Per: Clarissa Barros da Cruz (unicamp), andré dos santos barros (unicamp), rafael kakitani (unicamp), Thiago Soares Lima (unicamp), amauri garcia (unicamp), noé cheung (unicamp)
Abstract:
Thermal interface materials (TIMs) are responsible for the thermal exchange between the heat source of the integrated processor and the heatsink base. Due to their low melting point, good fluidity and compliance with regulatory requirements (Restriction of Hazardous Substances - RoHS), bismuth-based alloys have been investigated for application as high performance TIMs. In this context, the analysis of the properties of these alloys as functions of microstructural parameters becomes, therefore, of high scientific and technological interest for the electronic industry. Thus, this work aims to develop correlations between tensile properties and the microstructure of the Bi-0.28wt.%Ni alloy processed by an upward directional solidification technique under a range of cooling rates usually obtained in industrial processes. By means of optical and scanning electron microscopy, a typical lamellar eutectic morphology was observed, composed of lamellae bismuth-rich with the Bi3Ni intermetallic phase in the interlamellar region. Then, the lamellar spacings (λL) were correlated with solidification thermal parameters to propose microstructural growth laws. Finally, it was observed that, for λL <101 μm, Hall-Petch type equations characterize the variation of both the ultimate tensile strength and the yield strength.