It was 4:30 PM last Friday. I had just finished a complex connector library design, generated the package, and added it to the database. I was ready to close my laptop and enjoy the weekend.

Then, my phone buzzed. An email from the CAM Engineer at the fab house to EE and cc'd all of us.

My heart sank. Emails from CAM engineers on Friday afternoons are never good news.

I opened it. The subject line was: "EQ: Mask Issue on U14."

The message was short: “Hi, regarding U14 (the QFN package). The solder mask web between the pads is too thin. It is less than 3 mils. We cannot print this. Please advise if we can gang-relief the mask or if you will update the copper.”

I was confused. U14 was a standard QFN with a 0.4mm pitch. I didn't draw it by hand; …

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