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Article
Publication date: 16 January 2018

Peng Yao, Xiaoyan Li, Fengyang Jin and Yang Li

This paper aims to analyze the morphology transformation on the Cu3Sn grains during the formation of full Cu3Sn solder joints in electronic packaging.

Abstract

Purpose

This paper aims to analyze the morphology transformation on the Cu3Sn grains during the formation of full Cu3Sn solder joints in electronic packaging.

Design/methodology/approach

Because of the infeasibility of analyzing the morphology transformation intuitively, a novel equivalent method is used. The morphology transformation on the Cu3Sn grains, during the formation of full Cu3Sn solder joints, is regarded as equivalent to the morphology transformation on the Cu3Sn grains derived from the Cu/Sn structures with different Sn thickness.

Findings

During soldering, the Cu3Sn grains first grew in the fine equiaxial shape in a ripening process until the critical size. Under the critical size, the Cu3Sn grains were changed from the equiaxial shape to the columnar shape. Moreover, the columnar Cu3Sn grains could be divided into different clusters with different growth directions. With the proceeding of soldering, the columnar Cu3Sn grains continued to grow in a feather of the width growing at a greater extent than the length. With the growth of the columnar Cu3Sn grains, adjacent Cu3Sn grains, within each cluster, merged with each other. Next, the merged columnar Cu3Sn grains, within each cluster, continued to merge with each other. Finally, the columnar Cu3Sn grains, within each cluster, merged into one coarse columnar Cu3Sn grain with the formation of full Cu3Sn solder joints. The detailed mechanism, for the very interesting morphology transformation, has been proposed.

Originality/value

Few researchers focused on the morphology transformation of interfacial phases during the formation of full intermetallic compounds joints. To bridge the research gap, the morphology transformation on the Cu3Sn grains during the formation of full Cu3Sn solder joints has been studied for the first time.

Details

Soldering & Surface Mount Technology, vol. 30 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 12 August 2021

Xu Han, Xiaoyan Li and Peng Yao

This study aims to investigate the effect of ultrasound on interfacial microstructures and growth kinetics of intermetallic compounds (IMCs) at different temperatures.

Abstract

Purpose

This study aims to investigate the effect of ultrasound on interfacial microstructures and growth kinetics of intermetallic compounds (IMCs) at different temperatures.

Design/methodology/approach

To investigate the effect of ultrasound on IMCs growth quantitatively, the cross-sectional area of IMCs layers over a confirmed length was obtained for calculating the thickness of the IMCs layer.

Findings

The generation of dimensional difference in normal direction between Cu6Sn5 and its adjacent Cu6Sn5, formation of bossed Cu6Sn5 and non-interfacial Cu6Sn5 in ultrasonic solder joints made the interfacial Cu6Sn5 layer present a non-scallop-like morphology different from that of traditional solder joints. At 260°C and 290°C, the Cu3Sn layer presented a wave-like shape. In contrast, at 320°C, the Cu3Sn in ultrasonic solder joints consisted of non-interfacial Cu3Sn and interfacial Cu3Sn with a branch-like shape. The Cu6Sn5/Cu3Sn boundary and Cu3Sn/Cu interface presented a sawtooth-like shape under the effect of ultrasound. The predominant mechanism of ultrasonic-assisted growth of Cu6Sn5 growth at 260°C, 290°C and 320°C involved the grain boundary diffusion accompanied by grain coarsening. The Cu3Sn growth was controlled by volume diffusion during the ultrasonic soldering process at 260°C and 290°C. The diffusion mechanism of Cu3Sn growth transformed to grain boundary diffusion accompanied by grain coarsening when the ultrasonic soldering temperature was increased to 320°C.

Originality/value

The microstructural evolution and growth kinetics of IMCs in ultrasonically prepared ultrasonic solder joints at different temperatures have rarely been reported in previous studies. In this study, the effect of ultrasound on microstructural evolution and growth kinetics of IMCs was systematically investigated.

