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The purpose of this paper is to study the melting temperature of the nanoparticles of the new developed Sn‐0.4Co‐0.7Cu (wt%) lead‐free solder alloy.

Nanoparticles of Sn‐0.4Co‐0.7Cu lead‐free solder alloy were prepared by the self‐developed consumable‐electrode direct current arc technique, where ultrasonic vibration was applied during the manufacturing of the particles. X‐ray diffraction and field emission scanning electron microscope were employed to analyze the crystal structure and morphology of the nanopartiles, respectively. Differential scanning calorimetry was used to investigate the melting temperature of both the bulk alloy and as‐prepared nanoparticles.

The melting temperature of the nanoparticles was approximately 5°C lower compared to that of the bulk alloy.

As a novel developed lead‐free solder alloy, the Sn‐0.4Co‐0.7Cu (wt%) alloy provides a cost advantage compared to the extensively used Sn‐Ag‐Cu system. Some limitations still exist, however, mainly due to its relatively higher melting temperature compared to that of eutectic Sn‐37Pb solder. In view of this situation, the attempt to lower its melting temperature has recently attracted more attention based on the knowledge that the melting temperature for pure metals is reduced when the particle size is decreased down to a few tens of nanometers.

The purpose of this paper is to assess the effect of different temperature cycling profiles on the reliability of lead‐free 388 plastic ball grid array (PBGA) packages and to deeply understand crack initiation and propagation.

Temperature cycling of Sn‐3.8Ag‐0.7Cu PBGA packages was carried out at two temperature profiles, the first ranging between −55°C and 100°C (TC1) and the second between 0°C and 100°C (TC2). Crack initiation and propagation was analyzed periodically and totally 7,000 cycles were run for TC1 and 14,500 for TC2. Finite element modeling (FEM), for the analysis of strain and stress, was used to corroborate the experimental results.

The paper finds that TC1 had a characteristic life of 5,415 cycles and TC2 of 14,094 cycles, resulting in an acceleration factor of 2.6 between both profiles. Cracks were first visible for TC1, after 2,500 cycles, and only after 4,000 cycles for TC2. The crack propagation rate was faster for TC1 compared to TC2, and faster at the package side compared to the substrate side. The difference in crack propagation rate between the package side and substrate side was much larger for TC1 compared to TC2. Cracks developed first at the package side, and were also larger compared to the substrate side. The Cu tracks on the substrate side affected the crack propagation sites and behaved as SMD. All cracks propagated through the solder and crack propagation was mainly intergranular. Crack propagation was very random and did not follow the distance to neutral point (DNP) theory. FEM corroborated the experimental results, showing both the same critical location of highest creep strain and the independence of DNP.

Such extensive work on the reliability assessment of Pb‐free 388 PBGA packages has never been performed. This work also corroborates the results from other studies showing the difference in behavior between Pb‐free and Pb‐containing alloys.

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.

To determine the Coffin‐Manson (CM) equation constants for fatigue life estimation of Sn‐8Zn‐3Bi solder joints, since Sn‐8Zn‐3Bi solder has a melting temperature of around 199°C which is close to that of the conventional Sn‐Pb solder which has previously been used in the electronics assembly industry.

Three dimensional finite element (FE) simulation analysis was used for comparison with the experimentally measured data and to determine the CM constants. Low cycle fatigue tests and FE simulations were carried out for these lead‐free solder joints, and eutectic Sn‐37Pb solder was used as a reference.

The CM equation for Sn‐8Zn‐3Bi solder joints was fitted to the lifetimes measured and the shear strains simulated. The constants were determined to be 0.0294 for C, the proportional constant, and for the fatigue exponent, β, −2.833.

The CM equation can now be used to predict the reliability of Sn‐8Zn‐3Bi solder joints in electronics assembly and the knowledge base for the properties of the Sn‐Zn solder system has been increased.

The purpose of this paper is to fit Coffin‐Manson equation of Sn‐4.0Ag‐0.5Cu lead free solder joint by using results of solders joint reliability test and finite element analysis. Also to present a novel device for solder joint reliability test.

Two‐points bending test of Sn‐4.0Ag‐0.5Cu lead free solder joint was carried out at three deflection levels by using a special bending tester that can control displacement exactly by a cam system. The failure criterion was defined as resistance of solder joint getting 10 percent increase. The X‐section was done for all failure samples to observe crack initiation and propagation in solder joint. Finite element analysis was presented with ANSYS for obtaining shear strain range, analyzing distribution of stress and strain and supporting experimental results.

The experimental results indicate that the fatigue life decreased obviously with the displacement increased. By using optical microscope and SEM photographs, two kinds of failure mode were found in solder joint. The majority failure mode took place at the bottom corner of solder joint under the termination of resistor initially, and propagated into the solder matrix. Another failure mode was delamination. It appeared at the interface between the termination of resistor and its ceramic body. The distribution status of stress and strain in solder joint and the calculation results of shear strain range at different deflection levels were obtained from simulation result. The Coffin‐Manson equation of Sn‐4.0Ag‐0.5Cu lead free solder joint was fitted by combining experimental data with result of finite element analysis.

