Navegando por Autor "Brito, Crystopher"

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Interplay of wettability, interfacial reaction and interfacial thermal conductance in Sn-0.7Cu solder alloy/substrate couples
(Springer, 2020) Lima, Thiago Soares; Cruz, Clarissa Barros da; Silva, Bismarck Luiz; Brito, Crystopher; Garcia, Amauri; Spinelli, José Eduardo; Cheung, Noé
Directional solidification experiments coupled with mathematical modelling, drop shape analyses and evaluation of the reaction layers were performed for three different types of joints produced with the Sn-0.7 wt.%Cu solder alloy. The association of such findings allowed understanding the mechanisms affecting the heat transfer efficiency between this alloy and substrates of interest. Nickel (Ni) and copper (Cu) were tested since they are considered work piece materials of importance in electronic soldering. Moreover, low carbon steel was tested as a matter of comparison. For each tested case, wetting angles, integrity and nature of the interfaces and transient heat transfer coefficients, ‘h’, were determined. Even though the copper has a thermal conductivity greater than nickel, it is demonstrated that the occurrence of voids at the copper interface during alloy soldering may decrease the heat transfer efficiency, i.e., ‘h’. Oppositely, a more stable and less defective reaction layer was formed for the alloy/nickel couple. This is due to the suppression of the undesirable thermal contraction since the hexagonal Cu6Sn5 intermetallics is stable at temperatures below 186°C in the presence of nickel
Sn-0.5Cu(-x)Al solder alloys: microstructure-related aspects and tensile properties responses
(MDPI, 2019) Lima, Thiago Soares; Gouveia, Guilherme Lisboa de; Septimio, Rudimylla da Silva; Cruz, Clarissa Barros da; Silva, Bismarck Luiz; Brito, Crystopher; Spinelli, José Eduardo; Cheung, Noé
In this study, experiments were conducted to analyze the effect of 0.05 and 0.1 wt.% Al additions during the unsteady-state growth of the Sn-0.5wt.%Cu solder alloy. Various as-solidified specimens of each alloy were selected so that tensile tests could also be performed. Microstructural aspects such as the dimensions of primary, λ1, and secondary, λ2, dendritic arrays, and intermetallic compounds (IMCs) morphologies were comparatively assessed for the three tested compositions, that is, Sn-0.5wt.%Cu, Sn-0.5wt.%Cu-0.05wt.%Al, and Sn-0.5wt.%Cu-0.1wt.%Al alloys. Al addition affected neither the primary dendritic spacing nor the types of morphologies identified for the Cu6Sn5 IMC, which was found to be either globular or fibrous regardless of the alloy considered. Secondary dendrite arm spacing was found to be enlarged and the eutectic fraction was reduced with an increase in the Al-content. Tensile properties remained unaffected with the addition of Al, except for the improvement in ductility of up to 40% when compared to the Sn-0.5wt.%Cu alloy without Al trace. A smaller λ2 in size was demonstrated to be the prime microstructure parameter associated with the beneficial effect on the strength of the Sn-0.5wt.%Cu(-x)Al alloys. View Full-Text

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Navegando por Autor "Brito, Crystopher"