The demand for low temperature soldering in electronic manufacturing has surged, driven by the necessity for a hierarchy of solder alloys in packaging technology with the need for enhanced reliability. Among the potential solutions, the Sn-Bi series solder emerges as a promising candidate due to its low melting point, cost-effectiveness, and eco-friendliness. However, its brittleness has hindered widespread adoption. Consequently, extensive efforts have been directed towards enhancing the properties of Sn-Bi based solders. Third element additions have offered partial improvements but have not provided complete solutions. The Sn-58Bi based solder were prepared via the casting method. Indium (In) were then added to the based solder at different weight percentages which were 6.5, 10.5 and 12. Microstructure of the bulk solder were then examined by using Scanning Electron Microscope (SEM). Solidification graphs were simulated by using Thermo-Calc Software to further discuss the results of the microstructure. It is expected that by adding In to Sn-58Bi, the microstructure will consist primarily of β-Sn and Bi phases with the existence of InBi phases, where it will be consistent with the phase diagram simulated by Thermo-Calc Software.