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This paper investigates the ways digital media applications in rural areas have transformed the influence of social networks (SN) on farmers' adoption of various climate change mitigation measures (CCMM), and explores the key mechanisms behind this transformation.

The study analyzes data from 1,002 farmers’ surveys. First, a logit model is used to measure the impact of SN on the adoption of different types of CCMM. Then, the interaction term between digital media usage (DMU) and SN is introduced to analyze the moderating effect of digital media on the impact of SN. Finally, a conditional process model is used to explore the mediating mechanism of agricultural socialization services (ASS) and the validity of information acquisition (VIA).

The results reveal that: (1) SN significantly promotes the adoption of CCMM and the marginal effect of this impact varies with different kinds of technologies. (2) DMU reinforces the effectiveness of SN in promoting farmers' adoption of CCMM. (3) The key mechanisms of the process in (2) are the ASS and the VIA.

This study shows that in the context of DMU, SN’s promotion effect on farmers' adoption of CCMM is strengthened.

This study aims to focus on the surface mount technology (SMT) mass production process of Sn-9Zn-2.5Bi-1.5In solder. It explores it with some components that will provide theoretical support for the industrial SMT application of Sn-Zn solder.

This study evaluates the properties of solder pastes and selects a more appropriate reflow parameter by comparing the microstructure of solder joints with different reflow soldering profile parameters. The aim is to provide an economical and reliable process for SMT production in the industry.

Solder paste wettability and solder ball testing in a nitrogen environment with an oxygen content of 3,000 ppm meet the requirements of industrial production. The printing performance of the solder paste is good and can achieve a printing rate of 100–160 mm/s. When soldering with a traditional stepped reflow soldering profile, air bubbles are generated on the surface of the solder joint, and there are many voids and defects in the solder joint. A linear reflow soldering profile reduces the residence time below the melting point of the solder paste (approximately 110 s). This reduces the time the zinc is oxidized, reducing solder joint defects. The joint strength of tin-zinc joints soldered with the optimized reflow parameters is close to that of Sn-58Bi and SAC305, with high joint strength.

This study attempts to industrialize the application of Sn-Zn solder and solves the problem that Sn-Zn solder paste is prone to be oxidized in the application and obtains the SMT process parameters suitable for Sn-9Zn-2.5Bi-1.5In solder.

The interfacial structure is vitally important for achieving a good joint reliability during service. The purpose of this paper is to systematically explore the effects of Zn addition into the Sn-3.5Ag eutectic solder on the formation of intermetallic compound (IMC) layer at the interface between Sn-3.5Ag-xZn (x = 0, 0.9 and 3) solders and Cu pad.

To obtain useful information on the formation of interfacial structure and to determine an effective way to avoid the formation of brittle joints, a series of Sn-Ag lead-free solders with different Zn contents were prepared and soldered. To investigate the IMC layers between Sn-3.5Ag-xZn (x = 0, 0.9 and 3) lead-free solders and the Cu pads, three specimens of the Sn-3.5Ag-xZn/Cu were soldered at 250°C for one min.

It is found that the addition of Zn in the Sn-3.5Ag eutectic solder can prompt the formation of Cu₅Zn₈ IMCs, and restrain the formation of the Cu₆Sn₅ IMCs. Moreover, the addition of Zn in the Sn-3.5Ag eutectic solder will reduce the solubility of Cu in the liquid solder, which accelerates the growth of the formed IMCs. Consequently, the thickness of IMC layer increases with increasing the content of Zn.

This paper usefully demonstrates how the addition of Zn favoured the formation of the Cu₅Zn₈ phase and restrained the formation of the Cu₆Sn₅ phase. Moreover, the addition of Zn in the Sn-Ag eutectic solder would reduce the solubility of Cu in the liquid solder, which accelerates the growth of the formed IMCs. Consequently, the thickness of the IMC layer increased with increasing concentration of Zn.

The purpose of this paper is to investigate the effect of Al addition on the bulk alloy microstructure and tensile properties of the low Ag‐content Sn‐1Ag‐0.5Cu (SAC105) solder alloy.

