Heating rate dependent delamination of metal–polymer interfaces: experiments and modeling

Bimaterial interfaces in microelectronics packages are the most common regions of failure under thermo-mechanical excursions. In this work, we report experimentally observed role of heating rate on the delamination initiation and propagation across a metal-polymer interface in a microelectronic package. We observe that the rate of delamination propagation increases with increasing heating rate. When the heating rate increases, in addition to the higher amount of delamination growth per unit time, experimental results suggests that higher growth will also incur per unit temperature (loading). Correspondingly, the temperature at which complete delamination occur decreases. Using finite element modeling with cohesive interfaces, we provide a plausible explanation to this observed phenomenon. The analyses indicate that the mechanical behavior of the bimaterial interface is sensitive to both temperature and thermal rate.     

Support vector machines for urban growth modeling

This paper presents a novel method to model urban land use conversion using support vector machines (SVMs), a new generation of machine learning algorithms used in the classification and regression domains. This method derives the relationship between rural-urban land use change and various factors, such as population, distance to road and facilities, and surrounding land use. Our study showed that SVMs are an effective approach to estimating the land use conversion model, owing to their ability to model non-linear relationships, good generalization performance, and achievement of a global and unique optimum. The rural-urban land use conversions of New Castle County, Delaware between 1984–1992, 1992–1997, and 1997–2002 were used as a case study to demonstrate the applicability of SVMs to urban expansion modeling. The performance of SVMs was also compared with a commonly used binomial logistic regression (BLR) model, and the results, in terms of the overall modeling accuracy and McNamara’s test, consistently corroborated the better performance of SVMs.     

Influence of temperature, humidity, and defect location ondelamination in plastic IC packages

The modified J-integral and the stress intensity factor based on linear elastic fracture mechanics can be applied to predict the growth of interfacial delamination in integrated circuit (IC) packages. One of the key parameters required is the interfacial fracture toughness. This paper describes the measurement of the interfacial fracture toughness as a function of temperature and relative humidity using a three-point bending test. The interfacial fracture toughness was found to decrease with temperature and relative humidity. It is proposed that delaminations propagate from very small voids or defects present at the interface. The effect of the location of these interfacial defects or cracks on delamination was studied. The IC package evaluated in this paper was an 80-pin quad flat package with a 0.2 mm defect or crack at the edge or at the center of the interface. It was found that as the temperature of the package was increased, the stress intensity factor of the edge crack was higher than that of the center crack. However, whether the edge crack will propagate first as temperature is increased depends on the ratio of mode II interface toughness to that of the mode I interface toughness. For the package under investigation, it was established that when this ratio is less than 2.69 the edge crack would propagate first, otherwise the center crack would. For small defects, it was found that the water vapor pressure developed at the interface did not have a significant effect on the value of the crack-tip stress intensity factor     

Proposed algorithm for phase unwrapping

A new, to our knowledge, two-dimensional phase-unwrapping algorithm is proposed. The algorithm, which is based on the global continuity of physical information (e.g. the three-dimensional surface profile of an object) being measured, uses the principle of least-phase difference to rectify errors caused by an erroneous 2pi-phase jump in the initial unwrapped phase map obtained by the conventional phase-unwrapping method. Experimental results show that the proposed algorithm works well on a phase map that contains error sources, such as noises, phase discontinuity of more than pi, and insufficient sampling. Moreover, the algorithm is most suitable for unwrapping a phase map generated during shape measurement with a step-change surface on the test object, which is usually a critical problem in shape measurement.     

Investigation of membrane deformation by a fringe projection method

An optical method has been developed to measure the deformation of a membrane in a microphone. A fringe projector that consists of an optical fiber and an optical wedge is described and analyzed by geometric optics. A three-step phase-shifting technique that involves the introduction of an arbitrary phase is discussed. The fine fringe patterns projected onto a small test surface are captured by a CCD camera mounted on a long-distance microscope. With the aid of a phase-shifting technique and signal-demodulating techniques, the proposed setup is capable of measuring deformation of the membrane of the order of as much as submicrometers.     

