Patent ID: 8043893

Claim:
A method for forming an electrical structure comprising: providing a first substrate comprising a first electrically conductive pad, a second substrate comprising a second electrically conductive pad, a first transfer substrate comprising a first cavity, and a non-solder metallic core structure comprising a spherical shape, wherein said non-solder metallic core structure comprises a diameter that is less than a diameter of said first cavity, wherein said first electrically conductive pad comprises a first material layer formed over and in contact with a second material layer, wherein said first material layer comprises a different material from said second material layer, wherein said second material layer is formed within a first adhesive layer formed over said first substrate, wherein said second electrically conductive pad comprises a third material layer formed over and in contact with a fourth material layer, wherein said third material layer comprises a different material from said fourth material layer, and wherein said fourth material layer is formed within a second adhesive layer formed over said second substrate; dispensing said non-solder metallic core structure into said first cavity within said first transfer substrate; positioning, after said dispensing, said first transfer substrate such that a first section of a surface of said non-solder metallic core structure is in contact with said first electrically conductive pad; thermo-compression bonding said first section to said first electrically conductive pad; removing, after said thermo-compression bonding said first section, said first transfer substrate from said non-solder metallic core structure; forming a solder structure on said second electrically conductive pad; positioning said first substrate comprising said non-solder metallic core structure such that a second section of said surface of said non-solder metallic core structure is in contact with said solder structure; and heating, after said positioning said first substrate, said non-solder metallic core structure to a temperature sufficient to cause said solder structure solder to melt and form an electrical and mechanical connection between said second section of said surface of said non-solder metallic core structure and said second electrically conductive pad resulting in an electrical and mechanical connection between said first electrically conductive pad and said second electrically conductive pad.