• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.35-43
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• 2017

The three-dimensional integrated circuit (3D-IC) is a general trend for the miniaturized and high-performance electronic devices. The through-silicon-via (TSV) is the advanced interconnection method to achieve 3D integration, which uses vertical metal via through silicon substrate. However, the TSV based 3D-IC undergoes severe thermo-mechanical stress due to the CTE (coefficient of thermal expansion) mismatch between via and silicon. The thermo-mechanical stress induces mechanical failure on silicon and silicon-via interface, which reduces the device reliability. In this paper, the thermo-mechanical reliability of TSV based 3D-IC is reviewed in terms of mechanical fracture, heat conduction, and material characteristic. Furthermore, the state of the art via-level and package-level design techniques are introduced to improve the reliability of TSV based 3D-IC.

• Journal of Welding and Joining
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• v.29 no.1
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• pp.46-51
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• 2011

TSV technology raises several reliability concerns particularly caused by thermally induced stress. In traditional package, the thermo-mechanical failure mostly occurs as a result of the damage in the solder joint. In TSV technology, however, the driving failure may be TSV interconnects. In this study, the thermomechanical reliability of TSV technology is investigated using finite element method. Thermal stress and thermal fatigue phenomenon caused by repetitive temperature cycling are analyzed, and possible failure locations are discussed. In particular, the effects of via size, via pitch and bonding pad on thermo-mechanical reliability are investigated. The plastic strain generally increases with via size increases. Therefore, expected thermal fatigue life also increase as the via size decreases. However, the small via shows the higher von Mises stress. This means that smaller vias are not always safe despite their longer life expectancy. Therefore careful design consideration of via size and pitch is required for reliability improvement. Also the bonding pad design is important for enhancing the reliability of TSV structure.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.3
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• pp.9-17
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• 2003

In this paper, thermo-mechanical and rheological properties of NCPs (Non-Conductive Pastes) depending on silica filler contents and diluent contents were investigated. And then, thermal cycling (T/C) reliability of flip chip assembly using selected NCPs was verified. As the silica filler content increased, thermo-mechanical properties of NCPs were changed. The higher the silica filler content was added, glass transition temperature ($T_g$) and storage modulus at room temperature became higher. While, coefficient of thermal expansion (CTE) decreased. On the other hand, rheological properties of NCPs were significantly affected by diluent content. As the diluent content increased, viscosity of NCP decreased and thixotropic index increased. However, the addition of diluent deteriorated thermo-mechanical properties such as modulus, CTE, and $T_g$. Based on these results, three candidates of NCPs with various silica filler and diluent contents were selected as adhesives for reliability test of flip chip assemblies. T/C reliability test was performed by measuring changes of NCP bump connection resistance. Results showed that flip chip assembly using NCP with lower CTE and higher modulus exhibited better T/C reliability behavior because of reduced shear strain in NCP adhesive layer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.693-694
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• 2009

• Advances in Computational Design
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• v.2 no.2
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• pp.107-119
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• 2017

The Micro circular diaphragm (MCD) is the mechanical actuator part used in the micro electro-mechanical sensors (MEMS) that combine electrical and mechanical components. These actuators are working under harsh mechanical and thermal conditions, so it is very important to study the mechanical and thermal behaviors of these actuators, in order to do with its function successfully. The objective of this paper is to determine the thermo-mechanical behavior of MCD by developing the traditional bulge test technique to achieve the aims of this work. The specimen is first pre-stressed to ensure that is no initial deflection before applied the loads on diaphragm and then clamped between two plates, a differential pressure (P) and temperature ($T_b$) is leading to a deformation of the MCD. Analytical formulation of developed bulge test technique for MCD thermo-mechanical characterization was established with taking in-to account effect of the residual strength from pre-stressed loading. These makes the plane-strain bulge test ideal for studying the mechanical and thermal behavior of diaphragm in both the elastic and plastic regimes. The differential specimen thickness due to bulge effect to describe the mechanical behavior, and the temperature effect on the MCD material properties to study the thermal behavior under deformation were discussed. A finite element model (FEM) can be extended to apply for investigating the reliability of the proposed bulge test of MCD and compare between the FEM results and another one from analytical calculus. The results show that, the good convergence between the finite element model and analytical model.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.183-190
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• 2003

