Ball limiting metal mask and tin enrichment of high melting point solder for low temperature interconnection
AssigneeInternational Business Machines Corporation
InventorsChristina M. Boyko, Anthony P. Ingraham, Voya R. Markovich, David J. Russell
Life of this patent
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Abstract
A solder interconnection uses preferably lead-rich balls for making a low temperature chip attachment directly to any of the higher levels of packaging substrate. After a solder ball has been formed using standard processes, a ball limiting metal mask is formed using photoresist. A thin cap layer of preferably pure tin is deposited on a surface of the solder balls using a tin aqueous immersion process.
Claims20
A process of joining an integrated circuit (IC) chip to a microelectronic circuit card comprising the steps of:
- depositing a ball comprising a solder on solder wettable input/output (I/O) terminals of said IC chip such that said ball has an exposed surface for connecting to said microelectronic circuit card;
- immersing the exposed surface of said ball in an aqueous immersion solution thereby depositing a layer of a material having a thickness on the exposed surface of said ball;
- providing a matching footprint of solder wettable I/O terminals on said microelectronic circuit card;
- aligning said ball on said IC chip with the corresponding footprint on said microelectronic circuit card;
- and
- reflowing said layer of said material on said exposed surface to form an eutectic alloy on said ball to bond said IC chip to said microelectronic circuit card.
A process of capping a Pb-rich ball with at least one layer of Sn, said process comprising the steps of:
- a) forming said Pb-rich ball on a substrate such that said Pb-rich ball has an exposed surface;
- b) forming a photoresist barrier surrounding said Pb-rich ball;
- c) immersing the exposed surface of said Pb-rich ball in an aqueous immersion solution thereby depositing a capping layer of Sn having a thickness on the exposed surface of said Pb-rich ball;
- and
- d) heating said Pb-rich ball and said capping layer of Sn to form a Pb/Sn eutectic alloy.
A process of joining a device to a microelectronic circuit card comprising the steps of:
- depositing a ball comprising a solder on solder wettable input/output (I/O) terminals of said device such that said ball has an exposed surface, said device comprising at least one of the group consisting of an integrated circuit, a ball grid array, a flex laminate chip carrier, and a laminate chip carrier;
- immersing the exposed surface of said ball in an aqueous immersion solution thereby depositing a layer of a material having a thickness on the exposed surface of said ball;
- providing a matching footprint of solder wettable I/O terminals on said microelectronic circuit card;
- aligning said ball on said device with the corresponding footprint on said microelectronic circuit card;
- and
- reflowing said layer of said material to form an eutectic alloy on said ball to bond said device to said microelectronic circuit card.
Dependencies are inferred from the claim text.