Effect of Pd thickness on bonding reliability of Pd coated copper wire

In the study, the effects of Pd thickness on free air ball, wire elongation/strength on bonding strength and bonding interface of Pd coated copper wire bonding were discussed. It was found that the Pd thickness effects on free air ball, the free air ball will become golf ball when the Pd thickness is thin excessively, then the Pd thickness is not less than 0.47% to the wire diameter, and high tensile strength and low elongation of the Pd coated copper wire will cause the second bond neck crack and irregular wedge formation for the second bond. After PCT test, voiding phenomenon happens at the bonding interface and the bonding strength also significantly reduced because little Pd doesn't form an effective protected layer on the bonded interface, and Cu9Al4 cannot be detected anymore because of corroding by Br. In the high temperature and high humidity condition, Pd coated copper wire with more Pd thickness can form an effective protected layer and increase the bonded strength.