Major device failures such as die cracking, interfacial delamination and warpage in flip chip packages are due to excessive heat and thermal gradients- There have been significant researches toward understanding the thermal performance of electronic packages, but the majority of these studies do not take into account the combined effects of thermo-mechanical interactions of the different package constituents. This paper investigates the thermo-mechanical performance of flip chip package constituents based on the finite element method with thermo-mechanically coupled elements. Delaminations with different lengths between the silicon die and underfill resin interfaces were introduced to simulate the defects induced during the assembly processes. The temperature gradient fields and the corresponding stress distributions were analyzed and the results were compared with isothermal case. Parametric studies have been conducted with varying thermal conductivities of the package components, substrate board configurations. Compared with the uniform temperature distribution model, the model considering the temperature gradients provided more accurate stress profiles in the solder interconnections and underfill fillet. The packages with prescribed delaminations resulted in significant changes in stress in the solder. From the parametric study, the coefficients of thermal expansion and the package configurations played significant roles in determining the stress level over the entire package, although they showed little influence on stresses profile within the individual components. These observations have been implemented to the multi-board layer chip scale packages (CSP), and its results are discussed.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.65-74
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• 2013

The through-silicon via (TSV) technology is essential for 3-dimensional integrated packaging. TSV technology, however, is still facing several reliability issues including interfacial delamination, crack generation and Cu protrusion. These reliability issues are attributed to themo-mechanical stress mainly caused by a large CTE mismatch between Cu via and surrounding Si. In this study, the thermo-mechanical reliability of copper TSV technology is investigated using numerical analysis. Finite element analysis (FEA) was conducted to analyze three dimensional distribution of the thermal stress and strain near the TSV and the silicon wafer. Several parametric studies were conducted, including the effect of via diameter, via-to-via spacing, and via density on TSV stress. In addition, effects of annealing temperature and via size on Cu protrusion were analyzed. To improve the reliability of the Cu TSV, small diameter via and less via density with proper via-to-via spacing were desirable. To reduce Cu protrusion, smaller via and lower fabrication temperature were recommended. These simulation results will help to understand the thermo-mechanical reliability issues, and provide the design guideline of TSV structure.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.7-18
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• 2008

This paper reviews the current development of an ultra-slim SiP for Radio Frequency (RF) application, in which three flip chips, additional passive components and Surface Acoustic Wave (SAW) filters are integrated side-by-side. A systematic investigation is carried out for the design optimization, process and reliability improvement of the package, which comprises several aspects: a design study based on the 3D thermo-mechanical finite element analysis of the packaging, the determination of stress, warpage distribution, critical failure zones, and the figuration of the effects of material properties, process conditions on the reliability of package. The optimized material sets for manufacturing process were determined which can reduce the number of testing samples from 75 to 2. In addition the molded underfilling (MUF) process is proposed which not only saves one manufacturing process, but also improves the thermo-mechanical performance of the package compared with conventional epoxy underfilling process. In the end, JEDEC's moisture sensitivity test, thermal cycle test and pressure cooker tests have also been carried out for reliability evaluation. The test results show that the optimized ultra-slim SiP has a good reliability performance.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.12
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• pp.23-31
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• 2009

• Proceedings of the Korean Reliability Society Conference
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• 2006.05a
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• pp.27-31
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• 2006

Rubber hoses for automobile radiators are apt to degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under thermal and mechanical loadings. The aging behaviors of the skin part of the hoses due to thermo-oxidative and electro-chemical stresses were experimentally analyzed. Through the thermo-oxidative aging test, it was shown that the surface hardness IRHD(International Rubber Hardness Degrees) of the rubber increased with a considerable reduction of failure strain as the aging time and temperature were large. On account of the penetration of coolant liquid into the skin part the weight of rubber specimens influenced by electro-chemical degradation (ECD) test increased, whereas their failure strain and IRHD hardness decreased. The hardness decreased further as the test site on the hose skin approached to the negative pole.