Details

Soldering & Surface Mount Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 25 January 2021

Xu Han, Xiaoyan Li, Peng Yao and Dalong Chen

This study aims to investigate the interfacial microstructures of ultrasonic-assisted solder joints at different soldering times.

Abstract

Purpose

This study aims to investigate the interfacial microstructures of ultrasonic-assisted solder joints at different soldering times.

Design/methodology/approach

Solder joints with different microstructures are obtained by ultrasonic-assisted soldering. To analyze the effect of ultrasounds on Cu6Sn5 growth during the solid–liquid reaction stage, the interconnection heights of solder joints are increased from 30 to 50 μm.

Findings

Scallop-like Cu6Sn5 nucleate and grow along the Cu6Sn5/Cu3Sn interface under the traditional soldering process. By comparison, some Cu6Sn5 are formed at Cu6Sn5/Cu3Sn interface and some Cu6Sn5 are randomly distributed in Sn when ultrasonic-assisted soldering process is used. The reason for the formation of non-interfacial Cu6Sn5 has to do with the shock waves and micro-jets produced by ultrasonic treatment, which leads to separation of some Cu6Sn5 from the interfacial Cu6Sn5 to form non-interfacial Cu6Sn5. The local high pressure generated by the ultrasounds promotes the heterogeneous nucleation and growth of Cu6Sn5. Also, some branch-like Cu3Sn formed at Cu6Sn5/Cu3Sn interface render the interfacial Cu3Sn in ultrasonic-assisted solder joints present a different morphology from the wave-like or planar-like Cu3Sn in conventional soldering joints. Meanwhile, some non-interfacial Cu3Sn are present in non-interfacial Cu6Sn5 due to reaction of Cu atoms in liquid Sn with non-interfacial Cu6Sn5 to form non-interfacial Cu3Sn. Overall, full Cu3Sn solder joints are obtained at ultrasonic times of 60 s.

Originality/value

The obtained microstructure evolutions of ultrasonic-assisted solder joints in this paper are different from those reported in previous studies. Based on these differences, the effects of ultrasounds on the formation of non-interfacial IMCs and growth of interfacial IMCs are systematically analyzed by comparing with the traditional soldering process.

Details

Soldering & Surface Mount Technology, vol. 33 no. 4
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 18 February 2019

Li Yang, Li Xiaoyan and Peng Yao

The purpose of this paper is to investigate the diffusion behaviors of different atoms at the Cu/Cu3Sn interface and the vacancy formation energy, diffusion energy barrier…

Abstract

Purpose

The purpose of this paper is to investigate the diffusion behaviors of different atoms at the Cu/Cu3Sn interface and the vacancy formation energy, diffusion energy barrier and vacancy diffusion activation energy.

Design/methodology/approach

The diffusion behaviors of different atoms at the Cu/Cu3Sn interface are analyzed, and the vacancy formation energy, diffusion energy barrier and vacancy diffusion activation energy are obtained using molecular dynamics simulation. The nudged elastic band method is used to evaluate diffusion energy barrier for Cu/Cu3Sn system.

Findings

It is found that the vacancies in the Cu/Cu3Sn interface promote the interfacial diffusion, and the formation energy of Cu vacancy in the Cu crystal is larger than that in Cu3Sn crystal. In addition, the formation energies of Cu1 vacancy and Cu2 vacancy are close to each other in Cu3Sn crystal, and they are all less than the formation energy of Sn vacancy. Furthermore, the vacancy diffusion barrier and vacancy diffusion activation energy of the Cu/Cu3Sn interface are calculated, and the results show that the vacancy diffusion activation energy of Sn was higher than that of Cu. Finally, by comparison of diffusion activation energies of different diffusion mechanisms, Cu→Cu1vac is the most possible migration path at all temperatures.

Originality/value

It is concluded that the vacancies in Cu/Cu3Sn interface promote interfacial diffusion, and the activation energy of vacancy diffusion in most diffusion mechanisms decreases with the increase of temperature.

