• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.11-15
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• 2011

Heat transfer equation is first reviewed and then governing equation of moisture diffusion. Analogy scheme is applied to analysis the moisture absorption problem of polymers. It make possible to numerically analyze the diffusion problem for single medium by using commercial finite element code if it is under the isothermal loading condition. It is extended to special multimaterial system by introducing pressure ratio function, whose moisture characteristics of materials are proportional to temperature only. The weight changes of silicon-nonconductive-polymer joint model due to moisture absorption is measured and been very close to the numerical results as for single media with boundary condition with zero concentration, but yields numerical errors as for multisystem media.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3442-3447
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• 2014

A simple method to evaluate the hygroscopic characteristics of polymer of microelectronic plastic package is suggested. To evaluate the characteristics, specimens were prepared, and the internally absorbed moisture masses were measured as a function of the absorbing time and calculated numerically. The hygroscopic pressure ratio was calculated by heat transfer analysis supported by commercial FEM code because the hygroscopic diffusion equation has the same form as the heat transfer equation. The moisture masses were then summed by the self developed code. The nonconductive polymers had quite different characteristics for the different lots, even though they were the same products. The absorbed moisture mass variations were calculated for several different characteristics, and the optimal curve of the mass variation close to experimental data was selected, whose solubility and diffusivity were affected by the hygroscopic characteristics of the material. The method can be useful in the industrial fields to quickly characterize the polymer material of the semiconductor package because the fast correspondence is normally required in industry. The weight changes in the aluminum-nonconductive-polymer joint due to moisture absorption were measured. The deformed system was also measured using the Moire Interferometry system and compared with the results of finite element analysis.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.108-113
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• 2005

Strucutral and hygrothermal analysis for a composite tube is carried out in this study, that provides critical parameters for the design of a highly dimensionally stable space telescope. Carpet plots for laminate effective engineering constants are generated and used for the best tube lay-ups with high elastic modulus and highly insensitive to thermal and moisture expansion, which is essential for maintaining optical alignment of opto-mechanical system under random force applied during a launch campaign and orbital thermal load. Despace in the longitudinal direction under hygrothermal load of the tubes constructed with the selected lay-ups is calculated for the validation of lay-up designs on the dimensionalstability. Dynamic analysis is also carried out to feature the resonant behaviour. A zig-zag triangular element accurately representing through thickness stress variations for laminated structures is developed in this study and incorporated into the structural and hygrothermal analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.11
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• pp.977-984
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• 2013

A hygroscopic rotor comprises many microchannels with high adsorption characteristics. In this study, the iterative adsorption/desorption processes that were affected by the humid air flow in a channel were numerically simulated. In consideration of the accuracy and computational costs, in the desiccant layer, only surface diffusion was considered in this simulation. The results were compared with the previous numerical results and found to show good agreement. By conjugating the heat and mass transfer between the desiccant and the flow layers, temporal and spatial changes in the vapor mass fraction, adsorbed liquid water mass fraction, and temperature in the channel were presented.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.3
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• pp.37-42
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• 2022

Recently, the semiconductor package structures are becoming thinner and more complex. As the thickness decrease, interfacial delamination due to material mismatch can be further maximized, so the reliability of interface is a critical issue in industry field. Especially, the polymers, which are widely used in semiconductor packaging, are significantly affected by the temperature and moisture. Therefore, in this study, the delamination prediction at the interface of package structure was performed through finite element analysis considering the moisture absorption and desorption under the various temperature conditions. The material properties such as diffusivity and saturated moisture content were obtained from moisture absorption test. The hygro-swelling coefficients of each material were analyzed through TMA and TGA after the moisture absorption. The micro-shear test was conducted to evaluate the adhesion strength of each interface at various temperatures considering the moisture effect. The finite element analysis of interfacial delamination was performed that considers both deformation due to temperature and moisture absorption. Consequently, the interfacial delamination was successfully predicted in consideration of the in-situ moisture desorption and temperature behavior during the reflow process.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1347-1355
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• 1996