Effect of platelet-activating factor on the electrophysiology of the human Fallopian tube: early mediation of embryo-maternal dialogue?

Platelet-activating factor (PAF) is produced by preimplantation embryos and may be involved in the earliest stages of embryo-maternal dialogue. This study explored the potential effects of PAF acting as a signalling agent on human Fallopian tubal epithelial cells grown as a polarized layer in primary culture. The response of the tubal epithelium was assessed in terms of the transepithelial potential difference and short-circuit current (I(scc)), which were recorded using a modified Ussing chamber. Resistance was calculated from the measurements of potential difference and I(scc). PAF (1.9 nmol to 1.9 micromol l(-1)) administered to the apical surface of the cells produced a marked, transient increase in both potential difference and I(scc) in a dose-dependent manner. The mode of action of PAF on the electrophysiological responses of human tubal epithelial cells was investigated. Blockers of Na(+), K(+) and voltage-operated Ca(2+) channels had little effect on PAF action. However, incubation of the epithelial cells in Cl(-)free medium or with a blocker of the Na(+)-K(+)-2Cl(-) cotransporter (Furosemide) reduced the effect of PAF. Blockade of chloride-bicarbonate channels with 4-acetamido-4'-iso-thiocyanostilbene-2.2'-disulphonic acid (SITS) reduced the effect of low doses of PAF only. These results indicate that PAF influences the movement of chloride ions across the tubal epithelial cell and is a candidate molecule for initial embryo-maternal dialogue.     

A dielectrophoretic chip packaged at wafer level

The paper presents a dielectrophoretic chip, fully enclosed, with bulk silicon electrodes fabricated using wafer-to-wafer bonding techniques and packaged at the wafer level. The silicon electrodes, which are bonded to two glass dies, define in the same time the walls of the microfluidic channel. The device is fabricated from a silicon wafer that is bonded (at wafer level) anodically and using SU8 photoresist between two glass wafers. The first glass die includes drilled holes for inlet/outlet connections while the second glass die assure the electrical connections, through via holes and a metallization layer, between the silicon electrodes and a printing circuit board.     

Defect-free wet etching through pyrex glass using Cr/Au mask

This paper reports the highest etch depth of annealed Pyrex glass achieved by wet etching in highly concentrated HF solution, using a low stress chromium–gold with assistance of photoresist as masking layer. The strategies to achieve that are: increasing the etch rate of glass and simultaneously increasing the resistance of Cr/Au mask in the etchant. By annealing the Pyrex glass and using a highly concentrated HF acid, a high etch rate can be obtained. Furthermore, a method to achieve a good resistance of the Cr/Au masking layer in the etching solution is to control the residual stress and to increase the thickness of Au deposition up to 1 μm. In addition, the presence of a hard baked photoresist can improve the etching performance. As a result, a 500-μm thick Pyrex glass wafer was etched through.

     

A modified Chi2 algorithm for discretization

Since the ChiMerge algorithm was first proposed by Kerber (1992), it has become a widely used and discussed discretization method. The Chi2 algorithm is a modification to the ChiMerge method. It automates the discretization process by introducing an inconsistency rate as the stopping criterion and it automatically selects the significance value. In addition, it adds a finer phase aimed at feature selection to broaden the applications of the ChiMerge algorithm. However, the Chi2 algorithm does not consider the inaccuracy inherent in ChiMerge's merging criterion. The user-defined inconsistency rate also brings about inaccuracy to the discretization process. These two drawbacks are first discussed in this paper and modifications to overcome them are then proposed. By comparison, results with the original Chi2 algorithm using C4.5, the modified Chi2 algorithm, performs better than the original Chi2 algorithm. It becomes a completely automatic discretization method