Appeal No. 1998-3053
Application 08/677,755
substrate by solder bump connections, wherein the solder has a
specified composition. Claim 13 is illustrative:
13. A method for attaching an integrated circuit
component to a substrate by solder bump interconnections, said
substrate comprising a plurality of first bond pads, said
integrated circuit component comprising a plurality of second
bond pads formed of solder-wettable metal, said method
comprising:
forming a solder bump onto each second bond pad, said
solder bump being formed of a lead-free solder alloy composed
predominantly of tin and optionally up to 1.5 weight percent
silver and containing between 2 and 8 weight percent copper,
superposing the integrated circuit component onto the
substrate to form an assembly such that each solder bump rests
against a corresponding first bond pad,
heating the assembly for a time and at a temperature
effective to melt said lead-free solder, whereupon each solder
bump forms molten solder that wets the corresponding first
bond pad, and
cooling to solidify the solder to form solder bump
interconnections bonding the first bond pads and the second
bond pads.
THE REFERENCES
Tulman 4,806,309 Feb. 21,
1989
Melton et al. (Melton ‘341) 5,154,341 Oct. 13,
1992
Melton et al. (Melton ‘453) 5,269,453 Dec. 14,
1993
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