International Business Machines Corporation

Jerry A Gorrell

Sarah Huffsmith Knickerbocker

Christopher Lee Tessler

Srinivasa S N Reddy

John Joseph Garant

Phillip W Palmatier

Dale Curtis McHerron

James Edward Tersigni

Kaushal S Patel

Sean A Allen

A method is provided for making of interconnect solder bumps on a wafer or other electronic device without depositing any significant amount of tin or other solder component from the solder onto the wafer surface which tin can cause shorts or other defects in the wafer. The method is particularly useful for well-known C4NP interconnect technology. In one aspect of the invention, a reducing gas flow rate is used to remove oxides from the solder surfaces and wafer pad surfaces and is of a sufficient determined or pre-determined flow and/or chamber or mold/wafer spacing to provide a gas velocity across the solder surfaces and wafer pad surfaces so that Sn or other contaminants do not deposit on the wafer surface during solder transfer. In another aspect, the transfer contact is performed below the melting point of the solder and subsequently heated to above the melting temperature while in transfer contact. The heated solder in contact with the wafer pads is transferred to the wafer pads.

Process for making interconnect solder Pb-free bumps free from organo-tin/tin deposits on the wafer surface

A method is provided for the making of interconnect solder bumps on a wafer or other electronic device. The method is particularly useful for the well-known C4NP interconnect technology and determines if any off-set resulted between the solder mold array and the wafer capture array during the transfer process. The amount of off-set enables the operator to adjust the transfer tool before solder transfer to compensate for the off-set caused by the transfer process and provides a more cost-effective and efficient solder transfer process. A solder reactive material surrounding the capture pads is used to determine where the solder reacts with the solder reactive material showing the off-set resulting from the transfer process. Copper is a preferred solder reactive material.

Alignment verification for C4NP solder transfer

A fixture having a bottom plate, top plate and an expansion block interposed between the bottom plate and top plate. A workpiece is positioned between the expansion block and bottom plate. When the fixture is heated, there is a net displacement exerted by the expansion block so as to apply pressure to the workpiece. The pressure applied by the fixture to the workpiece is due solely to the thermal expansion of the fixture when it is heated.

Method and apparatus for application of pressure to a workpiece by thermal expansion

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Lagrangeville, NY, United States of America

Jerry A Gorrell