• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.133-137
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• 2014

As a preceding process for preparing several micrometer sized Ag-coated Cu flakes, ball milling of submicrometer-sized Cu particles synthesized through a wet chemical method was performed in order to convert the particles into flakes. To suppress oxidation and aggregation of the particles during ball milling, ethylene glycol and ethyl acetate were used as a medium and a surface modifying agent, respectively. Results obtained with different rotation speeds of a jar indicated that the rotation speed changes a rotating mode, and strikingly alters the final shapes and shape uniformity of Cu particles after milling. The diameter of zirconia ball was also confirmed. Although there was aggregates in the initial submicrometer-sized Cu particles, therefore, well-dispersed Cu flakes with a size of several micrometers were successfully prepared by ball milling through optimization of rotation speed, amount of ethyl acetate, and diameter of zirconia ball.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.51-56
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• 2016

To fabricate a copper (Cu)-based fine conductive filler having antioxidation property, submicron silver (Ag)-coated Cu particles were fabricated and their antioxidation property was evaluated. After synthesizing the Cu particles of $0.705{\mu}m$ in average diameter by a wet-reduction process, Ag-coated Cu particles were fabricated by successive Ag plating using ethylene grycol solvent. Main process parameters in the Ag plating were the concentration of reductant (ascorbic acid), the injection rate of Ag precursor solution, and the stirring rate in mixed solution. Thus, Ag plating characteristics and the formation of separate fine pure Ag phase were observed with different combinations of process parameters. As a result, formation of the separate pure Ag phase and aggregation between Ag-coated Cu particles could be suppressed by optimization of the process parameters. The Ag-coated Cu particles which were fabricated using optimal conditions showed slight aggregation, but excellent antioxidation property. For example, the particles indicated the weight gain not exceeding 0.1% until $225^{\circ}C$ when they were heated in air at the rate of $10^{\circ}C/min$ and no weight gain until 75 min when they were heated in air at $150^{\circ}C$.