Abstract: A die attach process employs a temperature gradient lead free soft solder metal sheet or thin film as the die attach material. The sheet or thin film is formed to a uniform thickness and has a heat vaporizable polymer adhesive layer on one surface, by which the thin film is laminated onto the back metal of the silicon wafer. The thin film is lead-free and composed of acceptably non-toxic materials. The thin film remains semi-molten (that is, not flowable) in reflow temperatures in the range about 260° C. to 280° C. The polymer adhesive layer is effectively vaporized at the high reflow temperatures during the die mount.

Abstract: A substantially lead-free solder composition having the composition (weight %): Sn, 76.0-83.9%; Ag, 8.0-12.0%; Sb, 8.0-10%; Cu, 0.1-2.0%. In some embodiments the solder composition contains 12 wt % Ag, 8 wt % Sb, 0.1 wt % Cu, the remainder being Sn. The solder can be formed into a wire, a ribbon or sheet, a solder paste or preform, or a powder, for example. Fillers, such as Si or Ag spherical fillers, with a particle size maximum at 35 ?m, can be added to any of the various solder forms during alloy fabrication. Also, a semiconductor package having a die attached to a support using the substantially lead-free solder composition.

Abstract: A die attach process employs a temperature gradient lead free soft solder metal sheet or thin film as the die attach material. The sheet or thin film is formed to a uniform thickness and has a heat vaporizable polymer adhesive layer on one surface, by which the thin film is laminated onto the back metal of the silicon wafer. The thin film is lead-free and composed of acceptably non-toxic materials. The thin film remains semi-molten (that is, not flowable) in reflow temperatures in the range about 260° C. to 280° C. The polymer adhesive layer is effectively vaporized at the high reflow temperatures during the die mount.