Shape evolution of lead frame by electrolytic etching

Two dimensional numerical analysis based on current distribution has been c alculated for electrolytic etching of lead frame from both sides. With an increase in anode width, the side etching widths become smaller, bo th for the forced primary and the secondary current distributions. A residu al hump forms for the forced primary current distribution of 200 mu m anode width. With an increase in current density, the side etching widths also b ecome smaller. With an increase in foil thickness, the side etching widths become larger and etched shapes become round, both for the forced primary a nd the secondary current distributions. A residue of 200 mu m anode width is eliminated completely with the aid of an isolated resist located from x = 45 mu m to 95 mu m. This residue of a 2 00 mu m anode is also eliminated completely with photo resists of more than 30 mu m thickness.