Electroformed bumped tape, a practical interconnect method forhigh-lead count devices

摘要

Electroformed bumped tape, gang or single-point-bonded, providessolid low-profile, higher-strength bonds. Electroforming of the bumpsinto precisely photodefined openings on the tape leads results in anabsolutely uniform, consistent (2.00 mil dia, 1.3 mil high) bumppattern, which is difficult to achieve with an etching process. Theheight of the bumps ensures sufficient clearance between the conductorand the die surface (stand-off), even after bump collapse during TCbonding. The uniform bump size means that the desired bonding pressureis applied to all pads repeatedly. The metallurgy and the hardness ofthe bumps can be chosen to suit specific requirements. Capping of theICs with compliant layers of metallization prior to bonding offers aneven broader range of bonding parameters and higher reliability. Ifdesired, these bonded leads can be pull-tested nondestructively to apreset value of 10 gm after assembly to assure 100% reliability of bonds