Details

Soldering & Surface Mount Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 18 February 2019

Peng Yao, Xiaoyan Li, Xu Han and Liufeng Xu

This study aims to analyze the shear strength and fracture mechanism of full Cu-Sn IMCs joints with different Cu3Sn proportion and joints with the conventional interfacial…

Abstract

Purpose

This study aims to analyze the shear strength and fracture mechanism of full Cu-Sn IMCs joints with different Cu3Sn proportion and joints with the conventional interfacial structure in electronic packaging.

Design/methodology/approach

The Cu-Sn IMCs joints with different Cu3Sn proportion were fabricated through soldering Cu-6 μm Sn-Cu sandwich structure under the extended soldering time and suitable pressure. The joints of conventional interfacial structure were fabricated through soldering Cu-100 μm Sn-Cu sandwich structure. After the shear test was conducted, the fracture mechanism of different joints was studied through observing the cross-sectional fracture morphology and top-view fracture morphology of sheared joints.

Findings

The strength of joints with the conventional interfacial structure was 26.6 MPa, while the strength of full Cu-Sn IMCs joints with 46.7, 60.6, 76.7 and 100 per cent Cu3Sn was, respectively, 33.5, 39.7, 45.7 and 57.9 MPa. The detailed reason for the strength of joints showing such regularity was proposed. For the joint of conventional interfacial structure, the microvoids accumulation fracture happened within the Sn solder. However, for the full Cu-Sn IMCs joint with 46.7 per cent Cu3Sn, the cleavage fracture happened within the Cu6Sn5. As the Cu3Sn proportion increased to 60.6 per cent, the inter-granular fracture, which resulted in the interfacial delamination of Cu3Sn and Cu6Sn5, occurred along the Cu3Sn/Cu6Sn5 interface, while the cleavage fracture happened within the Cu6Sn5. Then, with the Cu3Sn proportion increasing to 76.7 per cent, the cleavage fracture happened within the Cu6Sn5, while the transgranular fracture happened within the Cu3Sn. The inter-granular fracture, which led to the interfacial delamination of Cu3Sn and Cu, happened along the Cu/Cu3Sn interface. For the full Cu3Sn joint, the cleavage fracture happened within the Cu3Sn.

Originality/value

The shear strength and fracture mechanism of full Cu-Sn IMCs joints was systematically studied. A direct comparison regarding the shear strength and fracture mechanism between the full Cu-Sn IMCs joints and joints with the conventional interfacial structure was conducted.

Details

Soldering & Surface Mount Technology, vol. 31 no. 1
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 12 July 2021

Xiaoyan Li, Zhihui Zhang, Jiming Yao, MengQian Wang and Na Yang

To improve the problems as the heavy burden of sewage treatment and environmental pollution caused by the traditional sodium hydrosulfite reduction dyeing of indigo, this…

Abstract

Purpose

To improve the problems as the heavy burden of sewage treatment and environmental pollution caused by the traditional sodium hydrosulfite reduction dyeing of indigo, this study aims to carry out the direct electrochemical reduction dyeing for indigo with the eco-friendly Cu(II)/sodium borohydride reduction system under normal temperature and pressure conditions.

Design/methodology/approach

The electrochemical behavior of Cu(II)/sodium borohydride reduction system was investigated by cyclic voltammetry. And, the dyeing performance of the Cu(II)/sodium borohydride reduction system was developed by optimizing the concentration of copper sulfate in the anode electrolyte, applied voltage and reduction time via single-factor and orthogonal integrated analysis.

Findings

The dyeing performance of the Cu(II)/sodium borohydride reduction system is superior to that of the traditional reduction dyeing with sodium hydrosulfite. In the case of the optimized condition, the soaping fastness and dry/wet rubbing fastness of the dyed fabric in the two reduction dyeing processes were basically comparable, the K/S value of electrocatalytic reduction of indigo by Cu(II)/NaBH4 is 11.81, which is higher than that obtained by traditional sodium hydrosulfite reduction dyeing of indigo.

