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学者姓名：代岩伟
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摘要 ：
The mismatch effect in weldment is widely to be found in engineering practices. In this paper, the material mismatch effect on the mode II creep crack tip field is investigated and discussed. The mismatch effect on the C (t)-integral is presented. Both the local mismatch and the general mismatch are found to play important role in C (t)-integral under mode II condition. The mismatch effect on the stress field of mode II creep crack is also studied. The two-order term solutions are adopted to characterize the material mismatch effect on the mode II creep crack. The effect of creep coefficient, creep exponent as well as the HAZ thickness on the high order term solutions are also presented. Some typical cases by considering general mismatch and local mismatch effect are given to make a comparisons between the HRR field, FE solutions and the two-order term solutions. It can be seen that the two-order term solutions can coincide with the full field FE solutions quite reasonably regardless of creep extent, creep exponent, mismatch factor, and HAZ thickness. The material mismatch effect on the high order term solutions is significant under some conditions. A theoretical formula is presented to show the implication of material mismatch effect on creep crack growth under mode II condition based on stress damage model.
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| GB/T 7714 | Dai, Yanwei , Qin, Fei , Liu, Yinghua et al. Characteristics and implications of material mismatch on mode II creep crack tip field: Theoretical analysis and numerical investigation [J]. | THEORETICAL AND APPLIED FRACTURE MECHANICS , 2021 , 114 . |
| MLA | Dai, Yanwei et al. "Characteristics and implications of material mismatch on mode II creep crack tip field: Theoretical analysis and numerical investigation" . | THEORETICAL AND APPLIED FRACTURE MECHANICS 114 (2021) . |
| APA | Dai, Yanwei , Qin, Fei , Liu, Yinghua , Chen, Haofeng , Berto, Filippo . Characteristics and implications of material mismatch on mode II creep crack tip field: Theoretical analysis and numerical investigation . | THEORETICAL AND APPLIED FRACTURE MECHANICS , 2021 , 114 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
Cracking of sintered silver layer always leads to the reliability issues in power devices. In this paper, the cracking behaviors of sintered silver layer have been investigated through numerical analysis with fracture based method. Energy release rate of various interfacial cracks and vertical cracks in sintered silver are computed. It is found that the energy release rate of interfacial crack and vertical crack are significantly influenced by their thickness. The thinner of the sintered silver layer, the higher of the energy release rate it will meet. For interfacial crack, the adding of the metallization layer does not improve the energy release rate significantly. For vertical crack, two conditions are considered, i.e., vertical crack emanating from the chip sider or emanating from the copper baseplate side, and it is found that the energy release rate is strongly dependent on its location and the existence of metallization layer. The increase of the thickness of Ni layer enables to lower down the entire level of energy release rate for vertical crack. Otherwise, the energy release rate of vertical crack near the edge region of the sintered silver layer is much higher than other locations. It implies that the cracking risk is higher for thinner sintered silver layer around the edge region which should be avoided. It is also found that the porosity effect on interface cracking and vertical cracking of sintered silver is also important.
关键词 ：
Cracking Cracking Energy release rate Energy release rate Porosity effect Porosity effect Sintered silver Sintered silver Metallization layer Metallization layer
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| GB/T 7714 | Qin, Fei , Zhao, Shuai , Liu, Lingyun et al. Thickness and metallization layer effect on interfacial and vertical cracking of sintered silver layer: A numerical investigation [J]. | MICROELECTRONICS RELIABILITY , 2021 , 124 . |
| MLA | Qin, Fei et al. "Thickness and metallization layer effect on interfacial and vertical cracking of sintered silver layer: A numerical investigation" . | MICROELECTRONICS RELIABILITY 124 (2021) . |
| APA | Qin, Fei , Zhao, Shuai , Liu, Lingyun , Dai, Yanwei , An, Tong , Chen, Pei et al. Thickness and metallization layer effect on interfacial and vertical cracking of sintered silver layer: A numerical investigation . | MICROELECTRONICS RELIABILITY , 2021 , 124 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
Material mismatch effect on the cracking behavior is an important topic for those welding structures. Characterization of the material constraint effect based on rigorously asymptotic solution is studied in this paper. Based on decomposition of the second order term, the constraint effect characterization parameter is decomposed as material constraint parameter and geometry constraint parameter. In general, the total constraint level for crack tip under undermatch condition is higher than overmatch condition. The specimen with positive biaxiality could lead to a higher constraint level compared with that of negative biaxiality. Geometry constraint effect and material constraint effect could not be separated independently from rigorously asymptotic solution for those cases with positive biaxiality. For a crack tip field under non-positive biaxiality, the material constraint effect can be characterized independently although it is approximate. For these conditions, the proposed material constraint effect and geometry constraint effected characterized are approximately independent on material mismatch factor, crack depth ratio and stress biaxiality. An empirical formula has been presented to characterize the geometry constraint effect and material constraint effect for the crack tip in the weldment under biaxial loading, which has been verified with fine accuracy.
