Evaluation of the Moisture Sensitivity of Molding Compounds of IC’s Packages

2000 ◽  
Vol 123 (1) ◽  
pp. 16-18 ◽  
Author(s):  
H. Fre´mont ◽  
J. Y. Dele´tage ◽  
A. Pintus ◽  
Y. Danto
Keyword(s):  
Finite Element ◽  
Diffusion Coefficient ◽  
Diffusion Process ◽  
Moisture Diffusion ◽  
Fickian Diffusion ◽  
Lead Frame ◽  
Significant Cost ◽  
Moisture Sensitivity ◽  
Molding Compounds ◽  
Cost Reductions

Plastic encapsulated devices are of great interest against their ceramic or metallic counterparts, as they permit significant cost reductions. However, they are more sensitive to moisture ingress, which can lead to reliability problems. Moisture can penetrate either through the polymer or along the interface between the leads and the encapsulant. Samples of 3 different polymers usually used for IC’s encapsulation, either pure or containing a lead frame with the lead terminations, were aged under different RH conditions. Results show that the penetration through the polymer is preponderant face to the progression along the leads. In a first approach, this penetration can be considered as a diffusion process, following the Fick’s law; the diffusion coefficient D and the saturation coefficient S can be deduced from the measurements as a function of the relative humidity. These values can be used in finite element simulations, in order to evaluate the moisture ingress as a function of time within an IC of a given geometry. Moisture diffusion within these new resins is a very long process. In fact, a first “saturation” occurs after a few hours of aging, but if samples are left longer in the oven, a new diffusion process occurs, not leading to a real saturation. Hence processes different than pure fickian diffusion occur in the polymers.

Enhanced Diffusion Due to Swimming Bacteria

2003 ◽  
Author(s):  
Min Jun Kim ◽  
Kenneth S. Breuer
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Diffusion Coefficient ◽  
Diffusion Process ◽  
Effective Diffusion Coefficient ◽  
Effective Diffusion ◽  
Flow Cell ◽  
Fickian Diffusion ◽  
Enhanced Diffusion ◽  
Swimming Bacteria

The effect of bacterial motion of the diffusion of a high molecular weight molecule is studied by observing the mixing of two streams of fluid in a micro-fabricated flow cell. The presence of Escherichia coli (E.coli) in one of the streams results in an increase in the effective diffusion coefficient of Dextran, which rises linearly with the concentration of bacteria from a baseline value of 2 × 10−7 cm2/s to 8 × 10−7 cm2/s at a concentration of 2.1 × 109 /ml (approximately 0.5 % by volume). The diffusion process is also observed to undergo a change from standard “Fickian” diffusion to a superdiffusive behavior in which the diffusion exponent rises from 0.5 to 0.55 as the concentration of bacteria rises from 0 to 2.1 × 109/ml.

Effect of Externally Applied Stresses on the Moisture Diffusion Characteristics of Epoxy Glass Composites

2013 ◽  
Author(s):  
Mark T. Stoffels ◽  
David A. Miller
Keyword(s):  
Finite Element ◽  
Diffusion Process ◽  
Finite Element Model ◽  
Free Volume ◽  
Elastic Properties ◽  
Laminate Plate ◽  
Moisture Diffusion ◽  
Element Model ◽  
Fe Model ◽  
Stress Dependent

A model is proposed which relates externally applied tensile stresses to changes in absorption capacity as well as diffusion rate. The model postulates that changes seen in the diffusion process are the result of stress-dependent changes in the free volume of the epoxy resin. The free volume changes of the resin are calculated through laminate plate theory, which itself becomes a function of fiber angle as well as a host of elastic properties of the constituents. Consequently, according to the proposed model, changes in diffusion parameters are dependent upon the magnitude of applied stress, the loading angle, as well as elastic properties of the constituents. Additionally, a finite element model is presented. The proposed finite element model establishes an analogy between thermal and mass diffusion for use in solving the moisture diffusion problems, both in free and stressed states. Input parameters for the FE model are found through use of the previously established mathematical diffusion model. In order to experimentally verify the proposed models, a series of epoxy glass laminate samples were manufactured at varying fiber angles and immersed in a moist environment while subjected to varying levels of tensile loading. Weight gain measurements were recorded throughout the diffusion process until full saturation was achieved. The experimental values exhibited excellent agreement with both the suggested theoretical model and the finite element model.

