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 Post subject: Doughnut Shaped Pad
PostPosted: 08 Feb 2017, 14:16 
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Joined: 26 Oct 2016, 10:25
Posts: 3
I need to create a doughnut shaped pad, with a round pad in the middle for a tactile dome switch. See:
http://www.snaptron.com/products/pcb-pads/double-sided-contact-pad/
Attachment:
ScreenHunter_79 Feb. 08 11.06.jpg


I've created a DXF of the doughnut shape but when I import it, I get two pads, one solid pad the matches the outter diameter, and a second pad that matches the inner diameter. Is there a why to create this pad?

These switches are mounted with an adhesive tape, which can trap the air under the switch, so there is typically a vent hole, that also acts as through hole pad, so that the pad surrounded by the "doughnut" can be routed to. On the opposite side of the PCB the pad can be much smaller. Is there a why to make a through hole pad that has different shapes and/or sizes of the top and bottom layers?

Thanks


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 Post subject: Re: Doughnut Shaped Pad
PostPosted: 09 Feb 2017, 09:33 
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Joined: 20 Jun 2015, 14:39
Posts: 936
The DXF importer in the Pattern Editor has a bug in its "[X] Embedded Polygons" option. See this thread for more detail - http://www.diptrace.com/forum/viewtopic.php?f=9&t=11321. This bug seems to bite whenever the DXF drawing exceeds a certain size. Fortunately the PCB Layout editor's DXF import tool does not appear to have this bug, so as a work-around try the following...

PCB Layout editor
1) Launch the PCB Layout editor and make sure the Design Area is clear of all objects.
2) In the Main Menu click on File, choose Import in the drop-down menu and select DXF... in the fly-out menu.
3) In the Open dialog window navigate to and select/highlight the desired DXF file, then click on the [Open] button.
4) In the Import DXF dialog window set DXF Units: (same as DXF file units), Import Mode: Add, Convert to: Top (for the desired DXF layers), enable the [X] Fill closed areas and [X] Embedded Polygons options and click on the [Import] button.
5) In the Main Menu click on File, choose Export in the drop-down menu and select DXF... in the fly-out menu.
6) In the Export DXF dialog window select/highlight the Top layer, set Units: mm, enable [X] Use Design Origin and click on the [Export] button.
7) In the Save As dialog window enter the file name "PCB_pad", navigate to a convenient folder such as the desktop and click on the [Save] button.
8) Close the PCB Layout editor without saving.

Pattern Editor
1) Launch the Pattern Editor and select/highlight the desired custom pattern library.
2) Insert a new pattern and make sure it is selected/highlighted.
3) In the Main Menu click on Pattern and choose Import from DXF... in the drop-down menu.
4) In the Open dialog window navigate to and select/highlight the file named "PCB_pad.dxf" and click on the [Open] button.
5) In the Import DXF dialog window set DXF Units: Millimeters, Import Mode: Add, Convert to: Top Signal, enable the [X] Fill Closed Areas option, make sure [ ] Embedded Polygons is disabled and click on the [Import] button.
7) Right-click on the inner pad and choose Convert to Pad in the pop-up menu.
8) Right-click on the outer pad and choose Convert to Pad in the pop-up menu.
9) Resave the custom library (Ctrl + S).

Placing a hole
One method would involve replacing the inner pad with a through-hole pad in the Pattern Editor. Use care when selecting a hole size to make sure it will not run afoul of the DRC. A second method would involve dropping a Static Via next to the button pattern in the PCB Layout editor, routing a narrow trace between it and the inner pad and then moving the Static Via to its final position inside the inner pad.

A more involved method for converting the inner pad to a through-hole pad with an offset hole
1) In the Pattern Editor right-click on the inner pad and select Convert to Shape in the pop-up menu.
2) Right-click on the newly-created shape and select Properties... in the pop-up menu.
3) In the Shape Properties dialog window, select/highlight the point with the most positive value for "Y".
4) Add twice the desired hole offset to the value of "Y" and click on OK.
5) Right-click on the newly-modified shape and select Convert to Pad in the pop-up menu.
6) Right-click on the newly-created pad and select Properties... in the pop-up menu.
7) In the Pad Properties dialog window under the [Type/Dimensions] tab, set Type: Through-Hole, Hole Shape: Round, Hole Diameter: 0.3 mm (for example) and select OK.
8) Right-click on the same pad again and select Properties... in the pop-up menu.
9) In the Pad Properties dialog window under the [Type/Dimensions] tab, click on the [Points] button.
10 In the Polygon Points dialog window, re-adjust the "Y" value of the same offset point until the pad once again resembles a circle, then click on OK.
11 Back in the Pad Properties dialog window, click on OK.


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