A novel laser-assisted chip bumping technique is presented in which bumps are fabricated on a carrier and subsequently transferred onto silicon chips by a laser-driven release process. Copper bumps with gold bonding layers and intermediate nickel barriers are fabricated on quartz wafers with pre-deposited polyimide layers, using UV lithography and electroplating. The bumps are thermosonically bonded to their respective chips and then released from the carrier by laser machining of the polyimide layer, using light incident through the carrier. Bumps of 60 to 85 µm diameter and 50 µm height at a pitch of 127 µm have been fabricated in peripheral arrays. Parallel bonding and subsequent transfer of arrays of 28 bumps onto test chips have been successfully demonstrated. Individual bump shear tests have been performed on a sample of 13 test chips, showing an average bond strength of 26 gf per bump.
|Number of pages||6|
|Journal||IEEE Transactions on Electronics Packaging Manufacturing|
|Publication status||Published - Apr 2001|
- Flip chip assembly
- Flip chip bumping
- Laser ablation
- Thermosonic bonding