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1.
Modern electronics products relentlessly become more complex, higher in density and speed, and thinner and lighter for greater portability. The package of these products is therefore critical. The reliability of the interconnection of electronics packaging has become a critical issue. In this study, the novel testing methods for electronic packaging are introduced and failure mechanisms of electronic packaging are explained. Electronics packaging is subjected to mechanical vibration and thermal cyclic loads which lead to fatigue crack initiation, propagation and the ultimate fracture of the packaging. A small-sized electromagnetic-type bending cycling tester, a micro-mechanical testing machine, and thermal fatigue testing apparatus were specially developed for the reliability assessment of electronics packaging. The long-term reliability of an electronic component under cyclic bending induced high-cycle fatigue was assessed. The high-cycle bending-fatigue test was performed using an electromagnetic-type testing machine. The time to failure was determined by measuring the changes in resistance. Using the micro-mechanical tester, low cycle fatigues were performed and compared with the results of a finite element analysis to investigate the optimal shape of solder bumps in electronic packaging. Fatigue tests on various lead-free solder materials are discussed. To assess the resistance against thermal loads, pseudo-power cycling method is developed. Thermal fatigue tests of lead-containing and lead-free solder joints of electronic packaging were performed using the pseudo-power cycling tester. The results from the thermal fatigue tests are compared with the mechanical fatigue data in terms of the inelastic energy dissipation per cycle. It was found that the mechanical load has a longer fatigue life than the thermal load at the same inelastic energy dissipation per cycle. 相似文献
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Solder joint fatigue failure is a serious reliability concern in area array technologies, such as flip chip and ball grid array packages of integrated-circuit chips. The selection of different substrate materials could affect solder joint thermal fatigue life significantly. The reliability of solder joints in real flip chip assembly with both rigid and compliant substrates was evaluated by the accelerated temperature cycling test and thermal mechanical analysis. The mechanism of substrate flexibility on improving solder joint thermal fatigue lifetime was investigated by fracture mechanics methods. Two different methods (crack tip opening displacement, CTOD and virtual crack closure technique, VCCT) are used to determine the crack tip parameters which are considered as the indices of reliability of solder joints, including the strain energy release rate and phase angle for the different crack lengths and temperatures. It was found that the thermal fatigue lifetime of solder joints in flip chip on flex assembly (FCOF) was much longer than that of flip chip on rigid board assembly (FCOB). The flex substrates could dissipate energy that otherwise would be absorbed by solder joints, that is, substrate flexibility has a great effect on solder joint reliability and the reliability improvement was attributed to flex buckling or bending during thermal cycling. 相似文献
5.
Limeng Yin Song Wei Zhangliang Xu Yanfei Geng 《Journal of Materials Science: Materials in Electronics》2013,24(4):1369-1374
Solder joints in electronic packaging systems are becoming smaller and smaller to meet the miniaturization requirements of electronic products and high density interconnect technology. Furthermore, many properties of the real solder joints at the microscale level are obviously different from that of bulk solder materials. Creep, as one of the key mechanical properties at elevated temperatures, can impair the reliability of miniature solder joints in electronic devices. However, there is a lack of knowledge about the comparative creep properties of microscale solder joints of different sizes. Most previous studies have focused on the creep properties of bulk solder materials or solder joints of the same size. In this research, to determine whether a size effect exists for creep properties of solder joints or not, we characterized the creep behaviors of Sn–3.0Ag–0.5Cu lead-free solder joints under tensile loading modes using microscale butt-joint specimens with a copper-wire/solder/copper-wire sandwich structure with two different sizes. Also, the creep failure mechanisms were investigated. Experimental results show that the creep activation energy and creep stress exponent are very similar for both sizes of solder joint. However, under the same testing conditions, the joints with a larger size exhibit a much higher steady-state creep rate and a shorter creep lifetime than the smaller joints. 相似文献
6.
