Spray machine etching uniformity tests of copper clad laminate panel 90 x 220 mm , 35 / 35μm foil.


Images of progressive etching passes of the nozzle spray arm. At spray pass number 44 , the first sign of copper break through are visible. At pass number 50, the area is 100% etched. This tests demonstrates etching uniformity of the spray machine to be (50 / 44 - 1) or 14%,  In other words, some areas of the panel will inevitably be over etched 14% (factor of 1.14 ) at worst case.

These tests were made after many hours of experimentation of various nozzle positions before obtaining optimum etch uniformity. There is still some increased etching rate on the lower two nozzles, but the difference is minimal. These images are shown with the left of the picture is the upper side of the PCB.


Pass number 44

First signs of copper break through are visible
 pass 44

Pass number 46


 pass 46

Pass number 47


 pass 47

Pass number 48


 pass 48

Pass number 49


 pass 49

Pass number 50

All copper completely etched away. A 5 mm perimeter is not fully etched, however this area is outside the 305 x 200 mm printable panel zone. In practice a few more spray passes will be needed to guarantee removal of all traces of copper.
 pass 50