本論文在探討銅導線上鍍金或鎳/金對遷移性之影響及鍍金層對Sn-0.7Cu與In-48Sn BGA銲料迴銲後之接點強度影響。銅導線表面電鍍0.1 ~ 1.0 µm金後，分別在蒸餾水、0.01M NaCl及(NH4)2SO4水溶液中，施以5V偏壓，進行遷移研究。結果顯示：表層鍍金之銅導線，具有抑制銅遷移之效果。此鍍金銅導線在250°C持溫300秒後，在較低偏壓情況下，抗遷移性顯著增強；在較高偏壓情況下，熱處理降低鍍金0.1 µm之銅導線的遷移阻抗，當鍍金厚度大於0.5 µm時，則沒有影響。 銅導線表面電鍍5 µm鎳後，隨即電鍍0.1 ~ 1.0 µm金，之後在蒸餾水及(NH4)2SO4水溶液中，施以5V偏壓，進行遷移研究。結果顯示：表層鍍鎳/金之銅導線，同樣具有抑制銅遷移之效果。但此鍍鎳/金銅導線在250°C持溫300秒後，抗遷移性顯著減弱。 在0.01M (NH4)2SO4水溶液中進行陽極動態極化掃描及定電位陽極反應，配合ESCA表面分析，得知金在(NH4)2SO4水溶液中不會發生反應，因此金及鎳/金鍍層能夠有效地抑制銅遷移。 為了探討金層對於BGA銲接點強度影響，先在鍍鎳(5µm)銅銲墊上電鍍0.1 ~ 1.2 µm金層，再分別與Sn-37Pb、Sn-0.7Cu及In-48Sn銲球進行迴銲，迴銲後即進行剪力量測，結果顯示：隨著金鍍層愈厚，Sn-37Pb銲料的強度愈差，而Sn-0.7Cu及In-48Sn銲料的強度則些微增強。 Effects of Au and Ni/Au coatings on the electrolytic migration of copper conductors have been studied. The migration of the copper conductors in dionized water, 0.01M NaCl and (NH4)2SO4 solutions at a bias of 5V was inhibited by coating a layer of Au in thickness of 0.1 ~ 1.0 μm. When Au-coated copper conductors are under a lower bias (e.g. < 0.5VSCE), heat treatment (at 250 ℃ for 300 seconds) enhances the migration resistance. To the opposite, under a higher bias (e.g. > 1.4VSCE), heat treatment diminishes the migration resistance for the specimen coated with only 0.1 μm Au, but causes no influence with the thickness of Au-coats greater than 0.5 μm. The migration inhibition is more efficient with increasing thickness of the Au-coats from 0.1 to 1.0 μm in the case of Ni/Au-coated copper conductors. However, it is less efficient when the Ni/Au-coated conductors have been heat-treated at 250 ℃ for 300 seconds. Electrochemical polarization such as potentiodynamic and potentiostatic experiments were conducted. The ESCA analysis for the anode indicates that gold is un-reactive for Au-coated copper conductors and Ni/Au-coated copper conductors in the 0.01M (NH4)2SO4 solution. Effect of Au coatings on joint strength of ball grid array (BGA) estimated by conducting the shear test of the soldered system where Sn-37Pb, Sn-0.7Cu and In-48Sn solders have been reflowed, respectively, onto the Au-deposited Ni/Cu pads. The thickness of Au-deposits is ranging from 0.1 to 1.2 µm and that for Ni-coat is 5µm. The Sn-37Pb alloy had a slight decrement in ball shear strength with increasing the thickness of gold coat from 0.1 μm to 1.0 μm. The strength however was degraded drastically while the gold coat is 1.2 μm. On the other hand, the two lead free systems had a slight increment in ball shear strength with increasing the thickness of gold coat.