关键词 ：
Higher order asymptotic solution Higher order asymptotic solution Mismatch factor Mismatch factor Constraint effect Constraint effect Material constraint Material constraint Biaxial loading Biaxial loading
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| GB/T 7714 | Dai, Yanwei , Qin, Fei , Liu, Yinghua et al. Characterizations of material constraint effect for creep crack in center weldment under biaxial loading [J]. | INTERNATIONAL JOURNAL OF FRACTURE , 2021 , 234 (1-2) : 177-193 . |
| MLA | Dai, Yanwei et al. "Characterizations of material constraint effect for creep crack in center weldment under biaxial loading" . | INTERNATIONAL JOURNAL OF FRACTURE 234 . 1-2 (2021) : 177-193 . |
| APA | Dai, Yanwei , Qin, Fei , Liu, Yinghua , Berto, Filippo , Chen, Haofeng . Characterizations of material constraint effect for creep crack in center weldment under biaxial loading . | INTERNATIONAL JOURNAL OF FRACTURE , 2021 , 234 (1-2) , 177-193 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
Understanding the three-dimensional (3D) effect on the notch tip field is important for the fracture mechanics analysis of engineering materials and structures. This paper presents an asymptotic solution for 3D sharp V-notched structures subjected to mode I creep loading condition. The asymptotic solution, including the singularities and stress field distribution functions, is obtained by introducing the out-of-plane constraint factor. It is found that the singular behavior is related to the notch angle, material creeping exponents, and the out-of-plane constraint factor. Specifically, singularity changes sharply near the free surface. K-N (t) -T-z solution is presented to describe the mode I stress field around the tip of 3D V-notch under creep condition. Its accuracy and advantages compared with plane strain or plane stress solutions are validated by finite element analysis. The difference between effective ranges of K-N (t) -T-z solution and that of plane strain solution is clarified. Moreover, the effect of the creep time on the stress field is also shown. The solutions given in this paper could be beneficial for understanding the 3D effect on notch considering creep loading conditions.
关键词 ：
Creeping solids Creeping solids Out-of-plane effect Out-of-plane effect Asymptotic analysis Asymptotic analysis Notch tip field Notch tip field Sharp V-notch Sharp V-notch
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| GB/T 7714 | Kong, Weichen , Dai, Yanwei , Liu, Yinghua . Out-of-plane effect on the sharp V-notch tip fields in power-law creeping solids: A three-dimensional asymptotic analysis [J]. | INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES , 2021 , 236 . |
| MLA | Kong, Weichen et al. "Out-of-plane effect on the sharp V-notch tip fields in power-law creeping solids: A three-dimensional asymptotic analysis" . | INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES 236 (2021) . |
| APA | Kong, Weichen , Dai, Yanwei , Liu, Yinghua . Out-of-plane effect on the sharp V-notch tip fields in power-law creeping solids: A three-dimensional asymptotic analysis . | INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES , 2021 , 236 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
A two-order asymptotic solution for sharp V-notch tip mechanics field in elasto-viscoplastic solids with power-law form under mode I loading is developed. The stress exponents and angular distributions for various notch angles and viscoplastic exponents for the second terms are reported. The stress exponent of the first order is singular and is non-singular except for low creep exponent with small notch opening angle. Compared with finite element results from several V-notched specimens, it is found that the two-order solution can have a better estimate for those cases with small notch opening angles, e.g., α = 30° under n = 5, than that of one-order solution regardless of viscoplastic extent, specimen type and loading level. One-order term solution is demonstrated to be sufficient to characterize the full field of sharp V-notch specimen for those conditions that elastic term is considered into higher order term, e.g., α = 60° under n = 5, in all specimens under various viscoplasticity extents. © 2021 Elsevier Ltd
关键词 ：
Plasticity Plasticity Asymptotic analysis Asymptotic analysis Stress analysis Stress analysis Viscoplasticity Viscoplasticity
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| GB/T 7714 | Dai, Yanwei , Qin, Fei , Liu, Yinghua et al. On the second order term asymptotic solution for sharp V-notch tip field in elasto-viscoplastic solids [J]. | International Journal of Solids and Structures , 2021 , 217-218 : 106-122 . |
| MLA | Dai, Yanwei et al. "On the second order term asymptotic solution for sharp V-notch tip field in elasto-viscoplastic solids" . | International Journal of Solids and Structures 217-218 (2021) : 106-122 . |
| APA | Dai, Yanwei , Qin, Fei , Liu, Yinghua , Chao, Yuh J. . On the second order term asymptotic solution for sharp V-notch tip field in elasto-viscoplastic solids . | International Journal of Solids and Structures , 2021 , 217-218 , 106-122 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
Through silicon via (TSV) is a crucial interconnection structure in 3-D integrated circuits. However, protrusion and intrusion of TSV-Cu caused by annealing could lead to cracking and failure of back-end-of-line (BEOL) layers and TSV interconnects due to mismatch of coefficient of thermal expansion. In this paper, optimizations of TSV interconnects and BEOL layers under annealing process are investigated based on fracture evaluation. Influences of geometrical factors including the TSV geometry dimension, the distance between TSV and BEOL layers, and pitch size of Cu via on energy release rate and J-integral are studied for TSV interconnects and BEOL layers with cracks. Effect of material properties for low k dielectrics on interfacial fracture of BEOL layers and TSV interconnects is also given. Optimized geometrical factors and optimized material properties of low k dielectrics are presented in this paper. Fracture-based method sheds a light on emerging electronic packaging optimization.
