
• and
• cooling said copper and said substrate to form a bond.

A method of bonding copper to a substrate comprising the steps of:

• selecting a substrate from the group consisting of metals and ceramics;
• selecting copper containing from about 100 to about 2,000 parts per million oxygen distributed therein;
• positioning said copper on said substrate;
• heating said copper and said substrate in an inert atmosphere to a temperature between 1065.degree. and 1083.degree. Celsius for a time sufficient to form a hypoeutectic melt between said copper and said substrate;
• and
• cooling said copper and said substrate to form a direct bond.

A method of making a circuit board comprising the steps of:

• selecting a ceramic substrate;
• selecting for conductive leads, a metal which will form a direct bond with said substrate;
• providing a bonding agent compatible with said substrate, said bonding agent being one which forms a eutectic alloy with said metal, said eutectic alloy consisting predominately of said metal and having a eutectic temperature lower than the melting point of said metal;
• positioning said metal on said substrate;
• simultaneously exposing the interface between said metal and said substrate to a solid state source of said bonding agent by having said source in direct contact with said metal, and heating said metal and said substrate in an inert atmosphere to a temperature between said eutectic temperature and said melting point for at least a few seconds to form a melt at the interface between said metal and said substrate, wherein said steps of exposing and heating are carried out such that said melt is at least ultimately hypoeutectic;
• and
• cooling said melt to form a direct bond between said metal and said substrate.