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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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Chromic-Sulphuric Acid:-

Used to be the preferred etchent for tin tin-lead plated boards but has been replaced by Ammoniacal and Sulfuric Peroxide etchents. Chromic-Sulphuric etchent has only a slow etch rate and low copper holding capacity. The solution is also a serious pollution concern and very expensive to dispose off. Normal copper etching reaction is:-


3Cu + 2HCrO4- + 14H+ >> 3Cu2+ 2Cr3+ + 8H2O


The hydrogen ions are normally provided by Sulphuric acid, beware Hydrochloric acid must not be used as toxic chlorine gas would be liberated.

Std makeup with the addition of sodium sulfate which increases the etch rate is, 240g/l  Chromic Acid, 40g/l Sodium Sulfate, 180g/l 96% Sulphuric Acid. Oddly enough air agitation reduces etch rate.



Cupric Chloride


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 Rev  18 April 2024

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