The invention discloses a process for plating
nickel and gold to avoid gold
permeation, which comprises the following steps of: S1, back drilling: forming a through hole in a multi-layer circuit board according to production requirements, drilling a back drilling hole in one side of the multi-layer circuit board in a back drilling manner, and during design, enabling a base layer between a bonding pad and a grounding
copper layer to have an overlapping region with the back drilling hole, and then filling resin into the back drilling hole; s2, film covering is conducted, the circuit board is covered with a dry film, and the remaining dry film keeps away from the overlapping area after film removing; s3,
copper and
tin plating: firstly plating a
copper layer on the whole circuit board, then plating a
tin layer on the copper layer to protect the copper layer, and not plating copper and
tin on the area covered by the remaining dry film; s4,
laser ablation: ablating the tin layer on the overlapped region by using
laser, then removing the remaining dry film in the step S2, and
etching the copper layer which is not protected by the tin layer by using an
etching liquid
medicine so as to
expose the base layer between the bonding pad and the grounding copper layer; and S5,
nickel and
gold plating: after the tin layer for protection is removed,
nickel and
gold plating is carried out on the copper layer of the bonding pad.