Plotting Hints

Throughout the production process you should remember that it is very easy to re-plot the PCB if the art work has not turned out quite as you require. Nail polish remover will clean up the copper, easily removing the Staedtler ink.

The ink has to be of sufficient density so as to stop the ferric chloride etchant desolving copper where tracking is required. A number of ploys have been tried to achieve this.

1.    Lay the track, within the EasyEdit program, in duplicate.  This will
      cause the pen to draw the track twice (at least).  I think this method
      produces the sharpest tracks, assuming that the three key variables
      are setup correctly.

      The three variables are:-
                               a.    The track width, as set in EasyEdit
                               b.    The pen size, as set in the program
                               c.    The pen size, i.e. the actual tip size.

2.    The combination of the track width and pen tip size, as defined in
the software, will cause the program to draw a track repeateadly off-setting
such that the ink lines overlap.  This also has the effect of increasing
the density of the ink line but you will find that the edges are only one
coat of ink.  This produces a 'feathered' edge as the etchant may manage
to penetrate were the ink is thinest.  In order to keep this to a minimum
you should NOT warm the etchant.

Conclusion

So, the program setup should be:-

1.   Set the track width and pen tip size to be equal.
             This is to ensure the pen makes one pass.

2.   Lay the track twice, one on top of the other when editing the PCB.
             This will cause a second pass, thus thickening the ink but not the track width.
 
The actual track width is being determined by the actual pen tip and a second
thickness of ink will lay directly over the first. This will help stop the feathered
edge effect noted previously.

Areas of copper fill should be outlined with a track plot so as to overcome
the problem mentioned above, i.e. a filled area will be plotted as multiple overlapping
pen lines (tracks) but the edges would be only one thickness of ink.
Plotting a track at the edge fixes this problem.

The EasyPlot program allows the pen speed to be varied.  I set this to be
half an inch which allows a good flow of ink onto the copper.

Simple plot


The HP 7475A plotter.


A PIC16F84 Emulator software


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