Apparatus for Determining Etch Rate of Etching Solutions Under Controlled Operating Conditions

apparatustest piece

Basic Description

The picture above is the main part of the apparatus used to measure relative etch speeds of  etching solutions under controlled conditions. The temperature is maintained to within ±2°C by the thermal mass of the insulated surrounding water container as shown. The solution being measured is put in to one of the test tubes. Air is bubbled through the solution via a thin glass tube immersed to the bottom of the solution. Etch speed is measured by the time it takes to etch through a vertically positioned test piece of single sided 36 μm copper cladded PCB material measuring  20×10 mm. Two wires are soldered to the edge of the test piece (see other photo) and immersed to a  fixed depth in 25±3 ml of etchant solution When the copper has etched away, the resistance between the two connections goes high which then signals a timer to stop. The time it takes to etch the test piece is recored. This method would produce consistent of etch times better then ±10%.

There is a fair bit more to this experiment than what may first appear. Anyone who is interested in more detail then contact me.