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