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
Lead-free Sn-Ag and Sn-Ag-Bi solder powders prepared by mechanical alloying
H. L. Lai,J. G. Duh +1 more
TL;DR: In this paper, a mechanical alloying (MA) process was used to produce lead-free solder pastes of Sn-3.5Ag and the Sn-4Bi system, which showed good metallurgical bonding with a contact angle less than 20°.
Journal ArticleDOI
Nanoparticles of the Lead-free Solder Alloy Sn-3.0Ag-0.5Cu with Large Melting Temperature Depression
Chang Dong Zou,Yu Lai Gao,Bin Yang,Xin Zhi Xia,Qijie Zhai,Cristina Andersson,Johan Liu,Johan Liu +7 more
TL;DR: In this paper, the melting temperature of the nanoparticles, with an average size of 30 nm, was found to be 213.9°C, which is approximately 10°C lower than that of the bulk alloy.
Journal ArticleDOI
Effects of diamond nanoparticles reinforcement into lead-free Sn–3.0Ag–0.5Cu solder pastes on microstructure and mechanical properties after reflow soldering process
TL;DR: In this article, the effects of diamond nanoparticles reinforcement on lead-free SAC 305 solder paste after the reflow soldering process were investigated, and the results revealed that the addition of nanoparticles slightly decreased the melting point but significantly reduced the IMC thickness.
Journal ArticleDOI
Nanocalorimetry: Door opened for in situ material characterization under extreme non-equilibrium conditions
TL;DR: Nanocalorimetry has attracted extensive attention in the field of materials science, where it is applied to perform quantitative analysis of rapid phase transitions and evaluation of size effects.
Journal ArticleDOI
Effect of Oxidation on Indium Solderability
TL;DR: In this article, the fluxless solderability of pure indium on gold-coated surfaces is investigated using measurements of wetting angle and joint strength, focusing on the effects of indium's native oxides and those which form during heat treatment.
References
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