Faculty Publications
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Item Wetting behavior and evolution of microstructure of Sn-3.5Ag solder alloy on electroplated 304 stainless steel substrates(Springer India sanjiv.goswami@springer.co.in, 2012) Nayak, V.U.; Prabhu, K.N.; Stanford, N.; Satyanarayan, S.In the present study, wetting characteristics and evolution of microstructure of Sn-3.5Ag solder on Ag/Ni and Ni electroplated 304 stainless steel (304SS) substrates have been investigated. Solder alloy spread on Ag/Ni plated 304SS substrates exhibited better wetting as compared to Ni/304SS substrate. The formations of irregular shaped and coarser IMCs were found at the interface of solder/Ni/304SS substrate region whereas, solder/Ag/Ni/substrate interface showed continuous scallop and needle shaped IMCs. The precipitation of Ag3Sn, Ni-Sn, FeSn2 and lesser percentage of Fe-Cr-Sn IMCs were found at the interface of solder/Ag/Ni/substrate region whereas, solder/Ni/304 SS substrate exhibited predominantly FeSn2 and Fe-Cr-Sn IMCs. Presence of higher amount of Fe-Cr-Sn IMCs at the solder/Ni/304SS substrate interface inhibited the further wetting of solder alloy.Item Wetting behaviour and evolution of microstructure of Sn-Ag-Zn solders on copper substrates with different surface textures(2010) Satyanarayan, S.; Prabhu, K.N.The effect of surface roughness on wetting behaviour and evolution of microstructure of two lead-free solders (Sn-2.625Ag-2.25Zn and Sn-1.75Ag-4.5Zn) on copper substrate was investigated. Both solders exhibited good wettability on copper substrates having rough surface and lower wettabilty on smooth surfaces. The contact angles of solders decreased linearly with increase in surface roughness of the substrate. The exponential power law, ?=exp(-K ?n), was used to model the relaxation behaviour of solders. A high intermetallic growth was observed at the interface particularly on copper substrates with rough surface texture. A thin continuous interface showing scallop intermetallic compounds (IMC) was obtained on smooth surfaces. With an increase in surface roughness, the IMC morphology changed from scallop shaped to needle type at the Sn-2.625Ag-2.25Zn solder/substrate interface and nodular to plate like IMCs for Sn-1.75Ag-4.5Zn solder matrix. Copyright © 2010 by ASTM International.Item Wetting behaviour and evolution of microstructure of Sn-Ag-Zn solders on copper substrates with different surface textures(ASTM International, 2011) Satyanarayan, S.; Prabhu, K.N.The effect of surface roughness on wetting behaviour and evolution of microstructure of two lead-free solders (Sn-2.625Ag-2.25Zn and Sn-1.75Ag-4.5Zn) on copper substrate was investigated. Both solders exhibited good wettability on copper substrates having rough surface and lower wettabilty on smooth surfaces. The contact angles of solders decreased linearly with increase in surface roughness of the substrate. The exponential power law, ?=exp(-KT -1), was used to model the relaxation behaviour of solders. A high intermetallic growth was observed at the interface particularly on copper substrates with rough surface texture. A thin continuous interface showing scallop intermetallic compounds (IMC) was obtained on smooth surfaces. With an increase in surface roughness, the IMC morphology changed from scallop shaped to needle type at the Sn-2.625Ag-2.25Zn solder/ substrate interface and nodular to plate like IMCs for Sn-1.75Ag-4.5Zn solder matrix. Copyright © 2010 by ASTM International.Item Wetting behaviour and interfacial microstructure of Sn-Ag-Zn solder alloys on nickel coated aluminium substrates(2011) Satyanarayan, S.; Prabhu, K.N.Wetting behaviours of two lead free solders (Sn-2·625Ag- 2·25Zn and Sn-1·75Ag-4·5Zn) on nickel coated aluminium substrates were investigated. Sn-2·625Ag-2·25Zn exhibited better wettability compared to Sn-1·75Ag-4·5Zn solder. Contact angles of the solders increased with increasing roughness of the substrate. The Young-Dupre equation was used to evaluate the work of adhesion of solder on the substrate. Sn-2·625Ag-2·25Zn solder exhibited higher work of adhesion than Sn-1·75Ag-4·5Zn. A thin continuous layer of Ni 3Sn was detected at the