Browsing by Author "Satyanarayan, S."

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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.
Effect of cooling rate during solidification of Sn-9Zn lead-free solder alloy on its microstructure, tensile strength and ductile-brittle transition temperature
(Elsevier Ltd, 2012) Prabhu, K.N.; Deshapande, P.; Satyanarayan, S.
Solidification rate is an important variable during processing of materials, including soldering, involving solidification. The rate of solidification controls the metallurgical microstructure at the solder joint and hence the mechanical properties. A high tensile strength and a lower ductile-brittle transition temperature are necessary for reliability of solder joints in electronic circuits. Hence in the present work, the effect of cooling rate during solidification on microstructure, impact and tensile properties of Sn-9Zn lead-free solder alloy was investigated. Four different cooling media (copper and stainless steel moulds, air and furnace cooling) were used for solidification to achieve different cooling rates. Solder alloy solidified in copper mould exhibited higher cooling rate as compared to other cooling media. The microstructure is refined as the cooling rate was increased from 0.03 to 25 °C/s. With increase in cooling rate it was observed that the size of Zn flakes became finer and distributed uniformly throughout the matrix. Ductile-to-brittle transition temperature (DBTT) of the solder alloy increased with increase in cooling rate. Fractured surfaces of impact test specimens showed cleavage like appearance and river like pattern at very low temperatures and dimple like appearance at higher temperatures. The tensile strength of the solder alloy solidified in Cu and stainless moulds were higher as compared to air and furnace cooled samples. It is therefore suggested that the cooling rate during solidification of the solder alloy should be optimum to maximize the strength and minimize the DBTT. © 2011 Elsevier B.V.
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.
Effect of reflow temperature and substrate roughness on wettability, IMC growth and shear strength of SAC387/Cu bonds
(2014) Bhat, K.N.; Prabhu, K.; Satyanarayan, S.
The effect of reflow temperature and substrate surface roughness on wettability, intermetallics and shear strength of Sn-3.8Ag-0.7Cu solder alloy on copper (Cu) substrate was studied. It was found that increase in reflow temperature and substrate surface roughness improved the wettability of solder alloy. The size of needle shaped Cu6Sn5 IMCs (intermetallic compounds) increased with increase in temperature. The morphology of IMCs transformed from long to short needles with increase in substrate roughness. Shear strength and shear energy of the solder bond on rough Cu surfaces were found to be higher than that on smooth Cu surfaces. However, the sheared surfaces of the solder bond on rough Cu surface exhibited a transition ridge characterised by sheared IMCs whereas solder bond on smooth Cu surfaces exhibited completely ductile failure. Although, rough surface exhibited higher shear strength and shear energy, smoother surface is preferable due to its predominant bond failure in the solder matrix. © 2013 Springer Science+Business Media New York.
Effect of surface treatment on wetting behavior of copper
(Elsevier Ltd, 2019) Kalgudi, S.; Pavithra, G.P.; Prabhu, N.K.; Koppad, P.G.; Venkate Gowda, C.; Satyanarayan, S.
Super-hydrophobic surfaces are very useful in cleaning activities. Surfaces with water contact angles above 150Â° are regarded as superhydrophobic surfaces. In the present study an attempt has been made to achieve superhydrophobicity on copper substrate by electrochemical etching and electro-deposition of Co-Ni alloy and Co-Ni-Graphene composite. A contact angle of about 105Â° was obtained on Cu surface with electro-deposited Co-Ni alloy and on electro-deposited Co-Ni-G alloy contact angle was found to be 106Â°. The contact angle was significantly higher at about 142Â° with electro etched surface. Corrosion test was carried out with electrochemically etched Cu. Electrochemical etching time was varied from 30 to 240 min. The electro-etched Cu substrate etched for 60 min. showed better corrosion resistance with a corrosion rate of 0.197 mm/year. The surface topography of both etched and electrodeposited samples was studied by atomic force microscopy (AFM) and the results were correlated with the wettability data. Â© 2019 Elsevier Ltd.
Effect of temperature and substrate surface texture on wettability and morphology of IMCs between Sn-0.7Cu solder alloy and copper substrate
(2012) Satyanarayan, S.; Prabhu, K.N.
In the present work, the effect of soldering temperature (270 and 298 °C) and substrate surface texture (0.02 and 1.12 ?m) on wetting characteristics and morphology of intermetallic compounds (IMCs) between Sn-0.7Cu lead-free solder on copper substrates was investigated. It was found that increase in temperature and substrate surface roughness improved the wettability of solder alloy. However, the effect of surface roughness on wettability was significant as compared to that of temperature. The spreading of solder alloy was uniform on smooth substrate, whereas spreading of the alloy on rough substrate resulted in an oval shape. The morphology of IMCs transformed from long needle shaped to short and thick protrusions of IMCs with increase in surface roughness of the substrate. Needle shaped and thick protruded intermetallics formed at the solder/Cu interface were identified as Cu 6Sn 5 compounds. The formation of Cu 3Sn IMC was observed only for the spreading of solder alloy at 298 °C which contributed to improvement in the wettability of solder alloy on both smooth and rough substrate surfaces. © Springer Science+Business Media, LLC 2012.
