Cooling thermal parameters and microstructure features of directionally solidified ternary Sn–Bi–(Cu,Ag) solder alloys
- Department of Manufacturing and Materials Engineering, University of Campinas, UNICAMP, 13083-860 Campinas, SP (Brazil)
- Department of Materials Engineering, Federal University of São Carlos, UFSCar, 13565-905 São Carlos, SP (Brazil)
Low temperature soldering technology encompasses Sn–Bi based alloys as reference materials for joints since such alloys may be molten at temperatures less than 180 °C. Despite the relatively high strength of these alloys, segregation problems and low ductility are recognized as potential disadvantages. Thus, for low-temperature applications, Bi–Sn eutectic or near-eutectic compositions with or without additions of alloying elements are considered interesting possibilities. In this context, additions of third elements such as Cu and Ag may be an alternative in order to reach sounder solder joints. The length scale of the phases and their proportions are known to be the most important factors affecting the final wear, mechanical and corrosions properties of ternary Sn–Bi–(Cu,Ag) alloys. In spite of this promising outlook, studies emphasizing interrelations of microstructure features and solidification thermal parameters regarding these multicomponent alloys are rare in the literature. In the present investigation Sn–Bi–(Cu,Ag) alloys were directionally solidified (DS) under transient heat flow conditions. A complete characterization is performed including experimental cooling thermal parameters, segregation (XRF), optical and scanning electron microscopies, X-ray diffraction (XRD) and length scale of the microstructural phases. Experimental growth laws relating dendritic spacings to solidification thermal parameters have been proposed with emphasis on the effects of Ag and Cu. The theoretical predictions of the Rappaz-Boettinger model are shown to be slightly above the experimental scatter of secondary dendritic arm spacings for both ternary Sn–Bi–Cu and Sn–Bi–Ag alloys examined. - Highlights: • Dendritic growth prevailed for the ternary Sn–Bi–Cu and Sn–Bi–Ag solder alloys. • Bi precipitates within Sn-rich dendrites were shown to be unevenly distributed. • Morphology and preferential region for the Ag{sub 3}Sn growth depend on Ag content and Ṫ{sub L}. • Rappaz-Boettinger model reasonably estimated the experimental scatter of λ{sub 2}.
- OSTI ID:
- 22587126
- Journal Information:
- Materials Characterization, Vol. 114; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
77 NANOSCIENCE AND NANOTECHNOLOGY
ALLOYS
CORROSION
DENDRITES
ELECTRON SCANNING
EUTECTICS
HEAT
HEAT FLUX
MICROSTRUCTURE
MORPHOLOGY
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SEGREGATION
SOLDERED JOINTS
SOLIDIFICATION
TEMPERATURE RANGE 0400-1000 K
X-RAY DIFFRACTION
X-RAY FLUORESCENCE ANALYSIS