Multiple reflow study of ball grid array (BGA) solder joints on Au/Ni metallization

This paper evaluates the shearing behavior of ball grid array (BGA) solder joints on Au/Ni/Cu pads of FR4 substrates after multiple reflow soldering. A new Pb-free solder, Sn–3Ag–0.5Cu–8In (SACI), has been compared with Sn–3Ag–0.5Cu (SAC) and Sn–37Pb (SP) solders, in terms of fracture surfaces, shearing forces and microstructures. Three failure modes, ball cut, a combination of solder shear and solder/pad bond separation, and pad lift, are assessed for the different solders and reflow cycles. It is found that the shearing forces of the SP and SAC solder joints tend to increase slightly with an increase in the number of reflow cycles due to diffusion-induced solid solution strengthening of the bulk solder and augmentation of the shearing area. However, the shearing forces of the SACI solder joints decrease slightly after four cycles of reflow, which is ascribed to the thermal degradation of both the solder/intermetallic compound (IMC) and IMC/Ni interfaces. The SACI solder joints yield the highest strengths, whereas the SP solder joints give the smallest values, irrespective of the number of reflow cycles. Thickening of the interfacial IMC layer and coarsening of the dispersing IMC particles within the bulk solders were also observed. Nevertheless, the variation of shearing forces and IMC thickness with different numbers of reflow cycles was not so significant since the Ni under layer acted as an effective diffusion barrier. In addition, the initially-formed IMC layer retarded the further extensive dissolution of the pad material and its interaction with the solder

Ghost/Machine: cinema in a digital age

Cinema, with its passive cinematic apparatus and linear narrative is often characterised as a contrast to new media narrative strategies, yet from Vertov’s Man with a Movie Camera to Mike Figgis’ TimeCode and Wong Kar Wei’s 2046 cinema provides narrative strategies and spatial conceptualisations which prefigure or are contiguous with new media environments. Both our perception of what cyberspace constitutes and the technology that actualises those perceptions arise out of and are driven by fantasy and desire. This paper will explore the metaphors used to represent and understand new media aesthetics through cinematic representations of new media environments. Two key themes relevant to new media aesthetics emerge. Irigaray, Haraway, and Grosz are used to explore the de-essentialising haptic and penetrative potential of new technologies and their ability to collapse the boundary between the body and the machine. The second fantasy, of new media as a liminal space that expresses the memorialising function of technology and its relation to mourning, is analysed using Benjamin, Burgin and Rutsky. These altered spaces and perceptions of the body and memory of the post-cinematic subject are illustrated through an analysis of Gondry’s Eternal Sunshine of the Spotless Mind and Jonze’s Being John Malkovich. [From the Author]