We investigated interfacial reactions and structural changes occurring in 15 um -diameter goldbonding wires with varying palladium contents (0, 0.05, 0.1, 0.3, and 1.0%) bonded to 5 um-thick aluminumpads and subjected to accelerated high-temperature testing at 175°C for up to 1,000 h. Compared withconventional 1um aluminum pads, the increased aluminum thickness in 5 um pads caused most of the firstball bond area to transform into intermetallic compounds overtime. For gold bonding wires without palladiumaddition, rapid gold diffusion resulted in deformation of the first ball bond after 250 h at 175°C . After 1,000 h,all gold at the top of the first ball bond was consumed, forming a thin neck and leading to crack formation. As the palladium content increased, a Pd-rich barrier formed between the first ball bond region and the IMClayer, slowing the diffusion of gold into the aluminum pad. This helped preserve the gold at the top of thefirst ball bond and maintained a stable bonding interface even after 1,000 h. However, in the case of goldbonding wires containing 1.0% palladium, after 250 h, the Pd-rich barrier further slowed gold diffusion whileaccelerating aluminum diffusion, resulting in the formation of large voids in the aluminum pad area. Therefore, when applying 15 um fine gold bonding wires to relatively thick 5 um aluminum pads, the additionof an appropriate palladium content (approximately 0.05–0.3%) was found to be advantageous for ensuringhigh-temperature reliability.