In this paper, the characteristics of eutectic Sn–Bi microsolder bumps fabricated by electroplating are investigated. The underbump metallization (UBM) layers on a Si chip consist of Al, Cu, Ni, and Au, sequentially from bottom to top. The desired Sn–Bi bump size has a diameter of 22 and pitch of 44 . In order to obtain the optimal conditions for the eutectic Sn–Bi solder bumps, the polarization curves of Sn, Bi, and Sn–Bi electrolytes are analyzed, and the variation of the Sn–Bi composition as a function of the current density is measured. Experimentally, from the polarization curve, Bi and Sn start to deposit below and , respectively, and Sn–Bi codeposition occurs below an electropotential of . The Bi content of the electroplated bumps decreases from 92.4 to 38.2 wt% when the current density is increased from 20 to 50 , and near-eutectic composition of the Sn-61 wt% Bi bump is obtained by plating at 40 for 5 min. The surface of the Sn–Bi microsolder bumps show plate-like structures with acicular shapes, and the grain size increases with increasing current density. An intermetallic compound layer, estimated as with a thickness of about 0.5 , was observed between the UBM layers and the as-plated Sn–Bi bumps.