Predicting the relationship between reliability and geometric parameters of cu column bumped flip-chips

Cu column bumping is a novel flip chip packaging technique that allows Cu columns to be bonded directly with the dies. It has eliminated the under-bump-metallurgy (UBM) fonnation step of the traditional flip chip manufacturing process. This bumping technique has the potential benefits of simplifying the flip chip manufacturing process, increasing productivity and the UO counts. In this paper, a study of reliability of Cu column bumped flip chips will be presented. Computer modelling methods have been used to predict the shape of solder joints and the response of flip chips to cyclic thermal-mechanical loading. The accumulated plastic strain energy at the corner solder joints has been used as an indicator of the solder joint reliability. Models with a wide range of design parameters have been compared for their reliability. The design parameters that have been investigated are the copper column height and radius, PCB pad radius, solder volume and Cu column wetting height. The relative importance ranking of these parameters has been obtained. The Lead-free solder material 96.5Sn3.5Ag has been used in this modelling work.

The relationship between internet identification, internet anxiety and internet use

This paper reports a study investigating the relationship between Internet identification, Internet anxiety and Internet use. The participants were 446 students (319 females and 127 males) from two universities in the UK and one university in Australia. Measures of Internet identification and Internet anxiety were developed. The majority of participants were NOT anxious about using the Internet, although there were approximately 8% who showed evidence of Internet anxiety. There was a significant and negative relationship between Internet anxiety and Internet use. Those who were more anxious about using the Internet used the Internet less, although the magnitude of effect was small. There was a positive and significant relationship between Internet use and Internet identification. Those who scored high on the measure of Internet identification used the Internet more than those who did not. There was also a significant and negative relationship between Internet anxiety and Internet identification. Finally, males had a significantly higher Internet identification score than females. Implications of these findings are discussed.

Self-regulated learning and social media – a ‘natural’ alliance? Evidence on students’ self-regulation of learning, social media use and student-teacher relationship

Article is available at: http://www.tandfonline.com/doi/full/10.1080/17439884.2015.1064953.

Biological controls on resuspension and the relationship between particle size and the Kolmogorov length scale in a shallow coastal sea

Measurements of suspended particle matter (SPM) and turbulence have been obtained over five tidal surveys during spring and summer 2010 at station L4 (5025 degrees N 04.22 degrees W, depth 50 m), in the Western English Channel. The relationship between turbulence intensity and bed stress is explored, with an in-line holographic imaging system evaluating the extent to which material is resuspended. Image analysis allows for the identification of SPM above a size threshold of 200 pm, capturing particle variability across tidal cycles and the two seasons. Dissipation of turbulent kinetic energy, which exceeds 10(-5) W kg(-1), yields maximum values of bed stress of between 0.17 and 0.20 N m(-2), frequently resulting in the resuspension of material from the bed. Resuspension is shown to promote aggregation of SPM into flocs, where the size of such particles is theoretically determined by the Kolmogorov microscale, l(k). During the spring surveys, flocs of a size larger than lk were observed, though this was not repeated during summer. It is proposed that the presence of gelatinous, biological material in spring allows flocculated particles to exceed l(k). This suggests that under specific circumstances, the limiting factor on the growth of flocculated SPM is not only turbulence, as previously thought, but the presence or absence of certain types of biological particle.

A Possible Relationship Between Chitinozoa And Tintinnids

The biological affinity of the extinct microfossil order chitinozoa has been the source of much discussion in the fifty years since they were first discovered. Within this period these flask-shaped, organic-walled organisms have been variously attributed to rhizopods, flagellates, tintinnids, chrysomonads, metazoan eggs, dinoflagellates, and fungi. Most of these suggested relationships were made before it was recognised that chitinozoans were encapsulated and must therefore be resting cysts or eggs and not active individuals. There are no living organisms which combine all the characteristics of the chitinozoa. Of all the possibilities, a grouping of flask-shaped cysts which have been found in present-day marine plankton and sediment comes closest to characterising the morphology of chitinozoa. This grouping of flask-shaped cysts includes forms which have been found within tintinnid loricae. Another modern cyst type Pacillina arctica, which is believed to be a ciliate cyst, comes close to replicating the morphology of the chitinozoan genus Hoegisphaera. This paper discusses the structure of tintinnid, other flask-shaped cysts and Pacillina arctica in relation to chitinozoan morphology, drawing attention to similarities and differences. The occurrence and distribution of these cyst forms in present-day plankton is also described and interpreted.

Relationship Between Infestation By Mytilicola-Intestinalis Steuer (Copepoda Cyclopoidea) And Condition Index Of Mytilus-Edulis In Southwest England

Seasonal cycles in the condition index of Mytilus edulis from three sites in southwest England are described. These are analysed in relation to host length, stage of gonad development and parasite burden by linear regression analysis. An effect on the condition index due to the presence of Mytilicola intestinalis can be detected only in the sublittoral mussels in those few winter months when the mean intensity of infestation is over about 25 parasites per host. In all cases studied, the magnitude of the effect due to variation in host length, stage of gonad development, seasonal cycles and environmental factors is greater than that due to parasitism.