Effect of solder volume on joint shape with variable chip-to-board contact pad ratio

The objective of this paper is to investigate the effect of the pad size ratio between the chip and board end of a solder joint on the shape of that solder joint in combination with the solder volume available. The shape of the solder joint is correlated to its reliability and thus of importance. For low density chip bond pad applications Flip Chip (FC) manufacturing costs can be kept down by using larger size board pads suitable for solder application. By using “Surface Evolver” software package the solder joint shapes associated with different size/shape solder preforms and chip/board pad ratios are predicted. In this case a so called Flip-Chip Over Hole (FCOH) assembly format has been used. Assembly trials involved the deposition of lead-free 99.3Sn0.7Cu solder on the board side, followed by reflow, an underfill process and back die encapsulation. During the assembly work pad off-sets occurred that have been taken into account for the Surface Evolver solder joint shape prediction and accurately matched the real assembly. Overall, good correlation was found between the simulated solder joint shape and the actual fabricated solder joint shapes. Solder preforms were found to exhibit better control over the solder volume. Reflow simulation of commercially available solder preform volumes suggests that for a fixed stand-off height and chip-board pad ratio, the solder volume value and the surface tension determines the shape of the joint

An Analysis of the Effectiveness of Emergency Locator Transmitters to Reduce Response Time and Locate Wreckage in U.S. General Aviation Accidents

Emergency Locator Transmitters (ELT) help search crews to locate aircraft in distress and to rescue survivors. This study analyzed ELT data from U.S. General Aviation accidents during the period 2006 to 2010. This study examined the effectiveness of ELTs in terms of ELT Success Rate (ESR) and False Negative Rate (FNR) based on ELT-Aided. This study found a significant difference between ELT-Operated and ELT-Aided. The ESR was found to be 38.58% whereas the FNR was found to be 61.42 %. The Missing Data Ratio (MDR), where accident reports had no ELT information, was found to be above 95%. Recommendations were made to include ELT information in all accident reports and to stress the importance of including response time in the accident report. Also the significant differences between ELT-Operated and ELT-Aided were explained

The design, synthesis and evaluation of selective, non invasive imaging agents for atherosclerotic plaque.

The aim of this research study was the synthesis of an imaging agent, which could be used to non-invasively image atherosclerotic plaques via MRI. In order to achieve this, a library of peptide substrates designed to be substrate specific for either legumain or MMP-2/9 were synthesized. This was achieved via a combination of both solid and solution phase peptide synthesis. The first phase of the research study focused on the synthesis of a targeted MRI contrast agent designed to image legumain expressing atherosclerotic plaques. This was achieved by using a Fluorescent Resonance Energy Transfer (FRET) active system to evaluate the substrate specificity of synthesized peptide sequences for legumain. The self quenched FRET substrates were engineered to carry a legumain sensitive bond in between the donor (5(6)-carboxyfluorescein) and quencher (aminoanthraquinone) moiety. Legumain mediated activation of the FRET substrates was measured via fluorescence spectroscopic analysis which showed the release in fluorescence that was initially quenched by the anthraquinone moiety. Optimized peptide sequences were then covalently coupled to the gadolinium chelate (Gd-DOTA) so that, upon enzymatic cleavage, the contrast agent could be released at the site of activation. Mass spectrometric analysis on the post enzyme digested samples (incubated with recombinant human legumain) showed that the substrates were fragmented by the activated enzyme in vitro. The targeted MRI contrast agent and FRET substrates were successfully synthesized and then characterized by low/high resolution mass spectrometry. Additionally cytotoxic studies on selected compounds and a model of the enzyme-digested product [Lys(DOTA-Gd)-Sp-AQ] via MTT assay demonstrated that the compounds did not affect the cell viability of MDA-MB-231 cell line. The second phase of this project was the synthesis of an aminoanthraquinone peptide substrate coupled to a contrast agent (CA). This substrate was designed to be specific to MMP-2/9. Although the synthetic strategy was successful, subsequent reaction optimization will be required (increasing yield) before in vitro CA release could be evaluated. Thus, the targeted MRI CAs synthesized during this research study provide a starting point for novel imaging agents. These agents, which upon successful in vitro and in vivo trials could potentially be used to image legumain expression or MMP (2/9) expression or atherosclerotic plaques

