We reported laser-assisted maskless metal patterning on p-type silicon previously. The process uses photo-excited electrons, and therefore it is applicable only to p-type silicon, because the n-type has abundant free electrons, and selective metal deposition cannot be expected. In the present work, we studied the possibility of achieving the metal patterning on n-type silicon. Various noble metals can be deposited on silicon by immersion plating. In the immersion plating of copper, deposition is observed on a porous silicon surface, but not on a flat silicon surface. Porous silicon is formed by silicon anodization. The reaction requires holes, and n-type silicon lacks enough holes to promote the dissolution reaction. When the surface is locally illuminated by a laser, the photo-excited area can be locally anodized, and a porous silicon pattern can be formed in n-type silicon without a mask. Using the above, copper deposition dependent upon the surface state and porous silicon patterning on the surface, we succeeded in patterning copper on n-type silicon without using a mask.

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The sustaining voltage of aluminum electrolytic capacitors can be enhanced by the addition of colloidal silica into their operating nonaqueous electrolyte solutions. A systematic study on the effects of colloidal silica on the scintillation voltage of aluminum electrolytic capacitors was carried out using silica organo-sols dispersed in ethylene glycol and quaternary ammonium carboxylate/γ-butyrolactone solutions. It was confirmed that maintaining the dispersed state of nano-particles in electrolytes so as not to cause gelation is the prime requirement as a sustaining voltage booster. The synergetic effect of organo-phosphorous acids was also examined.

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The adhesion of the zincate film onto 2017 aluminum alloy was evaluated by a tape peeling test. It was found that the adhesion of the double zincate film is much better than single zincate film. This improvement in adherence can be attributed to the metallurgical bond.

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