Stephanie Bergman K. N. Subramanian 《Journal of Materials Science: Materials in Electronics》2012,23(7):1442-1448
Lead-free electronic packages intended for use in applications such as aerospace, military, and other highly demanding service conditions, necessitate exceptional mechanical reliability of lead-free electronic solder joints under realistic service conditions. Most current design strategies employed for improving the reliability of lead-free electronic solder joints are aimed at developing suitable alloying additions and reinforcements to the solder itself. At present there exists no suitable methodology to minimize the effects of service conditions while the solder joint is in service. Since thermomechanical fatigue reliability of electronic solder joints is closely related to the crack nucleation that occurs during very early stages of repeated thermal excursions, this study is based on subjecting solder joints to a limited number of thermal shock (TS) cycles in a chosen temperature regime to nucleate cracks, then evaluating their effectiveness in improving reliability when the solder joints are subjected to additional TS cycles in a different temperature regime. This study is a preliminary investigation, aimed at developing suitable methodology to minimize the effects of damage to lead-free solder joint specimens subjected to repeated thermal excursions during service, by imposing appropriate thermal treatments. These thermal treatments can be automatically implemented at programmed intervals during the service life of the electronic packages. Methods employed in these studies may also be useful to enhance long-term service reliability and to obtain a conservative estimate of long-term service reliability. 相似文献
7.
Solder joints are often the cause of failure in electronic devices, failing due to cyclic creep induced ductile fatigue. This paper will review the modelling methods available to predict the lifetime of SnPb and SnAgCu solder joints under thermo‐mechanical cycling conditions such as power cycling, accelerated thermal cycling and isothermal testing, the methods do not apply to other damage mechanisms such as vibration or drop‐testing. Analytical methods such as recommended by the IPC are covered, which are simple to use but limited in capability. Finite element modelling methods are reviewed, along with the necessary constitutive laws and fatigue laws for solder, these offer the most accurate predictions at the current time. Research on state‐of‐the‐art damage mechanics methods is also presented, although these have not undergone enough experimental validation to be recommended at present. 相似文献
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Liang Zhang Lei Sun Yong-huan Guo Cheng-wen He 《Journal of Materials Science: Materials in Electronics》2014,25(3):1209-1213
Finite element method and Garofalo–Arrheninus creep model were combined and used to evaluate the reliability of different lead-free solder joints (SnAgCu, SnAg, SnSb and SnZn) and SnPb solder joints in chip scale package (CSP) 14 × 14 device under thermal cyclic loading. The results show that von Mises stress and equivalent creep strain in each of the four lead-free solder joints and SnPb solder joints were strongly different, increasing in the order SnPb < SnAg < SnSb < SnZn < SnAgCu. It is found that maximum stress–strain concentrates on the top-surface of corner solder joints in the CSP device for all solder joints, and SnAgCu solder joints shows the highest fatigue life among those five kinds of solder joints. 相似文献
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Sn–Ag–Cu (SAC) alloys are regarded as the most promising alternative for traditional Pb–Sn solders used in electronic packaging applications. However, the higher reflow temperature requirement, possible intermetallic formation, and reliability issues of SAC alloys generate several key challenges for successful adoption of Pb-free solder for next generation electronic packaging needs. Localized heating in interconnects can alleviate thermal stresses by preventing subjection of entire package to the higher reflow temperatures associated with the SAC solders. It had been demonstrated that SAC solder–FeCo magnetic nanoparticles (MNPs) composite paste can be reflowed locally with AC magnetic fields, enabling interconnect formation in area array packages while minimizing eddy current heating in the printed circuit board.Solder/magnetic nanocomposite pastes with varying MNP concentration were reflowed using AC magnetic fields. Differential scanning calorimetry results show a reduced undercooling of the composite pastes with the addition of MNPs. TEM results show that the FeCo MNPs are distributed in Sn matrix of the reflowed solder composites. Optical and SEM micrographs show a decrease in Sn dendrite regions as well as smaller and more homogeneous dispersed Ag3Sn with the addition of MNPs. The MNPs promote Sn solidification by providing more heterogeneous nucleation sites at relatively low undercoolings. The mechanical properties were measured by nanoindentation. The modulus, hardness, and creep resistance, increase with the MNP concentration. The enhanced mechanical properties are attributed to grain boundary and dispersion strengthening.The reflow of solder composites have been modeled based on eddy current power loss in the substrate and magnetic power losses in the solder bumps. Induction reflow of pure solder bumps (<300 μm) in an area array package using 500 Oe magnetic field at 300 kHz requires excessive eddy current power loss in the substrate, resulting in extreme temperatures that lead to blistering and delamination of the substrate. Solder–MNP composites with modest MNP loading showed temperature increases sufficient to achieve solder reflow when subjected to the same AC magnetic fields. Thermomechanical behavior of a solder joint was also modeled under cyclic temperature variations. The stress and strain are highly localized at the interface between solder and substrate. Plastic work accumulated per cycle can be used for lifetime prediction.In this article we review lead-containing and lead-free solder systems, and the electronic packaging technologies pertinent to soldering process. Recent research on the effects of MNPs on localized heating, microstructure evolution, mechanical properties, and thermomechanical reliability are summarized. 相似文献
