Masks and other useful tricks in Eagle CAD

Projects / F103 Pod  Original post date: 04/29/2018

The default DRC file for OSH Park does not have solder mask for pads or vias. If you want to have a solder mask over your vias, you can change "limit" to the maximum via size that you want solder mask:

Here are some of the layers in Eagle that you might not have cared about:

Here is how I use them for making PCB footprint for a Dome momentary buttons.

I normally have all my vias with solder mask on, so I want to selectively override the vias inside the dome footprint.  To change the option, simply select the via and right click for "Properties"

Select the "Stop" to add a stop mask for the via (i.e. leave the copper bare).  Notice the difference between my regular vias (without the shade areas) and the highlighted one.

Eagle complains if I draw a via directly over the center of the dome button as it overlaps the "pin" for the footprint.  So I place a via off center and move it afterwards.

Misc

• I draw a donut circle (in tDocument layer)over my vias so that I know how much clearance I need to leave around it.
• I define my cream layer to reduce the amount of solder paste (60-70%) for my QFN footprints.  This fixes the issue of the QFN package floating on the solder paste of the center pad.
• Draw a thick line in Restrict layer for high voltage vs low voltage circuit isolation.  The width of the line should the creepage requirement for the working voltage.  DRC will warn you about violation and copper pour would avoid the area.
• Clearly label the high voltage and low voltage areas on your PCB.  It might save a life.

See here for an explanation

Add the Restrict in your opto-isolators/relays/Ethernet transformer footprints. This help DRC flag your isolation violations.  Don't run traces between rows of pins between a high voltage and low voltage circuit.  The spacing between the pins are for safety and isolation, not for routing.

Lots of layout on the web have violates this last one.  Do yourself a huge favour, unbookmark/unlike/unfollow those sites.  Don't learn bad habits from someone who don't care about the basic safety rules.