Lead-free solders for high-temperature applications
(Association of American Publishers, 2025) Satyanarayan, S.; Narayan Prabhu, K.
Due to the toxicity of Pb, efforts to develop alternatives to Pb-based solders have been increased significantly. However, only a limited number of lead (Pb)-free solder systems exist for high-temperature applications. In the present paper, a review of the selection of Pb-free solder alloys for high-temperature (300Â°Câ€“400Â°C) applications to replace traditional Pb-based alloys is carried out. A discussion on the research and development of high-temperature solder alloys is highlighted in the current review. The solder systems with alloying additions like Au, Sb, Ni and Zn must be investigated to be used as potential candidate materials for high-temperature applications Â© 2025 by authors.
Reactive wetting, evolution of interfacial and bulk IMCs and their effect on mechanical properties of eutectic Sn-Cu solder alloy
(2011) Satyanarayan, S.; Prabhu, K.N.
Lead free solders are increasingly being used in electronic applications. Eutectic Sn-Cu solder alloy is one of the most favored lead free alloys used for soldering in electronic applications. It is inexpensive and principally used in wave soldering. Wetting of liquid solder on a substrate is a case of reactive wetting and is accompanied by the formation of intermetallic compounds (IMCs) at the interface. Wettability of Sn-0.7Cu solder on metallic substrates is significantly affected by the temperature and the type of flux. The wettability and microstructural evolution of IMCs at the Sn-0.7Cu solder/substrate interfaces are reviewed in the present paper. The reliability of solder joints in electronic packaging is controlled by the type and morphology of interfacial IMCs formed between Sn-0.7Cu solder and substrates. The formation and growth mechanisms of interfacial IMCs are highlighted. Mechanical behavior of bulk solder alloy and solder joint interfaces are analyzed. The characteristics of the IMCs which have marked effect on the mechanical properties and fracture behavior as well as reliability of solder joints of the alloy are discussed. An attempt has also been made to discuss the effect of cooling rate and strain rate on shear strength, tensile properties and creep resistance of the solder alloy. It is recommended that future work should focus on evolving a standard procedure involving sequential assessment of wetting behavior, evolution of IMCs and mechanical properties. © 2011 Elsevier B.V.
Robustness Analysis of EV Charging System using Random Forest Algorithm
(Institute of Electrical and Electronics Engineers Inc., 2023) Barre, U.P.V.; Satyanarayan, S.; Reddy, H.; Pulikala, A.; Bajaj, A.
Electric cars offer numerous benefits and are considered the future of the automobile industry. However, their worldwide adoption still needs to grow. One of the primary reasons for this delay in electrification is charge anxiety, which refers to the uncertainty customers feel when connecting the charging cable to the car. To address this issue, this study analyses the performance of the charging system using a machine learning model to identify sensitive signals that influence the charging process and can cause successful charging or charge termination. The analysis will also help to define robust operating regions where the charging component can reliably function, regardless of external conditions. This study's findings will provide insights into electric vehicle charging behavior with the supply station. Â© 2023 IEEE.
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.N.
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.
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.
Solder joint reliability of Sn-Cu and Sn-Ag-Cu lead-free solder alloys solidified on copper substrates with different surface roughnesses
(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Satyanarayan, S.; Prabhu, K.
In the present work, the bond strength of Sn-0.7Cu, Sn-0.3Ag-0.7Cu, Sn-2.5Ag-0.5Cu and Sn-3Ag-0.5Cu lead free solders solidified on Cu substrates was experimentally determined. The bond shear test was used to assess the integrity of Snâ€“Cu and Snâ€“Agâ€“Cu lead-free solder alloy drops solidified on smooth and rough Cu substrate surfaces. The increase in the surface roughness of Cu substrates improved the wettability of solders. The wettability was not affected by the Ag content of solders. Solder bonds on smooth surfaces yielded higher shear strength compared to rough surfaces. Fractured surfaces revealed the occurrence of ductile mode of failure on smooth Cu surfaces and a transition ridge on rough Cu surfaces. Though rough Cu substrate improved the wettability of solder alloys, solder bonds were sheared at a lower force leading to decreased shear energy density compared to the smooth Cu surface. A smooth surface finish and the presence of minor amounts of Ag in the alloy improved the integrity of the solder joint. Smoother surface is preferable as it favors failure in the solder matrix. Â© (2015) Trans Tech Publications, Switzerland.
Spreading behavior and evolution of IMCs during reactive wetting of SAC solders on smooth and rough copper substrates
(2013) Satyanarayan, S.; Prabhu, K.