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Mrunali Sona K. N. Prabhu 《Journal of Materials Science: Materials in Electronics》2013,24(9):3149-3169
The use of Pb-bearing solders in electronic assemblies is avoided in many countries due to the inherent toxicity and environmental risks associated with lead. Although a number of “Pb-free” alloys have been invented, none of them meet all the standards generally satisfied by a conventional Pb–Sn alloy. A large number of reliability problems still exist with lead free solder joints. Solder joint reliability depends on mechanical strength, fatigue resistance, hardness, coefficient of thermal expansion which are influenced by the microstructure, type and morphology of inter metallic compounds (IMC). In recent years, Sn rich solders have been considered as suitable replacement for Pb bearing solders. The objective of this review is to study the evolution of microstructural phases in commonly used lead free xSn–yAg–zCu solders and the various factors such as substrate, minor alloying, mechanical and thermo-mechanical strains which affect the microstructure. A complete understanding of the mechanisms that determine the formation and growth of interfacial IMCs is essential for developing solder joints with high reliability. The data available in the open literature have been reviewed and discussed. 相似文献
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Wafer level chip scale package (WLCSP) has been recognized providing clear advantages over traditional wire-bond package in relaxing the need of underfill while offering high density of I/O interconnects. Without the underfill, the solder joint reliability becomes more critical. Adding to the reliability concerns is the safety demand trend toward "green' products on which unleaded material, e.g. lead-free solders, is required. The requirement of lead-free solders on the packages results in a higher reflow temperature profile in the package manufacturing process, in turn, complicating the reliability issue. This paper presents an optimization study, considering the fatigue reliability, for a wafer level chip scale IC package in which a Ti/Cu/Ni UBM is involved. A finite element model is developed for the package. The model employs Sn3.8Ag0.7Cu lead-free solders built on build-up layers with micro-vias. Finite element analyses are performed to study the mechanical behaviors of the package elements in which the solder as well as the UBM is of interest. Firstly, a Surface Evolver program is used to construct the solder based non-solder mask defined (NSMD) pad. Then, multi-purpose finite element software, ANSYStm, is used to create a double symmetric 3-D numerical model to investigate the mechanical behaviors including deformation, stress-strain relation as well as hysteresis loops for temperature cycles. The Garofalo-Arrhenius Creep Model is employed. A modified Coffin-Manson formula is also employed to estimate the fatigue life for the package. Finally, the Taguchi robust analysis is adopted for optimization analysis of UBM thicknesses and solder geometry. Our results show that thicker UBM layers tend to increase the fatigue life while a small solder pad will prolong the fatigue life and as volume increases so does the fatigue life. From the results of Taguchi robust analysis, it is shown that among the factors of UBM layer thickness, solder pad radius and solder volume, the solder volume is the most dominating factor on the fatigue life of the package. The optimal combination of UBM thickness set at 0.0066 mm (level 3), solder pad radius set at 0.10 mm (Level 1), and solder volume set at 0.020 mm3 (Level 3) contributes the greatest fatigue life of 1229 cycles which is 448% gained over our reference package model. 相似文献
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The characterization of lead-free solders, especially after isothermal aging, is very important in order to accurately predict
the reliability of solder joints. However, due to lack of experimental testing standards and the high homologous temperature
of solder alloys (T
h > 0.5T
m even at room temperature), there are very large discrepancies in both the tensile and creep properties provided in current
databases for both lead-free and Sn–Pb solder alloys. Some recent researches show that the room temperature aging has significant
effects on mechanical properties of solders. This paper is intended to review all available data in the field and give rise
to the possible factors including room temperature effects which causes the large discrepancies of data. This review of the
research literatures has documented the dramatic changes that occur in the constitutive and failure behavior of solder materials
and solder joint interfaces during isothermal aging. However, these effects have been largely ignored in most previous studies
involving solder material characterization or finite element predictions of solder joint reliability during thermal cycling.
