Papers by Keyword: Sn-Ag-Cu Solder

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Authors: Kittichai Fakpan, Rungsinee Canyook
Abstract: Pb–free solders have been widely developed by materials researchers as mainly focused on the replacement for Sn–Pb eutectic solder. In this study, Sn–3.0Ag–0.5Cu, Sn–3.0Ag–0.5Cu–xSb and Sn–3.0Ag–0.5Cu–xZn solders (x = 1.0, 2.0 and 3.0 wt%) were prepared using melting method. The effect of Sb and Zn addition on microstructure and properties, such as tensile strength, microhardness and corrosion resistance of Sn–Ag–Cu solders was investigated. The microstructure analysis revealed that addition of Sb and Zn to the Sn–Ag–Cu solders obviously decreased phase fraction of the dendritic β–Sn phase and the finer eutectic phase was obtained, resulting in superior mechanical properties of the Sn–3.0Ag–0.5Cu–xSb and Sn–3.0Ag–0.5Cu–xZn solders compared to the Sn–3.0Ag–0.5Cu solder. The results of potentiodynamic polarization tests indicated that the corrosion potentials of the Sn–3.0Ag–0.5Cu–xSb solders continuously increased with increasing of Sb content. While Zn content had little effect on the corrosion potentials of the Sn–3.0Ag–0.5Cu–xZn solders.
Authors: Nur Aishah Aminah Mohd Amin, Dhafer Abdul Ameer Shnawah, Mohd Faizul Mohd Sabri, Suhana Binti Mohd Said
Abstract: This paper reports on the effect of Fe addition in the range of 0.1 wt.% to 0.5 wt.% on the electrical resistivity of the Sn-1Ag-0.5Cu (SAC105) solder alloy. The electrical resistivity is characterized by the four-point probe technique. Results showed that the Fe-bearing SAC105 solder alloys exhibit lower electrical resistivity compared with the standard SAC105 solder alloy. Moreover, the electrical resistivity further decreases with increasing the amount of Fe addition. As Fe is a low-cost and non-hazardous element, along with the high mechanical reliability, the Fe-bearing SAC105 solder alloys also demonstrate good electrical characteristics, and hence may be an attractive candidate for a low cost, reliable formulation for lead free solders in electronics packaging.
Authors: Jeong Won Yoon, Chang Bae Lee, Seung Boo Jung
Abstract: The growth kinetics of intermetallic compound (IMC) layers formed between Sn-3.5Ag-0.75Cu BGA (ball grid array) solder and electroless Ni-P/Cu substrate by solid state isothermal aging were examined at temperatures between 70 and 170°C for 0 to 100 days. In the solder joints between the solder ball and electroless Ni-P/Cu pads, the IMC layer was (Cu,Ni)6Sn5. Also, a P-rich Ni layer formed at the interface between (Cu,Ni)6Sn5 and original Ni-P deposit layer because of the phosphorous accumulation. These IMC layer thicknesses increased linearly with the square root of aging time and the growth was faster for higher aging temperatures. On the contrary, the shear strength decreased with the increasing temperature and time. The growth of IMC layer was mainly controlled by diffusion-controlled mechanism over the temperature range studied. The apparent activation energy calculated for the growth of the (Cu,Ni)6Sn5 IMC was 69.75 kJ/mol.
Authors: Akio Hirose, Tomoyuki Hiramori, Mototaka Ito, Yoshiharu Tanii, Kojiro F. Kobayashi
Abstract: Sn-3.5Ag (Sn-Ag) and Sn-3.5Ag-0.75Cu (Sn-Ag-Cu) solder balls were reflowed on electroless Ni-P/Au plated Cu pad with varying thickness of Au layer (0 to 500nm). In the Sn-Ag solder joint, a P-rich layer including voids, which resulted from Ni diffusion from the Ni-P plating to form Ni3Sn4 interfacial reaction layer, formed at the interface regardless of Au plating thickness. This caused the degradation of the joint strength. On the contrary, the Sn-Ag-Cu solder joint had no continuous P-rich layer formed and showed a higher joint strength than the Sn-Ag solder joint in the case of Au plating of 50nm or less. Cu alloying to the solder promote the formation of (Cu, Ni)6Sn5 instead to Ni3Sn4 as the interfacial reaction layer. The (Cu, Ni)6Sn5 reaction layer can suppress the diffusion of Ni from the N-P plating and thereby inhibit the formation of the P-rich layer. However, in the case of thick Au plating of 250nm or more, a thin P-rich layer formed at the interface even in the Sn-Ag-Cu solder joint and the joint strength was degraded. Au dissolving into the solder from the Au plating during the reflow process may encourage the diffusion of Ni from the Ni-P plating into the solder. As a result, the Sn-Ag-Cu solder joints with 50nm Au coating provided the best joint strength, although its joint strength considerably degraded after the aging treatment at 423K.
Authors: Bo In Noh, Seung Boo Jung
Abstract: Thermal fatigue properties of solder joints encapsulated with underfill were studied conducting thermal shock tests. Flip chip package with electroless nickel-immersion gold plated on FR-4 substrate and the Sn-3.0Ag-0.5Cu solder ball was used. The fatigue property of package with underfill was better than the package without it. The fatigue property of package with underfill which has a higher glass transition temperature (Tg) and lower coefficient of thermal expansion (CTE) was better than that of package with underfill with lower Tg and higher CTE.
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