Still trying to figure out what is going on with the F.Cu traces. I cannot find any way to get them to appear as anything other than outlines. Selecting and right clicking gives me no usable option. âFill zoneâ doesnât do anything, and I donât see any options to âconvert to zoneâ, or to convert anything to anything else. Upon opening the 3D view, an error pops up saying âboard edges not detectedâ, even though the board outline is properly drawn on the Edge.Cuts layer. The only thing that appears to be displaying properly there are vias and anular rings. The traces on F.Cu and the unetched groundplane on B.Cu only display at a very narrow range of positions as the view is changed, and only display as a series of horizontal lines (I donât know how else to describe it) rather than solid shapes.
Working backwards, the PDF that was converted to DXF R12 shows the shapes of the traces to be solid, just as they are in the original design file. The DXF R12 does not open in Inkscape. The DXF R12 does import into two other graphic design programs (but is unable to be saved by those programs as a DXF R12 and must be converted into a different file type to save), and both of them show the shapes of the traces as unfilled. One program does not allow me the option to select a fill or stroke width as it does with any other vector graphic. The other program does allow me to select a color and fill the shapes of the traces, but does not allow me to save the result as a DXF R12. In both programs, the DXF R12 opens with both of the extra rectangles (mentioned earlier), demonstrating that they were somehow being added by Inkscape and not KiCAD.
This appears to be the case, that Inkscape removed the fill. But yet there doesnât appear to be a way to ensure that Inkscape saves the fill, the saved DXF R12 will not reopen or import in Inkscape, and multiple others have stated that a DXF R12 saved with Inkscape will import successfully into KiCAD. I think something is wrong somewhere, but no not know enough of what is supposed to be happening to be able to determine what it is.
I donât want this to drag the thread off topic here, but I have only given passing thought to this so far, it is a problem to be solved at a later stage of the project. On one of the boards, the dissipation is small and is not a concern. But one board will be required to dissipate a very significant amount of heat. Flatness of the groundplane side of the board, a copper heat block between the board and the heatsink, and the heatsink itself will all be important to maximizing thermal transfer. So sanding will be required for all of these surfaces, it will just have to be done very carefully on the board itself, as you said, the metal there is soft and there isnât much of it. If done carefully, youâll know well in advance when the high spots are mostly knocked down and youâre getting close to the copper, it should be pretty easily possible to get it flat for all practical purposes and not hit the copper at all.
To my knowledge, it is generally not considered wise to use thermal compound with large thicknesses to fill gaps, it is a better approach to remove or minimize the gaps and have flat surfaces. There is also the potential issue to be considered of dissimilar metal interaction between the copper block and the aluminum heatsink, and I have not yet investigated what would minimize any interaction and allow efficient heat transfer at the same time. Otherwise, the heatsink will be conservatively oversized, as will the forced air cooling system. The duty cycle will be low, even in prolonged periods of continuous operation, so I donât expect it to run much beyond warm in the worst case. This will of course be monitored closely in operational testing, and the cooling system modified accordingly if necessary. I expect that the biggest problem will be finding something to apply between the copper heat block and the heatsink to discourage dissimilar metal interaction, that will also provide efficient heat transfer, and is relatively inexpensive and readily obtained. In the US, there is a product called Nolox (if I remember the spelling correctly) which is used in house wiring on connections to the aluminum wire that was used for a period in the 1970âs, it is (or at least was, the last that I knew) readily available and inexpensive, but I do not know how efficient the heat transfer abilities are.