Stochastic Modelling of Particle Segregation in a Horizontal Drum Mixer

1992 ◽  
Vol 57 (10) ◽  
pp. 2100-2112 ◽  
Author(s):  
Vladimír Kudrna ◽  
Pavel Hasal ◽  
Andrzej Rochowiecki
Keyword(s):  
Differential Equation ◽  
Diffusion Coefficient ◽  
Stochastic Model ◽  
Diffusion Process ◽  
Stochastic Modelling ◽  
Solid Particles ◽  
Kolmogorov Equation ◽  
Particle Segregation ◽  
Drum Mixer ◽  
Horizontal Drum

A process of segregation of two distinct fractions of solid particles in a rotating horizontal drum mixer was described by stochastic model assuming the segregation to be a diffusion process with varying diffusion coefficient. The model is based on description of motion of particles inside the mixer by means of a stochastic differential equation. Results of stochastic modelling were compared to the solution of the corresponding Kolmogorov equation and to results of earlier carried out experiments.

Oxidation characteristics of commercial copper-based lead frame surface and the bonding with epoxy molding compounds

2019 ◽  
Vol 99 ◽  
pp. 161-167 ◽  
Author(s):  
Shih-Chieh Chao ◽  
Wei-Chen Huang ◽  
Jen-Hsiang Liu ◽  
Jenn-Ming Song ◽  
Po-Yen Shen ◽  
...  
Keyword(s):  
Lead Frame ◽  
Molding Compounds ◽  
Oxidation Characteristics ◽  
Commercial Copper

CALCULATION OF PARAMETERS OF A DIFFUSION PROCESS WITH A CONCENTRATION-DEPENDENT DIFFUSION COEFFICIENT

2020 ◽  
Author(s):  
Е.Г. СТЕПАНОВА ◽  
Б.Ю. ОРЛОВ ◽  
М.А. ПЕЧЕРИЦА
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Process ◽  
Transfer Problem ◽  
Extraction Process ◽  
Electrochemical Activation ◽  
Calculation Of Parameters ◽  
Sucrose Solutions ◽  
Diffusion Transfer ◽  
Preliminary Preparation ◽  
Series Of Experiments

Приведено решение нелинейной задачи диффузионного переноса с учетом предварительной подготовки экстрагента методом электрохимической активации. Для расчета параметров процесса использована капиллярная модель. Показаны результаты расчета симплекса концентраций от числа Фурье Е = f(Fo). Представлены экстракционные кривые в чистых сахарных растворах с различными видами экстрагентов и температурами процесса 20 и 70°С. Аналитическая обработка кинетических кривых позволила определить основные параметры диффузионного процесса экстрагирования сахарозы. Проведен полный двухфакторный эксперимент lnЕ= f(С; τ), получено уравнение регрессии и построена поверхность отклика, которая исследована методом неопределенных множителей Лагранжа с получением оптимальных значений для проведенной серии опытов С = 15,4% и τ = 750 с. Выполненные расчеты позволяют моделировать внутренний массоперенос экстрагирования концентрационно-зависимого коэффициента диффузии сахарозы при наложении электрического поля при обработке экстрагента. We present a solution to the nonlinear diffusion transfer problem, taking into account the preliminary preparation of the extractant by electrochemical activation (ECHA). A capillary model is used to calculate the process parameters. The results of calculating the concentration simplex from the Fourier number E= f(Fo) are shown. The description of the laboratory installation, the method of the process, and the modes of ECHA preparation of extractants are given. Extraction curves in pure sucrose solutions with different types of extractants and process temperatures are presented. Analytical processing of the kinetic curves of the sucrose extraction process for the regular stage of the process allowed us to determine the main parameters of the diffusion process. A complete two-factor experiment lnE= f(C; τ) was performed. A regression equation was obtained and the response surface was constructed, which was studied by the method of indeterminate Lagrange multipliers to obtain optimal values for the series of experiments С = 15,4% and τ = 750 s. The calculations performed allow us to model the internal mass transfer of extraction of the concentration-dependent sucrose diffusion coefficient when an electric field is applied during processing of the extractant.

scholarly journals AN INVERSE MOISTURE DIFFUSION ALGORITHM FOR THE DETERMINATION OF DIFFUSION COEFFICIENT

2001 ◽  
Vol 19 (8) ◽  
pp. 1555-1568 ◽  
Author(s):  
Jen Y. Liu ◽  
William T. Simpson ◽  
Steve P. Verrill
Keyword(s):  
Diffusion Coefficient ◽  
Moisture Diffusion
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