Sintering bonding using metal nanoparticles is considered a promising die-attach technique for high-temperature operating power devices, such as SiC. However, the thermal stress produced by the difference in coefficient of thermal expansion (CTE) between the chip and substrate, often affects the reliability of this technique. To address this limitation, we analyzed a sintering bonding using Ni nanoparticles and Al microparticles composite paste. The results revealed that the Al microparticles significantly reduced the voids and cracks in the bonding layer formed by Ni nanoparticles paste. Three chips with different sizes were bonded to Cu substrates, and the bonding strength was measured. The result revealed that the bonding strengths in the samples were higher than those of the samples bonded using conventional metal nanoparticles. In addition, the fracture observation after the shear test revealed that the Al particles suffered plastic deformation. Furthermore, the high-temperature storage test at 250°C confirmed the long-term bonding reliability.

In order to obtain ideal low Dk/Df film for 5G application, we have developed novel isotropic low Dk/Df film. Our newly modified PPE was soluble to organic solvents and crosslinked after curing. By formulating this new polymer and other components such as sillica filler, we have developed novel isotropic thermosetting film with low Dk/Df, high Tg, low CTE, low water absorption, high peel strength and HAST, which was supposed to be suitable film as substrate and interlayer insulating film for 5G packaging application.

Syndiotactic Polystyrene (SPS) has excellent electrical properties. So it has been strongly expected SPS to apply for Copper Clad Laminate (CCL) for high frequency use. We conducted to fabricate the CCLs using SPS films and electrolysis copper foils by using vacuum lamination process and considered the anchoring effects from mechanical properties of SPS film, copper foil's surface morphologies and XPS analysis. In addition, we examined total line losses for micro-striplines. It was defined that the sufficient anchoring effect resulted from softening of SPS film over Tg and the peel strength depended on the fine nodule shape and the existent of silicon atoms on the copper foil matte surfaces. And it was observed that the correlation between the losses and the size of nodules on them. We specified the suitable electrolysis copper foil for CCLs using SPS films for the high frequency use, which showed both sufficient bond strength and low electrical loss.

We propose silicon (Si)-photonics-embedded interposers as a novel packaging platform to achieve co-packaged optics. An interposer is an organic substrate that has Si-photonics transceiver dies buried in it and polymer optical waveguides connecting the embedded Si chips and optical connectors. We also developed a Si-photonics-device-embedding process and investigated the properties and operations of embedded Si-photonics devices as a feasibility study. The embedded arrayed waveguide grating and reflective optical filter showed a wavelength shift on the order of 0.1 nm with our embedding process. The shifts seem to be due to the difference in ambient temperature during the measurements and induced strain. Though this embedding process is presumed to affect the spectrum for Si-photonics devices, the difference is small enough to be controlled. Embedded Si-photonics transmitter- and receiver-integrated circuits successfully demonstrated 25-Gb/s operations. The proposed Si-photonics-embedded interposer is a promising candidate for a co-packaged optics platform to eliminate the interconnect bandwidth bottleneck for high-performance computing systems.

Non-destructive two- and three-dimensional neutron imaging was conducted for evaluation of small internal structure in the power module with double-sided cupper heat spreaders under thermal fatigue cycles. Although two-dimensional radiography could not visualize small internal structures, three-dimensional laminography was capable of the visualization. As an application, the commercially available power module was measured by neutron laminography before and after thermal fatigue. It was non-destructively found that the power module was free of degradation at least in the size of 100 µm for 1,000 cycles under this fatigue condition.

The super Pioneering High-Energy Nuclear Interaction eXperiment (sPHENIX), which aims to unravel the mysteries of the creation of the universe, is scheduled to be launched in 2023 at Brookhaven National Laboratory, U.S.A, using the relativistic heavy ion collider. As a typical high-energy particle accelerator-based experiment, the collision area of sPHENIX is to be tightly occupied with various radiation detectors, requiring a minimal special budget to run cables and transmit massive signals generated by these detectors to downstream electronics for data processing located in a remote distance. Accordingly, a long, high signal line-density cable has been developed based on the flexible printed circuit (FPC) technology. FPC comprises multilayers and has extraordinarily long and thin transmission lines. Liquid crystal polymer was employed to suppress losses in transmission lines. Electrical characteristics were evaluated using S-parameters, time domain reflectometry, and eye-diagrams. Furthermore, we have developed manufacturing technology to achieve high-precision microfabrication and improved reliability, which has been demonstrated in peel strength and thermal shock tests. FPC is currently in the mass production phase.

