A copper/polyimide Metal-base packaging technology

A unique substrate MCPM (Mitsubishi Copper Polyimide Metal-base) technology has been developed by applying our basic copper/polyimide technology.¹ This new substrate technology MCPM is suited for a high-density, multi-layer, multi-chip, high-power module/package, such as used for a computer. The new MCPM was processed using a copper metal base (110 × 110 mm), full copper system (all layers) with 50-μm fine lines. As for pad metallizations for the IC assembly, we evaluated both Ni/Au for chip and wire ICs and solder for TAB ICs. The total number of assembled ICs is 25. To improve the thermal dispersion, copper thermal vias are simultaneously formed by electro-plating. This thermal via is located between the IC chip and copper metal base, and promotes heat dispersion. We employed one large thermal via (4.5 mm^?) and four small vias (1.0 mm^?) for each IC pad. The effect of thermal vias and/or base metal is simulated by a computer analysis and compared with an alumina base substrate. The results show that the thermal vias are effective at lowering the temperature difference between the IC and base substrate, and also lowering the temperature rise of the IC chip. We also evaluated the substrate’s reliability by adhesion test, pressure cooker test, etc.     

An advanced laser application for controlling of electric resistivity of thick film resistors

When electric resistivity of Thick Film Resistor (TFR) is adjusted to the desired value, laser beam is irradiated onto the resistor material so that a part of the resistor material is instantaneously vaporized and cut away. This conventional laser trimming method to adjust the resistivity of TFRs is an indispensable technique for manufacturing elec-tronic devices such as hybrid ICs. A peculiar phenomena was revealed by us, that is, when specially selected pulse laser beams were irradiated to TFR, the TFR was surface modified without cutting grooves, and then resistivity of the TFR was decreased. We completed the advanced laser process to apply this peculiar phenomena. 8 By comparing with conventional trimming processes, we can show prominent features of the advanced process, for example, resistivity of fine size TFR (300 micrometers-width and under) can be easily controlled. The decrease in resistivity of the TFR is considered to result from the decrease in specific resistivity of glass in the TFR. Because it is considered that the glass in the TFR is heavily doped with ruthenium impurities during the surface modification due to results of morphology observations and x-ray diffraction analysis. We have applied this advanced laser process to fine size TFR (300 micrometers-width), and developed high density hybrid ICs.     

Conducting polypyrrole composite thin films chemically prepared by spreading on surface of aqueous solution containing oxidizing agent

Polypyrrole–PMMA composite films have been prepared with the chemical oxidative polymerization by spreading the water-insoluble solvent solution of pyrrole and PMMA mixture on the surface of the aqueous solution containing K₂S₂O₈, the oxidizing agent. The conductivity of the films increases rapidly, passes through a plateau, and then decreases gradually as the reaction time increases. The conductivity of the oxidized side of the film is higher by over 1 order of magnitude than that of the evaporated side. It is due to the fact that the former is rich in polypyrrole while the latter is rich in PMMA. The thickness of the films can be controlled by adjusting the PMMA concentration. However, the lower limit of the film thickness is practically in submicron order. The relationship between the transmittance and the logarithm of the conductivity of the films gives a straight line with a gradient, ca. −8. The conductivity of the films is stable on silicagels in a desiccator over 2000 h at 25°C. The conductivity of the film is, however, very sensitive to the moisture in atmosphere and gives rise to decrease with humidity.     

Ductility and strain-induced transformation in a high-strength transformation-induced plasticity-aided dual-phase steel

The influence of forming temperature and strain rate on the ductility and strain-induced transformation behavior of retained austenite in a ferritic 0.4C-1.5Si-1.5Mn (wt pct) dual-phase steel containing fine retained austenite islands of about 15 vol pct has been investigated. Ex- cellent combinations of total elongations (TELs), about 48 pct, and tensile strength (TS), about 1000 MPa, were obtained at temperatures between 100 °C and 200 °C and at a strain rate of 2.8 X 10_-4/s. Under these optimum forming conditions, the flow curves were characterized by intensive serrations and increased strain-hardening rate over a large strain range. The retained austenite islands were mechanically the most stable at temperatures between 100 °C and 200 °C, and the retained austenite stability appeared to be mainly controlled by strain-induced martensite and bainite transformations (SIMT and SIBT, respectively), with deformation twinning occur- ring in the retained austenite. The enhanced TEL and forming temperature dependence of TEL were primarily connected with both the strain-induced transformation behavior and retained aus- tenite stability.     

