• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.11-19
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• 2009

Thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Using the real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Experiments are conducted for three types of WB-PBGA package that have full grid pattern and perimeter pattern with/without central connections. Bending deformations of the assemblies and average strains of the solder balls are investigated, with an emphasis on the effect of solder interconnection grid patterns, Thermal strain distributions and the location of the critical solder ball in package assemblies are quite different with the form of solder ball grid pattern. For the WB-PBGA-PC, The largest of effective strain occurred in the inner solder ball of perimeter closest to the chip solder balls. The critical solder ball is located at the edge of the chip for the WB-PBGA-FG, at the most outer solder ball of central connections for the WB-PBGA-P/C, and at the inner solder ball closest to the chip for the WB-PBGA-P.

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1572-1581
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• 2004

The purposes of the paper are to apply the axiomatic design methodology to the design of PBGA package with polyimide coating under hygrothermal loading in the IR soldering process and to suggest more reliable design conditions by stress analysis. The analysis model is a 256-pin perimeter Plastic Ball Grid Array (PBGA) package with the polyimide coating surrounding chip and above surface of BT-substrate. The polyimide coating is suggested to depress the maximum stresses occurred on the stress concentration positions. The axiomatic design methodology is proved to be useful to find the more reliable design conditions for PBGA package. Finally, the optimal values of design variables to depress the stress in the PBGA package are obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1646-1655
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• 2004

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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1302-1308
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• 2002

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) package are characterized by high sensitive moire interferometry. Moire fringe patterns are recorded and analyzed for several bending loads and temperatures. At the temperature higher than $100^{\circ}C$, the inelastic deformation in solder balls become more dominant, so that the bending of the molding compound decreases while temperature increases. The deformation caused by thermally induced bending is compared with that caused by mechanical bending. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1027-1032
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• 2003

Thermo-mechanical behavior of flip-chip plastic ball grid array (FC-PBGA) packages are characterized by high sensitive $Moir{\acute{e}}$ interferometry. $Moir{\acute{e}}$ fringe patterns are recorded and analyzed for several temperatures. Deformation analysis of bending displacements of the packages and average strains in the solder balls for a single-sided package assembly and a double-sided package assembly are presented. The bending displacement of the double-sided package assembly is smaller than that of the single-sided one. The largest of effective strain occurred in the solder ball located at the edge of the chip and its magnitude of the double-sided package assembly is greater than that of single-sided one.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.3
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• pp.17-26
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• 2010

Pb-Sn solder is rapidly being replaced by lead-free solder for board-level interconnection in microelectronic package assemblies due to the environmental protection requirement. There is a general lack of mechanical reliability information available on the lead-free solder. In this study, thermo-mechanical behaviors of wire-bond plastic ball grid array (WB-PBGA) package assemblies are characterized by high-sensitivity moire interferometry. Experiments are conducted for two types of WB-PBGA packages that have Pb-Sn solder and lead-free solder as joint interconnections. Using real-time moire setup, fringe patterns are recorded and analyzed for several temperatures. Bending deformations of the assemblies and average strains of the solder balls are investigated and compared for the two type of WB-PBGA package assemblies. Results show that shear strain in #3 solder ball located near the chip shadow boundary is dominant for the failure of the package with Pb-Sn solder, while normal strain in #7 most outer solder ball is dominant for that with lead-free solder. It is also shown that the package with lead-free solder has much larger bending deformation and 10% larger maximum effective strain than the package with Pb-Sn solder at same temperature level.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.17-25
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• 2006

Thermo-mechanical behavior of flip-chip plastic ball grid array (FC-PBGA) packages are characterized by high sensitive $moir\'{e}$ interferometry. $Moir\'{e}$ fringe patterns are recorded and analyzed for several temperatures. Deformation analysis of bending displacements of the packages and average strains in the solder balls for both single and double-sided package assemblies are presented. The bending displacement of the double-sided package assembly is smaller than that of the single-sided one because of its symmetric structure. The largest effective strain occurred at the solder ball located on the edge of the chip and its magnitude of the double-sided package assembly is greater than that of single-sided one by 50%.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.17-28
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• 2012

It is known that thermo-mechanical properties of solder material and molding compound in WB-PBGA packages are considerably affected by not only temperature but elapsed time. In this paper, finite element analysis (FEA) taking material nonlinearity into account was performed for more reliable prediction on deformation behavior of a lead-free WB-PBGA package, and the results were compared with experimental results from moire interferometry. Prior to FEA on the WB-PBGA package, it was carried out for two material layers consisting of molding compound and substrate in terms of temperature and time-dependent viscoelastic effects of molding compound. Reliable deformation analysis for temperature change was then accomplished using viscoplastic properties for solder ball and viscoelastic properties for molding compound, and the analysis was also verified with experimental results. The result showed that the deformation of WB-PBGA packages was strongly dependent on material model of molding compound; thus, temperature and time-dependent viscoelastic behavior must be considered for the molding compound analysis. In addition, viscoelastic properties of B-type molding compound having comparatively high glass transition temperature of $135^{\circ}C$ could be recommended for reliable prediction on deformation of SAC lead-free WB-PBGA packages.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.4
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• pp.380-387
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• 2009

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 $moir{\acute{e}}$ 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 $moir{\acute{e}}$ inteferometry.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.2
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• pp.21-28
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• 2010

Creep behaviors of the solder balls in a flip chip package assembly during thermal cycling test is investigated.. A material models used in the finite element analysis are viscoplastic model introduced by Anand and creep model called partitioned model. Experiment of two temperature cycles using moir$\acute{e}$ interferometry is conducted to verify the reliability of material models for the analysis of thermo-mechanical behavior. Bending deformations of the assemblies and average strains of the solder balls due to temperature change and dwell time are investigated. The results show that time-dependent shear strain of solder by the partitioned model is in excellent agreement with those by moir$\acute{e}$ interferometry, while there is considerable difference between results by Anand model and experiment. In this paper, the partitioned model is employed for the time-dependent creep analysis of the FC-PBGA package. It is also shown that the thermo-mechanical stress becomes relaxed by creep behavior at high temperature during temperature cycles.