Ultra-thin high-density LSI packaging substrate for advanced CSPs and SiPs

An ultra-thin high-density LSI packaging substrate, called multi-layer thin substrate (MLTS), is described. It meets the demand for chip scale packages (CSPs) and systems in a package (SiPs) for use in recently developed small portable applications with multiple functions. A high-density build-up structure is fabricated on a Cu plate, which is then removed, leaving only an ultra-thin, high-density multi-layer substrate. MLTS has (1) excellent registration accuracy, which enables higher density and finer pitch patterning due to the use of a rigid, excellent-flatness Cu base plate; (2) a thinner multi-layer structure due to the use of a core-less multi-layer structure; (3) excellent reliability, supported by the use of an aramid-reinforced epoxy resin dielectric layer; and (4) a cost-effective design due to the use of fewer layers fabricated using a conventional build-up process. A prototype high-density CSP (0.4-mm pitch/288 pins/4 rows/10 mm²) was fabricated using a 90-μm-thick MLTS (with a solder resist layer). Testing demonstrated that it had excellent long-term reliability. A prototype ultra-thin, high-density SiP (0.5-mm pitch/225 pins/11 mm²/0.93 mm thick) was also fabricated based on MLTS. MLTS consists of only two conductor layers (total thickness: 90 μm) while an identical-function build-up printed wiring board needs four conductor layers (total thickness: 300 μm). With its thinner core-less multi-layer structure, MLTS enables the fabrication of ultra-thin, high-density SiPs.     

Transmission Characteristics of Hybrid Modes in Corrugated Waveguides Above the Bragg Frequency

We studied the transmission characteristics of hybrid modes in a corrugated circular waveguide above the Bragg frequency to develop a broad-band transmission line for millimeter waves. Millimeter waves at 294 GHz were transmitted into a straight waveguide. From observed power profiles in waveguide cross-sections, a high attenuation rate of 0.13 dB/m was obtained. To match a theoretical attenuation constant with the experimental one, we introduced an ad hoc coefficient of conventional surface reactance in the waveguide wall. This was necessary because the wall began to look like the surface with a decreasing anisotropic reactance owing to the frequency above the Bragg frequency. Using nonlinear optimization for mode content analysis, the observed power profiles in the waveguide cross-section were matched with theoretical profiles. There was good agreement between the calculated and observed centers of power profiles and attenuation rate along the waveguide. The theoretical analysis showed that the magnetic field at the waveguide wall increases and the substantial attenuation takes place. Above the Bragg frequency coupling to backwards propagating modes is a point of consideration. A combination of the backwards propagating EH_1,26 and the forward propagating HE₁₁ modes satisfied the Bragg condition at 294.7 GHz which was the nearest frequency of operating frequency. A strong attenuation of the incoming HE₁₁ mode by Bragg resonance was not expected due to large difference of 0.7 GHz. It becomes clear that the observed high transmission loss outside of the Bragg resonance can be explained by a decrease in anisotropic surface reactance at the wall.     

Video based estimation of pedestrian walking direction for pedestrian protection system

Pedestrian protection has played an important role for driver assistance systems. Our aim is to develop a video based driver assistance system for the detection of the potentially dangerous situation between the vehicle and pedestrian, in order to warn the driver. In this paper, we address the problem of detecting pedestrian in real-world scenes and estimation of the walking direction with a single camera from a moving vehicle. Considering all the available cues for predicting the possibility of collision is very important. The direction in which the pedestrian is facing is one of the most important cues predicting where the pedestrian may move in the future. So we first address the problem of single-frame pedestrian orientation estimation in real-world scenes. Then again, we estimate the pedestrian walking direction using multi-frame based on the result of single-frame orientation estimation. We propose a three-step method: pedestrian detection for single-frame step, orientation estimation for single-frame step and walking direction estimation for multi-frame step. To evaluate the proposed method in its robustness and accuracy, the experiments have been performed between numbers of images which is highly challenging uncontrolled conditions in real world. It shows a significant performance improvement in octant orientation estimation of about 64% accuracy in the orientation estimation step and achieved surprisingly good accuracy in estimating the walking direction against 212 targeted objects.     

