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Solder-Mask and Cream-Mask DFM Warnings on EAGLE Designs

EAGLE CAD (manufacturer link) has a neat feature for automatically generating the solder and cream masks for SMD pads and vias when designing printed circuit boards. A solder-mask is used to protect the copper from oxidization, while acting as something of an isolation channel to prevent solder from bridging across closely spaced pins/pads. A cream-mask is used to define a region for automated application of solder paste.

In EAGLE, the default setting for the mask placement over a board feature is to generate a region that is 3% larger than the feature on each side. This is occasionally enough to trigger all sorts of warnings when running a PCB design through a Design For Manufacturing check, especially with designs that include high-density IC packages. Such packages simply don’t have the space between pins to allow for an additional 3% clearance while adhering to the PCB shop’s manufacturing limitations.

The auto mask generation feature in EAGLE can be configured in the Design Rule Check tool, under the Masks tab. Here’s a screen shot of the tab, along with the settings I use when sending designs to SunStone Circuits for manufacturing.

Screenshot of the Design Rule Check --> Masks tab in EAGLE

Written by sturnfie

October 13th, 2010 at 12:09 pm

Posted in Design,EAGLE,PCB,Tip

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