Abstract: A lead-free solder preform includes a core layer and adhesion layer coated over surfaces of the core layer, where the preform delivers the combined merits from constituent solder alloys of the core and adhesion layers to provide both high temperature performance and improved wetting in high-temperature solder applications such as die attach. The core layer may be formed of a Bi Alloy having a solidus temperature above 260° C., and the adhesion layer may be formed of Sn, a Sn alloy, a Bi alloy, In, or an In alloy having a solidus temperature below 245° C. The solder preform may be formed using techniques such as: (1) electroplating a core ribbon with an adhesion material, (2) cladding an adhesion material foil onto a core ribbon, and/or (3) dipping a core ribbon in a molten adhesion alloy bath to allow thin layers of adhesion material to adhere to a core ribbon.

Abstract: A lead-free solder preform includes a core layer and adhesion layer coated over surfaces of the core layer, where the preform delivers the combined merits from constituent solder alloys of the core and adhesion layers to provide both high temperature performance and improved wetting in high-temperature solder applications such as die attach. The core layer may be formed of a Bi Alloy having a solidus temperature above 260° C., and the adhesion layer may be formed of Sn, a Sn alloy, a Bi alloy, In, or an In alloy having a solidus temperature below 245° C. The solder preform may be formed using techniques such as: (1) electroplating a core ribbon with an adhesion material, (2) cladding an adhesion material foil onto a core ribbon, and/or (3) dipping a core ribbon in a molten adhesion alloy bath to allow thin layers of adhesion material to adhere to a core ribbon.