The Sn‐1Ag‐0.5Cu‐xAl (x=0, 1, 1.5 and 2 wt.%) bulk solder specimens with flat dog‐bone shape were used for tensile testing in this work. The specimens were prepared by melting purity ingots of Sn, Ag, Cu and Al in an induction furnace. Subsequently, the molten alloys were poured into pre‐heated stainless steel molds, and the molds were naturally air‐cooled to room temperature. Finally, the molds were disassembled, and the dog‐bone samples were removed. The solder specimens were subjected to tensile testing on an INSTRON tester with loading rate 10⁻³ s⁻¹. The microstructural analysis was carried out using scanning electron microscopy/Energy dispersive X‐ray spectroscopy. Electron Backscatter Diffraction (EBSD) analysis was used to identify the IMC phases. To obtain the microstructure, the solder samples were prepared by dicing, molding, grinding and polishing processes.

The addition of Al to the SAC105 solder alloy suppresses the formation of Ag₃Sn and Cu₆Sn₅ IMC particles and leads to the formation of larger Al‐rich and Al‐Cu IMC particles and a large amount of fine Al‐Ag IMC particles. The addition of Al also leads to refining of the primary β‐Sn grains. The addition of Al results in a significant increase on the elastic modulus and yield strength. On the other hand, the addition of Al drastically deteriorates the total elongation.

The addition of Al to the low Ag‐content SAC105 solder alloy has been discussed for the first time. This work provides a starting‐point to study the effect of Al addition on the drop impact and thermal cycling reliability of the SAC105 alloy.

To determine the role of microstructure in the creep and thermomechanical fatigue (TMF) properties of solder joints made with eutectic Sn‐Ag solder, and Sn‐Ag solder with Cu and/or Ni additions.

Quaternary alloys containing small amounts of Cu and Ni exhibit better high temperature creep resistance and also better resistance to damage under TMF cycles with a longer dwell time at the high temperature extreme, than eutectic Sn‐Ag, and Sn‐Ag‐Cu ternary alloy solder joints. Microstructural evaluation was conducted to investigate the effects of Ni additions to Sn‐Ag‐based solder joints.

Microstructural studies of the quaternary solder alloys revealed the presence of small ternary Cu‐Ni‐Sn intermetallic compound particles at Sn‐Sn grain boundaries. These precipitates can retard the grain boundary sliding that will occur during TMF with longer dwell times at the high temperature extreme, and during high temperature creep.

The findings of this paper will help to provide an understanding of the effects of alloying elements on Sn‐Ag based solder joints.

Sn‐Zn based lead free solders with a melting temperature around 199°C are an attractive alternative to the conventional Sn‐Pb solder and the addition of bismuth improves its wetability. Whilst lead‐free soldering with Sn‐8Zn‐3Bi has already been used in the electronics assembly industry, it is necessary to study its low cycle fatigue properties since such data have not been reported up to now.

In this study, displacement‐controlled low cycle fatigue testing of Sn‐8Zn‐3Bi and Sn‐37Pb solder joints was done on lap shear samples. The test amplitude was varied whilst the frequency was kept constant at 0.2 Hz and failure was defined as a 50 per cent load reduction. Finite element (FE) modelling was used for analysis and the results were compared to the experimental data.

The microstructure of the Sn‐8Zn‐3Bi solder showed a mixed phase of small cellular‐shaped and coarser needle‐shaped areas. Au‐Zn intermetallic compounds were observed near the interface from the SEM‐EDS observation. The average lifetime for the Sn‐8Zn‐3Bi solder joints was 17 per cent longer compared to the Sn‐37Pb solder joints. The cross section observation indicated that the fatigue cracks propagated along the interface between the solder bulk and the Au/Ni layer. The locations of maximum equivalent stress from the FE simulation were found to be at the two opposite corners of the solder joints, coinciding with the experimental observations of crack initiation.

This is believed to be the first time, the low cycle fatigue properties of Sn‐8Zn‐3Bi solder have been reported.

This paper seeks to decrease the soldering temperature of capacitors using Sn‐Bi plated Sn‐3.5 wt%Ag solder.

Sn‐Bi layers were electroplated on Sn‐3.5 wt%Ag solder. As soldering examples, type 1608 capacitors electroplated with Sn, and printed circuit boards (PCBs) with a surface coating of electroless‐plated Ni/Au, were selected. Sn‐3.5Ag foil coupons plated with Sn‐95.7 wt%Bi were inserted as solder between the capacitors and the lands on the PCBs. The samples were reflowed at 220°C, which is below the normal reflow temperatures of around 240 ∼ 250°C used with Pb‐free solders. During heating, Bi in the plated layer diffuses into the Sn‐3.5Ag core solder resulting in a transient decrease in soldering temperature based on the concept of transient liquid phase bonding.