In this study, we developed a novel tissue-engineered oral mucosa with micropatterned fish scale collagen as a biomaterial scaffold. Marine collagen derived from the fish scale is considered to have a significant potential of becoming an alternative transplant material for mucosa regeneration due to its vast resources and minimal risk of transmitting infectious diseases. Eight different types of Grid-Rectangular (GR) negative patterns were manufactured using microelectromechanical systems technologies to evaluate size dependency in collagen replication and epithelial cell layer formation. Among the obtained histological images of the tissue-engineered oral mucosa, the height, width, and channel width of 100 μm showed the most successful formation of the epithelial layer and the most similar structure of oral mucosa in vivo. This study not only established a technique for fabricating a novel biomimetic scaffold but also made an extended approach to structural optimization for mold fabrication. We believe this study will be a crucial step for structural optimization in the future and will have a positive impact on the field of tissue regeneration.

Using the formic-acid type etching solution, when carrying out a spray etching, impedance measurement has been performed for the investigation about the etching process. If the flow rate of spray solution has been set adequately and under stabilization of the status of the patterned copper substrate with a watch-glass placed under a substrate, the impedance measurement data could be obtained without having noise. We could differentiate the equivalent circuit between spray etching and dip etching as reference. Furthermore, we have been able to prove that the Nyquist plot overview under spray etching was different from that under dip etching. We have succeeded in obtaining the impedance data under spray etching first in the world.

This paper describes a gamma-matched textile rectenna structure that is suitable for batteryless wearable accessories powered by microwaves using a conductive-yarn antenna. The proposed structure consists of a slidable button-shaped rectifier module with LED that allows the antenna to pass through its metal holes, thus making it possible to connect a soft textile antenna with a hard rectifier module to easily perform impedance matching by sliding the module on the antenna, while watching luminance of the LED light. To verify the effectiveness of our textile rectenna structure, we fabricated a button-shaped rectifier module 7.5 mm in diameter including an LED and a 6-cm-long bundled conductive-yarn antenna consisting of 0.5-mm-thick single yarns. The experimental results showed that, for 2.45-GHz wireless power transmission with an average transmitted power of 1 W, the LED on the rectifier module blinked while dissipating power of 0.355 mW at a distance of 70 cm from the wireless transmitter. We also fabricated a friendship bracelet and a pair of embroidered socks equipped with our rectenna as LED textile accessories.

Dielectric-metal-dielectric (DMD) films exhibit high optical transmittance and conductivity. In recent years, the application of these DMD materials to antennas has been actively investigated. However, the radiation efficiency of these antennas is less than 70%, so their performance as antennas remains a challenge. This study investigated the optical and electrical properties of indium tin oxide (ITO)/Ag/ITO, and a basic structural monopole antenna was fabricated and measured. As a result, the optical transmittance of 76.7% and radiation efficiency of 81.4% were achieved by using ITO (300 nm)/Ag (5 nm)/ITO (30 nm) as the DMD film. In particular, the obtained radiation efficiency was higher than that of small antennas built into standard mobile and wearable devices, which have excellent characteristics, practicality, and usefulness.

In this short note, we present a compact triplexer for the GPS, 2.4-GHz wireless systems, and the 5-GHz WLAN. This triplexer consists of chip filters, capacitors, and inductors on a printed circuit board. It is based on L-type matching networks. The design area of the prototype is less than 8 × 7 mm². Insertion losses are less than 1.9 dB, 2.7 dB, and 1.8 dB in each passband. The prototype also achieves high attenuation performances with sharp roll-off characteristics. The isolations are higher than 30 dB in each band.

Current advancements required for thermal management technology in semiconductors and electronic devices for systems are quantitatively investigated and analyzed based on statistical text analysis of patents and relevant literature. As aluminum-nitride and boron-nitride fillers exhibit excellent thermally conductive properties for resins, thermal management involving these materials can improve the performance and reliability of future semiconductor devices. Some required specifications such as thermal conductivity in the marketplace are estimated and discussed from a systems perspective.