COPPER-PILLAR INTERCONNECT FOR FLIP-CHIP-ON-MODULE (FCOM) PACKAGINGAuthors: Mark Huang and Yong Poo Chia et al.
Company: Micron Semiconductor Asia Pte. Ltd.
Date Published: 9/17/2007 Conference: IWLPC (Wafer-Level Packaging)
This paper focuses on Ni/Au-capped and Sn-capped copper-pillar interconnects using lead-free solder pastes (Sn-Ag-Cu [SAC]) in FCOM packages. The copper-pillar devices were flipped over and bonded to SAC-covered Cu/Ni/Au electrodes on printed circuit boards (PCB) or modules, followed by multiple reflows at 265°C. Both finishes can protect Cu-pillar bumps from oxidation in an oxygen-contained environment. After 1st reflow at 265 ºC, both systems can form a solid interconnection with the additional help of SAC soldering. The copper pillars are embedded into SAC alloys and can most likely improve FCOM reliability. Reliability testing inclusive of thermal cycle (TC), autoclave (AC), high-temperature storage (HTS), and thermal shock (TS) shows that Sn-capped Cu-pillar systems are more robust than Ni/Au-capped Cu-pillar systems. The different intermetallic interconnecting mechanisms are also discussed.
Keywords: Flip-chip-on-module, Copper-pillar interconnects, intermetallics, Sn-Ag-Cu alloy
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