PCB Fabrication

The process and principle of alkaline etching technology

by:A-TECH      2021-03-19
Etching is to use the corrosion resistance of dry film, wet film, tin layer, and nickel metal layer to protect the effective pattern part. The copper surface without corrosion protection layer is etched by alkaline ammonia copper chloride solution, and then according to the type of board The resist layer is removed with different processing methods to obtain the required pattern circuit. 1 Inner layer process etching → sub-liquid cleaning → water washing → film removal → water washing → anti-oxidation → water washing → drying 2 copper tin plate process film removal → water washing → film removal water washing → medium pressure water washing → blotting → etching → sub Liquid cleaning → water washing → blotting → stripping tin → water washing → drying → connecting plate 3 nickel-gold plate process flow stripping → water washing → film removal water washing → medium pressure water washing → blotting → etching → sub-liquid cleaning → water washing → blotting →Pickling→Water washing→Drying→Connecting board 4 Simple process principle Copper corrosion reaction: During the etching process, the copper on the board surface is oxidized by the [Cu(NH3)4]2+ complex ion in the etching solution, and the reaction is as follows :  Cu(NH3)4Cl2+Cu→2Cu(NH3)2Cl  Regeneration reaction: (1) The generated [Cu(NH3)2]1+ is a complex ion of Cu1+, which does not have the etching ability. When there is excess NH3 and Cl- Under the circumstance, it can be quickly oxidized by O2 in the air to generate [Cu(NH3)4]2+ complex ions with etching ability to complete the regeneration reaction.   2Cu(NH3)2Cl+2 NH4Cl+2 NH3+1/2 O2→2 Cu(NH3)4Cl2+H2O
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