pcb-rnd knowledge pool
Making power traces with the polyhatch command in pcb-rnd
power_traces by Erich Heinzle on 2018-01-16
Tags: howto, solder, mask, current, power, traces, polyhatch, menufile
Abstract: Show how the polyhatch and subtraction soldermask layer can be used to make high current traces on copper pours.
How to edit solder masks to achieve high current power traces.
The basic idea is to create openings in the solder mask along high current copper features that allow solder to adhere to the copper to increase the current carrying capacity.
The trick is to achieve this in a controlled, predictable way with linear apertures in the solder mask, rather than leaving large surfaces of copper exposed which may get an uneven coating or puddles of solder adhering to it.
In this howto, we will draw a polygon and demonstrate the application of high current traces to it. We begin by selecting the polygon tool in the menu:
Having done this, we now click on the layout at each point a vertex is needed.
The polygon can be completed by double clicking on the first vertex.
If the final edge of the polygon needs to be at an angle other than a multiple of ninety degrees the "all-direction" line setting can be selected in the menu:
Having drawn a polygon, we click on the "select" item in the menu. Hitting escape is another way to go back to the selection mode.
Having gone into select mode, we can now click on the polygon to select it.
With the polygon selected, we can invoke the :polyhatch(interactive) command, by first typing the colon character on the keyboard ':', and then typing polyhatch(interactive) as follows:
The interactive command brings up a window allowing the polygon hatching to be customised:
We deselect the vertical hatching, and modify the line spacing:
proceeding with these settings, we can create a set of lines that cross hatch the polygon. The lines are created in the active layer. The Polygon remains selected:
The still selected polygon can be deleted if needed by using the SHIFT-delete key combination. This is useful if cross hatching is needed to replace the original polygon:
For high current power traces, we want the lines on the negative-drawn solder mask layer to create apertures. Accordingly, we must select the top mask to be the active layer before invoking the :polyhatch(interactive) command:
This creates the set of lines in the top mask layer:
here is a rendering of the exported gerbers for this simple example layout, after the additrion of some vias, showing solder along the lines in the solder mask layer, meeting up with solder around the vias.