Solder bump interconnection formed using spaced solder deposit and consumable path
AssigneeMotorola, Inc.
InventorCynthia M. Melton
Life of this patent
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Abstract
A solder bump interconnection (34) bonding a metal bump (30) affixed to an integrated circuit component (10) to a terminal pad (18) of a printed circuit board (12) is formed using a consumable path (24) and a solder deposit (28) applied to the path spaced part from the terminal pad. In addition to the terminal pad, the printed circuit board includes a solder-nonwettable surface (21). The consumable path extends from the terminal pad on the solder-nonwettable surface and is formed oa solder-soluble metal. The solder deposit is heated, preferably by a laser beam, to form molten solder that is drawn along the pathdissolving the path as it proceeds. At the terminalmolten solder wets the pad and the metal bump and solidifies to complete the inerconnection.
Claims12
A method for forming a solder bump interconnection for attaching an integrated circuit component to a printed circuit board, said method comprising
- fabricating a printed circuit board comprising a solder-wettable terminal pad, a solder-nonwettable surface adjacent to the solder-wettable terminal pad, and a consumable path extending from the terminal pad and overlying the solder-nonwettable surface, said consumable path being formed of a solder-soluble metal,
- applying a solder deposit onto the expendable runner spaced apart from the terminal pad,
- superposing an integrated circuit component onto the circuit board, said integrated circuit component comprising a metal bump and being arranged relative to the printed circuit board such that the metal bump rests against the terminal pad,
- heating the solder deposit to a temperature effective to melt the solder deposit and form molten solder in contact with the consumable path, whereupon the molten solder dissolves the consumable path and is drawn along the consumable path to the terminal pad, and
- cooling to solidify the solder at the terminal pad, whereupon the solder bonds to the terminal pad and to the metal bump to form a solder bump interconnection.
A method in accordance with claim I wherein the solder deposit is composed of a solder paste.
A method for forming a solder bump interconnection for attaching an integrated circuit component to a printed circuit board, said method comprising
- providing a printed circuit board comprising a solder-wettable terminal pad, a solder-nonwettable polymeric surface adjacent to the terminal pad, and consumable path overlying the solder-nonwettable polymeric surface and extending from the terminal pad, said consumable path being formed of a solder-soluble metal and having an end section spaced apart from the terminal pad,
- applying a solder paste onto the end section to form a solder deposit composed of solder metal particles and a fugitive binder,
- affixing a metal bump to the integrated circuit component, said metal bump being formed of a solder metal or a solder-wettable metal,
- superposing the integrated circuit component onto the printed circuit board such that the metal bump rests against the terminal pad,
- heating the solder deposit to a temperature effective to vaporize the fugitive binder and to melt the solder metal particles to form molten solder in contact with the consumable path, whereupon the molten solder dissolves the consumable path and is drawn along the consumable path to the terminal pad, and further whereupon the molten solder wets the metal bump and the terminal pad, and
- cooling to solidify the solder at the terminal pad to form a solder bump interconnection.
A method for forming a solder bump interconnection for attaching an integrated circuit component to a printed circuit board, said method comprising
- providing a printed circuit board comprising a copper terminal pad, a solder-nonwettable polymeric surface adjacent to the terminal pad, and consumable path overlying the solder-nonwettable polymeric surface and extending from the terminal pad, said consumable path being formed of tin and having an end section spaced apart from the terminal pad,
- applying a solder paste onto the end section to form a solder deposit composed of solder metal particles and a fugitive binder, said solder metal particles being formed of alloy comprising tin and a metallic constitutent capable of alloying with tin to form a eutectic composition having a melting temperature, but wherein said alloy contains tin in an amount less than the eutectic composition and has an initial melting temperature greater than the eutectic melting temperature,
- affixing a metal bump to the integrated circuit component, said metal bump being formed of a solder metal,
- superposing the integrated circuit component onto the printed circuit board such that the metal bump rests against the terminal pad,
- irradiating the solder deposit with a laser beam to heat the deposit to a temperature effective to vaporize the fugitive binder and to melt the solder metal particles to form molten solder in contact with the consumable path, whereupon the molten solder dissolves the consumable path to form an alloy having a reduced melting temperature, and further whereupon the molten solder is drawn along the consumable path to the terminal pad, and wets the metal bump and the terminal pad, and
- cooling to solidify the solder metal at the terminal pad to form a solder bump interconnection.
Dependencies are inferred from the claim text.