关键词 ：
annealing process annealing process J-integral J-integral TSV interconnect TSV interconnect energy release rate energy release rate BEOL layer BEOL layer
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| GB/T 7714 | Qin, F. , Zhang, M. , Dai, Y. et al. Optimization of TSV interconnects and BEOL layers under annealing process through fracture evaluation [J]. | FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES , 2020 , 43 (7) : 1433-1445 . |
| MLA | Qin, F. et al. "Optimization of TSV interconnects and BEOL layers under annealing process through fracture evaluation" . | FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES 43 . 7 (2020) : 1433-1445 . |
| APA | Qin, F. , Zhang, M. , Dai, Y. , Chen, P. , An, T. , He, H. et al. Optimization of TSV interconnects and BEOL layers under annealing process through fracture evaluation . | FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES , 2020 , 43 (7) , 1433-1445 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
Sintered silver is a very promising die-attach material which is hopeful to be adopted in the third generation of power electronics. Thermal conductivity is an important index to characterize the heat conduction capacity of sintered silver. In this paper, a numerical model to compute equivalent thermal conductivity of sintered silver is proposed and verified based on the method with microstructure characteristics modelling. Based on the computations, the variations of the equivalent thermal conductivity for sintered silver are presented where porosity effect and aging effect are taken into account. Comparisons of heat flux distributions and temperature distributions of sintered silver with different porosity ratios and aging time are also made. A theoretical model is proposed to evaluate the equivalent thermal conductivity of sintered silver, which agrees quite reasonably with existed experimental results. Based on the proposed model, a theoretical model to predict the equivalent thermal conductivity of sintered silver considering aging effect is also presented. The method given in this paper can be used to predict the equivalent thermal conductivity of sintered silver under different loading conditions considering aging effect.
关键词 ：
Numerical simulation Numerical simulation Sintered silver Sintered silver Equivalent thermal conductivity Equivalent thermal conductivity Porosity Porosity Microstructure Microstructure
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| GB/T 7714 | Qin, Fei , Hu, Yuankun , Dai, Yanwei et al. Evaluation of thermal conductivity for sintered silver considering aging effect with microstructure based model [J]. | MICROELECTRONICS RELIABILITY , 2020 , 108 . |
| MLA | Qin, Fei et al. "Evaluation of thermal conductivity for sintered silver considering aging effect with microstructure based model" . | MICROELECTRONICS RELIABILITY 108 (2020) . |
| APA | Qin, Fei , Hu, Yuankun , Dai, Yanwei , An, Tong , Chen, Pei . Evaluation of thermal conductivity for sintered silver considering aging effect with microstructure based model . | MICROELECTRONICS RELIABILITY , 2020 , 108 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
In this paper, an improvement is made to an efficient direct method for numerical evaluation of high order singular curved boundary integrals. Then this improved singular integral evaluation method is employed to solve the strongly and hypersingular integrals involved in the dual boundary element method (Dual BEM), which combine the use of displacement and traction boundary integral equations to solve crack problems in a single domain formulation. The singular integral evaluation method is carried out based on a parameter plane expansion and radial integral approach, this paper proposed a new strategy for treating the singular radial integral, which plays a vital role in this method. In isoparametric coordinate system, the singular curved boundary integral is mapped into a singular square plane integral in intrinsic coordinates, then the radial integration method (RIM) is employed to transform the singular square plane integral into a regular line integral over the contour of intrinsic square plane and a singular radial integral over the path from source point to the contour of intrinsic square plane. A singularity isolation technique is utilized to divide the singular radial integral into two parts, the regular radial integral can be evaluated normally using Gauss quadrature and the singular radial that can be evaluated analytically by expanding the non-singular part of the integrand function into a power series. Compared with conventional local interpolation approach to deal with the singular radial integral, the newly proposed method has a more rigorous mathematical derivation, and can achieve more stable and precise results. Based on the successful implementation of direct evaluation of singular boundary integrals, Dual BEM is successfully applied to solve twoand three-dimensional elastic crack problems including straight and curved crack paths with continuous or discontinuous elements. Two different approaches, geometrical extrapolation method and J-integral method are used in the evaluation of stress intensity factors. Several numerical examples are given to validate effectiveness of the presented method.