This paper presents Coffin‐Manson equation of Sn‐4.0Ag‐0.5Cu solder joint with two‐points bending test. An effective and economical device was designed and applied.

The purpose of this paper is to consider PTH solder joint reliability, particularly on the PTH solder joints with partial hole‐fill and without pin protrusion. Also, the impact of voiding on the solder joint reliability is discussed.

Thermal cycling tests for samples of different hole‐fill percentages and voiding were conducted, and cross‐sections of the PTH solder joints were performed to evaluate the solder microstructure, intermetallic formation, via hole‐fill, and the condition of the PTH metallization and PCB dielectric prior to thermal cycling and at different times during thermal cycling.

Different failure mechanisms were observed for solder joints with and without pin protrusion. PTH components with pin protrusion had better through hole‐fill and less voids than PTH components without pin protrusion.

The paper discusses in detail the effect of hole‐fill percentage and voiding on PTH solder joint reliability.

The paper aims to investigate the interfacial reactions between two Sn‐Cu based multicomponent Pb‐free solders, Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au (wt per cent), and Ni substrates during soldering and aging.

Differential scanning calorimetry (DSC) was performed to measure the melting behaviors of the solders and determine the temperature of soldering. DSC tests showed that the onset temperature were 227.47 and 224.787°C for Sn‐2Cu‐0.5Ni and Sn‐2Cu‐0.5Ni‐0.5Au, respectively. Two intermetallic compounds (IMCs), Cu₆Sn₅ and (Cu,Ni)₆Sn₅, were formed in Sn‐2Cu‐0.5Ni solder. While the IMCs detected in Sn‐2Cu‐0.5Ni‐0.5Au matrix were (Cu,Ni)₆Sn₅, (Cu,Au)₆Sn₅ and (Cu,Ni)₆Sn₅. The IMC layer formed at the both solder/Ni interfaces was (Cu,Ni)₆Sn₅ with stick‐lick morphology after soldering at 260°C.

The interfacial IMC layers became planar when aged at 170°C for 500 h. However, cracks were found in the IMC layers at both joints when the aging time reached 1,000 h, that implies reliability problem may exist in the joints. Moreover, Au‐containing IMCs were found on the top of the IMC layer in Sn‐2Cu‐0.5Ni‐0.5Au/Ni joint after for 1,000 h.

This study focuses on the interfacial reactions of Sn‐2Cu‐0.5Ni/Ni and Sn‐2Cu‐0.5Au/Ni during soldering and isothermal aging.

The increasing utilization of Al‐matrix composites in electronics packaging industry raises demands of solder materials with melting temperature at 400‐500°C. The purpose of this paper is to determine the thermal properties of two Ag‐Cu‐Sb alloys with the composition close to two eutectic points, and two Au‐Ag‐Ge alloys along the eutectic line, to observe the microstructures and to investigate the wettability of the alloys, and to evaluate the possibility for them to be used as medium temperature solders.

Four candidates of solder alloys in the Au‐Ag‐Ge (AAG1, AAG2) and Ag‐Cu‐Sb systems (ACS1, ACS2) were studied to reveal microstructures, melting points, wettabilities, and the interfaces between the solder and Al/SiC substrate coated with Au and Ni.

The paper finds that the ACS1 and ACS2 alloys possess small temperature gaps between solidus and liquidus: 422.9°C/429.2°C and 483.3°C/488.1°C, respectively. For two AAG alloys, the temperature ranges between solidus and liquidus are larger than 40°C. The wettability tests showed that two ACSs and AAG1 alloys have good wettability to the substrate. Similarly, except ACS2 alloy, the other alloys exhibit good adhesion with the substrate.

The paper shows that the ACS1 alloy and the AAG1 alloy could be used as the optimum solder materials for 400‐500°C owing to the good wettability and proper melting point.

The aim of this paper is to investigate the growth behaviours of intermetallic compound (IMC) layers in solid‐liquid interfacial reactions of Sn1.5Cu/Cu in various intensities of high‐magnetic field.

Sn1.5Cu solder was prepared and melted in a vacuum furnace at 873 K and cast into solder bars. Samples were mounted using resin and etched after being carefully polished. Then the IMC layers were observed by using scanning electron microscopy.

The results show that the growth of IMC layers has been accelerated by high‐magnetic field through the comparison of growth kinetics of IMC layers among 0‐2.5 T magnetic filed. IMC grains in high‐magnetic field are much bigger than that in 0 T. By the analyzing of X‐ray diffractometer patterns of IMC layers, it can be found that the orientations of IMC have been changed by magnetic field.

This paper investigates the growth behaviour of IMC layers during the solid‐liquid interfacial reactions of Sn1.5Cu/Cu in a high magnetic field.