SELECTIVE REMOVAL METHOD BY APPLYING EQUIPOTENTIAL

PURPOSE:To allow the etching of only the surface metal of a work even with a printed wiring board integrated to a high density by using an external power source exclusive of the work and connecting the work to a soln. CONSTITUTION:Metals generate respectively different potentials when the potentials of the metals are measured at the time of melting of the metals. For example, the melting potential of copper is 50mV and the melting potential of nickel is 80mV. The potential of a laminate formed by laminating the nickel on the copper, therefore, maintains 80mV until the nickel melts first when this laminate is melted. The copper is exposed on the surface when the nickel melts completely and, therefore, the melting potential of 50mV is maintained if the treating liquid is thereafter weakened and the surface of the metal is measured. The work 2 is, thereupon, immersed in the treating liquid 3 and the melting potential is applied on the surface metal of the work 2 by using the external power source to maintain the potentials specific to these metals, by which only the desired metal is etched.