An interconnection structure suitable for the connection of microelectronic circuit chips to packages is provided by this invention. In particular, the invention pertains to the area-array or flip-chip technology often called C4 (controlled collapse chip connection). The structure comprises an adhesion/barrier layer deposited on a passivated substrate (e.g., a silicon wafer), optionally an additional adhesion layer, a solderable layer of a metal selected from the group consisting of Ni, Co, Fe, NiFe, NiCo, CoFe and NiCoFe on the adhesion/barrier layer, and a lead-free solder ball comprising tin as the predominate component and one or more alloying elements selected from Bi, Ag, and Sb, and further optionally including one or more elements selected from the group consisting of Zn, In, Ni, Co and Cu.

Flip-Chip interconnections using lead-free solders

A solder composition and associated method of formation. The solder composition comprises a substantially lead-free alloy that includes tin (Sn), silver (Ag), and copper. The tin has a weight percent concentration in the alloy of at least about 90 %. The silver has a weight percent concentration X in the alloy. X is sufficiently small that formation of Ag3Sn plates (57, 58) is substantially suppressed when the alloy in a liquefied state is being solidified by being cooled to a lower temperature at which the solid Sn phase is nucleated. This lower temperature corresponds to an undercooling δT relative to the eutectic melting temperature of the alloy. Alternatively, X may be about 4.0 % or less, wherein the liquefied alloy is cooled at a cooling rate that is high enough to substantially suppress Ag3Sn plate (57, 58) formation in the alloy. The copper has a weight percent concentration in the alloy not exceeding about 1.5 %.

Lead-free tin-silver-copper alloy solder composition

A lead-free alloy for joining and sealing which is useful as a plumbing solder comprises from 0.08 to 20% by weight of bismuth, from 0.02 to 1.5% by weight of copper, from 0.01 to 1.5% by weight of silver, from 0 to 0.10 percent by weight of phosphorus, from 0 to 0.20% of a rare earth mixture and the balance tin, together with incidental impurities. The alloy has a similar pasty range (i.e. melting temperature and melting range) to the traditional tin-lead plumbing solders.

Low toxicity alloy compositions for joining and sealing

PROBLEM TO BE SOLVED: To provide a lead-free alloy used for soldering. SOLUTION: The lead-free solder alloy compsn. has a solid phase transforming temp. in the range from 167 to 212°C and a liq. phase transforming temp. in the range from 179 to 213°C and contains, by weight, 85 to 92% tin, 1 to 6% silver and 4 to 10% indium. COPYRIGHT: (C)1996,JPO

Lead-free alloy containing tin silver and indium

The lead free alloy is a low solidus temperature, multi-component solder alloy containing at least about 50 weight percent Bi, up to about 50 weight percent Sn (basis total Sn and Bi), and an effective amount of a physical and mechanical property enhancing third component. The third component can be Cu, In, Ag, and combinations of Cu and Ag.

Lead free, tin-bismuth solder alloys

A lead-free solder composition of approximately 90% to 95% by weight tin, approximately 3% to 5% by weight antimony, approximately 1% to 4.5% by weight bismuth, and approximately 0.1% to 0.5% by weight silver.

Stanley Tulman

Papers

Tin base lead-free solder composition containing bismuth, silver and antimony