Superior Reliability of SAC105 Solder on BGA Package Pad with NiPdAu Coating
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The reliability of Sn-Ag-Cu (SAC) solder welded with Cu-organic solderability preservative (OSP) and NiAu- or NiPdAu-coated ball grid array (BGA) package pads has been investigated after isothermal aging. Moreover, the interfacial reaction and diffusion reaction are discussed. The intermetallic compound (IMC) layer was found to be too thick to withstand large stresses, leading to poor reliability of the solder joints on Cu-OSP pads. Additionally, for NiAu-coated pads, not only irregular Au-rich phases but also more diffused Ni without the barrier effect of Pd promoted formation of IMC in the solder balls, resulting in a potential mismatch with the initial solder. Compared with the NiAu-coated pad, the IMC layer that formed between the NiPdAu-coated pads and SAC105 solder was thinner, indicating an effective diffusion barrier effect of the Pd layer in the NiPdAu coating. Hence, SAC105 solder showed superior reliability on BGA package pads coated with NiPdAu.
KeywordsReliability fracture interfacial reaction intermetallic compound diffusion reaction
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The authors wish to thank the Instrumental Analysis Center of Shanghai Jiao Tong University for SEM equipment. This work was supported by the National Basic Research Program of China (973 Program No. 2015CB057200) and the National Nature Science Foundation of China (Nos. 61176097 and 61376107).
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