The purpose of this paper is to evaluate the delamination and fracture integrity of the IC plastic package under hygrothermal loading by stress analysis and fracture mechanics approaches. The plastic SOJ package with a dimpled diepad under the reflow slodering process of IR heating type is considered. On the package without a crack, the stress variation according to the change of the design variables such as the material and shape of the package is calculated and the possibility of delamination is considered. For the model fully delaminated between the chip and diepad, J-integrals are calculated for the various design variables and the fracture integrity is discussed. From the results, optimal design values of variables to prevent the delamination and fracture of IC package are obtained. In this study, FDM program to obtain the vapor pressure from the content of moisture absorbed into the package is developed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.5
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• pp.619-624
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• 2013

A bendable electronic module is developed. In this module, thin silicon electronic chips are embedded in a polymer-based encapsulating adhesive between flexible copper-clad polyimide layers. During the qualification test of a harshly thermal-hygroscopic complex loading condition, delaminations occur inside the module layers. A finite element model is developed for the module. To investigate the effect of hygroscopic stress on delamination, the results of the thermal and thermal-hygroscopic loads are compared. The analysis results reveal that the hygroscopic effect more strongly affects delamination than does the thermal effect. The potential failure mechanisms of the module are investigated based on the stress analysis.

• Composites Research
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• v.12 no.1
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• pp.19-27
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• 1999

A design development test for carbon/epoxy composite laminates for an aircraft flight control system is performed. The design development test includes moisture absorbing test, tensile, compressive, bearing and lap shear tests. The moisture absorbing behavior for different fiber orientation angles is investigated and the changes in mechanical characteristics are compared. In the in-plane tensile test, the effect of damages such as scratches and impacts is studied. The bearing test is performed for different fastening types. The resulting design allowable stress and environmental load enhancement factor are used for the structural analysis and certification tests for the flight control system.

• Korean Journal of Food Science and Technology
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• v.31 no.1
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• pp.164-170
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• 1999

Cracking of rice caused by moisture migration during storage under different relative humidity conditions was investigated for the establishment of safe storage condition of rice. Rice was cracked when a large difference in equilibrium relative humidity $({\Delta}ERH)$ between the rice and the environment was present. External and internal cracks were generated as the results of moisture desorption and adsorption, respectively. The external cracks by moisture desorption generated in all directions and shaped irregularly, while the internal cracks by moisture adsorption did in radial direction and showed a typical shape. The cracking trend could be analyzed by the Weibull function, and the cracking constant increased with ${\Delta}ERH$. The frequency of cracked rice increased linearly with In $({\Delta}ERH)$. The critical crack-inducing ${\Delta}ERH$ was $11.3{\sim}16.4%$ during desorption and $10.8{\sim}17.1%$ during adsorption. A diagram for the safe storage of rice was developed with respect to the initial moisture content and the water activity of rice.

• Korean Journal of Food Science and Technology
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• v.19 no.3
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• pp.231-238
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• 1987

Two kinds of soy pastes with different colors (reddish brown and yellowish white) were dehydrated by freeze drying in powder form. Hygroscopic behaviors of powdered soy pastes were investigated under the conditions of various water acitivities (0.11-0.88) and three different temperatures (25,40 and $50^{\circ}C$), and presented a kinetic and thermodynamic interpretatons in the view point of qualities and storage stability. Moisture absorption isotherms of powdered soy pastes were of type II according with BET classification and can be described by the Henderson's empirical equation. The safe storage moisture levels calculated by the Laurie's equation were ranging from 5.5 to 3.98% dry basis with oaring temperatures. The moisture absorption process for powdered soy paste followed the Ist order kinetic in the difference of equilibrium moisture content and arbitrary moisture content and the initial step was characterized by very fast absorption of moisture. The change of, dispersion capacity and color difference for powdered soy paste were extremely dependent upon water activity under the storage and the maximum stability was found at safe storage moisture levels. Also, the variation of thermodynamic parameters with moisture content was significant at safe storage moisture content levels and suggested d the considerable correspondence to storage stability of powdered soy paste.