System packaging & integration for a swallowable capsule using a direct access sensor

Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic capsules are an example of this. In this paper, a diagnostic capsule technology is described based on direct-access sensing of the Gastro Intestinal (GI) fluids throughout the GI tract. The objective of this paper is two-fold: i) develop a packaging method for a direct access sensor, ii) develop an encapsulation method to protect the system electronics. The integrity of the interconnection after sensor packaging and encapsulation is correlated to its reliability and thus of importance. The zero level packaging of the sensor was achieved by using a so called Flip Chip Over Hole (FCOH) method. This allowed the fluidic sensing media to interface with the sensor, while the rest of the chip including the electrical connections can be insulated effectively. Initial tests using Anisotropic Conductive Adhesive (ACA) interconnect for the FCOH demonstrated good electrical connections and functionality of the sensor chip. Also a preliminary encapsulation trial of the flip chipped sensor on a flexible test substrate has been carried out and showed that silicone encapsulation of the system is a viable option

Development and reliability of a direct access sensor using flip chip on flex technology with anisotropic conductive adhesive

Technological developments in biomedical microsystems are opening up new opportunities to improve healthcare procedures. Swallowable diagnostic sensing capsules are an example of these. In none of the diagnostic sensing capsules, is the sensor’s first level packaging achieved via Flip Chip Over Hole (FCOH) method using Anisotropic Conductive Adhesive (ACA). In a capsule application with direct access sensor (DAS), ACA not only provides the electrical interconnection but simultaneously seals the interconnect area and the underlying electronics. The development showed that the ACA FCOH was a viable option for the DAS interconnection. Adequate adhesive formed a strong joint that withstood a shear stress of 120N/mm2 and a compressive stress of 6N required to secure the final sensor assembly in place before encapsulation. Electrical characterization of the ACA joint in a fluid environment showed that the ACA was saturated with moisture and that the ions in the solution actively contributed to the leakage current, characterized by the varying rate of change of conductance. Long term hygrothermal aging of the ACA joint showed that a thermal strain of 0.004 and a hygroscopic strain of 0.0052 were present and resulted in a fatigue like process. In-vitro tests showed that high temperature and acidity had a deleterious effect of the ACA and its joint. It also showed that the ACA contact joints positioned at around or over 1mm would survive the gastrointestinal (GI) fluids and would be able to provide a reliable contact during the entire 72hr of the GI transit time. A final capsule demonstrator was achieved by successfully integrating the DAS, the battery and the final foldable circuitry into a glycerine capsule. Final capsule soak tests suggested that the silicone encapsulated system could survive the 72hr gut transition

Studies on host selectivity by Cuscuta gronovii

The host selectivity of the plant parasite Cuscuta gronovii, and its growing patterns were investigated among pairings of corn, bean, and tomato plants in various combinations. These pairings were set up in pots, in a greenhouse environment. Seeds of C. gronovii were germinated and a single seedling was placed between each pairing. Observations were made over a two week period. It was observed that only 11% of Cuscuta gronovii seedlings made a choice with regards to host selection, the remaining 89% failed to make a choice as they either died, showed inhibited growth or nondirectional growth. Suggestions are made to explain why these results deviated from those found previously in the scientific literature

Praziquantel Resistance in the Zoonotic Cestode Dipylidium caninum

Dipylidium caninum is a cosmopolitan cestode infecting dogs, cats, and humans. Praziquantel is a highly effective cestocidal drug and resistance in adult cestodes has not been reported. From 2016 to 2018, a population of dogs with cestode infections that could not be eliminated despite multiple treatments with praziquantel or epsiprantel was identified. Cases of D. caninum were clinically resistant to praziquantel and could not be resolved despite increasing the dose, frequency, and duration of treatment. Resistant isolates were identified and characterized by sequencing the 28S, 12S, and voltage-gated calcium channel beta subunit genes. Cases were only resolved following treatment with nitroscanate or a compounded pyrantel/praziquantel/oxantel product. Clinicians should be aware of this alarming development as treatment options for cestodes are limited in both human and veterinary medicine