Colored Fluorescent Silk Made by Transgenic Silkworms

Silk is a protein fiber used to weave fabrics and as a biomaterial in medical applications. Recently, genetically modified silks have been produced from transgenic silkworms. In the present study, transgenic silkworms for the mass production of three colors of fluorescent silks, (green, red, and orange) are generated using a vector originating from the fibroin H chain gene and a classical breeding method. The suitability of the recombinant silks for making fabrics is investigated by harvesting large amounts of the cocoons, obtained from rearing over 20 thousand silkworms. The application of low temperature and a weakly alkaline solution for cooking and reeling enables the production of silk fiber without loss of color. The maximum strain tolerated and Young's modulus of the fluorescent silks are similar to those of ordinary silk, although the maximum stress value of the recombinant silk is slightly lower than that of the control. Fabrics with fluorescent color are demonstrated using the recombinant silk, with the color persisting for over two years. The results indicate that large amounts of genetically modified silk can be made by transgenic silkworms, and the silk is applicable as functional silk fiber for making fabrics and for use in medical applications.     

Direct Growth of Germanene at Interfaces between Van der Waals Materials and Ag(111)

Germanene, a 2D honeycomb germanium crystal, is grown at graphene/Ag(111) and hexagonal boron nitride (h-BN)/Ag(111) interfaces by segregating germanium atoms. A simple annealing process in N₂ or H₂/Ar at ambient pressure leads to the formation of germanene, indicating that an ultrahigh-vacuum condition is not necessary. The grown germanene is stable in air and uniform over the entire area covered with a van der Waals (vdW) material. As an important finding, it is necessary to use a vdW material as a cap layer for the present germanene growth method since the use of an Al₂O₃ cap layer results in no germanene formation. The present study also proves that Raman spectroscopy in air is a powerful tool for characterizing germanene at the interfaces, which is concluded by multiple analyses including first-principles density functional theory calculations. The direct growth of h-BN-capped germanene on Ag(111), which is demonstrated in the present study, is considered to be a promising technique for the fabrication of future germanene-based electronic devices.     

Production technology of large-area multicrystalline silicon solar cells

In 1996 a conversion efficiency of 17.1% had been obtained on 15 cm×15 cm mc-Si solar cell. In this paper, large-scale production technology of the high-efficiency processing will be discussed. Enlarging reactive ion etching (RIE) equipment size, technology of passivation, and fine contact grid with low resistance by screenprinted metallization, which is firing through PECVD SiN, have been investigated.     

Fabrication by Coaxial-Type Vacuum Arc Evaporation Method and Characterization of Bismuth Telluride Thin Films

We prepared both n- and p-type bismuth telluride thin films by using a coaxial-type vacuum arc evaporation method. The atomic compositions of the as-grown thin films and several annealed thin films were comparable to that of bulk bismuth telluride. Their thermoelectric properties were measured and found to be comparable to those of bulk materials. The Seebeck coefficient and electrical conductivity of the as-grown thin films were improved by the annealing process. The measured figures of merit (ZT) of the films were 0.86 for the n-type and 0.41 for the p-type at 300 K for annealing temperatures of 573 K and 523 K, respectively.     

All solid-state battery with sulfur electrode and thio-LISICON electrolyte

A high-capacity type of all solid-state battery was developed using sulfur electrode and the thio-LISICON electrolyte. New nano-composite of sulfur and acetylene black (AB) with an average particle size of 1–10 nm was fabricated by gas-phase mixing and showed a reversible capacity of 900 mAh g⁻¹ at a current density of 0.013 mA cm⁻².     

Enhanced Hole‐Transporting Behavior of Discotic Liquid‐Crystalline Physical Gels

Discotic liquid‐crystalline (LC) physical gels have been prepared by combining the self‐assembled fibers of a low‐molecular‐weight gelator and semiconducting LC triphenylene derivatives. The hole mobilities of the discotic LC physical gels measured by a time‐of‐flight method become higher than those of LC triphenylenes alone. The introduction of the finely dispersed networks of the gelator in the hexagonal columnar phases may affect the molecular dynamics of the liquid crystals, resulting in the enhancement of hole transporting behavior in the LC gel state.