Issue Title: Special Sections: Pb-free Solders and Materials for Emerging Interconnect and Packaging Technologies; Phase Stability, Phase Transformations, and Reactive Phase Formation in Electronic ...Materials XIII; and Advanced Materials for Power Electronics and Power Conditioning Systems We have investigated the effect of small amounts of Cu on suppression of metastable betaSn-NiSn^sub 4^ eutectic growth in solder joints between Sn-3.5Ag-xCu solders and Ni-based substrates. For Sn-3.5Ag/electroless nickel immersion gold (ENIG) and Sn-3.5Ag/Ni solder joints we showed that the eutectic mixture contains betaSn, Ag^sub 3^Sn, and metastable NiSn^sub 4^. It was found that addition of only 0.005 wt.% Cu to Sn-3.5Ag-xCu/ENIG or Sn-3.5Ag-xCu/Ni joints promoted formation of a stable betaSn-Ni^sub 3^Sn^sub 4^ eutectic and that both Ni^sub 3^Sn^sub 4^ and NiSn^sub 4^ occur in the eutectic at this Cu level. We also showed that for complete prevention of formation of metastable NiSn^sub 4^ during eutectic solidification of the solder joint, addition of at least 0.3 wt.% Cu was required.
Room Temperature Soldering
In article number 2303286, Seung Hwan Ko and co‐workers present a room‐temperature universal stretchable sticker‐like soldering process that stretchably solders multiple ...spots at once and fabricates a stretchable device in an in situ manner while a target conductor is installed on one's body. This process allows the integration of stretchable conductors with advanced chips for next‐generation stretchable electronics.
The wetting of 3% yttria-stabilized zirconia (YSZ) by Sn–8Zr, Sn–4Zr–4Ti, and Sn–8Ti alloys was studied at 800–900 °C. Both Zr and Ti improve the wettability via the formation of reaction products ...and adsorption. In the systems containing Zr additives in the alloys, ZrO2-x precipitates preferentially, and the wettability is dominated by interface adsorption. An anomalous temperature dependence was found in the final wettability of these systems owing to the decrease in adsorption with an increase in the temperature. The spreading dynamics are controlled by the dissolution of Zr, followed by the formation of a wetting ridge. The wettability of the Sn–8Ti/YSZ system is dominated by the precipitation of reaction products (Ti2O3 and Ti11.31Sn3O10). The reaction kinetics is the limiting factor for spreading in Sn–8Ti/YSZ, and the adsorption at the interface significantly decreased the energy barrier for wetting.
Researchers are eagerly developing various stretchable conductors to fabricate devices for next‐generation electronics. Most of the major problems in stretchable electronics happen at the connection ...between rigid and soft parts and the development of reliable soldering material is a major hurdle in stretchable electronics. Though there are attempts to devise new soldering processes for integrating chips and stretchable conductors, they still possess limitations such as mechanical stability, mass production, sophisticated processes, and restricted candidates for conductors and substrates. Here, this study presents a room‐temperature universal stretchable sticker‐like soldering process that can stretchably solder multiple spots at once and directly fabricates a stretchable device in an in situ manner while a target conductor is installed on one's body. The solder developed in this research possesses high conductivity with a unique freestanding feature enabling the process. It can be elongated when directly positioned between a rigid chip and a rigid conductor, demonstrating its extraordinary stretchability. It is expected that this simple but unique stretchable soldering technique utilizing the invented solder will allow the integration of functional stretchable conductors with highly advanced rigid chips for next‐generation stretchable electronics.
Major challenges in stretchable electronics occur when connecting rigid chips and soft parts. Thus, a reliable solder and soldering process are necessary. To solve the issue, this study presents a room‐temperature universal stretchable sticker‐like soldering process that solders multiple spots at once and directly fabricates a stretchable device while a target conductor is installed on one's body.
Review: Special brazing and soldering Li, Yuxiang; Chen, Chao; Yi, Ruixiang ...