It is widely acknowledged that the large discrepancies in measured solder mechanical properties from one study to another
arise due to differences in the microstructures of the tested samples. This problem is exacerbated by the aging issue, as
it is clear that the microstructure and material behavior of the samples used in even a single investigation are moving targets
that change rapidly even at room temperature. Furthermore, the effects of aging on solder behavior must be better understood
so that more accurate viscoplastic constitutive equations can be developed for SnPb and SAC solders. Without such well-defined
relationship, it is doubtful that finite element reliability predictions can ever reach their full potential. 相似文献
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《Materials Science & Technology》2013,29(3):257-273
AbstractSince 2006 and the implementation of environmental regulations, the electronic industry has moved to Pb-free solders. Harsh environment industries that were exempted from the regulations will soon have to follow suit. However, a suitable replacement solder for use in harsh environments still has to be validated and reliability models are yet to be established. In this review, research that led to the selection of currently used Pb-free alloys and the continuing search for high reliability alloys are described. Sn pest and Sn whiskers, potential major threats for electronics operating in harsh environments, are highlighted. This review also focuses on the microstructure, mechanical properties and deformation mechanisms of Pb-free alloys. Emphasis is placed on Sn–Ag–Cu alloys, now considered to be the alloys of choice for replacement of Sn–Pb solders. The reliability of Pb-free electronic assemblies is studied, focusing on thermal fatigue, believed to be the main source of failure through creep–fatigue mechanisms. The validity of models for Pb-free solder joints life time prediction is assessed and the lack of cohesiveness among the available reliability data is examined. 相似文献
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Solder alloys of lead-rich composition have been commonly used as joining materials in electronic package. However, because of environmental concerns, lead-free solders will replace lead-rich solders more and more in the future. The fatigue characteristics of the solders used are most important in assessing the reliability of joints in electronic packaging. In the present study, the fatigue crack growth (FCG) behavior of a wide variety of solders of both lead-rich and lead-free types has been investigated under a range of mean stresses and frequencies. Both time dependent and time independent (cyclic dependent) behaviors were observed. In the cyclic dependent crack growth regime, the FCG rates could be expressed as a function of either ΔKeff or ΔJ. Further, the lead-free solders were found to have a higher resistance to FCG than did the lead-rich solders. In the time dependent crack growth regime, the FCG rates were found to be a function of C∗. The point of transition between time dependent and time independent behavior was found to depend on the homologous temperature and strength of the alloys. 相似文献
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X. P. Zhang L. M. Yin C. B. Yu 《Journal of Materials Science: Materials in Electronics》2008,19(4):393-398
In our previous study, the creep behavior of the lead-free Sn–Ag–Cu–Bi solder joints has been proven to follow the Arrhenius
power-law relationship, and the thermal fatigue behavior of the solder joints exhibits the typical creep deformation characteristics
with a superposition of the pulsating features. In this study, the thermal creep and fracture behaviors of the lead-free Sn–Ag–Cu–Bi
solder interconnections were characterized under different stress levels, with a systematical comparison to that of a traditional
Sn60Pb40 near-eutectic solder. The results show that the creep strain rate of both solder connections follows Weertman-Dorn
equation, and the calculated creep stress exponent for two solders is reasonably close to other published data. The SEM inspection
and analysis of fractographies of creep fractured solder joints manifest that the creep failure of the lead-free Sn–Ag–Cu–Bi