The joints made with the Sn‐95.7%Bi plated Sn‐3.5Ag solder at 220°C showed good appearance, and evidence of significant Bi segregation was absent in the microstructure. The shear strengths of the capacitor joints bonded with Sn‐95.7%Bi plated Sn‐3.5%Ag solder were approximately 5,000‐6,000 gf. After 1,000 thermal cycles between −40 and +125°C, the shear strengths of the joints decreased approximately 5‐10 percent from the strengths in the as‐reflowed state for all plated solders. This confirmed that the soldered joints were stable and not significantly degraded by thermal cycles.

Reduced temperature soldering using Sn‐Bi plated Sn‐3.5%Ag solder was applied to attach capacitors to PCBs. In a production application, the foil coupons could be replaced by pre‐solder on the PCB pads.

The purpose of this paper is to study the relationship between microstructure and mechanical properties of Sn‐4.0Bi‐3.7Ag‐0.9Zn (in wt%) solder, and the structural evolution of the soldered interfaces.

The solder was prepared by a vacuum arc furnace. Scanning electron microscopy (SEM) and X‐ray diffraction were used to identify the microstructure and composition. The melting temperature, microhardness and tensile strength were measured. Solder joints were prepared by reflowing at 250°C for 1 min in a vacuum oven and the soldered interfaces were observed by using SEM.

The microstructure of the slowly cooled Sn‐4.0Bi‐3.7Ag‐0.9Zn specimen is composed of bulk Ag₃Sn, AgZn intermetallic compounds (IMCs), Bi precipitates and a β‐Sn phase. The developed solder exhibits good comprehensive properties, such as low‐melting temperature, high microhardness and ultimate tensile strength. A complicated IMC layer forms at the interface with Cu pads and it turns into a thinner Ni₃Sn₄ layer with Ni/Cu substrates.

The paper shows how a high performance, lead‐free solder was developed.

This paper reviews the status of lead‐free solder development works. Some of the solder systems — Bi‐Sn, Bi‐Sn‐Fe, ln‐Sn, Sn, Sn‐Ag, Sn‐Ag‐Zn, Sn‐Ag‐Zn‐Cu, Sn‐Bi‐Ag, Sn‐Cu, Sn‐Cu‐Ag, Sn‐In‐Ag, Sn‐Sb, Sn‐Zn and Sn‐Zn‐ln — are discussed in more detail, while others are briefly commented on. In general, compared with eutectic Sn‐Pb solder, all the lead‐free solder alternatives investigated more or less exhibit some shortcomings, such as price, physical, metallurgical or mechanical properties. Relatively, Sn‐ln‐containing systems are more promising in terms of solder mechanical properties and soldering performance, although the price of ln may be a concern. Eutectic Sn‐Ag solder doped with Zn, Cu or Sb exhibits good mechanical strength and creep resistance, due to refined microstructure. The Bi‐Sn systems doped with other elements may have a niche in the low temperature soldering field. Eutectic Sn‐Cu has good potential due to its good fatigue resistance. The eutectic Sn‐Zn system modified with ln and/or Ag may be promising in terms of mechanical properties. Finding a lead‐free alternative for high temperature solders presents the biggest challenge to the industry.

This study seeks to investigate the electrochemical migration (ECM) behaviour of printed circuit boards (PCBs) with Sn‐37Pb and Sn‐3.0Ag‐0.5Cu (wt.%) solders under various factors such as the distance between the electrodes and bias voltage.

This study investigated the ECM phenomena with different surface finishes of Sn‐37Pb and Sn‐3.0Ag‐0.5Cu solders using water drop (WD) and temperature and humidity bias (THB) tests. After the WD and THB tests, the dendrite phase was identified using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).

The ECM resistance of the conventional Sn‐37Pb alloy was lower than that of the Pb‐free Sn‐3.0Ag‐0.5Cu alloy. The dendrites grew at the cathode electrodes on the PCB and expanded to the anode electrode. The main elements in the dendrites on the Sn‐37Pb and Sn‐3.0Ag‐0.5Cu finished PCBs were tin and lead, respectively.

This study evaluates the ECM phenomena of representative solder alloys on PCBs.