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Hybrid atomization method suitable for production of fine spherical lead-free solder powder

Minagawa K., Kakisawa H., Takamori S., Osawa Y., Halada K.

Nukleonika

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2006

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Vol. 51,suppl.1

83-88

EN

In response to the problem of environmental protection, the electronic industry is studying the lead-free alloys as substitutes for lead-containing solder alloys. At the same time, with progress in electronic devices in recent years, smaller size and higher precision are strongly demanded in electronic board connections. Therefore, it is necessary to prepare fine powders of solder paste for these connections. To produce such lead-free solder balls, a novel powdermaking process, “hybrid atomization” that combines gas atomization and centrifugal atomization, was used. This technique produces very fine and spherical tin alloy powders with a mean diameter of about ten micrometers and very narrow size distribution with few satellites at low production cost. Taking a Sn-9mass%Zn alloy as an example, process experiments were carried out, and the effect of temperature, spray distance and disk rotating speed on the resultant powder properties were examined. The optimal processing conditions were determined from the results; the influences of the processing parameters on the properties of the obtained powders were quite different from those in the conventional atomization processes. The spherical powder with a mean diameter of 10.6 žm and a standard deviation of 1.3 ~ 1.7 was obtained in the determined optimum condition.

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Foreword

Michalik J., Halada K.

Nukleonika

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2006

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Vol. 51,suppl.1

1-2

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Advanced processing for recycling of iron scrap with impurities

Osawa Y., Takamori S., Minagawa K., Kakisawa H., Halada K.

Nukleonika

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2006

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Vol. 51,suppl.1

113-119

EN

The present research focuses on the recycling of steel in combination with copper or aluminum alloys. To use iron scrap with a copper content in the range of 0.5 to 15%, a water atomization process was carried out, producing a rapidly solidified powder with copper of nano-order size dispersed in it. The powder was then hot rolled in the 600°C to 1000°C temperature region, where there is no liquid phase of copper, to produce a solid body. The solid bodies obtained presented a porosity of less than 1% for all the values of temperature and copper concentration, and it was established that the proposed process can be used for a wide range of concentrations of metallic impurities. The tensile strength increased with the copper content for all the temperatures, reaching stability at a copper concentration over 5%. Rapidly solidified powder was annealed and compacted at 600°C, resulting in a reduction of strength compared to non-annealed powder. The microstructure with a finely dispersed copper content seemed to have a considerable effect on the tensile strength of the compacted bodies. In the case of the use of aluminum-containing iron scrap, the results show that addition of aluminum to cast iron increased the resistance to abrasion, the high temperature oxidation characteristics, and the vibration control characteristics. When this cast iron was kept in air at temperatures ranging from 800°C to 1000°C, it was observed that the graphite on the surface was substituted by alumina.