Last weekend
I started etching my own PCBs. Actually, I started etching in 2012, using the
“Toner-Transfer-Method” where the etching mask is transferred to the board
using an electric iron. However, the achievable resolution with this method is
limited and removing the paper which carries the toner is quite a hassle. Waiting
minutes for the paper to dissolve in water, only to see the toner did not
properly melt onto the board (i.e. do it all over again) just sucks. So I
finally bit the bullet and bought a professional UV-exposure box for using PCBs
with photosensitive coating.
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| Etching machine in use, filled with almot two litres of etching solution at 45°C |
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| My very first try. The rectangles are drawn with 12, 10, 8 and 6 mil traces. |
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| close-up of 10 and 8-mil traces. The white stuff left on the blank pcb is probably some residual photo coating. |
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| One more close-up of the 8-mil traces. The ruler on the right is divided in 1mm-steps. |
Tests were
conducted using original bungard PCBs coated with 70 micrometers of copper. The
photo mask was a design recently posted by another hobbyist from mikrocontroller.net containing traces of 12,10,8 and 6 mil width and printed on
transparency film with my old brother-2030 office laser printer. Exposed to
ultraviolet light for 90 seconds, the developed in NAOH at room temperature for
one minute and etched in Na2S2O8 at 45°C, the board comes out nicely.
Pretty good
for my very first test using this equipment, and by far sufficient for soldering
an Invensense MPU-6050 (4x4x0.9 mm QFN footprint) which requires solder pads of
about 10 mil width. As you can see, the six mil traces on the test PCB still
retain some copper in between, efficiently shorting them out, same with the
very top row of the 12 mil traces. Obviously, the board would have needed some
more time in the etching bath.
