Sn-Ag-Cu lead-free composite solders for ultra-fine-pitch wafer-level packaging

Abstract

SAC (SAC) based composite solders functionalized with single-wall carbon nanotubes (SWCNTs), nano particles such as nano-Ni, nano-Mo with various weight proportions ranging from 0.01 wt% to 5 wt% were successfully produced The composite solders with different wt% of nano particle and nanotube addition were synthesized using the sintering technique The microstructural, melting and mechanical properties of the SAC-based composite solders were evaluated as a function of different wt% of SWCNT, nano-Ni, and Nano-Mo. It is observed that SWCNTs are homogeneously distributed at the edges of Ag3Sn compounds that are distributed evenly in the β-Sn solder matrix. Microstructure analysis revealed that the nano Ni and nano Mo particles were transformed to the intermetallic compounds during processing and distributed uniformly throughout the β-Sn solder matrix. The different wt% addition of SWCNTs to SAC engendered a higher tensile strength, higher hardness and better melting characteristics. The nano particle reinforced solders are harder and stronger than the un reinforced counterparts. FE-SEM observations of fractured surfaces, revealed that the failure is ductile in nature. © 2006 IEEE.