High-strength solder interconnect for copper/electroless nickel/immersion gold metallization solder pad and method

• Main Authors: ESLAMBOLCHI ALI, MEI ZEQUN
• Format: Patent
• Language: English
• Published: 23.10.2001
• Edition: 7
• Subjects: BASIC ELECTRIC ELEMENTS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR; ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; MACHINE TOOLS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS; METAL-WORKING NOT OTHERWISE PROVIDED FOR; PERFORMING OPERATIONS; PRINTED CIRCUITS; SEMICONDUCTOR DEVICES; SOLDERING OR UNSOLDERING; TRANSPORTING; WELDING; WORKING BY LASER BEAM

A high-strength solder interconnect formed on a copper/electroless nickel/immersion gold metallization solder pad and method. The invention provides a low cost, high-strength solder interconnect on a copper/electroless nickel/immersion gold metallization (CENIGM) pad that can be formed at a temperature at or below the temperature used in eutectic tin-lead (Sn-Pb) solder applications. The invention includes a first substrate having a solder-wettable pad and a second substrate having a copper/electroless nickel/immersion gold metallization (CENIGM) solder pad. The invention also provides a solder interconnect between the solder-wettable pad and the CENIGM solder pad. The invention may provide a solder interconnect that includes a solder body including at least 2% indium (In) by weight and wetted to both the CENIGM solder pad and the solder-wettable pad. The invention may alternatively includes both a solder bump wetted to the solder-wettable pad and a solder joint, including at least 2% In by weight, wetted to the solder bump and the CENIGM solder pad. The method includes obtaining a first substrate including a solder-wettable pad and forming a solder bump on the solder-wettable pad. A second substrate is obtained including a CENIGM solder pad. Next, solder paste, including at least 5% In, is applied to the CENIGM solder pad and the solder bump is moved into contact with the solder paste. The solder paste is then reflowed to generate a solder joint wetted to the solder bump and the CENIGM solder pad.