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P&M Services (R) Ltd

Printed circuit board Manufacturer, Photoplotting Established 1964  All types of Pcb, surface mount sm, PTH, SS single     UK Printed Circuit Board manufacturers. UK PCB Manufacture since 1964. single sided SS PCB, PTH PCB, IMS PCB, PCB JPG, DFX PCB

ML multi layer printed circuit board  prototypes. Cheap high quality PCBs Printed circuit boards. Fast cheap UK Prototype PCB

Printed circuit boards tooled up from Gerber,JPG,DXF,and most common file types, or camera ready artworks either 2:1 or 1:1 std scale.

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Ammoniacal Etchant:-

Probably the main etchant used within the circuit board industry. Due to it's very smelly nature it is only used in spray etching applications.  Normal copper etching reaction is:-


Initial reaction, which results in a build up of cuprous ions,


Cu2+  + Cu>>  2Cu+


Secondary reaction, oxygen is absorbed from the air which re-oxidizes the cuprous ions back to cupric ions,


2Cu+ + 1/2O2 + H2O >>  2Cu2+ + 2OH


The basic etching reaction is the same as cupric chloride etching but to work the copper (II) ions require complexing with ammonium chloride and ammonia.


Cu2+ + 2(NH4)Cl + 4NH3 >> 2NH4+ + Cu(NH3)4Cl2


To work free ammonia is present, which always finds it's way past any extraction equipment resulting in strong odours. Ammonia loss results in sludging, as do excess water or excess copper. Its an almost trouble free process when correctly run but can result in hours of machine cleaning if not.


Chromic Sulphuric Etching


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 Rev  18 April 2024

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