Effect of surface finish of substrate on mechanical reliability of In-48Sn solder joints in MOEMS package

Abstract

Interfacial reactions and shear properties of the In-48Sn (in wt.%) ball grid array (BGA) solder joints after bonding were investigated with four different surface finishes of the substrate over an underlying Cu pad: electroplated Ni/Au (hereafter E-NG), electroless Ni/immersion Au (hereafter ENIG), immersion Ag (hereafter I-Ag) and organic solderability preservative (hereafter OSP). During bonding, continuous AuIn 2 , Ni 3 (Sn,In) 4 and Cu 6 (Sn,In) 5 intermetallic compound (IMC) layers were formed at the solder/E-NG, solder/ENIG and solder/OSP interface, respectively. The interfacial reactions between the solder and I-Ag substrate during bonding resulted in the formation of Cu 6 (Sn,In) 5 and Cu(Sn,In) 2 IMCs with a minor Ag element. The In-48Sn/I-Ag solder joint showed the best shear properties among the four solder joints after bonding, whereas the solder/ENIG solder joint exhibited the weakest mechanical integrity.

Characterization of Cu-Sn-In thin films for three-dimensional heterogeneous system integration

“…According to the ternary Cu-Sn-In phase diagram [125], this composition corresponds to the h phase (Cu 6 (Sn,In) 5 ), which is consistent with the observed XRD peaks. This observation is in line with previous studies which showed that only the h phase forms at temperatures below 200 o C [126,127,147]. The solder peaks are associated with the InSn 4 phase, as expected from the Sn-In phase diagram [53].…”

“…The There have been several reports on the potential use of Sn-In solder material as a`glue' agent. However, most of these studies have focused on bulk solders [127,147,148]. A few groups [28,126] have reported investigations of Sn-In thin lms bonded with Cu, but those were mainly focused on bonding of Cu/Sn-In bilayers to Cu, to sandwich the solder between Cu layers.…”

Influence of Bonding Parameters on the Interaction Between Cu and Noneutectic Sn-In Solder Thin Films

“…This observation is in line with previous studies which showed that only the g-phase forms at temperatures below 200°C. 8,10,20 The solder peaks are associated with the InSn 4 phase, as expected from the Sn-In phase diagram. 7…”

“…It can be seen that IMC has not formed in unannealed samples. Based on EDS measurements, the IMC that forms in annealed samples has a composition in the range of (53-64)Cu-(24-34)Sn- (7)(8)(9)(10)(11)(12)(13)(14)In. According to the ternary Cu-Sn-In phase diagram, 19 this composition corresponds to the g-phase [Cu 6 (Sn,In) 5 ], which is consistent with the observed XRD peaks.…”

“…However, most of these studies have focused on bulk solder. [8][9][10] A few groups have reported investigations of Sn-In thin films bonded with Cu, but those were mainly focused on bonding of Cu/Sn-In bilayers to Cu, to sandwich the solder between the Cu layers. 2 In a sandwich structure, the interaction between the Cu and Sn-In layers is relatively complex, as the reaction at one interface can be affected by an interaction at the other interface.…”