| Popis: |
Fine-pitch three-dimensional (3D) interconnects have become a favored choice for next-generation packaging technology, helping to meet industry demands for small form factors, large bandwidth, and low power requirements in electronic devices. Critical changes are being made to meet fine-pitch and narrow-gap joint specifications, such as changing the solder to a micro pillar bump, using thermal compression instead of mass reflow to connect chips, and replacing capillary underfill (UF) material with wafer-level UF material. Consequently, a chip can be connected to another chip or a Si interposer, subsequently transforming the entire joint to an intermetallic compound (IMC). This paper proposes an alternative fine-pitch 3D chip-stacking technology that involves using a bump material, bonding method, and UF material that are similar to those of the current chip-on-film inner-lead bonding technology typically used in the liquid crystal display driver IC industry. In applying the Au-rich AuSn eutectic characteristic, one side of the joint is using Au, and the other side is bumped using a Cu pillar. A thermal compression bonding process is performed in an ambient atmosphere without the presence of flux. Subsequently, the UF material is applied to fill the gap. A simulated 30-μm pitch, 6-die stacked structure was examined in this study. Critical parameters affecting the joint structure and reliability were evaluated. A robust interconnect was fabricated using optimal bump structures, bonding parameters, and capillary UF material without a filler. The proposed joint structure exhibits an increase in resistance of less than 20% after performing a critical high-temperature storage test. The thermal stability of the joint is comparable with that of a normal C4 joint and improves upon the Cu 3 Sn/Cu 6 Sn 5 IMC or AuSn joints that are fabricated using a Au stud bump and solder. Furthermore, the thermal stability of the joint increases when the number of bonding increases, making it particularly effective for die-stacking operations. |
