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Fine grained and nanotwinned Au has many excellent properties and is widely used in electronic devices. We have fabricated ⟨ 110 ⟩ preferred-oriented Au thin films by DC plating at 5 mA/cm2. Microstructure analysis of the films show a unique fine grain structure with a twin formation. Hardness tests performed on electroplated ⟨ 110 ⟩ Au films show a hardness 47% greater than random and untwinned Au. We then achieved direct bonding between two Au ⟨ 110 ⟩ surfaces operating at 200 °C for an hour in a vacuum oven. The highly-oriented ⟨ 110 ⟩ nanotwinned Au films could be an ideal material in many gold products. [ABSTRACT FROM AUTHOR]

Abstract: 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 η-Cu6Sn5 intermetallic compound in microbumps by using 〈111〉 oriented and nanotwinned Cu pads as the under-bump-metallization. By electroplating arrays of large numbers of 〈111〉 oriented and nanotwinned Cu pads and by electroplating the Sn2.3Ag solder on the pads, we form η-Cu6Sn5 in the reflow at 260°C for 1min. The η-Cu6Sn5 showed a highly preferential growth along the 〈0001〉 direction. As reflow time is extended, the preferred texture of η-Cu6Sn5 changed to { }. The results indicate that we can control the uniform microstructure of η-Cu6Sn5 intermetallic by controlling the microstructure of the Cu under-bump-metallization. [Copyright &y& Elsevier]