solder joint shows obviously intergranular fracture mechanism, while the Sn60Pb40 joint ruptures dominantly by a transgranular
sliding mechanism. 相似文献
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Mingyu LI Chunqing WANG State Key Lab. of Advanced Welding Production Technology Harbin Institute of Technology Harbin China Shenzhen Graduate School of Harbin Institute of Technology Shenzhen ChinaAssoc. Prof. Ph.D. 《材料科学技术学报》2005,21(1):63-67
Solder bridge is a serious defect of solder joints in ultrafine pitch electronic device assemblies. Generation of the solder bridge is closely related to forming process of the solder joints. A three-dimensional model to simulate the formation of the solder bridge of QFP256 (quad flat packaging with 256 leads) is established and numerically calculated to predict the formation shape of the solder joints using surface evolver program. Based on the model, influence of structure of pads printed on circuit board on solder bridging is investigated. The results show that there is a critical solder volume Vc for solder joints to avoid solder bridging, and parameters of the pad size influence the critical solder volume. 相似文献
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In order to enhance the properties of SnAgCu lead-free solders in microelectronic packaging, various contents of rare earth Yb were incorporated into the alloys. Results indicated that the addition of Yb can improve the wettability, tensile strength, thermal fatigue behavior of lead-free alloys. The lead-free solder with 0.05%Yb addition exhibited the best comprehensive properties as compared to the alloys with other Yb weight fractions. And found that after soldering, the initial interfacial IMC thickness of SnAgCuYb solder joint was smaller than that of SnAgCu solder joints, and this signified that the addition of Yb was effective in retarding the growth of the IMC layer. In addition, the Yb can refine the microstructures of SnAgCu solder, excessive Yb added can form bulk Sn–Yb phase and deteriorate the properties. 相似文献
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A series of multiaxial ratcheting–fatigue interaction tests have been carried out on Sn–3Ag–0.5Cu lead-free solder specimens. All tests were conducted under cyclic shear strain with the constant axial stress at the room temperature with the shear strain rate of 5 × 10−3 s−1. It was found that the ratcheting strain increased with increasing axial stress and shear strain amplitude while the fatigue life decreased at the same time. The ratcheting strain rate was linear with axial stress in double logarithmic coordinate. The Ohno–Wang II constitutive model was employed to simulate the stress–strain responses. Several fatigue life prediction models were applied to predict the multiaxial ratcheting–fatigue life of the Sn–3Ag–0.5Cu lead-free solder. The Gao–Chen model which adopted the maximum shear strain and the ratcheting strain rate as the damage parameter predicted the multiaxial ratcheting fatigue life well. 相似文献
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M. Erinc T. M. Assman P. J. G. Schreurs M. G. D. Geers 《International Journal of Fracture》2008,152(1):37-49
The ongoing miniaturization trend in the microelectronic industry enforces component sizes to approach the micron, or even
the nano scale. At these scales, the underlying microstructural sizes and the geometrical dimensions are comparable. The increasing
influence of microscopic entities on the overall mechanical properties makes conventional continuum material models more and
more questionable. In this study, the thermomechanical reliability of lead-free BGA solder balls is investigated by microstructural
modeling. Microstructural input is provided by orientation imaging microscopy (OIM), converted into a finite element framework.
Blowholes in BGA solder balls are examined by optical microscopy and a statistical analysis on their size, position and frequency
is conducted. Combining the microstructural data with the appropriate material models, three dimensional local models are
created. The fatigue life of the package is determined through a critical solder ball. The thermomechanical reliability of
the local models are predicted using cohesive zone based fatigue damage models. The simulation results are validated by statistical
analyses provided by the industry. 相似文献