The effect of surface roughness of copper substrate on the reactive wetting of Sn-Ag-Cu solder alloys and morphology of intermetallic compounds (IMCs) was investigated. The spreading behavior of solder alloys on smooth and rough Cu substrates was categorized into capillary, diffusion/reaction, and contact angle stabilization zones. The increase in substrate surface roughness improved the wetting of solder alloys, being attributed to the presence of thick Cu 3Sn IMC at the interface. The morphology of IMCs transformed from long needle shaped to short protruded type with an increase in the substrate surface roughness for the Sn-0.3Ag-0.7Cu and Sn-3Ag-0.5Cu solder alloys. However, for the Sn-2.5Ag-0.5Cu solder alloy the needle-shaped IMCs transformed to the completely scallop type with increase in the substrate surface roughness. The effect of Ag content on wetting behavior was not significant. © 2013 TMS.
The Effect of Thermal Ageing on Solder/Substrate Interfacial Microstructures During Reflow of Sn–37Pb and Sn–3Ag–0.5Cu
(Springer, 2019) Satyanarayan, S.; Kumarswamy, M.C.; Prabhu, N.
In the current study, the influence of thermal ageing on evolution of microstructures in the interfacial region between solders (Sn–37Pb, Sn–3.5Ag–0.5Cu) and copper substrates was investigated. Pb-containing and Pb-free solders were reflowed on Cu substrates at 230 °C for 15 min and were isothermally aged at 100 °C for 24 h. As-reflowed Sn–Pb solder/Cu substrate interfacial region exhibited continuous and layered type of IMC at the interface, and this IMC morphology changed to scallop type with isothermal ageing. SAC solder/Cu as-reflowed samples showed continuous and needle-shaped Cu6Sn5 and Ag3Sn IMCs at the interface. However, in an isothermally aged condition, plate-shaped Cu6Sn5 and flower-shaped Ag3Sn IMCs were found inside the solder matrix. Scanning electron microscopic (SEM) study showed that the thickness of Cu6Sn5 IMC was higher in reflowed Sn–Pb/Cu region than in SAC/Cu region. © 2019, The Indian Institute of Metals - IIM.
Wettability of root canal sealers on intraradicular dentine treated with different irrigating solutions
(2013) Nidambur, N.V.; Tweeny, A.; Khechen, K.; Prabhu, K.; Satyanarayan, S.; Tay, F.R.
Objectives The aim of this in vitro study was to evaluate the wettability of AH Plus and ThermaSeal Plus sealers on intraradicular dentine treated with different irrigating solutions. Methods Fifty anterior teeth were decoronated and split longitudinally. Each root half was divided into 5 groups (n = 10). Group I: 5 mL of 2.5% NaOCl + QMix. Group II: 5 mL of 2.5% NaOCl + 17% EDTA. Group III: 5 mL of 2.5% NaOCl + 7% maleic acid. Group IV: 5 mL of 2.5% NaOCl. Group V: 5 mL of distilled water. Irrigation regimens were performed for 1 min. Each specimen was placed inside a Dynamic Contact Angle Analyser. A controlled-volume droplet of sealer was placed on each specimen and the static contact angle was analysed. Results The contact angle made by both sealers with EDTA-irrigated dentine was significantly larger when compared to the other irrigants (P < 0.05). For ThermaSeal Plus, contact angles produced on maleic acid-, NaOCl- and distilled water-irrigated dentine were not significantly different, but were all significantly larger than the contact angle produced on QMix-irrigated dentine (P < 0.05). For AH Plus, contact angles produced on NaOCl- and distilled water-irrigated dentine were not significantly different, but were significantly larger than those made by maleic acid and QMix. Conclusion When used as a final irrigant, QMix favours the wetting of root canal dentine by both AH Plus and ThermaSeal Plus sealers. Maleic acid shows a promising result when compared to EDTA and NaOCl. Wettability of both sealers is the worst on EDTA-irrigated dentine. Clinical significance The present study highlights the effect of newer endodontic irrigating solutions on the wettability of sealers on to the root canal dentine, which is required for obtaining good obturation seal. © 2013 Elsevier Ltd.
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.
Wetting behavior of lead-free solders on copper substrates
(Institution of Engineering and Technology jbristow@theiet.org, 2013) Satyanarayan, S.; Prabhu, K.N.
The effect of substrate surface roughness on the wetting behavior of Sn-0.7Cu and Sn-0.3Ag-0.7Cu solder alloys on copper (Cu) substrates was investigated. The contact angles of both solder alloys decreased with increase in substrate surface roughness. The exponential power law (EPL), Ï† = exp (-KÏ„n), was used to model the relaxation behaviour of solders. Solder spreading kinetics was successfully represented by the (EPL). EPL parameters (K and n) alloy decreased with an increase in surface roughness. Spreading of solder alloys on both substrates exhibited capillary, gravity and viscous regimes. High spreading rates in the capillary regime, moderate in gravity regime and almost constant rates in viscous regimes were observed.
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.
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.
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.