This tutorial requires:
DesignSpark PCB V11.0.0DesignSpark PCB provides multiple options for the generation of Gerber plots for power planes, and you must select and configure the options to meet your manufacturer's requirements.
In the Output Manufacturing Plots, you will find four options under the "Setting" tab for the Power plane Positive/Negative.
Select the layer which highlights in blue, then click on the "Settings" tab.
In the Positive/Negative pull-down menu options the two plot options highlighted will meet the manufacturer's requirements, just select if they require a positive or negative plot file for the power plane layers.
Positive (plane and items): Produces a full plot of everything that is required as copper on the finished board. This is the normal recommendation for most manufacturers.
Negative (plot isolation): Plots only the gaps between items and is a full negative plot. It is the exact negative image of ‘Positive (plane and items)’.
You will also observe in the Plot files list the option to plot an 'extra' plot highlighted in orange (in the above image) if you have placed any tracks or copper areas on the Power plane layer.
In the Plots list it has the name <layer name> (Power plane Positive)
This plot is not required if you have selected either of the (yellow highlighted) options above and may cause confusion if sent to the manufacturer, so simply deselect the generation of this plot.
For completeness, the other two plot options which will rarely if ever be required are described below:
Negative (only plot gaps): Only plots the power plane to produce a negative plot, no tracks etc., will be included.
Positive (only plot items): Plots the plane without the actual power plane copper, i.e., only any tracks as though it were a normal positive electrical layer.
it can be combined with a photo-reversed ‘negative (only plot gaps)’ output to produce a full positive plot.
History of power planes
Power planes for a PCB are another area which has features from many years of different techniques.
Historically the outer layer copper track layouts were produced using taped tracks at 2x or 4x scale and then photographically reduced.
The power plane layer images were derived from the pads on the outer layers and produced photographically and due to the process, they were produced as negative images. This method also restricted copper tracks from being placed on the power planes.
With PCB CAD power planes initially followed the 'artwork' methods as the file size was important and a negative image power plane has a much smaller file size.
Tracks on power planes were also then possible to produce but it is not recommended as it will reduce the efficiency of the power plane.
If you wish to have a power plane layer with tracks or a split power plane the recommended method is to use inner signal layers with copper pours for maximum flexibility.
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