Abstract
Reduced Ni films were obtained on iron substrate from the electroless plating bath containing NaBH4 as an reducing agent.
The initial precipitation behavior of the plated Ni films was examined by direct observation and electron diffraction method with an electron microscope.
The following results were obtained:
1) No difference of precipitation behavior was observed between the inoculation process by an instantaneous galvanic contact with Al and the process by a momentary current. At first, Ni micro-granules of less than 150Å in diameter were precipitated in the early stage, and then, developed to the diameter size of 300-1300Å, when nebulous crystals were distributed independent of the granular crystals. The nebulous crystals grew into acicular form with the progress of plating time.
2) The granular crystals of 300-1300Å had no coherency with the substrate and did not grow up to above 1300Å. The precipitation density of these granules was 106/mm2.
3) The diffraction pattern of the nebulous crystals observed consisted of rings having an intense spot.
4) The granular crystals were precipitated on the substrate from a new bath only. Whereas, the nebulous crystals were immediately precipitated from an old bath which had been practised for a long period.
5) The initial precipitation behavior of Ni films electroplated from a plating bath not containing NaBH4 was observed to be under the same conditions as in the electroless plating.