interface between Sn-2·625Ag- 2·25Zn solder and nickel coated Al substrate. Sn-1·75Ag- 4·5Zn solder exhibited scallop intermetallic compounds (IMCs) growing into the solder field as well as a thin continuous IMC in some cases. Ni 3Sn and Ni3Sn4 IMCs were observed at the interface of Sn-1·75Ag-4·5Zn solder and nickel coated Al. © 2011 Institute of Materials, Minerals and Mining.Item Comparison of spreading behaviour and interfacial microstructure in Sn-0·7Cu, Sn-0·3Ag-0·7Cu and Sn-2·5Ag-0·5Cu lead free solder alloys on Fe-42Ni substrate(Maney Publishing michael.wagreich@univie.ac.at, 2013) Satyanarayan, S.; Prabhu, K.In the present work, spreading behaviour and development of interfacial microstructure in Sn- 0·7Cu, Sn-0·3Ag-0·7Cu and Sn-2·5Ag-0·5Cu lead free solder alloys on Fe-42Ni substrates having two different surface textures were investigated. Smooth textured surfaces yielded better wettability than rough surfaces particularly for Sn-0·7Cu solder alloy. Wettability of Sn-0·7Cu solder on rough textured surfaces was found to be poor compared to other solder alloys. Spreading of Sn-0·7Cu solder on substrate surface showed longer viscous regime, Sn-2·5Ag- 0·5Cu solder exhibited shortest viscous regime. Sn-0·3Ag-0·7 solder showed intermediate behaviour. Sn-Cu solder alloy exhibited needle and coarse shaped (Cu,Ni)6Sn5 intermetallics at the interface and in the matrix of the solder alloy on smooth substrate, whereas on rough substrate, formation of only coarse shaped (Cu,Ni)6Sn5 intermetallic compounds (IMCs) was observed. For Sn-0·3Ag-0·7Cu solder alloy, Fe-Ni-Sn and FeSn2 IMCs identified at the interface. (Cu,Ni)6/Sn5 IMCs were found to be less coarser than as observed at Sn-0·7Cu/substrate interface. Sn-2·5Ag-0·5Cu alloy exhibited (Cu,Ni) 3Sn4 and (Cu,Ni)6 Sn5 IMCs at the interface and in the bulk of solder alloy. © 2013 Institute of Materials, Minerals and Mining.Item Effect of purging gas on wetting behavior of Sn-3.5Ag lead-free solder on nickel-coated aluminum substrate(Springer Science and Business Media, LLC, 2013) Prabhu, K.; Varun, M.; Satyanarayan, S.The wetting characteristics of Sn-3.5Ag lead-free solder alloy on nickel-coated aluminum substrates in air (ambient), nitrogen, and argon atmospheres were investigated. The contact angles for the solder alloy obtained under air and argon atmospheres were in the range of 36 -38. With nitrogen atmosphere the contact angle was found to be significantly lower at about 26. Solder solidifying in air exhibited needle-shaped tin-rich dendrites surrounded by a eutectic matrix. The amount of tin dendrites decreased in argon atmosphere. However, the morphology of tin dendrites transformed from needle-shaped to nearly non-dendritic shape as the soldering atmosphere was changed from air to nitrogen. The interfacial microstructures revealed the presence of Ni 3Sn and Ni3Sn4 IMCs at the interface. The enhanced wettability observed under nitrogen atmosphere is attributed to the higher thermal conductivity of nitrogen gas and the formation of higher amount of Ni3Sn IMCs at the interface compared to air and argon atmospheres. © 2012 ASM International.Item Solder joint reliability of Sn-0·7Cu and Sn-0·3Ag- 0·7Cu lead-free solder alloys solidified on copper substrates with different surface roughnesses(2013) Satyanarayan, S.; Prabhu, K.The bond shear test was used to assess the integrity of Sn-0·7Cu and Sn-0·3Ag-0·7Cu lead-free solder alloy drops solidified on copper substrates with smooth and rough surface finishes. Solder alloys solidified on smooth substrates required higher shear force compared to that on rough substrates. Sn-0·3Ag-0·7Cu alloy required higher shear energy than Sn-0·7Cu alloy. Solder alloys solidified on smooth substrate surfaces exhibited complete ductile failure. On rough copper surfaces, solder alloys showed a transition ridge characterized by sheared intermetallic compounds (IMCs) and the presence of dimples. The peak shear strength decreased with increase in contact area of the solder bond on the substrate. Smooth surface and the presence of minor amount of Ag in the solder alloy enhance the integrity of the solder joint. © 2013 Institute of Materials, Minerals and Mining.