Originality/value

The innovative electrocatalytic reduction system applied herein uses sodium borohydride as the hydrogen source combined with Cu(II) complex as the catalyst, which can serve as a medium for electron transfer and active the dye molecule to make it easier to be reduced. The electrochemical dyeing strategy presented here provides a new idea to improve the reduction dyeing performance of indigo by sodium borohydride.

Details

Pigment & Resin Technology, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 29 October 2018

Lanying Sun and Xiaoyan Li

The purpose of this paper is under the analysis framework of the system theory, analyzing the optimal contract mode of agricultural supply chain to guarantee the stability…

Abstract

Purpose

The purpose of this paper is under the analysis framework of the system theory, analyzing the optimal contract mode of agricultural supply chain to guarantee the stability of agricultural supply chain and the equilibrium of agricultural product market, to analyze the effect of farmers’ risk attitude on the selection of contract modes and to find the way to encourage farmers’ productive effort and to avoid farmers’ hitchhiking behavior, to guarantee the stability of agricultural supply chain.

Design/methodology/approach

Under the guidance of the system theory, using the Stackelberg model and the nonlinear programming theory, this paper comparatively analyzes farmers’ effort (productive effort and sales effort), farmers’ income and the stability of agricultural supply system of four types of contract modes between farmers, third-party organizations and market.

Findings

First, in the agricultural market, market-type contract cannot maximize farmers’ income. The main reason is that farmers do not have enough ability to avoid market risk and to bargain. Second, for farmers of risk seeking, choosing a market-type contract and secondary-income contract can increase their income. Third, under the fixed-purchase price contract, the hitchhiking behavior would happen. Fourth, when farmers’ productive efforts are the same, farmers’ income under the secondary-income contract is higher than under the fixed-purchase price contract. Because under the secondary-income contract, farmers have the opportunity to obtain the secondary distribution of benefits, farmers’ hitchhiking behavior could be avoided.

Originality/value

Analyzing the contract modes between farmers and the third-party organization in the agricultural market could reduce the influence of price fluctuation, avoid the uncertainty of the relationship between the supply and demand, stimulate the productive effort of farmers and provide theoretical guidance for establishing efficient and stable agricultural supply system.

Details

Kybernetes, vol. 48 no. 5
Type: Research Article
ISSN: 0368-492X

Keywords

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Article
Publication date: 8 December 2020

Xiaoyan Li, MengQian Wang, Gang Wu and Jiming Yao

The purpose of this study is to improve the performance of sodium borohydride in reducing indigo at room temperature, the divalent copper ion complex was combined with…

Abstract

Purpose

The purpose of this study is to improve the performance of sodium borohydride in reducing indigo at room temperature, the divalent copper ion complex was combined with electrochemical technology for the reduction of indigo by sodium borohydride.

Design/methodology/approach

According to the K/S value of the dyed cloth sample, find a more suitable ligand for the copper ion in the catholyte. Response surface analysis tests were performed to evaluate the effects of sodium borohydride concentration, sodium hydroxide concentration and copper sulfate pentahydrate concentration on the reduction potential of the dye solution and the K/S value of the dyed fabric samples.

Findings

Sodium gluconate was found to be a more suitable ligand for copper ions in catholyte. The effects of NaOH concentration as well as the interaction of NaBH4 and NaOH on the reduction potential of the catholyte and the K/S value of the dyed fabric samples were extremely significant. The optimal concentrations of NaBH4, NaOH and CuSO4•5H2O were 0.5, 2.5 and 0.65 g/L. In the case of the optimized condition, the absolute value of the reduction potential was 968, and the K/S value was 11.92, which is comparable with that of the conventional reduction process with sodium dithionite.

Originality/value

The divalent copper ion complex combined with electrochemical technology was applied in the process of reducing indigo with NaBH4 at room temperature.

