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

Electroformed bumped tape, gang or single-point-bonded, provides solid low-profile, higher-strength bonds. Electroforming of the bumps into precisely photodefined openings on the tape leads results in an absolutely uniform, consistent (2.00 mil dia, 1.3 mil high) bump pattern, which is difficult to achieve with an etching process. The height of the bumps ensures sufficient clearance between the conductor and the die surface (stand-off), even after bump collapse during TC bonding. The uniform bump size means that the desired bonding pressure is applied to all pads repeatedly. The metallurgy and the hardness of the bumps can be chosen to suit specific requirements. Capping of the ICs with compliant layers of metallization prior to bonding offers an even broader range of bonding parameters and higher reliability. If desired, these bonded leads can be pull-tested nondestructively to a preset value of 10 gm after assembly to assure 100% reliability of bonds.<>