We have now plated the panel with 25 microns of copper through the hole and an additional 25 – 30 microns on the tracks and pads.  The copper is covered with a thin layer of tin as an etch resist.  Now we will remove the unwanted copper foil from the surface.

We do this on a single continuous process line.  The first step is to dissolve and wash off the resist which covers the unwanted copper.

Then we remove the unwanted copper using a powerful alkaline solution to etch away the exposed copper.  The process is carefully controlled to ensure that as we etch down we don’t etch sideways as well.  This means that the finished conductor widths are exactly as designed.  But designers should be aware that thicker copper foils need wider spaces between the tracks.

Finally we strip off the thin tin coating which protected the copper image.  So now you can see that only designed copper pattern remains.

As the boards emerge from the line they are stacked automatically.