DEENP - Artigos publicados em periódicos

URI permanente para esta coleçãohttp://www.hml.repositorio.ufop.br/handle/123456789/557

Navegar

Filtros

2020 - 20212

Configurações

Autor: search.filters.author.Cheung, NoéAssunto: search.filters.subject.Heat transfer

Resultados da Pesquisa

Agora exibindo 1 - 2 de 2
  • Nenhuma Miniatura Disponível
    Item
    Interface evaluation of a Bi–Zn eutectic solder alloy : effects of different substrate materials on thermal contact conductance.
    (2021) Azeredo, Rudimylla Septimio; Cruz, Clarissa Barros da; Xavier, Marcella Gautê Cavalcante; Lima, Thiago Soares; Garcia, Amauri; Spinelli, José Eduardo; Cheung, Noé
    Industry is searching for ways of improving the process control required for the manufacture of electronic circuitry. In this respect, a numerical mathematical model for thermal contact conductance of solder/substrate couples is developed based on an inverse heat conduction problem. The intention of this research is combining the model results and wetting experiments in order to determine if there is a compromise between them in the matter of the Bi–Zn eutectic alloy. Substrate materials considered as priority for the electronics industry were tested. It was found that the heat transfer coefficients (h) and the contact angles (θ) might be related to each other. The Bi–Zn/copper, Bi–Zn/nickel, Bi–Zn/Invar and Bi–Zn/steel couples, in this order, generated θ varying from the smallest to the largest as well as h from the largest to the smallest. Microstructural coarsening effect has been realized with higher spacing between Zn fibers (λZn) referring to a condition of worse heat extraction imposed by an alloy/substrate couple during solidification.
  • Nenhuma Miniatura Disponível
    Item
    Interplay of wettability, interfacial reaction and interfacial thermal conductance in Sn-0.7Cu solder alloy/substrate couples.
    (2020) Lima, Thiago Soares; Cruz, Clarissa Barros da; Silva, Bismarck Luiz; Brito, Crystopher Cardoso de; 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 sup-pression of the undesirable thermal contraction since the hexagonal Cu6Sn5 intermetallics is stable at temperatures below 186C in the presence of nickel.