The Effect of Neodymium and Lutetium Additions On the Properties of In-49Sn Solder
Date Issued
2010
Date
2010
Author(s)
Hsu, Chieh-Wei
Abstract
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.
Subjects
Pb-free solder
rare-earth element
Intermetallic compound
interfacial reaction
High speed ball shear test
Type
thesis
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