Journal ArticleDOI
Lead-free Solders in Microelectronics
Mulugeta Abtew,Guna S Selvaduray +1 more
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TLDR
The most widely used Pb-free solders have the eutectic composition as mentioned in this paper, which has been identified as a major factor affecting alloy selection, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation.Abstract:
Practically all microelectronic assemblies in use today utilize Pb–Sn solders for interconnection. With the advent of chip scale packaging technologies, the usage of solder connections has increased. The most widely used Pb–Sn solder has the eutectic composition. Emerging environmental regulations worldwide, most notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies, due to the inherent toxicity of Pb. This has made the search for suitable “Pb-free” solders an important issue for microelectronics assembly. Approximately 70 Pb-free solder alloy compositions have been proposed thus far. There is a general lack of engineering information, and there is also significant disparity in the information available on these alloys. The issues involved can be divided into two broad categories: manufacturing and reliability/performance. A major factor affecting alloy selection is the melting point of the alloy, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation. Other important manufacturing issues are cost, availability, and wetting characteristics. Reliability related properties include mechanical strength, fatigue resistance, coefficient of thermal expansion and intermetallic compound formation. The data available in the open literature have been reviewed and are summarized in this paper. Where data were not available, such as for corrosion and oxidation resistance, chemical thermodynamics was used to develop this information. While a formal alloy selection decision analysis methodology has not been developed, less formal approaches indicate that Sn-rich alloys will be the Pb-free solder alloys of choice, with three to four alloys being identified for each of the different applications. Research on this topic continues at the present time at a vigorous pace, in view of the imminence of the issue.read more
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Journal ArticleDOI
A corrosion investigation of solder candidates for high-temperature applications
TL;DR: In this article, a corrosion investigation was carried out on potential ternary lead-free candidate alloys based on these binary alloys for high-temperature applications, and the results revealed that the Au-Sn-based and Au-Ge-based alloys close to the eutectic composition (20 wt.% Sn) are more corrosion resistant than the Au Ge-based ones.
Journal ArticleDOI
Effects of the melt state on the microstructure of a Sn–3.5%Ag solder at different cooling rates
TL;DR: In this article, the effects of the melt state on the microstructure of Sn-3.5%Ag solder were investigated at two different cooling rates, and the results showed the solid-liquid interface energy is found to increase when the alloy is melted at above liquid-liquid structure transition (L-LST) temperature.
Journal ArticleDOI
Impact of 5% NaCl Salt Spray Pretreatment on the Long-Term Reliability of Wafer-Level Packages with Sn-Pb and Sn-Ag-Cu Solder Interconnects
Bo Liu,Tae-Kyu Lee,Kuo-Chuan Liu +2 more
TL;DR: In this paper, the impact of a marine environment on Sn-Pb and Sn-Ag-Cu interconnects was investigated and the salt spray test did not reduce the characteristic lifetime of the Sn-pb solder joints, but it did reduce the lifetime of Sn-ag-cu solder joints by over 43%.
Journal ArticleDOI
Effects of Bi and Pb on oxidation in humidity for low-temperature lead-free solder systems
TL;DR: In this article, the oxidation behavior of various Sn-Zn(-Bi) alloys during 60°C/90% and 85°C /85% relative humidity (RH) exposure were investigated by microstructure observation and x-ray diffraction analysis.
Journal ArticleDOI
Hazardous metals emissions from e-waste-processing sites in a village in northern Vietnam
Natsuyo Uchida,Hidenori Matsukami,Masayuki Someya,Nguyen Minh Tue,Le Huu Tuyen,Pham Hung Viet,Shin Takahashi,Shinsuke Tanabe,Go Suzuki +8 more
TL;DR: In this article, surface soil samples collected from e-waste-processing sites, open burning sites, and rice paddy sites were also collected from a river that runs through the village.
References
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Journal ArticleDOI
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Jerome O. Nriagu,Jozef M. Pacyna +1 more
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Journal ArticleDOI
Interdiffusion and Reaction in Bimetallic Cu-Sn Thin Films
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