Eutectic Bonding in Sequential Bi and Sn Layers for Low-Temperature Interconnections

In the current study, low-temperature bonding of SAC 305 solder balls is achieved using electroplated Bi and Sn layers. The Bi and Sn interface initiates melting at the eutectic temperature, providing the opportunity to bond the electroplated layers with SAC 305 solder ball at 170°C. Compared to the conventional use of Sn58Bi solder paste, the current method allows for control over the quantity of bismuth within the solder joint. A nanocomposite solder ball is fabricated using ultrasonic melt treatment dispersion and disc punching technique. The hybrid bond formed with the nanocomposite solder ball displays higher shear strength, attributed to Bi-phase refinement and dispersion strengthening.