| Title |
Effect of Palladium Content in Gold Bonding Wire on High-Temperature Reliability of Thick Aluminum Pads |
| Authors |
김상엽(Sang-Yeob Kim) ; 송오성(Oh-Sung Song) |
| DOI |
https://doi.org/10.3365/KJMM.2026.64.5.433 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Al pad thickness; Gold alloy wire; High-temperature reliability; Palladium contents; Kirkendall void |
| Abstract |
We investigated interfacial reactions and structural changes occurring in 15 um -diameter gold
bonding wires with varying palladium contents (0, 0.05, 0.1, 0.3, and 1.0%) bonded to 5 um-thick aluminum
pads and subjected to accelerated high-temperature testing at 175°C for up to 1,000 h. Compared with
conventional 1um aluminum pads, the increased aluminum thickness in 5 um pads caused most of the first
ball bond area to transform into intermetallic compounds overtime. For gold bonding wires without palladium
addition, 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 IMC
layer, slowing the diffusion of gold into the aluminum pad. This helped preserve the gold at the top of the
first ball bond and maintained a stable bonding interface even after 1,000 h. However, in the case of gold
bonding wires containing 1.0% palladium, after 250 h, the Pd-rich barrier further slowed gold diffusion while
accelerating 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 addition
of an appropriate palladium content (approximately 0.05?0.3%) was found to be advantageous for ensuring
high-temperature reliability. |