Transient liquid phase bonding of silicon and direct bond copper via electroplating of tin-copper interlayers for power device applications

Joining technology of silicon semiconductors devices to direct bond copper (DBC) substrates in high-temperature power electronics packages is of utmost importance today. In this study, Sn–Cu solder was prepared by electroplating on a direct bonded copper (DBC) substrate. The electroplated DBC system thus prepared was TLP bonded with Si chip at 250 °C for 10 min under a vacuum atmosphere. The effect of electrical charge used for plating Sn–Cu solder, void fraction in the joint, Sn–Cu solder composition on the joining characteristics, and shear strength of the Si-DBC system were analyzed. The experimental results showed that the plating thickness increased almost linearly with plating time and electrical charge. A sound Sn–Cu solder plating thickness was obtained at 40 mA cm⁻², 11 C cm⁻², 20 min with 20 at% Cu in the deposit. Furthermore, the plated Sn–Cu solder layer transformed to Cu₆Sn₅ and Cu₃Sn after joining at 250 °C for 10 min. The shear bonding strength of the Si/DBC joint increased with Cu content in the Sn–Cu solder until 20 at% in the Sn–Cu interlayer. (paper)