Failure of materials and interfaces are commonly linked to the fracture parameters such as the stress intensity factors and the energy release rate. However, there exists no experimental procedure for the direct measurement of these fracture parameters. This dissertation reports on the development of a new technique to obtain these parameters by testing specimens created from post-production electronic packages. The results from the experimental testing are then used as the input for an analytical model which computes the desired parameters. The specimens are thin strips of post production electronic packages. A crack is introduced along the interface in the specimen. Loading is applied to the specimen using the bend fixture inside the chamber of a scanning electron microscope, and images are captured following each load step. Digital image analysis on these images provides the displacement field around the crack tip to be used as boundary conditions in the analytical model. A hybrid formulation is developed utilizing the exact solution for the stress and displacement fields based on the eigenfunction expansion method under general loading. The region has two dissimilar elastic or viscoelastic material wedges with perfect bonding, and is not limited to a particular geometric configuration. The solution method is based on the principle of virtual work in conjunction with the use of Laplace transformation to eliminate time dependency. The strength of the singularity is obtained in the time space without resorting to approximate Laplace inversion techniques. However, the intensification of the stress components is obtained by employing an approximate inversion technique. One of the main contributions of this dissertation is the development of multiple techniques for the creation of test specimens from electronic packages. These methods involve different procedures of encapsulation for sectioning and techniques for the introduction of the crack to the interface. A second development is the technique of testing using image capture in conjunction with digital image correlation to find localized displacements. The third contribution from this work is the development of an analytical model to accurately model the region near the junction of two dissimilar viscoelastic materials.

Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Mechanical and Aerospace Engineering." Includes bibliographical references (p. 93-97).

The effects of microbial growth, packaging film permeability, and freezing on the discoloration of beef was assessed by measuring myoglobin derivatives and specifically the rate of formation of metmyoglobin on the surface of Longissimus dorsi and Semimembranosus bovine muscles during 12 days of storage at 2°C. Frozen thawed sterile beef samples experienced higher metmyoglobin formation than fresh sterile beef samples. By day 2, up to 20% metmyoglobin was formed in the thawed samples whereas, the fresh samples reached this value after day 6. After 6 days, the growth of Pseudomonas florescence had a significant effect on myoglobin oxidation and this behavior continued for the remaining period of the storage. Gas barrier film and gas permeable film exhibited similar results at day 0 and day 3 of storage, however at day 6 of storage, samples packaged with the gas barrier film showed metmyoglobin percentage significantly higher that those packaged with gas permeable film. (Abstract shortened by UMI.)

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 1214. Adviser: Jian-Ming Jun. Includes bibliographical references (leaves 122-128) Available on microfilm from Pro Quest Information and Learning.

A model for the shapes and residual forces for an individual, axisymmetric BGA solder interconnect is developed from the basic assumption that the surface bounding the solder possesses constant mean curvature. The inputs for the model include: pad radius, stand-off height, and the volume of the solder. The model is contrasted with simpler ones to identify the combinations of parameters for which more relaxed assumptions regarding the shape of the interconnect (e.g., a cylinder, truncated sphere, or circular arc meridian) may lead to unacceptable errors when designing for the demanding requirements of aerospace applications. The parameter combinations include situations when there exists a large stand-off height in conjunction with residual tension in the interconnect and when there is considerable tension or compression in the interconnect. The errors can be especially significant if one is designing around presumed surface contact angles at the solder/pad/PCB junction The results of this model are incorporated into a fatigue life analysis for BGA packages. In the aerospace industry the fatigue loading on the individual interconnects is Mode II shearing due to cyclic temperatures. A fracture mechanics approach is taken which accounts for this Mode II fatigue loading as well as a constant Mode I loading that is due to the residual forces arising from the surface tension within the molten interconnect. This model, which is referred to as the relative life model, is capable of demonstrating how the relative fatigue life of an interconnect can be altered as a result of a change in the residual force (and, therefore, the shape) of the interconnect. The model is capable of capturing this relationship for variable joint dimensions (i.e., volumes, stand-off heights, radii), service loading, and material constituents (i.e., solder alloys, PCBs, and IC carriers). For an array of pads of known radii, a procedure is presented for determining the optimal volumes of each solder joint so as to optimize the relative life of the entire package / acase@tulane.edu

