| 摘要 |
PURPOSE:To obtain the titled soln. retardind the rusting of an electroless-plated copper film by properly adjusting the pH of an aqueous soln. contg. adequate amounts of formaldehyde and a cupric ion complexing agent and by regulating the concn. of dissolved oxygen in the soln. to a prescribed value or less. CONSTITUTION:The pH of an aqueous soln. contg. >=4g/l (para)formaldehyde and >=5g/l N,N,N',N'-tetrakis-2-(2-hydroxypropyl)ethylenediamine or cyclohexane- 1,2-diamine-N,N,N',N'-tetraacetic acid as a cupric ion complexing agent is adjusted to >=11 with an aqueous soln. of NaOH or KOH, and the concn. of dissolved oxygen in the soln. is regulated to >=3ppm by blowing gaseous nitrogen or by other method to obtain a soln. for holding the activity of an electroless- plated copper film. When a printed wiring board subjected to through hole electroless copper plating is immersed in the soln., the oxidation of the electroless- plated copper film is inhibited, and the film can be held active until copper electroplating is carried out. |
