Conference Papers
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Item Wetting characteristics of sn-0.7cu lead-free solder alloy on copper substrates(Trans Tech Publications Ltd ttp@transtec.ch, 2012) Satyanarayan, S.; Prabhu, K.N.In the present work, the effect of surface texture on wetting characteristics of lead-free solder Sn-0.7Cu on copper substrates have been investigated at 298°C. The wetting tests were carried out using FTA 200 (First Ten Angstrom) dynamic contact angle analyzer. The surface texture of copper substrate significantly affected the wetting properties of Sn-0.7Cu solder alloy. Contact angles of about 30° were obtained on Cu substrate having smooth surface texture (Ra = 0.0155μm). On other hand contact angles on rough copper surface texture (Ra = 1.1194μm) were reduced to 20°. The contact angles decreased with increasing surface texture of Cu substrate. For rough Cu substrate, it seems that the solder atoms dissolve into the substrate in the time period of 200-600s. © (2012) Trans Tech Publications.Item 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 Sn–Cu and Sn–Ag–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. © (2015) Trans Tech Publications, Switzerland.