Nano tube Functionalized Composite Solders for Fine Pitch Interconnect Applications, a Study on Micro strure, Mechanical Properties, Melting Characteristics

Keywords:
SWCNTs, eutectic lead- tin solder, Sn-3.8Ag-0.7Cu solder, mechanical properties

Abstract:
Single walled carbon Nano tube (SWCNT) reinforced 63Sn-37Pb; Sn-3.8Ag-0.7Cu solders were synthesized by exploring the powder metallurgical technique. Composite solders up to 1wt% reinforcement of SWCNTs were prepared. The composite specimens were characterized by X-ray diffraction (XRD), Field-Emission Scanning Electron Microscope (FE-SEM). Melting characteristics of the SWCNT based solders were determined by Differential scanning calorimetry (DSC). Microstructures of the composite solders were observed by FE-SEM at higher magnification for the observation of the CNT distribution. The typical distribution of SWCNTs in the solder matrix is shown in Fig. 1. Mechanical properties of the composite specimens were compared with those of the pure 63Sn-37Pb solder specimens and found that the UTS increased by 30% with the 1 wt% addition of CNTs, where as the UTS increased by 49% with the addition of SWCNTs to Sn-3.8Ag-0.7Cu solder specimens. The mechanical properties of the composite solder specimens as a function of nano tube wt% addition is shown in Fig. 2. Hardness values of the CNT based composites have shown higher Vickers hardness values compared to unreinforced counterparts. The enhanced mechanical properties are resulting from the possible load-transfer mechanisms of the CNTs, which is discussed in detail. The fractrographic examination conducted by FE-SEM indicated the existence of ductile features in the form of dimples in all the composite solders with different weight proportions; it is evident from the micrographs that much reduced ductility is observed in the specimens reinforced with the higher wt% of CNTs.

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Nanotech 2006 Conference Program Abstract