Browsing by Author "Azeredo, Rudimylla Septimio"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    Item
    Microstructural and segregation efects afecting the corrosion behavior of a high‐temperature Bi‐Ag solder alloy in dilute chloride solution.
    (2021) Azeredo, Rudimylla Septimio; Cruz, Clarissa Barros da; Silva, Bismarck Luiz; Garcia, Amauri; Spinelli, José Eduardo; Cheung, Noé
    In electronic devices the solder joint is exposed not only to the air but also to moistures and other corrosive media such as chlorine and sulfur compounds. Bi–Ag alloys meet the melting temperature requirement to be classifed as high-temperature solders, therefore, knowledge of corrosion behavior is important for a long-term reliability of Bi–Ag solder connections. However, corrosion studies of Bi–Ag alloys are quite restricted in the literature. In this study, the role of the representative length scale of the microstructure as well as of the efects of Ag segregation on the resulting corrosion behavior of Bi–4 wt% Ag alloy samples are investigated. Cyclic potentiodynamic polarization and electrochemical impedance spectroscopy measurements were performed, and an equivalent circuit was also proposed to simulate the electrochemical corrosion behavior. All the used techniques indicated a tendency of better corrosion resistance associated with the sample having coarser microstructure and less Ag content.