Four experiments were carried out to examine the extent to which the container shape and color of a consumer product package influence hazard perceptions of that product. The experiments further examined the extent to which consumer product hazard perception influenced consumer precautionary intent. The first experiment demonstrated that participants could design product packages signaling the identity and potential hazard level of the contents. Experiments 2 and 3 validated the results of Experiment 1. Experiment 3 further introduced the concept of precautionary intent; participants were more likely to express precautionary intent for those products perceived as being more hazardous. Experiment 4 examined whether these stated intentions would be acted upon when participants were asked to actually interact with a product; it was found that participants were more likely to engage in precautionary behaviors than had been indicated in Experiment 3.

This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 μm thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and ~10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2 - 5 ml/cm².s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.

We focused on a non-cooling room temperature microbolometer infrared imaging array device which includes a sensing layer of p-type a-Si:H component layers doped with boron. Boron incorporation and bonding configuration were investigated for a-Si:H films grown by plasma enhanced chemical deposition (PECVD) at varying substrate temperatures, hydrogen dilution of the silane precursor, and dopant to silane ratio using multiple internal reflection infrared spectroscopy (MIR-IR). This study was then confirmed from collaborators via Raman spectroscopy. MIR-IR analyses reveal an interesting counter-balance relationship between boron-doping and hydrogen-dilution growth parameters in PECVD-grown a-Si:H. Specifically, an increase in the hydrogen dilution ratio (H2/SiH4) or substrate temperature was found to increase organization of the silicon lattice in the amorphous films. It resulted in the decrease of the most stable SiH bonding configuration and thus decrease the organization of the film. The new chemical bonding information of a-Si:H thin film was correlated with the various boron doping mechanisms proposed by theoretical calculations. The study revealed the corrosion morphology progression on aluminum alloy (Al, 0.5% Cu) under acidic chloride solution. This is due to defects and a higher copper content at the grain boundary. Direct galvanic current measurement, linear sweep voltammetry (LSV), and Tafel plots are used to measure corrosion current and potential. Hydrogen gas evolution was also observed (for the first time) in Cu/Al bimetallic interface in areas of active corrosion. Mechanistic insight that leads to effective prevention of aluminum bond pad corrosion is explored and discussed. (Chapter 4) Aluminum bond pad corrosion activity and mechanistic insight at a Cu/Al bimetallic interface typically used in microelectronic packages for automotive applications were investigated by means of optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and electrochemistry. Screening of corrosion variables (temperature, moisture, chloride ion concentration, pH) have been investigated to find their effect on corrosion rate and to better understand the Al/Cu bimetallic corrosion mechanism. The study revealed the corrosion morphology progression on aluminum alloy (Al, 0.5% Cu) under acidic chloride solution. The corrosion starts as surface roughening which evolves into a dendrite structure and later continues to grow into a mud-crack type corrosion. SEM showed the early stage of corrosion with dendritic formation usually occurs at the grain boundary. This is due to defects and a higher copper content at the grain boundary. The impact of copper bimetallic contact on aluminum corrosion was explored by sputtering copper microdots on aluminum substrate. Copper micropattern screening revealed that the corrosion is activated on the Al/Cu interface area and driven by the large potential difference; it was also seen to proceed at much higher rates than those observed with bare aluminum. Direct galvanic current measurement, linear sweep voltammetry (LSV), and Tafel plots are used to measure corrosion current and potential. Hydrogen gas evolution was also observed (for the first time) in Cu/Al bimetallic interface in areas of active corrosion. Mechanistic insight that leads to effective prevention of aluminum bond pad corrosion is explored and discussed. Micropattern corrosion screening identified hydrogen evolution and bimetallic interface as the root cause of Al pad corrosion that leads to Cu ball lift-off, a fatal defect, in Cu wire bonded device. Complete corrosion inhibition can be achieved by strategically disabling the mutually coupled cathodic and anodic reaction cycles.