Details

Pigment & Resin Technology, vol. 50 no. 3
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 15 October 2019

Wei Zhang, Weiwei Lv, Xiaoyan Li and Jiming Yao

In this study, the oxidative degradation performance of indigo wastewater based on electrochemical systems was explored. The decolourization degrees, removal rate of…

Abstract

Purpose

In this study, the oxidative degradation performance of indigo wastewater based on electrochemical systems was explored. The decolourization degrees, removal rate of chemical oxygen demand and biochemical oxygen demand of the indigo wastewater after degradation were evaluated and optimized treatment conditions being obtained.

Design/methodology/approach

The single factor method was first used to select the electrolyte system and electrode materials. Then the response surface analysis based on Box–Behnken Design was chosen to determine the influence of four independent variables such as FeCl3 concentration, NaCl concentration, decolourization time and voltage on the degradation efficiency.

Findings

On the basis of single factor experiment, the electrode material of stainless steel was selected in the double cell, and the indigo wastewater was electrolyzed with FeCl3 and NaCl electrolytes. The process conditions of electrochemical degradation of indigo wastewater were optimized by response surface analysis: the concentration of FeCl3 and NaCl was of 16 and 9 g/L, respectively, with a decolourization time of 50 min, voltage of 10 V and decolourization percentage of 98.94. The maximum removal rate of chemical oxygen demand reached 75.46 per cent. The highest ratio of B/C was 3.77, which was considered to be more biodegradable.

Research limitations/implications

Dyeing wastewater is bringing out more and more pollution problems to the environment. However, there are some shortcomings in traditional technologies such as adsorption and filtration. As a kind of efficient and clean water treatment technology, electrochemical oxidation has been applied to the treatments of various types of wastewater. The decolourization and degradation of indigo wastewater is taken as an example to provide reference for the treatment of wastewater in actual plants.

Practical implications

The developed method provided a simple and practical solution for efficiently degrading indigo wastewater.

Originality/value

The method for the electrochemical oxidation technology was novel and could find numerous applications in the degradation of printing and dyeing wastewater.

Details

Pigment & Resin Technology, vol. 49 no. 1
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 21 October 2019

Kangkang Wang, MengQian Wang, Weiwei Lv, Jiming Yao, Wei Zhang and Xiaoyan Li

An indirect electrochemical reduction and dyeing with indigo were carried out here to solve problems of low dye reduction rate and poor dyeing depth in the current…

Abstract

Purpose

An indirect electrochemical reduction and dyeing with indigo were carried out here to solve problems of low dye reduction rate and poor dyeing depth in the current electrochemical dyeing process.

Design/methodology/approach

Response surface analysis tests were performed to evaluate the effects of ferrous sulfate concentration, medium concentration, sodium hydroxide concentration and reduction time on the reduction efficiency of indirect electrochemical reduction of indigo.

Findings

The conditions obtained by design-expert optimization showed that the concentration of FeSO4·7H2O has the most significant effect on the reduction performance of dye liquor. Under the optimized electrochemical reduction dyeing process, the rate of dye reduction could be reached 91.21 per cent and the K/S value of indirect electrochemical dyeing of indigo can be achieved to 12.96, which is increased by about 9.56 per cent compared with that of Na2S2O4 dyeing with the same color fastness basically.

Research limitations/implications

The recyclability and biodegradability of the dye remain to be explored.

Practical implications

The strategy presented here can be developed to replace a substantial part of electrochemical dyeing with optimized product quality and reduced environmental pollution in denim production.

Social implications

The strategy presented here can be developed to replace a substantial part of electrochemical dyeing with optimized product quality and reduced environmental pollution in denim production.

Originality/value

Application of the Fe(II)-DGS-Abal B complex media system in the indirect electrochemical reduction of indigo.

Details

Pigment & Resin Technology, vol. 49 no. 2
Type: Research Article
ISSN: 0369-9420

Keywords

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