Microstructure control of unidirectional growth of eta-Cu6Sn5 in microbumps on %26lt; 1 1 1 %26gt; oriented and nanotwinned Cu

作者：Lin Han wen; Lu Chia ling; Liu Chien min; Chen Chih^*; Chen Delphic; Kuo Jui Chao; Tu K N

来源：Acta Materialia, 2013, 61(13): 4910-4919.

DOI：10.1016/j.actamat.2013.04.056

• Intermetallic compounds
• Soldering
• Copper

Anisotropic microstructure is becoming a critical issue in microbumps used in 3-D integrated circuit packaging. We report here an experimental approach for controlling the microstructure of eta-Cu6Sn5 intermetallic compound in microbumps by using %26lt; 1 1 1 %26gt; oriented and nanotwinned Cu pads as the under-bump-metallization. By electroplating arrays of large numbers of %26lt; 1 1 1 %26gt; oriented and nanotwinned Cu pads and by electroplating the Sn2.3Ag solder on the pads, we form eta-Cu6Sn5 in the reflow at 260 degrees C for 1 min. The eta-Cu6Sn5 showed a highly preferential growth along the %26lt; 0 0 0 1 %26gt; direction. As reflow time is extended, the preferred texture of eta-Cu6Sn5 changed to {2 (1) over bar (1) over bar 3}. The results indicate that we can control the uniform microstructure of eta-Cu6Sn5 intermetallic by controlling the microstructure of the Cu under-bump-metallization.

• 出版日期2013-8