本論文在探討鎳、錫電鍍層對銅導線遷移性之影響，以及Sn-3.5Ag BGA銲料在鍍金之鎳/銅銲墊上迴銲導致之金脆現象。銅導線表面電鍍2.5∼10µm鎳後，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：表層鍍鎳之銅導線，具有抑制銅遷移之效果，隨鎳鍍層厚度增加(2.5∼10µm) 抗遷移性增強，但此鍍鎳銅導線在250°C持溫300秒後，抗遷移性顯著減弱。 銅導線表面電鍍1、2及3µm錫後，雖在蒸餾水及0.01M (NH4)2SO4水溶液中5V偏壓下不能抵抗遷移，但將鍍1µm錫之銅導線在250°C持溫300秒後，立即具有良好抗遷移性，顯然鍍錫銅導線因加熱處理而增強其抗遷移性。 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，得知鎳、錫鍍層抑制銅遷移的原因如下：鎳鍍層在銅導線表面因陽極鈍化而生成保護膜，此鈍化膜在鎳表層為NiO及Ni(OH)2；另一方面，經加熱後之錫鍍層生成SnO2，可以抑制底層銅的溶解及氧化。 金脆研究先在鍍鎳(5µm)銅銲墊上電鍍0.1、0.5及1µm金層，再分別與Sn-Pb(63/37)及Sn-3.5Ag銲球進行迴銲，迴銲後即進行剪力量測，結果顯示：Sn-3.5Ag銲料比Sn-Pb銲料有更好的抗剪力強度（因生成Ag3Sn介金屬強化相）；金鍍層愈厚，抗剪力強度愈差。 Effect of Ni and Sn coating on the migration of Cu-conductors, and gold-embrittlement induced by reflow of the Sn-3.5Ag BGA solder on the gold deposited Ni/Cu pads have been studied. The migration of the Cu-conductors in distilled water, 0.01M Nacl and (NH4)2SO4 solutions at a bias of 5V was inhibited by coating a layer of Ni in thickness of 2.5∼10µm. This inhibition is more efficient with increasing the thickness of the Ni-coats from 2.5 to 10µm. However, it is less efficient when the Ni-coated conductors have been heat-treated at 250℃ for 300s. The migration inhibition is not so efficient in the case of Sn-coated Cu-conductors at the same conditions. However, heat treatment (at 250℃ for 300s) tremendously enhances the resistance of the Sn-coated conductors to migration, even though the thickness of the Sn-coat only at 1µm. Electrochemical polarization such as potentiodynamic and potentiostatic experiments were conducted. The XPS analysis for the reaction products formed on the anode indicates that NiO and Ni(OH)2 are responsible for migration inhibition of the Ni-coated conductors, and SnO2 is for the heat-treated Sn-coating conductors. Gold-embrittlement was estimated by conducting the shear test of the soldered system where Sn-Pb (63/37) and Sn-3.5Ag solders have been reflowed, respectively, onto the Au-deposited Ni/Cu pads. The thickness of Au-deposits is ranging from 0.1 to 1µm and that for Ni-coat is 5µm. It was found that the shear strength is stronger for the Sn-3.5Ag soldering bond than for the Sn-Pb soldering. Intermetallic phase (Ag3Sn) strengthens the soldering bond. The shear strength decreases with an increase of the thickness of gold coats.
