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Optimization of shrinkage and crack resistance performance of Engineered Cementitious Composites (ECC) is investigated due to ECC with higher drying shrinkage. Free shrinkage tests were used to research the influence of fiber content, superplasticizer (SP) and finely ground quartz powder (QP) on the total drying shrinkage value of ECC. Restrained drying shrinkage tests (ring tests) were used to research...
Excavation in soft soil will lead to changes in stress state ground mass and subsequent ground losses inevitably occur. These changes affect the surrounding ground in the form of lateral movement which eventually impose direct strains onto nearby structures and can cause pile deviation and cracks. This study models the lateral movement in soft clay due to excavation using finite element simulation...
Cracking along the intermetallic compound (IMC) interface in solder joints is the most important failure mechanism in electronics packages. In order to understand the failure mechanism well, a 2D solder/IMC interface model is used to examine the stress around the interface. Three solder materials, Sn37Pb, Sn3.5Ag and Sn3.0Ag0.5Cu, and various IMC thicknesses, which represent different growth stages...
During the process of excavations, blasting can induce damage inside surrounding rock, which may change the mechanical properties of rock mass and influence the stability of structure. Considering the effects of material properties and loading conditions, two numerical models, a rock blasting excavation model with two excavation steps and a planar rock model with four boreholes, are developed through...
Based on ABAQUS finite element analysis software, metallurgical composite bimetallic tube containing crack is analyzed and obtained the process of pipe rupture and the internal change of Mises stress and displacement at different crack depths and loading conditions. As the crack depth increases, the minimum values of the pipe Mises stress will increase and the maximum remain unchanged; as the load...
In this paper a method is presented for detailed finite element modelling of probe insertion into an elastic material. This is part of an ongoing investigation into the mechanics of a novel, biomimetic, soft-tissue probe currently under development at Imperial College, London. Analysis is performed using a `cohesive zone' approach by integrating multiple cohesive elements into a finite element mesh...
Natural materials such as bone, shell, tendon and the attachment system of gecko exhibit multi-scale hierarchical structures. Here we summarize some recent studies on an idealized self-similar hierarchical model of bone and bone-like materials, and discuss mechanical principles of self-similar hierarchy, in particular to show how the characteristic length, aspect ratio and density at each hierarchical...
Adopting cement with sand to make intermittent cracked Rock-like samples, this article, through cracked samples with different cracked obliquity is tested with WDT-1500 multifunctional material test apparatus, study the mechanics characteristic and the destruction properties of rock mass, which under the combined action of cyclic load and the static load. Using computer processed the experimental...
This study addresses the mechanics of the relatively brittle solder/intermetallic (IMC) interface fracture process using damage mechanics concept. The damage state, ?? of a material point in the solder/IMC interface, is expressed in terms of orthogonal traction components in a quadratic failure criterion of a cohesive zone model. The model is then employed in a finite element analysis of a solder...
The interfacial failure behavior of a single solder joint is investigated under the pure tensile or shear loading at 5 mm/s. The brittel failure is detected for the specimen under pure tension loading, while a ductile failure is found after pure shear loading. A cohesive zone model is employed herein to explore the dynamic fracture behavior at the solder/IMC and IMC/Cu pad interfaces. The simulated...
Through an aggressive product development program which includes experiment and simulation, Amkor has developed the next level of WLCSP (CSPnltrade), a product which exhibits superior board level reliability when subjected to drop impact, a strong requirement for portable electronics. Failure mechanism of WLCSP under drop test has been established. Depending on type of WLCSP and test board design,...
One of the driving factors for a steady reduction in wafer and cell thickness is the present shortage of polysilicon feedstock combined with the need to reduce manufacturing costs in photovoltaic module production. Therefore materials and manufacturing processes must adapt to maintain acceptable mechanical yields and module reliability. The soldering of solar cell strings is a critical step in the...
The electronic industry drive for miniaturization and increasing functional integration forces the development of feature sizes down to the nanometer range. Moreover, harsh environmental conditions and new porous or nano-particle filled materials introduced on both chip and package level - low-k and ultra low-k ILD materials in back-end of line (BEoL) layers of advanced CMOS technologies, in particular...
The development of Cu/low-k interconnects to meet continuous tighter specifications (lower RC time delay, power consumption...) and consequently the introduction of mechanically weak materials is widely identified as a contributor of interfacial cracks propagating during manufacturing flow or qualification tests. Moreover, a raise in Front-End/Back-End (FE/BE) compatibility issues has been also observed...
Most semi-conductor devices are encapsulated by epoxy moulding compound (EMC) material. Even after curing at the prescribed temperature and time in accordance with the supplier's curing specifications often the product is not yet 100% fully cured. As a consequence, the curing process of a product continues much longer, leading to curing effects of the EMC during the lifetime of the package. In this...
Taking the advantage of the thermo-elastic effect, while using an infrared camera system, the mechanical stress could be made visible. The stress concentrations at the tip of a subcritical crack growth could clearly be detected. Through the observation during the periodic loading of a CT-specimen the crack growth rate can be determined. For this purpose, a specially developed loading stage will be...
The impact of Chip-Package Interaction (CPI) which is caused by the mismatch in the coefficient of thermal expansion (CTE) between substrate and chip in a Flip Chip Ball Grid Array (FCBGA) on the mechanical reliability of Cu/Ultra low-k in a larger die was investigated using Finite Element Analysis (FEA). In order to associate the deformation and thermal stresses in FCBGA with those in the Cu/Ultra...
The Chemical-Mechanical Polishing (CMP) process is still challenging for the semiconductor industry: during this key step, decohesion/adhesion fracture often occurs. The authors have developed a specific methodology in order to estimate this potential risk. This methodology uses finite element simulations in conjunction with a post-treatment computing the Energy Release Rate (ERR) which is related...
In this study, cohesive damage zone model is evaluated and employed to model solder/intermetallics (IMC) interface crack initiation and propagation in solder interconnects. Interface materials damage is quantified in terms of stress-to-strength ratios of orthogonal components in a quadratic failure criterion along with a mixed-mode displacement formulation for crack initiation event. Subsequent crack...
Interfacial delamination has become one of the key reliability issues in the microelectronic industry and therefore is getting more and more attention. The analysis of delamination of a laminate structure with a crack along the interface is central to the characterization of interfacial toughness. Due to the mismatch in mechanical properties of the materials adjacent to the interface and also possible...
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