抄録
The effects of KAu(CN)2 concentration and cathodic current density of the bath on the grain size and twin frequency of gold deposits obtained from the citrate baths, A and B in the previous paper, were studied.
The results obtained were as follows:
1) The grain size of gold deposits obtained from the bath A increased with current density and decreased with KAu(CN)2 concentration. It also increased with the thickness as expressed by the formula:
Gs=K′lnT+K″. (where Gs: grain diameter, T: thickness, and K′ and K″: constants depending on plating conditions)
It was also found that twin frequency increased with grain size.
2) The bath B was more effective than the bath A in controlling the grain growth. Therefore, it was found that the structure of gold deposits on copper substrate from the bath B agreed with the structure of the substrate and the positions of twins observed in gold deposits agreed with those in copper substrate.
Most of crystal grains of gold deposits were single crystals and the direction of bands observed in them was always [111] without exception. It was supposed that gold was preferentially deposited in the direction of the highest atomic density in the early stage of deposition.
3) The presence of twins in grains had greater effects on mechanical strength of deposits with the increase of twin frequency in the same grain size. Therefore, it was found that the twin frequency, which increased with the increase of grain size, had effects on mechanical strength of gold deposits.
