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A theoretical method is proposed to evaluate the creep damage in a 91 steel by using ultrasonic nonlinear technique. A 2-dimensional finite element model is developed to simulate the creep damage of steel P91 and the ultrasonic wave propagation through the degraded material. The micro-structural changes in the degraded material cause the distortion in the ultrasonic wave, and this material's nonlinearity...
Proportional-integral-derivative (PID) controllers have been widely used in temperature control system. It is difficult to obtain good control performances if the fixed PID parameters are used. The adaptive control schemes are complexity in practice and difficult to obtain suitable results for strong nonlinearity systems. The learning cost of neural networks and genetic algorithms are considerably...
This paper describes a method for calculating the thermal resistance of a vertical MOSFET power amplifier. The method for measuring the thermal resistance under a given set of input conditions is given. From this data a thermal transient model with the thermal resistance and capacitance parameters is created. This model can be utilized to determine the thermal resistance of any input signal condition...
Previous efforts aimed at modeling solar cell bowing due to the aluminum back surface field (BSF) have focused on relatively simple two or three layer models. This paper will outline the effort to develop a more sophisticated finite element (FE) model approach. This approach is superior to previous modeling efforts since it allows a more accurate representation of the cell structure and can handle...
Moisture induced failure in plastic encapsulated packages is one most important failure mechanisms in microelectronics. This failure is driven by the mismatch between different material properties, such as CTE, CME (Coefficient of Moisture induced Expansion) caused by moisture absorption in plastic packaging materials. Therefore, it is important to know moisture effects on mechanical properties of...
This paper describes the effects of temperature changes on the operation of a 25 kHz sonochemical reactor, which is being developed as a reference facility for studying acoustic cavitation at NPL. Field measurements, acquired using a hydrophone in different locations inside the cavitation reactor, are compared with Finite Element Models at different temperatures, showing that significant changes in...
This paper reports on the thermal characteristics of the high power LED package. The increment of input power generates more heat in the chip, decreasing the luminance and life span of LEDs. To enhance the efficiency of high power LEDs, challenges related to thermal management need to be addressed. In this research, a detailed finite element model of the high power LED package with proper input power...
Longitudinal leaky surface acoustic wave (LLSAW) is attracting considerable attention for its high velocity and reasonable coupling coefficient. The intrinsic temperature coefficient of frequency (TCF) for these waves for different longitudinal cuts with metal gratings is in the range of -110 to -90 ppm/degC. However, for certain filter applications the TCF of the LLSAW waves must be quite low in...
The reliability of Chip-On-Film (COF) packages is fundamentally dependent upon the quality of the thermal performance. The present study commences by performing an experimental investigation to establish the temperature at surface of driver IC within the COF packaging application under electric power conditions. A finite element (FE) model is then constructed to simulate the thermal behavior within...
Electronic package plays an important part in the development of IC industry. As we all known, strip warpage is a critical issue for the MAP-QFN manufacturing, results from the package structure, the thermal mismatch of materials and the manufacturing process. In this paper, a new finite element model was used to predict the warpage of one MAP-QFN block. And in this model, the temperature-dependent...
The objective of this study is to experimentally and numerically investigate thermal and residual deformation of plastic ball grid array (PBGA) package and assembly. Shadow moire was used to measure their real-time out-of-plane deformations (warpages) during heating and cooling conditions. A finite element model with material properties characterized by dynamic mechanical analyzer and thermomechanical...
Experimental and numerical studies were conducted to investigate Cu/low-k delamination potentials of a flip-chip package assembly implemented with different underfills under an accelerated thermal cycling test condition. A total of six underfills were considered and compared. Their temperature-dependent Young's moduli, coefficients of thermal expansion, and glass transition temperatures were measured...
During reflow process, it is the temperature of solder balls that is the most concerned. However, it is difficult to directly measure its temperature and reflow profile is obtained by measuring the package surface temperature. Based on our previous study of reflow profile simulation (Shen Liang et al., 2005), a comprehensive finite element model (FEM) has been built for precisely simulating relow...
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