关键词 ：
J-integral J-integral Stress intensity factor Stress intensity factor Hypersingular integral Hypersingular integral Traction boundary integral equation Traction boundary integral equation Dual boundary element method (dual BEM) Dual boundary element method (dual BEM)
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| GB/T 7714 | Feng, Wei-Zhe , Gao, Lan-Fang , Qu, Meng et al. An improved singular curved boundary integral evaluation method and its application in dual BEM analysis of two- and three-dimensional crack problems [J]. | EUROPEAN JOURNAL OF MECHANICS A-SOLIDS , 2020 , 84 . |
| MLA | Feng, Wei-Zhe et al. "An improved singular curved boundary integral evaluation method and its application in dual BEM analysis of two- and three-dimensional crack problems" . | EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 84 (2020) . |
| APA | Feng, Wei-Zhe , Gao, Lan-Fang , Qu, Meng , Zhou, Ling , Dai, Yan-Wei , Yang, Kai . An improved singular curved boundary integral evaluation method and its application in dual BEM analysis of two- and three-dimensional crack problems . | EUROPEAN JOURNAL OF MECHANICS A-SOLIDS , 2020 , 84 . |
| 导入链接 | NoteExpress RIS BibTex |
摘要 ：
A six-side molded wafer-level chip scale package (mWLCSP) is a novel and attractive packaging method for smart phone applications due to its lower cost, better electrical performance, and higher long-term reliability. Nevertheless, wafer warpage in different manufacturing processes is a significant issue for the six-side mWLCSP. This article focuses on wafer warpage evolution in different packaging processes and the development of control method for the six-side mWLCSP. A quarter wafer-level finite-element (FE) model and a strip-level FE model were established to simulate the actual packaging processes by element birth and death method and restart technology. Both the FE models were proved quite efficient and accurate for warpage prediction compared to the experimental results. The effects of geometric parameters and material parameters on the maximum warpage value were studied based on the two established FE warpage models, and some recommendations were given for warpage optimization. Based on the above studies, an improved manufacturing process flow for the six-side mWLCSP was presented and proved feasible to control the maximum warpage value under 3 mm. It offers an insight work for the development and warpage control of the six-side mWLCSP and other wafer-level molded packages.
关键词 ：
Control Control Semiconductor device modeling Semiconductor device modeling wafer-level compression molding wafer-level compression molding Semiconductor device reliability Semiconductor device reliability Finite element analysis Finite element analysis Silicon Silicon six-side molded wafer-level chip scale package (mWLCSP) six-side molded wafer-level chip scale package (mWLCSP) finite-element method (FEM) finite-element method (FEM) warpage warpage Computational modeling Computational modeling Packaging Packaging
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| GB/T 7714 | Qin, Fei , Zhao, Shuai , Dai, Yanwei et al. Study of Warpage Evolution and Control for Six-Side Molded WLCSP in Different Packaging Processes [J]. | IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY , 2020 , 10 (4) : 730-738 . |
| MLA | Qin, Fei et al. "Study of Warpage Evolution and Control for Six-Side Molded WLCSP in Different Packaging Processes" . | IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY 10 . 4 (2020) : 730-738 . |
| APA | Qin, Fei , Zhao, Shuai , Dai, Yanwei , Yang, Mengke , Xiang, Min , Yu, Daquan . Study of Warpage Evolution and Control for Six-Side Molded WLCSP in Different Packaging Processes . | IEEE TRANSACTIONS ON COMPONENTS PACKAGING AND MANUFACTURING TECHNOLOGY , 2020 , 10 (4) , 730-738 . |
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