Study on Space-confined Ni/Sn/Cu Diffusion Couples

• Main Authors: Wen-Lin Shih, 施玟伶
• Other Authors: 高振宏
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/16463552026970631211

博士 === 國立臺灣大學 === 材料科學與工程學研究所 === 103 === It is obvious that 3D IC integration is the mainstream in electronic packaging for the following decades. However, large volume fractions of IMC grains in 3D IC micro-joints would undoubtedly weaken the mechanical properties of the joints. Therefore, researching on the microstructural and mechanical properties of IMCs under space confinement is quite essential. Although the usage of Ni/Sn/Cu structure has been well established for decades, its application in 3D IC architecture is still in the building stage. In space-confined Ni/Sn/Cu diffusion couples, the remaining Sn would convert into IMCs rapidly. Since Ni is found to be effective in the elimination of the allotropic transformation in Cu6Sn5, it could also help to reinforce the thermo-mechanical properties in Cu6Sn5. Yet, what would happen in space-confined Ni/Sn/Cu diffusion couple? The aims of this thesis is uncovered the influence of space confinement on Ni/Sn/Cu diffusion couples. There are four parts in the thesis, including: (1) Peculiar microstructure evolution in space-confined Ni/Sn/Cu (2) Influences of solder volume reduction on the growth kinetics (3) Growth mechanism of Cu3Sn in space-confined Ni/Sn/Cu (4) Influence of Ni concentration on the mechanical properties in space-confined Ni/Sn/Cu According to the research, the originated (Cu,Ni)6Sn5 layer would suppress the growth of Cu3Sn as the Sn still remained. However, as the Sn exhausted, Cu3Sn grew rapidly along the grain boundaries of (Cu,Ni)6Sn5 grains. The kinetic analysis shows that there is a distinct cut-off point in the growing curves for (Cu,Ni)6Sn5 and Cu3Sn. It would result in the dominant reaction in Ni/Sn/Cu/diffusion couples. Comparing with the microstructure evolution in Ni/Sn (10μm)/Cu, the cut-off points is exactly located at the time the Sn was exhausted. Therefore, it is rational to believe that the reason for Cu3Sn growth along the grain boundaries of (Cu,Ni)6Sn5 is due to the exhausted of Sn. Moreover, the thesis also investigate on the Ni concentration induced mechanical property variations in space-confined Ni/Sn/Cu. The results shows that the concentration gradient of Ni in IMC grains would result in a laminar distribution of mechanical properties.