Hideo Takamizawa

A1N Substrates with High Thermal Conductivity

A new aluminum nitride (AIN) substrate, which has high thermal conductivity of 160 W/mK at room temperture, has been developed using the hot press sintering technique. The new AIN substrate has the following excellent characteristics. 1) The thermal conductivity is eight times as high as that of AI 2 O 3 at room temperature and is almost equal to that of 99.5 percent BeO at 150°C. 2) The thermal expansion coefficient is smaller than that of AI 2 O 3 and BeO, and is close to that of a silicon semiconductor chip. 3) The electrical properties are almost as good as those for AI 2 O 3 and BeO in the wide frequency range. 4) It not only has higher mechanical stength but also easier machinable property than AI 2 O 3 . It is characterized by its light transparency from visible light to the infrared wavelength region. It was proved that the new AIN substrate is able to be metallized with good adhesion strength by the conventional evaporating method and the conventional sputtering method. The new AIN was found to be applicable to three kinds of semiconductor devices: 1) silicon epitaxial transistor, 2) GaAIAs light emitting diode, and 3) InGaAsP laser diode. Also, another AIN substrate was developed using the normal sintering technique, which has high thermal conductivity of 140 W/mK at room temperature.

Low Firing Temperature Multilayer Glass-Ceramic Substrate

A glass-ceramic material, which has a low constant (7.5) and can be sintered at 900°C in air or in a neutral atmosphere, has been found. As a result, it has become possible to prepare a multilayer glass-ceramic substrate which is advantageous for decreasing propa- gation delay. The new multilayer glass-ceramic (MGC) substrate has the following excellent characteristics. 1) Gold and silver-palladium alloys can be used in fabricating wirings or circuit patterns. 2) The new MGC substrate has a high flexural strength of 3000 kg/cm2 (43000 Ib/in2). 3) During the firing process, shrinkage is around 12.5 percent and shrinkage tolerance is extremely small (0.3 percent or less). 4) The thermal expansion coefficient is about 42 x 10 -7 deg -1 (from room temperature to 250°C) and is close to that for silicon semicon- ductor chips. The MGC substrate was experimentally produced and used in multilayer substrates for a multichip package computer sys- tem. It is possible to form via holes easily with 100 pm diameter and to use loo-pm linewidth on a 200~pm line-to-line grid. A green sheet (120 mm square) may have as many as 110 000 via holes punched into it. It has become possible to provide a high-density packaging substrate using this method.

Large Capacitance Multilayer Ceramic Capacitor

Large capacitance multilayer ceramic capacitors were made using a ceramic dieletric in the binary system Pb(Fe 2/3 W l/3 )O 3 -Pb(Fe l/2 Nb l/2 )O3. The new capacitors used silver alloy as an internal electrode, reducing the capacitor cost significantly. It was then possible to make economical 10 µF ~ 400 µF muitilayer ceramic capacitors. Typical electrical properties of the new capacitors are listed below: Size 4.5 cm3Capacitance at 20° C, 1 kHz 400 µF Dissipation factor at 1 V rms, 1 kHz 0.6 percent Insulation resistance 5000 \Omega -F Capacitance change with temperature change (-30° C ~ +85° C) -83 to 0 percent Impedance at 100 kHz 2m \Omega 2 Equivalent series resistance at 100 kHz 0.8 m \Omega Maximum permissible ripple current 20 A. The new multilayer ceramic capacitors exhibit the following benefits in comparison with conventional multilayer ceramic capacitors, tantalum electrolytic capacitors, and aluminum electrolytic capacitors. a) Dimensions are small and capacitance is large; b) impedance at high frequency band is small; c) equivalent series resistance is small; d) maximum permissible ripple current is large. The new multilayer ceramic capacitors are useful in various electronic circuits, particularly in switching regulators, in place of tantalum electrolytic capacitors and aluminum electrolytic capacitors.

Large scale multilayer glass-ceramic substrate for supercomputer

A large-scale multilayer glass-ceramic (MGC) substrate, which has a low dielectric constant

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...

Properties of the Large-Capacitance Multilayer Ceramic Capacitor

Electrical properties of the large-capacitance multilayer ceramic capacitor made of the ceramics of Pb(Fe2/3W1/3)O3–Pb(Fe1/2Nb1/2)O3 system were studied. The ceramics are sintered at 900°C in air, and therefore, it is possible to use Ag–Pd alloy as the internal electrode. The size of the capacitor with capacitance of 400 µF is fairly small. Dissipation factor is extremely small (0.6%) under the D.C. voltage bias in wide frequency range. Insulation resistance is more than 6000 M Ω µF. Impedance at high frequency band is small compared with those of other electrolytic capacitors with the same capacitance. Electrical properties are hardly changed in lifetime test.

Low dielectric constant new materials for multilayer ceramic substrate

A low-dielectric-constant glass-ceramic material system with improved thermal expansion coefficient and flexural strength is described. This material system consists of quartz glass, cordierite, and borosilicate glass. It can be sintered at temperatures below 1000 degrees C, making it possible to use low-electrical-resistivity conductors, for example, Au, Ag, Ag-Pd, and Cu, as signal lines and interconnections. A dielectric constant in the 3.9 to 4.7 range can be realized. The thermal expansion coefficient can be controlled to match that of the chips carried. The flexural strength (2000 kg/cm/sup 2/) is relatively high. Using green-sheet-lamination technology, a low-dielectric-constant multilayer glass-ceramic substrate with Ag-Pd wiring, suitable for use as a substrate for a high-speed VLSI multichip package, was developed.<<ETX>>

Application of Designed-Space Forming Technology

A completely new designed-space forming technology using ceramic green sheet technology and photolithographic technology has been developed for ceramics. With this technology, it is possible to make any fine space accurately and at will in ceramics. A monolithic ceramic ink jet head and a piezoelectric multilayer ceramic sound transducer were developed using this new technology. A piezoelectric ceramic material was used for these devices. Spaces for nozzles, pressure chambers and an ink chamber in the ink jet head and cabities in the ceramic sound transducer were formed in the piezoelectric ceramic body with photosensitive polymer by photolithographic technology. The ink jet head showed stable ink ejection action with low drive voltage. The ceramic sound transducer showed wide-band sound responce characteristics with low drive voltage. The new designed-space forming technology can be applied to many kinds of electronic ceramic components and devices. Using this technology, miniaturization and cost reduction can be achieved.