| Summary: | 碩士 === 逢甲大學 === 材料科學學系 === 88 === Abstrate
By adding different weight percent ( 0.3 wt% ~ 10.0 wt% ) of Lead on the eutectic SnBi solder alloy, the phase transformation, behavior of melting and solidification, microstructure, mechanical properties, composition and elemental distribution of alloys are investigated. Solid diffusion and formation of intermetallic compound in interface between solder alloys and oxygen free copper are also characterized.
Experimental results showed that the Sn-rich phase (dendrite structure) will precipitated in the matrix of lamellar eutectic structure, gray Pb-rich phase is also found in more less area. Both of Sn-rich and Pb-rich phase is increased with the Pb content. Pb-rich phase is then identified by X-ray diffraction, ε phase(Pb7Bi3), and it is more specific in high lead content specimens. The melting point is slightly lowered when SnBi adding lead, second phase transformation reveals the Sn-Pb-Bi ternary eutectic reaction point at 97℃, by the heat flow data in DSC curve, the production volume of this reaction is undetected in low lead content specimen. Faster cooling rate will inhibit the ternary eutectic reaction and result in fine microstructure. Tensile test showed highest strain and lowest yield strength at 0.5 wt% Pb composition. Diffusion layer thickness has highest quanity when adding 2.0 wt% Pb, the microstructure and mophology of IMC layer is not coincident with the 5.0 wt% Pb due to the change of the diffusion mechanism is also studied in this research.
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