Journal of manufacturing processes,
December 2020, 2020-12-00, Letnik:
60
Journal Article
Recenzirano
The bonding of dissimilar materials can make the joint possess the select performances of two materials. Suitable brazing/soldering methods can be adopted for different materials and joint structures ...to achieve high strength bonding. By comparison with other joining technologies, the special brazing/soldering joints have better bonding performances, greater rigidity of the brazing/soldering structure, and good integrity. The best advantage of the brazing/soldering process is that the variety of brazing types. This paper classifies these special brazing/soldering processes to infrared brazing, wave soldering, laser brazing, ultrasonic brazing, and plasma arc brazing process according to their different heat sources and other aspects. The applications of these special brazing/soldering processes in material joining are introduced in this paper. The characteristics and functions of these heat sources and ultrasound in brazing are introduced in this paper. The applicable occasions of these special brazing/soldering processes are sorted out and summarized. Most importantly, the merits and demerits of special brazing/soldering processes are analyzed, and suggestions of the further research are mentioned.
The intermetallic compound that appears during the soldering reaction between pure Sn and Ni substrate at temperatures ranging from 250 to 400 °C is analyzed to be Ni
Sn
A similar reaction at the Sn– ...58Bi/Ni interface results in the formation of the Ni
Sn
Bi
phase. At the Sn/Ni and Sn–58Bi/Ni interfaces, each kind of intermetallic compound formation exhibits a similar scallop-type morphology. However, the growth rate of intermetallic compounds at the Sn/Ni interface is greater than that at the Sn– 58Bi/Ni interface. The growth kinetics for both cases is diffusion controlled. The activation energy for the intermetallic growth at the Sn/Ni interface is 43.7 kJ/mol, which is higher than that at the Sn–58Bi/Ni interface (28.3 kJ/mol).
The combined effect of solder volume and Cu concentration in solder on the Cu consumption rate is of significant practical importance but has never been satisfactorily addressed in literature so far. ...In this study, lead-free solder balls of different volumes (400, 500, 760 and 960
μm in diameter) and different Cu concentrations (Sn3Ag
xCu with
x
=
0, 0.3, 0.5, and 0.7
wt.%) were reflowed over Cu soldering pads in order to resolve this issue. The data obtained afforded the establishment of an empirical equation that could predict the Cu consumption during reflow. Such consumption rate information is crucial for designing the Cu conduction traces with minimum but reliable dimensions. Both the solder volume and the Cu concentration had marked effects on the morphology of the reaction product. Rationalizations for the effects on the consumption rate and the morphology are presented.
Sorghum is an important grain with a high economic value for liquor production. Tracing the geographical origin of sorghum is vital to guarantee the liquor flavor. Soldering iron‐based rapid ...evaporative ionization mass spectrometry (REIMS) combined with chemometrics was developed for the real‐time discrimination of the sorghum's geographical origin. The working conditions of soldering iron‐based ionization were optimized, and then the obtained MS profiling data were processed using chemometrics analysis methods, including principal component analysis–linear discriminant analysis and orthogonal projection to latent structures discriminant analysis (OPLS‐DA). A recognition model was established, and discriminations of sorghum samples from 10 provinces in China were achieved with a correct rate higher than 90%. On the basis of OPLS‐DA, the specific ions of m/z 279.2327, 281.2479, and 283.2639 had relatively strong discrimination power for the geographical origins of sorghum. The developed method was successfully applied in the discrimination of sorghum origins. The results indicated that the soldering iron‐based REIMS technique combined with chemometrics is a useful tool for direct, fast, and real‐time ionization of poor conductivity samples and acquisition of metabolic profiling data.
•The formation and growth of the IMC at the Sn–Ag–Cu solder/Cu interface after laser soldering and during isothermal aging were investigated.•A quite thin IMC layer is formed at the interface in the ...case of the laser soldering.•The growth of the IMC layer was faster by the laser soldering than by the reflow soldering.•The laser soldering under certain conditions is certainly effective for ensuring the impact reliability of the joint.
The formation and growth of an intermetallic compound (IMC) layer at the Sn–Ag–Cu solder/Cu interface after laser soldering and during isothermal aging were investigated to elucidate the basic characteristics of the laser soldering process. The impact reliability of joints soldered using the laser process was also examined. It was found that, in the as-soldered condition, a relatively thin IMC layer is formed at the interface of the joints soldered by the laser process. The impact reliability of the joints soldered by the laser process at 20W for 40s was superior to that of the joints soldered by the conventional reflow process.
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