Jin-Won Joo

Temperature Dependent Deformation Analysis of Ceramic Ball Grid Array Package Assembly Under Accelerated Thermal Cycling Condition

A robust scheme of moireinterferometry for real-time observation is employed to study the temperature dependent thermo-mechanical behavior of a ceramic ball grid array package assembly. The scheme is implemented with a convection-type environmental chamber that provides the rapid temperature control required in accelerated thermal cycling. Thermal deformations are documented at various temperatures. Thermal-history dependent analyses of global and local deformations are presented. A significant nonlin- ear global behavior is documented due to complete stress relaxation at the maximum temperature. An analysis of solder interconnections reveals that inelastic deformation accumulates at the bottom eutectic solder fillet only at high temperatures. @DOI: 10.1115/1.1646426#

Characterization of flexural and thermo-mechanical behavior of plastic ball grid package assembly using moiré interferometry

Flexural and thermo-mechanical behavior of a wire-bond plastic ball grid array (WB-PBGA) package assembly is characterized using moire interferometry. Fringe patterns are recorded and analyzed at several bending loads and temperatures. Detailed global and local deformations of the assembly are investigated. The deformations caused by the thermally induced bending are compared with those caused by the mechanical bending. The results reveal that global bending modes are similar but the deformations at the critical locations are significantly different; the sign (direction) of the shear strain caused by the mechanical bending is the opposite of that caused by the thermal loading. The implication of the opposite bending on board level reliability is discussed.

The Effect of Finite Element Models in Thermal Analysis of Electronic Packages

Abstract The reliability concerns of solder interconnections in flip chip PBGA packages are produced mainly by the mismatch of coefficient of thermal expansion(CTE) between the module and PCB. Finite element analysis has been employed extensively to simulate thermal loading for solder joint reliability and deformation of packages in electronic packages. The objective of this paper is to study the thermo-mechanical behavior of FC-PBGA package assemblies subjected to temperature change, with an emphasis on the effect of the finite element model, material models and temperature conditions. Numerical results are compared with the experimental results by using moire interferometry. Result shows that the bending displacements of the chip calculated by the finite element analysis with viscoplastic material model is in good agreement with those by moire inteferometry. 1. 서 론 반도체 칩은 주위의 전자부품들과 전기적, 기계적으로 연결되어야할 뿐만 아니라, 주위환경으로부터 보호할 수 있는 장치가 필요하며, 이와 같은 장치에 대한 기술을 전자패키징이라고 한다. BGA(ball grid array) 패키지는 면적대비 높은 연결밀도, 좋은 표면 실장특성과 더 나은 전기적, 열적 성능, 낮은 높이 등의 장점으로 개발되어 WB-PBGA(wire bond PBGA) 패키지나 FC- PBGA(flip chip PBGA) 패키지의 형태로 널리 사용되고 있다. 이러한 BGA 패키지의 특성을 평가하고 설계의 신뢰성을 확보하기 위해서는 먼저

Evaluation of thermal deformation model for BGA packages using moiré interferometry

A compact model approach of a network of spring elements for elastic loading is presented for the thermal deformation analysis of BGA package assembly. High-sensitivity moiré interferometry is applied to evaluate and calibrated the model quantitatively. Two ball grid array (BGA) package assemblies are employed for moiré experiments. For a package assembly with a small global bending, the spring model can predict the boundary conditions of the critical solder ball excellently well. For a package assembly with a large global bending, however, the relative displacements determined by spring model agree well with that by experiment after accounting for the rigid-body rotation. The shear strain results of the FEM with the input from the calibrated compact spring model agree reasonably well with the experimental data. The results imply that the combined approach of the compact spring model and the local FE analysis is an effective way to predict strains and stresses and to determine solder damage of the critical solder ball.

Thermo-mechanical and flexural behavior of WB-PBGA package using moire interferometry

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) package assembly is characterized using high-sensitivity moire interferometry. Using the real-time moire setup, fringe patterns are recorded and analyzed at several bending loads and temperatures. Detailed global and local deformations of the assembly are investigated. The deformations caused by thermally induced bending were compared with those caused by mechanical bending. The results reveal highly nonlinear behavior of the package assembly under thermal loading. The sign (direction) of the shear strain caused by the mechanical bending was the opposite of that caused by the thermal load. The results also show that real-time moire interferometry is a powerful and effective tool in experimental studies of electronic packaging.

