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In multi-layer printed wiring boards (PWBs), electrical connections between different layers are accomplished with plated through holes (PTHs). The reliability of the PTH barrel and the PTH-inner plane (IP) connection depends not only on the design but also on the conditions of manufacturing and assembly processes of the board. The concerns associated with manufacturing arise from drilling which heats up and smears the surrounding epoxy onto the copper inner plane surfaces and also from subsequent chemical hole-clean operations which desmear the drilled holes. Good adhesion of the PTH copper to the desmeared PTH wall and to the copper inner planes is important for the reliability of the PTHs during assembly and field service. PWB coupons consisting of resin-glass bundle areas as well as resin filled clearance areas surrounding the PTH have been considered for a series of experiments and tests. On these coupons, accelerated stress tests and failure analysis of the PTHs at the end of these tests have been conducted. An elasto-plastic finite element analysis of the PTH strains for a temperature excursion of 102°C has been carried out for signal PTHs without and with IP connections. A peel test, using a micro-mechanical tester, has also been carried out to assess the adhesion of PTH copper to different regions along the drilled hole. All of the testing techniques have been supplemented by suitable analytical techniques for studying the distribution of smear on the copper inner planes. A birefringence technique to estimate the temperature of the hole wall during drilling has been described. All of the fails observed during stress testing are in the form of cracks in the PTH barrel, the plane of the crack being perpendicular to the barrel axis. The cracks are localized near the glass bundle-resin rich interface. It has also been observed in the failure analysis that the PTH/IP connections are not susceptible to failure during the accelerated stress testing conditions considered. These observations are also supported by the results of stress analysis. The results of stress analysis show that the interior clearance holes show higher strains than those closer to board surfaces, suggesting that the PTH barrel failure is likely to occur at the clearance hole and that the likelihood of failure at the interior clearance holes is higher than those closer to the PWB surfaces. The results of the peel test reveal that in the glass bundle-resin regions, the adhesion along the PTH wall is determined by the mechanical interlocking between the plated copper and the glass bundles and is relatively insensitive to desmear operations. However, adhesion in the resin-rich areas is a strong function of the desmear operation, which enhances the adhesion of the PTH to the resin. Finally, it is shown that the birefringence technique may be used effectively to estimate the drilling temperature and, hence, the degree of smearing and PTH quality. It is concluded that while smear may play an important role in the failure of PTHs in PWBs, for thick packaging boards with high aspect ratio PTHs, the predominant failure mechanism is less likely to be smear related. Such a failure mechanism would be preceded by failure in the PTH barrels as a result of the large strain concentrations imposed at specific locations within the cross-section.

Hepatities C Virus (HCV) is a significant health problem worldwide due to the lack of effective vaccines. HCV plasmid DNA (pDNA) vaccine represents a promising means to induce a Th1-biased cell-mediated response which tends to be associated with HCV clearance. However, the immune responses induced by naked pDNA vaccine in large animals as well as in humans are usually too weak to show sufficient protection against new infections. Therefore, it is interesting to look for new ways to deliver HCV pDNA vaccine. In this research, carbon nanotube (CNT) is used as a carrier to deliver the pDNA vaccine of HCV to induce high immune responses, because CNT has some excellent properties such as high strength and good biocompatibility. One of the key approaches to make this idea work is to treat CNT so that it can bind with HCV pDNA with good stability. An approach called 1, 3-dipolar cycloaddition of azomethine ylides was modified. We analyzed the complex of f-CNTs combined with pDNA vaccines expressing HCV E2 protein by using Enzyme-linked immunospot (ELISPOT) or Enzyme-linked immunosorbent assay (ELISA) assay in vitro. The result showed that the CNT approach can induce stronger protective immune responses than the needle delivery of naked pDNA vaccine. We have also found an optimal way to treat CNT in light of the highest immune response in the same testing environment. The success of this research will warrant testing HCV vaccine in large animal models and human clinical trials.

In this paper, we study the elasticity problem of a spherically isotropic elastic medium bounded by two concentric spherical surfaces. General solutions in terms of infinite series are presented. Specifically, we consider some axisymmetric problems such as: concentrated force in an infinite medium, stress concentration due to a spherical cavity, and a steadily rotating shell. In all these cases, the infinite series terminate, and closed-form solutions are possible. Steady-state thermal stress problems are also considered.

When a uniform heat flow in an infinite orthotropic solid is disturbed by the presence of a long circular insulated cavity, local intensification of the temperature gradient occurs in the neighborhood of the cavity. This report describes a study of the stress field induced by the temperature distribution. The linear plane (plane stress or plane strain) thermoelastic problem is solved by using the complex variable technique. The analysis may also be used for other steady-state thermal stress problems in an orthotropic medium.

This paper presents an exact solution for the stress distribution around an elastic spheroidal inclusion in an infinite transversely isotropic elastic body which is otherwise under a pure shear stress. The stresses and displacements are expressed in terms of elementary functions. The technically important consideration of the stress concentrations around a spheroidal cavity is discussed. Numerical results are given for a number of hexagonal crystals.

A spheroidal inclusion is embedded in an elastic matrix composed of a different material. Both materials are transversely isotropic with the material property axes parallel to the geometric axis of the spheroid. At the interface, the two materials are bonded. The matrix is subjected to a uniform axisymmetric stress field at infinity. Explicit expressions for the stress and displacement fields in the inclusion and the matrix will be presented. The analysis is within the realm of classical linear elasticity.

This paper treats some problems in a homogeneous transversely isotropic elastic material, occupying an infinite space, or an infinitely long circular cylinder. The analysis is based upon the potential function method by Elliott, with the addition of another potential function. The static solution is extended to include quasi-static, or steady-state problems. Closed-form solution is found for the problem of an arbitrarily oriented concentrated force in an infinite medium. The case of discontinuous pressure over an infinitely long circular cylinder is also studied with the aid of a numerical method of integration. The applied forces are assumed to be moving with uniform velocity along the anisotropic direction.

An elastic solid is composed of a transversely isotropic material bounded by a single-sheeted hyperboloid of revolution, which is traction free. This solid is subjected to a finite tensile force at infinity. A closed-form solution based upon the potential functions approach is obtained. Numerical examples of the tensile stress at the narrowest section are presented.