Following femtosecond (fs) laser pulse irradiation, the formation of a new type of low-spatial-frequency laser-induced periodic surface structure (LSFL) patterns, namely, omnidirectional LSFLs (OD-LSFLs) with the periodic ordering of their orientations, are investigated on Ni in this Letter. Using a liquid crystal polymer patterned depolarizer, we periodically rotate the polarization of fs laser pulses across the laser spot and create OD-LSFLs by raster scanning fs laser pulses. We also show that the period of the OD-LSFL orientation rotation can be controlled with the defocused distance, and OD-LSFLs can significantly expand the viewing angle of the structural colors in the azimuthal direction without noticeable color degradations.
The study on rheocasting has been conducted based on examination for destruction, growth,
ripening of solid state in accordance with various changes in cooling. And flow characteristics of
slurry for high liquid range rather than practical use has gotten attention. However, the characteristics
of existing rheocasting and thixocasting are better mechanical property than competing process die
casting but it’s competitiveness as automotive or electric electronic parts which cost of product is
important. And productivity also has been decreased. Because die-casting techniques has been
advanced such as vacuum, mold auto temperature control etc. Most of the work reported at this
conference concerned the semi-solid processing of low melting point alloys, and in particular light
alloys of aluminum and magnesium. Therefore, the aim of this study is to devise the original strength
of semi-solid process by sequential semi-solid process. The size of primary solid particle and the
degree of sphericity as a function of the variation in cooling rate, stirring speed, and holding time were
observed. By applying electromagnetic stirring, primary solid particles became finer and rounder
relative to as-cast sample. With this background, this research conducted electromagnetic stirring
through slurry deliverance of sequential process through A356 alloy electromagnetic stirring pump
(30Hz, 130A) with Sequential Semi-Solid Process device to assess the microstructures, primary
particle size, degree of sphericity change in A356 alloy in accordance of solid-fraction, stirring speed,
and stirring maintenance time.
The μ-via in microelectronic substrate should have multiple purposes, one of them is to
allow to the path of signal or current from electronic devices. The micro void can be easily formed
in μ-via because μ-vias are filled with a screen printing process and the size of via is small. The
residual void has been known as crack initiation of copper layer during a reliability test. The solder
resist filling process and the behavior of a residual void in μ-vias were investigated. The void
extraction process was very effective comparing with the conventional process to remove a residual
void. As extracted with 1.5 atm for more than 30 sec, the residual void in μ-BVH was perfectly
eliminated.
Through femtosecond laser irradiation, we observed the formation of columnar structures above the surface level of Al and showed the control of their morphological profiles with the laser fluence and the number of irradiating pulses.
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