This paper presents a novel encapsulation resin that can relieve the impact of electrostatic discharge (ESD) on electronic devices. The encapsulation resin employs ZnO-based ceramic varistor ...particles instead of SiO 2 fillers. It shows a typical voltage-dependent resistance (VDR) property, i.e., steep resistance drop with the rise of applied voltage. To adopt the resin (hereinafter referred to as the VDR resin) as an ESD-suppressing material, the VDR resin itself has to possess sufficiently strong ESD immunity. Prior to improvement, the VDR resin brought about short-circuit failure in the case that the human-body model (HBM) ESD of 4 kV or more was applied. Cross-sectional analysis indicated it was caused by delamination and damaged layer at the interface between matrix polymer and varistor particle. The matrix polymer's dielectric constant showed strong dependence on ESD immunity of VDR resin, i.e., the lower the better. The optimized VDR resin had an excellent VDR property, ESD immunity, and reliability. The ability of the optimized VDR resin to protect electronic devices, namely, CSP-LEDs, from ESD was demonstrated.
We proposed a novel wafer level chip scale package in which Laser Lift Off (LLO) was adopted for substrate removal. We confirmed that the LLO did not cause both mechanical and thermal damages into ...GaN layer.
An optoelectronic interconnection module for mobile devices is required to have not only optical interconnection for high-speed and noise-free signal transmission but also many electrical wirings for ...multiple power supplies and low-speed signal transmission. It leads to great challenges of cost increase, flexibility degradation and electromagnetic noise emission. We propose a novel optoelectronic interconnection module for mobile devices in this paper. A hybrid configuration of an optoelectronic flexible printed circuit (OE-FPC) and an electrical FPC enables to minimize the cost, and a multi-fin structure fabricated by splitting the interconnection area realizes 3D flexibility which is not feasible with a conventional FPC. Magnetic near-field intensities of the optoelectronic interconnection module for mobile devices are shown for the first time. An ultralow-power and ultralow electromagnetic interference (EMI) optical signal transmission performance is demonstrated. It proves that the module developed in this work is highly promising for mobile devices in which signal integrity and EMI are growing into serious problems.
Reduction of cost has become the most important challenge for solid state lighting. We proposed a novel Wafer-Level LED Packaging (WL2P) technology, which enables both extremely low cost and small ...size for future solid state lighting. Where a conventional package needs individual assembly steps, resulting in high fabrication cost, we carried out from growth of the GaN layer, over formation of Inter Layer Dielectric (ILD), wiring for solder pad to printing the phosphor layer on a whole wafer in our WL2P. Thus, for the first time a fully integrated wafer-level process was successfully applied to light emitting diode (LED) devices. It was clearly demonstrated that our WL2P has an excellent thermal resistance as low as 24.2K/W in the 0.6×0.3mm size prototype structure because of the direct connection of Cu wiring to the light emitting layer and a maximum injection power density was as high as 1157W/cm 2 in a difference of 50°C between junction temperature and ambient temperature on the aluminum based printed wiring board (PCB)
Actuators used in RF-MEMS tunable capacitors have an issue of creep-induced deformation. The creep is caused by a ductile-metal beam which is indispensable to attain the low loss. To avoid this ...issue, we previously reported an actuator structure that uses a brittle material, silicon nitride (SiN), at the stress-concentrated spring portions. The present paper aims to clarify a long-term creep immunity of the actuator. We first determined parameters of Norton's law by measurements and then carried out Finite Element Method (FEM) simulations. As a result, we found that the shift of the up-state capacitance is 2.2% after keeping the actuator in down-state position for 3 years at 85°C.
In this paper, we report in-line wafer level hermetic packages (WLP) for MEMS variable capacitors. The beam structure of MEMS vibrates strongly under decompression. Since this vibration causes RF ...noise, it is necessary to set the pressure around the beam structure at 40000Pa or greater. Therefore, a structure that carries out a resin seal of the hole for etching the cap of a formed in the sacrificial layer process, at atmospheric pressure (101300Pa) is crucial for what. To prevent moisture permeation inside a cap, the resin was coated with a PECVD SiN layer. The developed packages become a hybrid hermetic encapsulation, which consists of PECVD SiN layers. Moreover, the deformation of the cap by external pressure was reduced using a corrugated cap. The developed package is comparatively large (340 times 1100 mum). Nevertheless, after the 265degC reflow test (5 times) and -55degC/125degC thermal cycle test (20 cycles), no cracks were observed in the packages. Since all of such processes and materials are compatible with the CMOS process, this package has very low cost. We present a summary of several aspects of our development activities in this MEMS variable capacitor packaging technology.
Novel wafer-level chip scale package (WL-CSP) applicable to configurations involving stacking of multiple dies has been developed. Since stacked die makes high topography and it is difficult to apply ...conventional WL-CSP process, gold bonding wires were used for not only connecting stacked dies with one another but also for connecting from each die to CSP terminals. The WL-CSP is also applicable to microelecrromechanical system (MEMS) that requires hermetic sealing. Thin-film encapsulation for MEMS was formed by conventional back end of line (BEOL) process. Followed by die stacking and gold wire forming, chemical vapor deposition (CVD) was applied to make hermetic sealing. The WL-CSP does not require photolithography process on topography wafer. It promises a cost-effective solution for MEMS/IC dies coupled device.
Ionic liquids, known as non-volatile solvents, have potential for realizing microanalysis with a minute quantity of sample. Here, in this paper, we report the measurement of the <inline-formula> ...<tex-math notation="LaTeX">\text{I}_{\mathrm {d}} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">\text{V}_{\mathrm {g}} </tex-math></inline-formula> characteristics during the enzymatic catalytic reactions and streptavidin-biotin binding in ionic liquids by using the graphene FET sensors we fabricated, and successfully monitored the biological reactions in much smaller amount of solvents. These findings suggest the possibility of ionic liquids for application in bio-microanalysis with high sensitivity.
We aimed to evaluate the additional debulking efficacy of low-speed rotational atherectomy (RA) after high-speed RA by using intravascular imaging. A total of 22 severe calcified coronary lesions in ...19 patients (age, 74 ± 10 years; 74% male) were retrospectively analyzed. All of these lesions underwent RA under optical coherence tomography (OCT) or optical frequency domain imaging (OFDI) guidance. At first, we performed high-speed RA with 220,000 rpm until the reduction of rotational speed disappeared; then, low-speed RA with 120,000 rpm using the same burr size was performed. OCT or OFDI was performed after both high-speed and low-speed RAs, and the minimum lumen area were compared. The initial and final burr sizes of high-speed RA were 1.5 (1.5–1.75) and 1.75 (1.5–2.0) mm, respectively. The number of sessions, total duration time, and maximum decreased rotational speed during high-speed RA were 11 ± 5 times, 113 ± 47 s, and 4000 (3000–5000) rpm, respectively. During low-speed RA, the number of sessions, total duration time, and maximum reduction of rotational speed were 3 ± 1 times, 32 ± 11 s, and 1000 (0–2000) rpm, respectively. The minimum lumen area was similar between after high-speed and after low-speed RA 2.61 ± 1.03 mm
2
(after high-speed RA) vs. 2.65 ± 1.00 mm
2
(after low-speed RA); P = 0.91. Additional low-speed RA immediately after sufficient debulking by high-speed RA was not associated with increased lumen enlargement. There was no clinical efficacy of low-speed RA after high-speed RA.
