Masahide Okamoto

Oral toxicity of bismuth in rat: Single and 28-day repeated administration studies

Oral Toxicity of Bismuth in Rat: Single and 28‐Day Repeated Administration Studies: Yuri Sano, et al. Department of Preventative Medicine and Public Health, School of Medicine, Keio University—The consumption and production of bismuth are increasing, however there is very little information about the direct toxic effect of bismuth. The present study aimed to characterize the potential toxic effects of bismuth through oral administration and observation for fourteen days following single dose of 0 and 2,000 mg/kg (acute oral toxicity study), and repeated oral administration for twenty‐eight days at dose levels of 0, 40, 200, and 1,000 mg/kg daily (28‐d repeated oral dose toxicity study) to male and female Crj:CD (SD) IGS rats (SPF). We found no deaths and no abnormalities in clinical signs, body weights, and necropsy findings for any of the animals in the acute oral toxicity study and no changes attributable to bismuth in either males or females in the dose group up to 1,000 mg/kg of the 28‐d repeated‐dose toxicity study. Therefore, we determined that the lethal dose with a 50% mortality rate (LD50) is greater than 2,000 mg/kg and the no‐observed‐adverse‐effect level (NOAEL) of bismuth is 1,000 mg/kg in both sexes. We conclude that the adverse toxic effects of bismuth as a simple metal substance are low compared to lead toxicity under the conditions tested in our studies.

Genotoxicity Studies of Heavy Metals: Lead, Bismuth, Indium, Silver and Antimony

Genotoxicity Studies of Heavy Metals: Lead, Bismuth, Indium, Silver and Antimony: Keiko Asakura, et al. Department of Preventive Medicine and Public Health, Keio University School of Medicine

A 13-Week Toxicity Study of Bismuth in Rats by Intratracheal Intermittent Administration

A 13‐Week Toxicity Study of Bismuth in Rats by Intratracheal Intermittent Administration: Yuri Sano, et al. Department of Preventative Medicine and Public Health, School of Medicine, Keio University—Although bismuth is widely used as a lead substitute in the industrial field, the toxicity of bismuth by inhalation is little known. We performed a 13‐wk intratracheal intermittent bismuth dose toxicity study. Bismuth was administered at dose levels of 0, 0.8, 4, 20 mg/kg to male Crj:CD(SD)IGS rats (SPF) by intratracheal intermittent administration once a week for thirteen weeks to investigate its potential toxic effects; especially for specific adverse effects and changes related to pre‐neoplastic lesions. Our results showed foreign body inflammation in the lungs, which was caused by intratracheal administration of bismuth, and physical changes related to pulmonary lesions; however, there were no serious changes in other organs. We concluded that dose‐dependent, but not specific adverse effects, were attributable to bismuth inhalation in the rat.

Cavity down AlN PGA with inter-polyimide wiring

A low-thermal-resistance, high-speed pin-grid-array (PGA) package is discussed. To obtain low thermal resistance, a silicon chip was soldered onto a metallized aluminum nitride ceramic substrate that directly contacts an air-cooled fin (a cavity-down structure). Low propagation delay was realized by placing signal lines between low-dielectric-constant polyimide layers that were coated on the substrate. The thermal resistance from the silicon chip to the air environment was 2.7 degrees C/W with a 20-mm-high fin when the air velocity was 2 m/s. The self-inductance of the longest signal line was 20 nH, and the capacitance between the longest signal lines was 1.7 pF. The helium leakage level was about 10/sup -9/ atm-cm/sup 3//s even after 24 cycles in a thermal cycle test from -55 degrees C to 150 degrees C.<<ETX>>

Recovery of Rare Earth Metals in Used Magnets by Molten Magnesium

We report here Hitachi’s approach to recycle rare earth (RE) metals in used magnets by using molten magnesium (Mg). The process consists of 3 steps; (1) extraction of RE metals from magnets into molten Mg, to form Mg-RE melt, (2) mechanical separation of magnets from the Mg-RE melt, (3) collection of RE metals by evaporation of Mg in the Mg-RE melt. In the step 1, extraction of RE metals proceeds rapidly and completes in about 3 h. The efficiency strongly depends on the temperature (T) and Mg/magnet ratio (r)). One of the optimal conditions is T=1273 (K) and η is 10, where the efficiencies for Nd and Dy extraction are almost 100 % and 60 %, respectively. Further increase of Dy extraction efficiency is possible by addition of Ca to suppress the oxidation of Dy.