Effects of applied potentials on permselectivity of ions through polypyrrole/porous-polypropylene composite membrane

A composite membrane was prepared by the combination of polypyrrole with a porous-polypropylene film, and its permselectivity was investigated. The permeability and selectivity of various sodium salts through the membrane were changed with an applied potential. The permeation of anions at the positive potentials was due to the migration through the positive sites of the polypyrrole layer, as well as the diffusion from the difference of concentration and potential. The contribution of the migration effect to the anion permeation was very large. The main factors dominating the permeation character of different anion species were the size and valence of the anions. The composite membrane worked effectively as a functional separation membrane to control the ionic permeability by potential application. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 647–653, 1998     

Experiments on bubble behavior in a horizontal narrow divergent passage

This paper investigates a bubble, placed so that it bridges the cross section of a horizontal narrow divergent passage under Earth gravity (1-G). In a narrow passage, inertial forces are known to be small in comparison with viscous forces. Gravitational force is not dominant in bubble behavior in a horizontal narrow passage under the 1-G condition. In this sense, the bubble behavior in the passage is similar to that under a low-gravity condition. Understanding bubble behavior is important in relation to separating a gas from a two-phase gas-liquid flow and controlling a gas-liquid interface under low-gravity conditions. Thus, a single bubble is placed under the 1-G condition. The bubble geometry and its behavior are studied experimentally for gap sizes ranging from 0.5 mm to 2 mm and divergent angles from 1° to 5° using ethyl alcohol as the working fluid. The following results were obtained: (1) the bubble was found to move to the greater cross-sectional area; (2) the gas-liquid interface geometry in a top view can be expressed as a contact circle model that takes the maximum radius in the passage; and (3) the effects of gap size and the projected bubble area on bubble behavior are clarified. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(6): 447–461, 1998     

Preparation of TiO2 thin films using octadecylamine Langmuir-Blodgett films and evaluation of their photocatalytic activity

A study was conducted to demonstrate that nanometer-thick titanium dioxide (TiO(2)) thin films could be prepared by the hydrolysis of titanium potassium oxalate using octadecylamine (ODA) Langmuir-Blodgett (LB) films as templates. The amount of TiO(2) generated in the LB film was found to be proportional to the number of deposited ODA layers, which enables precise control of the TiO(2) film thickness. After heat treatment of the LB films at 300-600°C, the photocatalytic activities of the resulting TiO(2) films were determined from the decomposition of stearic acid cast films when irradiated with UV light for different time periods. Higher photocatalytic activity was observed in TiO(2) films heat treated at lower temperatures.     

Properties of column spacers on a flexible color filter using a roll‐to‐roll process

Abstract— Column spacers were manufactured by a roll‐to‐roll process for a flexible plastic substrate and an LCD prototype was demonstrated for the first time. The purpose of this paper is to obtain a stable cell gap for plastic LCDs by designing the column spacers. The optimum condition was derived for the properties of the column spacers parameters, such as the cross section, density, and hardness. As a result, we could determine the optimum elastic modulus of the column spacers needed in order to precisely maintain the cell gap of the LCD as well as that of conventional glass plates, resulting in a uniform display luminance.     

Bubble behavior in a horizontal narrow divergent passage (one-dimensional approximate analysis)

This paper investigates the behavior of a bubble which bridges the gap in a cross section of a horizontal narrow divergent passage under Earth's gravity conditions (1 G) analytically. In a narrow passage, inertia forces are known to be small compared with viscous forces. Also, gravity force is not dominant for bubble behavior in a horizontal narrow passage. In this sense, the bubble behavior in the passage is similar to that under microgravity conditions. It is important to understand the bubble behavior in relation to separating gas from a gas–liquid two-phase flow and controlling a gas–liquid interface under microgravity conditions. A one-dimensional momentum equation for the bubble behavior is derived. The equation is arranged as an ordinary differential equation with respect to the upstream interfacial location and is solved. Analytical results are compared with experimental ones. As a result, the effects of gap size, bubble projected area, and divergent angle on bubble behavior are explained qualitatively. © 1999 Scripta Technica, Heat Trans Asian Res, 28(2): 102–114, 1999