Search

Silicon interposer (Si-IP) technology has been used in accelerated processing units such as graphic processing units in high-performance computing because it can package a system-on-chip and high bandwidth memories. However, the conventional Si-IP has difficulty developing larger packages because of the mismatch in the coefficient thermal expansions (CTE) of the Si-IP and the organic substrate. Therefore, the Si-IP has limited capacity for improving computing performance by the application which requires more chips. We developed a multilayer glass substrate (Glass-ST) that features a stacked glass core and propose to apply this Glass-ST to a computer board. The proposed structure has no CTE mismatch and can use high density wiring. Thus, the Glass-ST enables the assembly of more large chips than is possible using the conventional Si-IP. In this study, we prepared a 100X100 mm Glass-ST with a 5/5 µm line/space and 20 µmΦ vias. We mounted nine 21X21 mm chips with 40 µm pitch micro bumps. The results revealed that conformal plated through glass vias and a fine wiring pattern had been fabricated in the Glass-ST, and that the nine chips and Glass-ST were connected by micro bumps. The maximum warpage of the nine chips was 23 µm between temperatures of 30°C and 250°C. This means that the Glass-ST can mount chips with micro bumps due to the very slight resulting warpage. In addition, we performed thermomechanical simulation to investigate the stress experienced by the micro bumps. The results show that the maximum stresses of micro bumps with pitches ranging between 10 µm and 55 um are very similar to that of 40 µm pitch micro bumps with which the real sample was packaged. We believe the improvements in the computing performance are significant by the Glass-ST technology compared to that of the conventional Si-IP technology.

We developed a millimeter-wave (MMW) exposure system for in vivo experiments for operating frequencies ranging from 24.5 to 95 GHz. The MMWs are localized to the rabbit ocular tissue with a spot-focus lens antenna. The MMW energy absorption and consequent temperature elevation are evaluated by numerical simulation using measured antenna distribution and precisely modeled rabbit ocular data. Results suggest that corneal damage occurs at an incident power density of 300 ${\hbox{mW/cm}}^{2}$ with our exposure system at frequencies from 26.5 to 95 GHz.

This study proposes a temperature compensation method of the complex permittivities of biological tissues and organs. The method is based on the temperature dependence of the Debye model of water, which has been thoroughly investigated. This method was applied to measured data at room temperature for whole blood, kidney cortex, bile, liver, and heart muscle. It is shown that our method can compensate for the Cole-Cole model using measured data at 20 ℃, given the Cole-Cole model based on measured data at 35 ℃, with a root-mean-squared deviation of 3～11 % and 2～6 % for the real and imaginary parts of the complex permittivities, respectively, among the measured tissues.

The ellipsometry method is well known as one of methods to measure a refractive index in optical region. This method is extended to a measurement for complex permittivities of materials at a millimeter-wave frequency. This method has little limitation on a sample size because of the free space method. The uncertainty on the measurement of phases in reflection doesn’t occur because this method is based on a scalar measurement. But a large uncertainty due to a free-space method was realized. Only 2nd order Fourier coefficients are obtained in an ideal case. But measured data contained higher order coefficients up to the 6th, because all reflected electromagnetic power could not be received by a horn antenna. We propose an effective method to extract Fourier coefficients only corresponding to ellipsometry parameters. Complex permittivitie of a lossy material in millimeter-wave region can be measured in high accuracy by the improved ellipsometry method.

In this paper, a large 2.5D glass interposer is demonstrated with 50 um chip-level interconnect (FLI), 3/3 um line and space (L/S) escape routing, and six metal layers, which are targeted for JEDEC high bandwidth memory (HBM). Our routing design suggests that double sided panel processing with 3/3 um L/S can accommodate required signal lines for HBM. Then, 3/3 um L/S transmission lines on 25mm × 30mm glass interposers with 300 um core thickness can be realized by utilizing semi additive process. Finally, 10mm × 10m dies with daisy chains can be successfully bonded to 25mm × 30mm glass interposer with 6 metal lines using copper microbumps with SnAg solder caps.

Low pressure axial flow fans without stator blades or guide vanes are generally used in order to achieve light weight, low cost and a simple structure, and to conserve space when mounted for automobile cooling system. However, since flow resistances in front and back of the fan are very strong, air tends to flow diagonally at the fan outlet side. The fan does not operate as an axial flow fan. In this report, we describe work conducted on a motor fan, mainly from the standpoint that analysis and improved understanding of actual air flow conditions lead to improved design. As for the measurement of air flow at the outlet and inlet side of the fan, the five hole-pitot tubes were used. And the reverse flow area was visualized to adhere tracer particles which are in the air flow to the pressure surface of the blades. As a result, we could predict the air flow among fan blades and portion and shape of the reverse flow area. These data were useful for designing the mixed flow fan which has the structure of an axial flow fan.

The experiment exposing the millimeter-wave (MMWs) is performed to investigate the relation between the temperature elevation at the ocular tissue and MMW exposure. The temperature and velocity distributions in front part of the eye are simultaneously measured by using Micro-Encapsulated Thermo-chromic Liquid Crystal and Fluoroptic Thermometer. It is found that the flowing patterns of aqueous humor depend on the incident power density, and these patterns affect the heat transport mechanism.

The acute ocular injury threshold of 76 GHz band millimeter wave (MMW) exposure was investigated using an in vivo rabbit model. Pigmented rabbits were exposed unilaterally to 200, 100, 75, 50, 10 mW/cm2 76 GHz band MMW for 6 min with a lens antenna. Corneal opacity, epithelial injury, miosis, and ocular inflammation were present up to 2–3 days after exposure at a dose of 200 mW/cm2. No ocular changes other than reversible corneal epithelial injury were seen following exposure at 100 and 75 mW/cm2. There were no ocular changes after exposure at doses of 50 or 10 mW/cm2. Six-minute exposure to 76 GHz 10 mW/cm2 did not induce any detectable ocular tissue damage.

The ellipsometry method is extended to a measurement for complex permittivities; of materials in millimeter-wave region. We propose an effective technique based on the Fourier analysis method to eliminate an uncertainty due to the free-space method. Complex permittivities can be measured with a high degree of accuracy by the improved ellipsometry method, as named Fourier Analysis Correction Ellipsometry (FACE) Method.