Recent progress in SLID bonding in novel 3D-IC technologies

In this study, the feasibility of low-cost Cu-sintering technology for power electronics packaging and the effect of sintering conditions on the bonding strength of the Cu-sintered joint have been evaluated. A Cu paste with nano-sized Cu powders and a metal content of ~78% as a high-temperature bonding material was fabricated. The sinter-bonding reactions and mechanical strengths of Cu-sintered joints were evaluated at different sinter bonding pressures, temperatures, and durations during the sintering process. The shear strength of the Cu-sintered joints increased with increasing sintering pressure. Good interfacial uniformity and stable metallurgical microstructures were observed in the Cu joints sintered at a high sintering pressure of 10 MPa, irrespective of the sintering time. It was confirmed that a high-pressure-assisted sintering process could create relatively dense sintered layers and good interfacial uniformity in the Cu-sintered joints, regardless of the sintering temperatures being in the range of 225–300 °C. The influence of the sinter bonding pressure on the shear strengths of the Cu-sintered joints was more significant compared to that of the sintering temperature. Durations of 10 min (at 300 °C) and 60 min (at 225 and 250 °C) are sufficient for complete sintering reactions between the Si chip and the direct bond copper (DBC) substrate. Relatively good metallic bonding and dense sintered microstructures created by a high sintering pressure of 10 MPa resulted in high shear strength in excess of 40 MPa of the Cu-sintered joints.

Effect of Sintering Conditions on the Mechanical Strength of Cu-Sintered Joints for High-Power Applications

In this paper, the wettability and growth behaviors of interfacial intermetallic compounds (IMCs) in the Sn/Co and Sn/Cu liquid/solid couples were comparatively investigated. In situ tensile tests were conducted to evaluate the mechanical properties of the Co/Sn(IMCs)/Co and Cu/Sn(IMCs)/Cu joints. The wettability of Sn on Cu substrate was better than that of Co substrate. The lath-like CoSn3 IMCs limited the improvement of wettability of Sn on Co substrate, even if the soldering temperature was increased. The Sn/Co couples showed an acceptable wettability for electronic application. During liquid aging, the rapid growing interfacial CoSn3 were controlled by the combination of chemical reaction and atomic diffusion. Grain boundary diffusion should be responsible for the growth of Cu6Sn5 in the Sn/Cu liquid/solid couples. The tensile strength and elongation of the Co/CoSn3/Co joints were basically equal to that of the Cu/IMCs/Cu full IMCs joints. Interfacial IMCs cracks were more likely to occur in the joints fabricated by Co substrate. The Co/CoSn3/Co sandwich structure can be fabricated within a remarkable short period of time at low temperature without pressure.

Microstructure, interfacial reactions and mechanical properties of Co/Sn/Co and Cu/Sn/Cu joints produced by transient liquid phase bonding

A novel method of low temperature all-Cu bonding was developed, which has a large tolerance for Cu surface oxidation and can even bond Cu with a thick oxide layer at 250 °C. It is significant for the chip level bonding because traditional methods have strict requirements for surface quality. The key process is to combine Cu nanoparticle paste and Pt-catalyzed formic acid vapor, which improved the bonding strength of oxidized-Cu by ∼78.5% and is expected to simplify the bonding process. To understand the mechanisms, interfacial analyses of the microstructure and composition were carried out, along with a surface analysis.

Low temperature Cu bonding with large tolerance of surface oxidation

Reliability analysis of sintered Cu joints for SiC power devices under thermal shock condition

Microstructure evolution and mechanical strength evaluation in Ag/Sn/Cu TLP bonding interconnection during aging test

Solderless bonding with nanoporous copper as interlayer for high-temperature applications

Poly(Divinylbenzene-Maleic Acid) Hollow Nanospheres Coordinated with Zirconium: Effective Catalyst for Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol

Siyu Sun

Papers

Microstructure evolution and mechanical strength evaluation in Ag/Sn/Cu TLP bonding interconnection during aging test

Solderless bonding with nanoporous copper as interlayer for high-temperature applications

Poly(Divinylbenzene-Maleic Acid) Hollow Nanospheres Coordinated with Zirconium: Effective Catalyst for Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol