Kazuaki Utsumi

Effect of oxygen deficiency on the crystal structure and superconducting properties of the Ba2YCu3Oy

Effect of oxygen deficiency on crystal structure and superconductivity of Ba2YCu3O7-δ was studied by annealing and quenching experiments. With increasing oxygen deficiency superconductivity was suppressed remarkably while axial ratio, a0/b0 in the orthorhombic phase approached to unity and c0 value increased. Structural transformation from orthorhombic to tetragonal lattice took place in the temperature range, 950~980°C and maximum oxygen deficiency, δ=0.7 was observed for the tetragonal phase.

Preparation of superconducting Y‐Ba‐Cu‐O thick films with preferred c‐axis orientation by a screen‐printing method

Superconducting Y‐Ba‐Cu‐O thick films with preferred c‐axis orientation were obtained by a screen‐printing method. Thick films with preferred c‐axis orientation appeared only when the substrate material was YSZ, the film thickness was around 10 μm, and the film was fired at 980 °C for 6 min. The preferred c‐axis orientation was caused by an interface reaction between the Y‐Ba‐Cu‐O thick film and the YSZ substrate. The superconducting characteristics of the thick film were T zeroc =89 K and Jc (77 K)=7 A/cm2 .

Determination of the Orthorhombic-Tetragonal YBa2Cu3O7-δ Phase Boundary in the δ-T Diagram

The orthorhombic-tetragonal YBa2Cu3O7-δ phase boundary in the δ-T diagram was determined by a detailed isobar TG measurement under the oxygen partial pressures of 1 to 0.01 atm. The phase boundary was found not to be located at δ = const., but to have a slope of dδ/dT~-4.7×10-4 K-1. The experimental results are discussed with a simple order-disorder transformation model of oxygen atoms on the Cu plane sandwiched by Ba planes.

Cu/photosensitive-BCB thin-film multilayer technology for high-performance multichip modules

A new MCM-D technology which enables reliable fabrication of high-performance and low cost MCMs has been developed. The technology is based on Cu/photosensitive-BCB thin-film multilayer structure. The fabrication process is reduced by using the newly developed photosensitive-BCB, with a conventional photolithography process. The flexibility on design rules is allowed, because the Cu/BCB structure has the advantages of excellent planarization and low electrical resistance of signal line. The following long-term reliability tests were successfully done: thermal cycle (-45/spl deg/C/125/spl deg/C), high-temperature aging at 125/spl deg/C, and high-temperature/humidity (85/spl deg/C/85%). A prototype of the high density RISC module fabricated with the developed technology passed all the long-term reliability tests. The excellent electrical performance was also proved through the signal transmission tests with the prototype module. >

Metalization of AlN Ceramics by Electroless Ni‐P Plating

Highly thermally conductive aluminum nitride ceramics were metalized by an electroless plated Ni‐P film for the purpose of utilizing them in practical electronic circuit substrates. Aluminum nitride substrates were effectively etched by solution, and the adhesion strength between and the Ni‐P film was found to increase with an increase in surface roughness. At value greater than 0.63 μm, adhesion strength increased to 2.0 kg mm−2, and a maximum of 3.0 kg mm−2 was obtained at . The substrates, however, had a higher adhesion strength than substrates of abraded or abraded with the same roughness. SEM observation showed that the surface of substrate was selectively etched in the regions between adjoining large particles, and that Ni‐P projections became effective interlocking points. It was therefore concluded that substrates of new aluminum nitride of high thermal conductivity are capable of being effectively metalized by electroless plating method, and that the main factor contributing to film adhesion strength is interlocking surface structures that are formed through selective etching by .

Monolithic multicomponents ceramic (MMC) Substrate

Abstract New monolithic multicomponents ceramic (MMC) substrates were made using the glass-ceramic material, low firing high dielectric constant ceramic material, metal oxide resistance materials and metal conductors with green sheets laminating cofiring process technologies. In the MMC substrates, many passive components, such as capacitors, resistors and wiring conductors can be involved. The new MMC substrates have the following excellent characteristics: 1) Many large capacitance capacitors can be formed in the substrate (10 pF - 3 μF); 2) Many large resistance resistors can be formed in the substrate (10 Ω/□ - 1 MΩ/□); 3) Silver, silver-palladium and gold can be used in wiring conductors or internal electrodes; 4) A plurality of resistor and capacitor elements can be three-dimensionally constructed in the substrate; 5) Miniaturization and cost reduction can be accomplished in the substrate. The MMC substrates were applied to voltage controlled crystal oscillator (VCXO) circuits and RC active filter c...

Cu/Photosensitive-BCB Thin-Film Multilayer Technology for High-Performance Multichip Module

A new MCM-D technology which enables reliable fabrication of high-performance and low cost MCMs has been developed. The technology is based on Cu/Photosensitive-BCB thin-film multilayer structure. The fabrication process is reduced by using the newly developed Photosensitive-BCB, with a conventional photolythography process. The flexibility on design rules is allowed, because the Cu/BCB structure has the advantages of excellent planarization, and low electrical resistance of signal line. Long-term reliability test was successfully done; thermal cycle(-45/spl deg/C/125/spl deg/), high-temperature aging at 125/spl deg/C, and high-temperature/humidity(85/spl deg/C/85%). A prototype of high-density RISC module fabricated with the developed technology passed all the long-term reliability tests. The excellent electrical performance was also proved through the signal transmission tests with the prototype module.

The Orthorhombic-Tetragonal Phase Transformation and Oxygen Deficiency in LnBa2Cu3O7-δ

The orthorhombic-tetragonal phase transformation in LnBa2Cu3O7-δ (Ln=Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) was studied using careful isobar TG measurements under an oxygen partial pressure of 1 atm. As the atomic number within the lanthanide series increases, the transformation temperature tends to increase as well. This tendency is strongly related to the spacing of the nearest-neighbor oxygen atoms and is successfully interpreted in terms of the repulsion energy between them on the basis of a simple order-disorder transformation model proposed in our previous paper.

Resin and flexible metal bumps for chip-on-glass technology

LCDs (Liquid Crystal Displays) are now widely used in various display terminals: as a result, there is great demand for an LCD performance which has such factors as excellent display quality, high resolution and large capacity. In the LCD field, not only device technology but also packaging technology significantly influences display performance. Therefore, it is a most urgent matter to develop a structure and a process interconnecting LCD driver LSIs with hundreds of electrodes to a glass substrate at a fine pitch. For this reason, the authors have developed a novel COG (Chip-on-Glass) interconnection technology, in which an LSI chip like a sticker is electrically and mechanically connected quickly to a glass substrate, using flexible metal bumps formed selectively on electrode pads of an LSI chip and adhesive portions formed by photo-thermosetting resin between electrode pads. To acquire the novel interconnection method, the following technology has been developed: (1) New photo-thermosetting resin which is not thermoplastic, can adhere to a substrate even after being patterned and uses a photolithographic process; (2) Original process, using the photo-thermosetting resin and flexible metal bumps where flexible indium bumps are formed on electrode pads of LSI chip. Adhering portions by photo-thermosetting resin are formed selectively where there are no connecting pads. The LSI chip is mounted and connected to a glass substrate at low temperature(less than 150/spl deg/C). The LSI chip is electrically and mechanically connected to the glass substrate at a fine pitch; (3) Inspection/repair technique. It is possible to electrically inspect driver LSI chips which have been mounted and precure bonded on the LCD panel, before postcure bonding. If the driver LSI or mounting character is defective, appropriate repair is possible, With this new COG technology, fine pitch, such as 50 /spl mu/m electrode pads for driver LSIs, can be interconnected to ITO electrode terminals on an LCD panel. The reliability tests on test samples fabricated by the developed COG technology demonstrated good results. This paper describes the process and features of the developed COG technology.<<ETX>>

New high-density multilayer technology on PCB

We have developed a new high-density multilayer technology on PCB (Printed Circuit Board), named DSOL (Deposited Substrate On Laminate) technology. The first characteristic of the DSOL technology is the dielectric fabrication, which uses a new photosensitive material, a bulky fluorene unit bonded epoxy acrylate resin. The fluorene based resin has interesting properties such as good electrical properties, low curing temperature (160/spl deg/C) for a heat-resistant resin (glass transition temperature: 230/spl deg/C), low coefficient of thermal expansion (40 ppm), and high resolution. In particular, the dielectric formation process has the advantage that fine and high-aspect-ratio via holes are formed on FR-4 laminates through exactly the same process and manufacturing facilities as a conventional photosensitive epoxy resin. The second characteristic is the technology which patterns fine-pitch copper conductors using a semi-additive process with a sputtering method. This technology makes 40 /spl mu/m pitch lines on large-area laminates possible, as this process consists of flash wet etching of only 0.3 /spl mu/m thick sputtered thin-films. We have successfully developed a high-density packaging substrate for high-pin-count area array ASIC (Application Specific Integrated Circuit) chips (3828 pins). A high-density substrate based on the DSOL technology is the most suitable for achieving high-density packages (MCMs, CSPs, and BGAs) using fine-pitch and area array interconnection technologies.