Joining of lotus-type porous copper to alumina substrate by direct bonded copper technique

초록

This study investigates the Direct Bonded Copper (DBC) process using lotus copper, a unidirectional porous material, for direct bonding to alumina ceramic substrates. Lotus copper is fabricated via a continuous casting process in a hydrogen-nitrogen atmosphere. When using the conventional DBC method, the lotus structure tends to collapse due to excessive molten copper flow driven by high surface tension. Therefore, a modified DBC bonding process was specifically designed for lotus copper, as the conventional approach proved unsuitable. A key aspect of successful DBC bonding is the reaction between molten copper and alumina surface to form an intimate interfacial bond. By controlling the oxidation rate on the surface of the lotus copper, the mobility of molten copper should be limited to satisfy the conditions for reaction and bonding with alumina. A redesigned DBC process was implemented, and bonding experiments were conducted under various time conditions. Under the integrated DBC process, the bonded DBC specimens retained the morphology of lotus copper. The shear strength evaluation of the bonding interface confirmed that lotus copper could be successfully joined to the alumina substrate even without a separate oxidation pretreatment step. This demonstrates the potential applicability of the porous copper structure in advanced ceramic-metal joining applications.

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