Takahiro Daikoku

Effects of Pore Diameters and System Pressure on Saturated Pool Nucleate Boiling Heat Transfer From Porous Surfaces

The porous surface structure was manufactured with precision for the experimental study of nucleate boiling heat transfer in R-11. Boiling curves and the data of bubble formation were obtained with a variety of geometrical and operational parameters; the pore diameters were of 50, 100, 150 ..mu..m, there was a combination of pores of different sizes; and the system pressures were of 0.04, 0.1, 0.23 MPa. The boiling curves exhibit certain trends effected by the diameter and population density of pores. A combination of high system pressure and pore sizes of 100 or 150 ..mu..m dia enables boiling to persist even when the wall superheat is reduced to an extremely low level of 0.1 K. A noteworthy feature of porous surface boiling is that intense bubble formation does not necessarily yield a high heat-transfer performance. Examination of the data indicates that liquid suction and evaporation inside the cavities are a proable mechanism of boiling with small temperature differences.

Hardware technology for Hitachi M-880 processor group

The authors explain the high-speed high-density semiconductor technology and high-density installation technology developed for the super-high-speed high-reliability M-880 processor groups. To achieve the design goals, a set of advanced hardware technologies has been developed in such areas as semiconductor, ceramic module board, printed circuit board, electric part, cooling, and power feeding. The innovative hardware technologies have been brought into realization by the development of advanced manufacturing techniques and process techniques in addition to the conventional design automation techniques, inspection and diagnosis techniques, and reliability evaluation techniques. During the design, high-precision high-efficiency design evaluations were carried out using software simulation technologies including a three-dimensional electrical characteristic analyzing program a circuit analyzing program, and a thermal stress analyzing program.<<ETX>>

Forced Convective Heat Transfer from LSI Packages in an Air-Cooled Wiring card Array

The resistance to heat flow from finned LSI packages to the cooling air flow has been studied by combining the physical models with the results of heat transfer experiments, flow visualization experiments, and pressure drop measurements. Although crude assumptions are employed in analytical modeling, the proposed method of prediction of heat transfer and pressure drop has proved useful to cooling system designers. A notable finding is the advantage obtained by placing the packages in a staggered arrangement on the card. This reduces the local air temperature rise by as much as 70% over the conventional in-line arrangement, where the fan power is given as a constraint.

Conditions for Homogeneous and Rapid Deposition of Si Film on Semiconductor Wafers

The paper investigates the method of improving deposition rate in semiconductor deposition process, while maintaining film thickness uniformity and step coverage in a vertical LPCVD (Low-Pressure Chemical Vapor Deposition) system. In general increasing pressure improves deposition rate, but it decreases uniformity of thickness. The result of experiment and the numerical simulation showed that the non-uniformity of film thickness in high-pressure condition can be improved by controlling flow patterns in the space between wafers. In the molecular flow region (low pressure), the deposition rate and the step coverage were not influenced by the source gas flow rate. In the viscous flow region (high pressure), the step coverage can be improved by increasing source gas flow rate. For the flow the nozzle design and exhaust port location are important. Installation of rings outside of wafers is also effective for the improvement of thickness uniformity.