Concentration Gradient of Ni in Reduced SnAg Thickness in Ni/SnAg/Cu Microbumps during Solid-State Aging

• DOI: 10.1149/2.009302ssl
• Publication Date: 2012-11-29T00:31:10Z
• Authors: T.-C. Liu; Y.-S. Huang; C. Chen
• Keywords: 02 engineering and technology; 0210 nano-technology

We investigate the cross-interaction in Cu/SnAg/Ni microbumps with a reduced solder thickness of 30 and 10 μm. The concentration of Ni atoms at the opposite site increased with the decrease in solder-height. A considerable concentration gradient of Ni was detected in 10-μm microbumps sample, which strongly triggers the diffusion of Ni atoms to the Cu side. The diffused Ni atoms at Cu side form the ternary intermetallic compounds of (Cu,Ni)6Sn5, which possesses a lower free energy than Cu6Sn5 does. Eventually, the growth of the Cu3Sn was inhibited due to the formation of the thermodynamically stable (Cu,Ni)6Sn5. © 2012 The Electrochemical Society. [DOI: 10.1149/2.009302ssl] All rights reserved.