Method for fabricating microelectronic assemblies
AssigneeTessera, Inc.
InventorsThomas H. DiStefano, Joseph Fjelstad
Life of this patent
Estimating the term…
Abstract
Solder pads for microelectronic connections are formed with a set of solder-wettable strips extending radially outwardly from a central point. A solid core solder ball is positioned on each pad and reflowed. The pad configuration helps to center the solder ball and keeps the solder ball down in the desired position thereby minimizing variations in height of the resulting solder bumps. Also, the solder pad may include non-wettable surfaces defined by a non-wettable metal, a metal compound or a dielectric material. The non-wettable areas on the pad confine the solder and avoid the need for a separate solder mask.
Claims26
A method of fabricating a microelectronic assembly comprising:
- providing a component including one or more conductive pads, each said conductive pad including a plurality of solder-wettable strips extending outwardly away from a center, said solder wettable strips being bounded by non solder-wettable material;
- positioning a conductive element atop at least one of said conductive pads, said conductive element including a solid conductive core and a layer of solder material overlying said solid conductive core, said solid conductive core having a higher melting temperature than said layer of solder material;
- heating said conductive element for transforming said layer of solder material into a molten state while maintaining said solid conductive core in a solid state, wherein said layer of solder material in the molten state contacts said solid conductive core and said solder-wettable strips;
- and
- cooling said conductive element so as to solidify said layer of solder material, wherein said conductive element is electrically interconnected with said at least one of said conductive pads.
A method of making conductive bumps on a component comprising:
- providing said component including one or more conductive pads on said component, each said conductive pad including a plurality of solder wettable strips extending outwardly away from a center;
- providing a conductive element atop at least one of said conductive pads, said conductive element including a solid conductive core and a layer of solder material overlying said solid conductive core, said solid conductive core having a higher melting temperature than said layer of solder material;
- heating said conductive element to a temperature whereby the layer of solder material is in a molten state for wetting to said conductive pad while said solid core remains in a solid state;
- and
- cooling said conductive element for returning said layer of solder material to a solid state, wherein said conductive element is electrically interconnected with said conductive pad.
A method of fabricating microelectronic assemblies comprising the step of:
- providing a component including a base and one or more pads on said base, each said pad including a plurality of solder-wettable strips extending outwardly away from a center, said solder-wettable strips being bounded by non-solder-wettable material;
- providing conductive elements atop said one or more conductive pads, each said conductive element including a solid conductive core and a layer of solder material overlying said solid conductive core, said solid conductive core having a higher melting temperature than said layer of solder material;
- heating said conductive elements to a temperature whereby the layers of solder material are in a molten state for wetting to said conductive pads while said solid cores remains in a solid state;
- and
- cooling said conductive elements for returning said layers of solder material to a solid state, wherein said conductive elements are electrically interconnected with said conductive pads.
Dependencies are inferred from the claim text.