添加Nd及Lu對共晶銦錫銲錫之特性影響研究

Abstract

在In-49Sn銲錫合金中，各添加0.5wt.%的Nd和Lu，分別會在銲錫基地內形成Nd(Sn0.6In0.4)3及 Lu(Sn0.5In0.5)3介金屬化合物。經過迴銲完，In-49Sn、In-49Sn-0.5Nd和In-49Sn-0.5Lu三種銲錫與化鎳金(ENIG)基板界面會生成Ni3(In,Sn)4介金屬層，與有機保銲膜(OSP)基板界面則會生成Cu6(In,Sn)5介金屬層。介金屬層的厚度隨著時效溫度與時效時間的增加而呈線性增加，當中添加稀土元素會抑制界面介金屬層的成長，尤其以In-49Sn-0.5Nd抑制效果較好。 強度測試方面，無論是推球、拉球或是快速推球試驗，破斷都發生在銲錫球內部，為延性破斷。添加稀土元素會提升銲錫的抗拉強度，但快速推球強度反而會下降，這是由於稀土元素活性大易氧化，迴銲時氧化物被助銲劑帶出在銲錫與基板界面間產生孔洞，同時快速推球會使破斷面轉而發生在銲錫接近界面處，導致接點強度下降。

Adding 0.5wt.% Nd and Lu into In-49Sn solder alloy form Nd(Sn0.6In0.4)3 and Lu(Sn0.5In0.5)3 intermetallic compounds in solder matrix. After reflowing, In-49Sn、In-49Sn-0.5Nd and In-49Sn-0.5Lu solder alloys form Ni3(In,Sn)4 interfacial intermetallic compound with ENIG pads and form Cu6(In,Sn)5 interfacial intermetallic compound with OSP pads. The thickness of interfacial intermetallic compound grows linearly with aging temperature and aging time. Within the three solder alloys, addingrare-earth elements will suppress the thickness of interfacialintermetallic compound, especially In-49Sn-0.5Nd. As to the bonding strength tests which are ball shear tests, pull tests and high speed shear tests, all cleavages occur in the solder balls and show ductile fracture. Adding rare-earth elements results in the higher tensile strength, but high speed ball shear strength declines. The reason is that the rare-earth elements are very active and oxidize easily which leads the oxidation to be brought out by the flux during reflowing and then voids formed on the interface between solder and pad. Meanwhile, high speed shear test will make the fracture occur in the solder near the interface and result in the lower bonding strength.