Flip-Chip interconnections using lead-free solders

An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising:

• a two-layer ball-limiting metallurgy comprising an adhesion/barrier layer and a copper-free solderable layer wherein said adhesion/barrier layer is between a microelectronic device and said copper-free solderable layer and wherein said copper-free solderable layer is of a metal selected from the group consisting of Ni, Co, Fe, NiFe, NiCo and NiCoFe, each said metal from said group being sufficiently non-reactive with components of a tin-containing lead free solder, such that said copper-free solderable layer remains after being placed in contact therewith in a soldering action;
• and
• one or more lead-free solder balls selectively situated on said copper-free solderable layer, said lead-free solder balls consisting of tin as the predominant component, one or more alloying components selected from the group consisting of Bi, Ag and Sb, and one or more additional alloying components selected from the group consisting of Zn, In, Ni, Co, and Cu in the range of about 0.5 to 5% for Zn, 0.5 to 5% for Ni, 0.5 to 5% for Co, 0.5 to 5% for Cu and 0.5 to 10% for In, whereby said lead-free solder ball substantially avoids alpha particle emission and induced soft logic errors which result therefrom.

An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising:

• a three-layer ball-limiting metallurgy comprising an adhesion/barrier layer, an adhesion layer on top of said adhesion/barrier layer and a copper-free solderable layer wherein said adhesion/barrier layer is between a microelectronic device and said adhesion layer and wherein said copper-free solderable layer is of a metal selected from the group consisting of Ni, Co, Fe, NiFe, NiCo and NiCoFe, each said metal from said group being sufficiently non-reactive with components of a tin-containing lead free solder, such that said copper-free solderable layer remains after being placed in contact therewith in a soldering action;
• and
• one or more lead-free solder balls selectively situated on said copper-free solderable layer, said lead-free solder balls consisting of tin as the predominant component and one or more alloying components selected from the group consisting of Bi, Ag and Sb, whereby said lead-free solder ball substantially avoids alpha particle emission and induced soft logic errors which result therefrom.

An interconnection structure suitable for flip-chip attachment of microelectronic device chips to packages, comprising:

• a three-layer ball-limiting metallurgy comprising an adhesion/barrier layer, an adhesion layer on top of said adhesion/barrier layer and a copper-free solderable layer wherein said adhesion/barrier layer is between a microelectronic device and said adhesion layer and wherein said copper-free solderable layer is of a metal selected from the group consisting of Ni, Co, Fe, NiFe, NiCo and NiCoFe, each said metal from said group being sufficiently non-reactive with components of a tin-containing lead free solder, such that said copper-free solderable layer remains after being placed in contact therewith in a soldering action;
• and
• one or more lead-free solder balls selectively situated on said copper-free solderable layer, said lead-free solder balls consisting of tin as the predominant component, one or more alloying components selected from the group consisting of Bi, Ag and Sb, and one or more additional alloying components selected from the group consisting of Zn, In, Ni, Co and Cu in the range of about 0.5 to 5% for Zn, 0.5 to 5% for Ni, 0.5 to 5% for Co, 0.5 to 5% for Cu and 0.5 to 10% for In, whereby said lead-free solder ball substantially avoids alpha particle emission and induced soft logic errors which result therefrom.