Pb-free Sn-Ag-Cu ternary eutectic solder

A Pb-free electrical conductor solder including a ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-1.7 weight % Cu having a eutectic melting temperature of about 217.degree. C. and variants of said ternary eutectic composition wherein the relative concentrations of Sn, Ag, and Cu deviate from said ternary eutectic composition to provide a controlled liquid plus solid temperature range with a liquidus temperature not exceeding 15.degree. C. above said eutectic melting temperature and at least two intermetallic compounds dispersed in a beta Sn matrix wherein one intermetallic compound includes Cu and Sn and another intermetallic compound includes Ag and Sn.

A Pb-free solder comprising a ternary eutectic composition consisting of about 93.6 weight % Sn-about 4.7 weight % Ag-about 1.7 weight % Cu having a melting temperature of about 217.degree. C. wherein said composition promotes formation of intermetallic compounds that improve solder strength and fatigue resistance.

A solder joint comprising a Pb-free solder solidified in contact with an electrical conductor wherein said solder comprises a ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-1.7 weight % Cu having a eutectic melting temperature of about 217.degree. C. and variants of said ternary composition wherein the relative concentrations of Sn, Ag, and Cu deviate from said ternary composition to provide a controlled liquid plus solid temperature range with a liquidus temperature not exceeding 15.degree. C. above said eutectic melting temperature, said solder joint having a microstructure comprising beta Sn phase matrix and at least two intermetallic compounds, one intermetallic compound including Cu and Sn and another intermetallic compound including Ag and Sn, distributed uniformly in the beta Sn matrix phase.

A solder joint comprising a Pb-free solder solidified about copper electrical conductors and consisting essentially of about 3.5 to about 7.7 weight % Ag, about 1.0 to about 4.0 weight % Cu and the balance essentially Sn wherein Sn is present in an amount of at least about 89 weight % Sn to promote formation of intermetallic compounds that improve solder strength and fatigue resistance, said solder joint having a microstructure comprising beta Sn phase matrix and at least two intermetallic compounds, one intermetallic compound including Cu and Sn and another intermetallic compound including Ag and Sn, distributed uniformly in the beta Sn matrix phase.

A solder joint comprising a Pb-free solder ternary eutectic composition solidified in contact with an electrical conductor and consisting of about 4.7 weight % Ag, about 1.7 weight % Cu and the balance Sn wherein intermetallic compounds are formed in said solder for improving solder joint strength and fatigue resistance.

In a soldering process involving solidifying a molten solder, the improvement comprising solidifying a Pb-free solder comprising a ternary eutectic composition consisting essentially of about 93.6 weight % Sn-about 4.7 weight % Ag-1.7 weight % Cu having a eutectic melting temperature of about 217.degree. C. and variants of said ternary composition wherein the relative concentrations of Sn, Ag, and Cu deviate from said ternary composition to provide a controlled liquid-solid temperature range with a liquidus temperature not exceeding 15.degree. C. above said eutectic melting temperature and upon solidification at least two intermetallic compounds, one intermetallic compound including Cu and Sn and another intermetallic compound including Ag and Sn, dispersed in a beta Sn matrix phase.

In a soldering process involving solidifying a molten solder about copper electrical conductors, the improvement comprising solidifying a Pb-free solder consisting essentially of about 3.5 to about 7.7 weight % Ag, about 1.0 to about 4.0 weight % Cu and the balance essentially Sn wherein Sn is present in an amount of at least about 89 weight % Sn to promote formation of intermetallic compounds that improve solder strength and fatigue resistance, said solidified solder having a microstructure comprising a beta Sn matrix and at least two intermetallic compounds dispersed in the matrix wherein one intermetallic compound includes Cu and Sn and another intermetallic compound includes Ag and Sn.

In a soldering process involving solidifying a molten solder, the improvement comprising solidifying a molten Pb-free solder consisting of about 4.7 weight % Ag, about 1.7 weight % Cu and the balance Sn including forming in said solidified solder intermetallic compounds that improve solder strength and fatigue resistance.

A Pb-free solder consisting of about 3.6 to about 4.7 weight % Ag, about 0.9 to about 1.7 weight Cu, and the balance Sn in an amount to promote formation of intermetallic compounds that improve solder strength and fatigue resistance.

A solder joint comprising a Pb-free solder solidified in contact with an electrical conductor and consisting of about 3.6 to about 4.7 weight % Ag, about 0.9 to about 1.7 weight Cu, and the balance Sn in an amount to promote formation of intermetallic compounds that improve solder strength and fatigue resistance, said solidified solder having a microstructure comprising a beta Sn matrix and at least two intermetallic compounds dispersed in the matrix wherein one intermetallic compound includes Cu and Sn and another intermetallic compound includes Ag and Sn.

In a soldering process involving solidifying a molten solder, the improvement comprising solidifying a Pb-free solder consisting of about 3.6 to about 4.7 weight % Ag, about 0.9 to about 1.7 weight % Cu and the balance Sn in an amount to promote formation of intermetallic compounds that improve solder strength and fatigue resistance, said solidified solder having a microstructure comprising a beta Sn matrix and at least two intermetallic compounds dispersed in the matrix wherein one intermetallic compound includes Cu and Sn and another intermetallic compound includes Ag and Sn.