2010 Volume 59 Issue 3 Pages 70-74
Anodic polarization method was applied for the investigation of pinhole defects in a gold-plated or a nickel-plated layer of FFCs (Flexible Flat Cables). Pinhole defects in a gold-plated layer were quantitatively determined using 5 M H2SO4 as the electrolyte. The ratio of pinhole defects over 0.05% could be evaluated. Although pinhole defects in a gold-plated layer tend to decrease with an increase of the plating thickness, an excessive use of gold results in a cost problem. But generally, pinhole defects in a gold-plated layer are considered to decrease adequately, if the qualities of a base nickel-plated layer are high enough. The method of measuring pinhole defects in a nickel-plated layer was also developed for the quality estimation. In the case with acidic electrolytes, the anodic dissolution of nickel started before that of copper. However, the use of an alkaline electrolyte (i.e., 7 M KOH) enabled us to detect the current peak due to the formation of a copper oxide without the interference of the anodic reaction of a nickel-plated layer. The evaluation lower limit of the ratio of nickel pinhole defects was around 0.01%.