Material Parameters Identification of Adhesive in Layered Plates Using Moiré Interferomety and Optimization Technique

In this study, a method to characterize material properties of adhesive that is used in a layered plates bonding process is developed by combined evaluation of experiment, simulation and optimization technique. A small bonded specimens of rectangular plate are prepared to this end, and put into a thermal loading conditions. interferomety is used to measure submicron displacements occurred during the process. The elevated temperature is chosen as control factors. FE analysis with constant values for the adhesive materials is also carried out to simulate the experiment. Significant differences are observed from the two results, in which the simulation predicts the monotonic increase of the bending displacement whereas the measurement shows decrease of the displacement at above . In order to minimize the difference of the two, material parameters of the adhesive at a number of different temperatures are posed as unknowns to be determined, and optimization is conducted. As a result, optimum material parameters are found that excellently matches the simulation and experiment, which are decreased with respect to the temperature.

Submicro-displacement Measuring System with Moire Interferometer and Application to the Themal Deformation of PBGA Package

A description of the basic principles of moire interferometry leads to the design of a eight-mirror four-beam interferometer for obtaining fringe patterns representing contour-maps of in-Plane displacements. The technique is implemented by the optical system using an environmental chamber for submicro-displacement mesurement. In order to estimate the reliability and applicabili쇼 of the system developed, the measurement of coefficient of thermal expansion (CTE) for a aluminium block is performed. Consequently, the system is applied to the measurement of thermal deformation of a WB-PBGA package assembly. Temperature dependent analyses of global and local deformations are presented to study the effect of the mismatch of CTE between materials composed of the package assemblies. Bending displacements of the packages and average strains of solder balls are documented. Thermal induced displacements calculated by FEM agree quantitatively with experimental results.

Material Parameter Identification of Viscoplastic Model for Solder Alloy in Electronics Package Using Bayesian Calibration

In this study, a method of computer model calibration is applied to quantify the uncertainties arising in the material characterization of the solder joint in the microelectronics package subject to a thermal cycle. In this study, all uncertainties are addressed by using a Bayesian calibration approach. A special specimen that characterizes the solder property due to the shear deformation is prepared, from which the Moire fringe is measured by running a thermal cycle. Viscoplastic finite element analysis procedure is constructed for the specimen based on the Anand model. Gaussian process model known as Kriging is employed to approximate the original finite element analysis (FEA) model. Posterior distribution for the unknown Anand parameters is formulated from the likelihood function for joint full-field displacements of computation and experiment. Markov Chain Monte Carlo (MCMC) method is employed to simulate posterior distribution. As a result, the displacements are predicted in the form of confidence interval. The results show that the proposed approach can be a useful tool in the estimation of the unknown material parameters in a probabilistic manner by effectively accounting for the uncertainties due to the experimental and computational models.© 2010 ASME

Material Identification of Solder Joint in Microelectronics Package Using Bayesian Approach

In this study, a method of computer model calibration is applied to quantify the uncertainties arising in the material characterization of the solder joint in the microelectronics package subject to a thermal cycle. The uncertainties include inherent experimental error and insufficient number of experiments. In the case of costly computation, surrogate model is also employed to approximate the original response function using a finite number of analyses, which adds another uncertainty. In this study, all these uncertainties are addressed by using a Bayesian calibration approach. A special specimen that characterizes the solder property due to the shear deformation is prepared, from which the Moire fringe is measured by running a thermal cycle. Viscoplastic finite element analysis procedure is constructed for the specimen based on the Anand model. Gaussian process model known as Kriging is employed to approximate the original FEA model. Posterior distribution for the unknown Anand parameters is formulated from the likelihood function for joint full-field displacements of computation and experiment. Markov Chain Monte Carlo (MCMC) method is employed to simulate posterior distribution. As a result, the displacements and stresses are predicted in the form of confidence interval. The results show that the proposed approach can be a useful tool in the estimation of the unknown material parameters in a probabilistic manner by effectively accounting for the uncertainties due to the experimental and computational models.