Solderable intergrated circuit lead frames plated with tin and palladium
AssigneeNational Semiconductor Corporation
InventorDavid H. Kinghorn
Life of this patent
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Abstract
A solderable lead frame is disclosed which includes a copper base lead frame containing a one layer or plated tin or tin alloy and another layer of plated palladium. The tin plating covers only external portions of the leads, whereas the palladium covers the external regions including the tin plating, and extends into internal portions of the lead frame. A diffusion barrier, of cobalt or nickel, is provided on the base lead frame beneath the tin plating.
Claims16
A solderable lead frame having a multiplicity of leads, the lead frame having an internal region being disposed toward its center and an external region disposed away from its center, the lead frame comprising:
- a base lead frame made from a base lead frame material;
- a layer of tin or tin alloy coating the external region of the base lead frame, wherein the layer of tin or tin alloy has an inner edge defining a boundary between the external and internal regions of the lead frame;
- and
- a layer of palladium coating both the external region of the lead frame and the boundary such that the tin or tin alloy and at least a part of the base lead frame are coated with palladium, wherein said tin alloy includes tin alloyed with one or more elements chosen from a group consisting of antimony, arsenic, bismuth, cadmium, gallium, gold, indium, iridium, lead, platinum, rhodium, ruthenium, thallium, and zinc.
A packaged integrated circuit comprising:
- a solderable lead frame having a multiplicity of leads, an internal region disposed toward the center of the lead frame and an external region disposed away from the center of the lead frame, the lead frame also comprising a base lead frame made from a base lead frame material, a layer of tin or tin alloy coating the external region of the lead frame, wherein said layer of tin or tin alloy has an inner edge defining a boundary between the external and internal regions of the lead frame and whereby solderability of the external leads coated with tin or tin alloy is enhanced, and a layer of palladium coating both the external region and the boundary such that at least a portion of the base lead frame and the tin or tin alloy are coated with palladium;
- an integrated circuit die;
- a plurality of bonding wires electrically connecting the internal regions of the leads to the integrated circuit die;
- and
- an outer molding encasing the solderable lead frame, the die and the bonding wires such that the external regions of the leads are exposed, wherein said tin alloy includes tin alloyed with one or more elements chosen from a group consisting of antimony, arsenic, bismuth, cadmium, gallium, gold, indium, iridium, lead, platinum, rhodium, ruthenium, thallium, and zinc.
Dependencies are inferred from the claim text.