Microstructure and reaction layer of Sn-Bi-In soldered joints

Abstract

This proposal aims to deepen the knowledge of Sn-Bi alloys modified with indium (In). Sn-Bi-In alloys have aroused interest as low melting soldering alloys in the sense of composing vertical packages of Si chips as well as serving as alloys for thermal joints, acting in the increase of heat dissipation in electronic systems of high power density. Understanding Sn-Bi-In alloys involves not only the microstructural formation, but also the evaluation of the resulting reaction film interfaces between these alloys in contact with copper (Cu) substrate, most commonly used in microelectronic components. In the case of joint interfaces joined by the soldering process, aspects such as wettability, thickness and nature of the reaction layer, dissolution of the substrate forming element and generated solidification microstructure are of fundamental importance, which control application properties such as, for example, mechanical strength and corrosion resistance. As such, the objectives of this proposal are: i. establish correlations between the dendritic / eutectic growth of the Sn-40 wt.% Bi-10 wt.% In alloy with cooling rates associated with solidification and ii. Evaluate the behavior of the reaction layer interface by replicating exposure conditions of the as-soldered joints, such as time and temperature in service conditions.