Method of removing palladium in NPTHs of PCB

Abstract

The invention discloses a method of removing palladium in NPTHs (Non-Plated Through Hole) of a PCB. The method is characterized in that after the procedure of eletcroless plating copper of PTHs (Plated Through Hole) is completed, and before a chemical gold procedure is performed, a palladium removing agent is sprayed to the PCB to remove colloid palladium on the walls of NPTHs, wherein the palladium removing agent is formed by 0.4-0.8 mol / L of hydrochloric acid, 50-80 g / L of sulfourea and the balance of water. According to the invention, concentration of sulfourea solution and hydrochloric acid solution in the palladium removing agent and proportion of the sulfourea solution to the hydrochloric acid solution are optimized, and as for colloid palladium, the palladium removing agent has favorable removal rate and shorter reaction equilibrium time, which is particularly conducive to use in large-scale industrial production.

Description

technical field

[0001] The invention relates to the technical field of PCB production, in particular to a method for removing palladium from non-sinking copper holes of PCBs. Background technique

[0002] In the field of printed circuit board (PCB) production, the surface treatment is mainly based on electroless nickel-gold. Since the hole wall of the substrate is adsorbed with a layer of colloidal palladium during the hole formation of the metallized through hole (PTH), the When the dry film is pasted after a comprehensive copper plating, the corresponding non-sinking copper holes (NPTH, holes whose walls are not plated with metal and are used for mechanical installation or mechanical fixing components) are also covered by the dry film together, so in the second After copper plating and second etching, although the copper in each non-conducting hole has been completely etched away, the palladium adsorbed on the hole wall substrate before copperization cannot be removed. Ni...