Thermal Fatigue Life of Sn-2Ag Solder Bump with Small Al Addition

Recently, in accordance with environmental demands, Pb-free solders are being widely used. Our research was done to further promote the use of Pb-free solders. And it is tried to improve the thermal fatigue life by adding a small amount of Al to conventional Sn-Ag Pb-free solders. Ceramic ball grid arrays (C-BGAs), whose uses will increase in the future, were selected as the most crucial issue in thermal fatigue. Moreover, Sn-Ag solder as the mother solder alloy is used, to which we added a 0.1 and 0.05% wt. of Al. There were two kinds of fatigue fracture. In the first, the crack propagates inside the solder bump, and in the second, the crack propagates near the jointed solder and substrate interface. The fatigue life showed considerable improvement for the first mode, but no improvement for the second

Overall Technological Results of IMS-EFSOT Japanese Project --- Environmental Impact of Lead-Free Soldering ---

As for lead-free solder, jointability (workability and joint reliability) is not only evaluated but also energy consumption i.e. CO 2 emission, toxicity, resource depletion, recyclability and reusability of various types of solder. Next it is attempted to integrate the environmental impacts of these factors of each solder and compare them among these solders. Finally some types of solder whose integrated environmental impact was assumed to be relatively low is recommended. Sn-Ag-Cu and Sn-Cu types of solder as the best solutions in the present state is recommended. That is, total environmental impact of these solders is minimum, although they have a problem of Ag and Sn scarce. Then, suggested it was necessary to construct recycling system of Ag and Sn in the long term. 2nd Selection was Sn-Zn(-Bi) type solder. This solder has only problem about jointability. If this problem should be solved by improvement, this solder would be one of the best selections of lead-free solder. Furthermore refraining from use of Sb containing solder and In containing solder because of their toxicity and scarce respectively is proposed

Overview of IMS project; next generation environmental friendly soldering technology "EFSOT"

The 21st century can be called the era of the environment, and various efforts are being made to protect the global environment. For the materials used in the soldering of electronic circuits, there is also concern over the harmful effects of Pb, which is an important component of those materials, and so there is a trend to eliminate the Pb component. Under this background, and founded on the recognized importance of developing an alternative connection technology that has little environmental impact and harm, the IMS Project: Development of the Next Generation Environmental Friendly Soldering Technology began in June, 2000 in cooperation of industry and academia, and supported by the Ministry of Economy, Trade and Industry and the IMS (Intelligent Manufacturing Systems) Promotion Center. The project comprises four areas, which are evaluation of the impact of Pb-free soldering on the environment, evaluation of the safety of the metals with respect to living creatures, recycling technology, and the development of production technology. To achieve a worldwide consensus and application, the project is being internationalized.

Low thermal resistance AlN PGA with low inductance of power lines

A low-thermal-resistance and high-speed pin-grid-array (PGA) package with low-inductance power lines was proposed, and its feasibility was confirmed. To obtain low-inductance power lines, the wiring system in the package kept power-line layers and signal-line layers separate. Low inductance of power lines was realized by using conductive layers with a large area in an aluminium nitride (AlN) substrate and arranging the power pins just under the silicon chips. A high signal-propagation speed was realized by sandwiching radial signal lines between low-dielectric-constant polyimide layers. To obtain low thermal resistance, a silicon chip was soldered onto the metallized AlN ceramic substrate. High thermal conductivity of AlN ceramics and the arrangement of pins on the AlN substrate surface opposite the side of the silicon chip resulted in low thermal resistance of the package. The package on the printed wiring board had a thermal resistance of 3.0 degrees C/W at an air velocity of 1 m/s using a 14-mm-high aluminium cooling heat sink. The self-inductance of the power lines was 1.4 nH in the package substrate without pins and bonding wires.<<ETX>>