While not strictly necessary, adding an additional outline that goes on the silkscreen of your PCB can be very useful during placement, since it's a good visual indicator of where you should place the part.
This isn't a replacement for the dimension details we added in the last step -- The silk screen on your PCBs isn't very reliable since it often gets shifted a bit to the side during manufacturing -- but it's worth adding as a visual indicator for assembly.
The process is identical to the way we added our dimension details in the last step, but there are a few things to keep in mind here:
Tips on Creating Proper Silk Screen Outlines
The following guidelines are a good starting point when adding a printer outline to your PCB:
- Always place the lines or text on Layer 21 (tPlace)!
- Be sure not to place any lines on top of the copper pads, since you can't print silk screen on bare copper pads!
- Create your outline slightly larger than the actual physical dimensions, so that you can still see the outline once the part is physically place (perhaps 0.1 - 0.2mm larger on each side)
Drawing Our Silk Screen Outline
The silk screen outline is drawing exactly the same way as out dimension details in the previous step ... using the 'Wire' tool.
The important thing here is to make sure that you are on the right layer, Layer 21 (tPlace):
Once that's done, just draw a rectangle that's slightly larger than the mechanical dimensions of the board, making sure that we don't place the lines over any copper pads!
Something like this should be fine. It's a bit bigger than I would usually place, but this avoids any overlap on the pads, and everything is smaller looking than you think when you actually see it on a PCB:
It's also important to indicate the location of pin 1 on our packages, to make sure they get placed in the right orientation. We can do this by selecting the 'circle
' tool and drawing a small circle on the silk screen layer beside pin one, as follows:
You can tweek the 'Width' and 'Radius' settings until you get a solid circle about the size that you think its appropriate.
This guide was first published on Apr 22, 2013. It was last
updated on Apr 22, 2013.
This page (Adding a Silk Screen Outline to your Package) was last updated on May 04, 2015.