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 hightemperature 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 electroplatedDBC system thus prepared was TLP bonded with Si chip at 250 °Cfor 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 40mA 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 °Cfor 10 min. The shear bonding strength of the Si/DBCjoint increased with Cu content in the Sn-Cu solder until 20 at% in the Sn-Cu interlayer.