In the present research, in order to fundamentally investigate the strength and interfacial microstructure of the joints between Sn–3.5Ag–0.7Cu (SAC) and Sn–8Zn–3Bi (SZB) solders and Cu, examinations using the standardized solder joint specimen for measuring the shear strength were performed. The effects of the addition of Ag, Bi and Pb to the solders, which are the ingredients of possible lead plating materials of quad plat package, solder layer thickness and aging treatments ranging from 358 to 423 K were investigated. The SAC base solder joints, whose strength hardly degraded after aging, were more reliable than the SZB base solder joints. Since no detrimental effect of the Bi or Pb addition was recognized, the lead plating materials are found to have no significant effect on the strength of the SAC solder joints. Although the SZB base solder joints had higher strength than the SAC base solder joints in as-soldered condition, a significant degradation of the joint strength occurred after aging. In the case of thinner solder layer of 20 μm, the Cu6Sn5 layer that formed at both the solder/Cu5Zn8 and Cu5Zn8/Cu interfaces after aging caused the fracture of the solder joints and resulted in the degradation of the joint strength. In the case of thicker solder layer of 100 μm, the Cu5Zn8 interfacial layer continuously grew during aging, which caused the fracture of the solder joints and resulted in the decrease in the joint strength. As for the effect of the addition elements, while Pb addition caused a marked degradation of the joint strength, Ag addition and Bi addition had no detrimental effect on the strength of the solder joints. In particular, the joint with the Ag addition solder had the better strength in the case of thinner solder layer. Thus, as for lead plating for the SZB solder, Sn–Pb should be avoided and Sn–Bi or Sn–Ag as Pb-free plating has no detrimental effect on the joint strength. In particular, Sn–Ag plating is preferable in the viewpoint of the joint strength.

Near-field coupling between a silicon quantum dot (Si-QD) monolayer and a plasmonic substrate fabricated by nano-imprint lithography and having broad multiple resonances in the near-infrared (NIR) window of biological substances was studied by precisely controlling the QDs-substrate distance. A strong enhancement of the NIR photoluminescence (PL) of Si-QDs was observed. Detailed analyses of the PL and PL excitation spectra, the PL decay dynamics, and the reflectance spectra revealed that both the excitation cross-sections and the emission rates are enhanced by the surface plasmon resonances, thanks to the broad multiple resonances of the plasmonic substrate, and that the relative contribution of the two enhancement processes depends strongly on the excitation wavelength. Under excitation by short wavelength photons (405 nm), where enhancement of the excitation cross-section is not expected, the maximum enhancement was obtained when the QDs-substrate distance was around 30 nm. On the other hand, under long wavelength excitation (641 nm), where strong excitation cross-section enhancement is expected, the largest enhancement was obtained when the distance was minimum (around 1 nm). The achievement of efficient excitation of NIR luminescence of Si-QDs by long wavelength photons paves the way for the development of Si-QD-based fluorescence bio-sensing devices with a high bound-to-free ratio.

A 1mm-pitch 80×80-channel 322Hz-frame-rate touch sensor is reported. Multiple touch points are detected by a two-step dual-mode capacitance scan, where self- and mutual-capacitance measurements are hierarchically performed in two steps to reduce scan time that is otherwise increased due to high resolution. 160 dedicated row and column ADCs are used for the parallel read-out to further reduce scan time. A time-domain digital conversion that uses a counter-based slope ADC significantly reduces power and area for the parallel ADC approach. The signal attenuation due to the sensor capacitance reduction in the 1mm fine-pitch electrode is compensated by using thorough noise-reduction techniques in the sensor analog front-end (AFE). A 0.35μm CMOS prototype demonstrates 41dB SNR with >3× higher pitch resolution, >10× faster touch-point scan, 12× and 4× higher energy and area efficiency compared to state-of-the-art touch sensors [1,2].

Nanoimprinting followed by metal deposition is a low-cost, high-throughput, and highly reproducible process for the fabrication of large-size plasmonic substrates required for commercial products. However, the plasmonic substrates prepared by the process usually have very broad surface plasmon resonances, which cannot be well reproduced by numerical simulations. The poor agreement between experiments and calculations has prevented the detailed analysis of the field enhancement behavior and the improvement of the performance as plasmonic substrates. In this work, we demonstrate that large-area plasmonic substrates with sharp surface plasmon resonances, which can be well reproduced by numerical simulations, are produced by sputter-deposition of gold (Au) on a commercially available nanoimprinted substrate. The good agreement between experiments and simulations allow us to identify the locations and field distributions of the hot spots. The angle dependence of specular reflectance and diffuse reflectance measurements in combination with numerical simulations reveal that a dipolelike bright mode and a higher-order dark mode exist at gaps between Au nanorods. Finally, we demonstrate the application of the developed plasmonic substrates for surface-enhanced fluorescence in sandwich immunoassays for the detection of influenza virus nucleoprotein. We show that the sharp resonance and the capability of precise tuning of the resonance wavelength significantly enhance the luminescence signal.