Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
The melting temperature of the nanoparticles was approximately 5°C lower compared to that of the bulk alloy.
Originality/value
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.
Details
Keywords
Jennifer Nguyen, David Geiger, Dan Rooney and Dongkai Shangguan
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
The paper discusses in detail the effect of hole‐fill percentage and voiding on PTH solder joint reliability.
Details
Keywords
Ning Zhao, Hai‐tao Ma and Lai Wang
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
This study focuses on the interfacial reactions of Sn‐2Cu‐0.5Ni/Ni and Sn‐2Cu‐0.5Au/Ni during soldering and isothermal aging.
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Keywords
Chunyuan Li, Xitao Wang and Wenxia Yuan
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
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Keywords
Cong‐qian Cheng, Jie Zhao, Yang Xu, Fu‐Min Xu and Ming‐liang Huang
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
This paper investigates the growth behaviour of IMC layers during the solid‐liquid interfacial reactions of Sn1.5Cu/Cu in a high magnetic field.
Details
Keywords
S. Chen, P. Sun, X.C. Wei, Z.N. Cheng and J. Liu
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
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Keywords
M. Norén, S. Brunner, C. Hoffmann, W. Salz and K. Aichholzer
One of the major driving forces for the electronic industry is the consumer handheld units, where even more functions in a smaller volume and with longer battery time are…
Abstract
Purpose
One of the major driving forces for the electronic industry is the consumer handheld units, where even more functions in a smaller volume and with longer battery time are requested. This leads to a higher energy‐ and interconnect‐density. Two challenges related to this request, that the industry is facing, are thermal management and reliability. This paper aim to discuss some aspects of using flip chip (FC) technology on low temperature cofired ceramics (LTCC) for this kind of products and to focus on the heat dissipation problem of an FC mounted die.
Design/methodology/approach
Test designs were developed and built to investigate SnAgCu bumps on LTCC, underfill and five different LTCC designs. The LTCC design parameters were thermal vias and heat spreaders. In the experimental part, the semiconductor junction temperature was measured over a diode in the semiconductor. Cross sections and infrared thermal imaging were used. The experiments were accompanied by FE‐modeling using ANSYS workbench.
Findings
The main reduction in temperature is related to the use of thermal vias and a via offset smaller than 60 μm. A 100 μm via diameter gives only a minor increase in the semiconductor junction temperature. Reducing the LTCC substrate thickness will decrease the junction temperature further.
Originality/value
This paper shows that FC on LTCC is a promising key technology for power amplifier modules.
Details
Keywords
C. Andersson, B. Vandevelde, C. Noritake, P. Sun, P.E. Tegehall, D.R. Andersson, G. Wetter and J. Liu
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…
Abstract
Purpose
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.
Design/methodology/approach
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.
Findings
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.
Originality/value
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.
Details
Keywords
Kamil Janeczek, Tomasz Serzysko, Małgorzata Jakubowska, Grażyna Kozioł and Anna Młożniak
The purpose of this paper is to investigate the durability of radio‐frequency identification (RFID) chips assembled on flexible substrates (paper and foil), with materials…
Abstract
Purpose
The purpose of this paper is to investigate the durability of radio‐frequency identification (RFID) chips assembled on flexible substrates (paper and foil), with materials evaluated with regard to mechanical stresses and dependence on the applied substrate, antenna materials, chip pad printing and chip encapsulation.
Design/methodology/approach
RFID chips were assembled to antennas screen printed on flexible substrates. Shear and bending tests were conducted in order to evaluate the mechanical durability of the chip joints depending on the materials used for mounting the RFID chip structures. X‐ray inspection and cross sectioning were performed to verify the quality of the assembly process. The microstructure and the resistance of the materials used for chip pads were investigated with the aim of determining the conductivity mechanism in the printed layers.
Findings
Addition of carbon nanotubes to the conductive adhesive (CA) provided a higher shear force for the assembled RFID chips, compared to the unmodified conductive adhesive or a polymer paste with silver flakes. However, this additive resulted in an increase in the material's resistance. It was found that the RFID substrate material had a significant influence on the shear force of mounted chips, contrary to the materials used for printing antennas. The lower shear force for chips assembled on antennas printed on paper rather than on foil was probably connected with its higher absorption of solvent from the pastes. Increasing the curing temperature and time resulted in an additional increase in the shear force for chips assembled to antennas printed on foil. A reverse dependence was observed for chips mounted on the antennas made on paper. An improvement in the durability of the RFID chip structures was achieved by chip encapsulation. Bending tests showed that a low‐melting adhesive was the best candidate for encapsulation, as it provided flexibility of the assembled structure.
Research limitations/implications
Further studies are necessary to investigate the mechanical durability of RFID chips assembled with a conductive adhesive, with different addition levels and types of carbon nanotubes.
Practical implications
The results revealed that the best candidate for providing the highest RFID chip durability related to mechanical stresses was the low‐melting adhesive. It can be recommended for practical use, as it simplified the assembly process and reduced the curing step in the encapsulation of the RFID devices. From the results of shear testing, conductive adhesives with carbon nanotubes can be used in RFID chip assembly because of their ability to increase the shear force of joints created between the antenna and the chip.
Originality/value
In this paper, the influence of the materials used for antenna, chip pads, encapsulation and the curing conditions on the mechanical durability (shear and bending) of RFID chips was analyzed. Commercial and elaborated materials were compared. Some new materials containing a conductive adhesive and carbon nanotubes were proposed and tested in RFID chip assembly to antennas printed on flexible substrates (paper and foil).