We see a lot of different, unique assemblies come through our shop. On average we are introducing a new job to our factory every single day. This means the assembly has never been built by us and likely has never been built by anybody. With this amount of new work, we've seen the good, the bad, and the downright ugly when it comes to footprints.
The most sinister of all footprints is the 0402 footprint. There's something about the 0402 component that just loves to drive us insane! The issue is that many footprints inadvertently cause the component to "tombstone" or worse "head-in-pillow". Here's what those defects look like.
The biggest culprit of all 0402 issues is the default 0402 footprint in the Eagle library that comes with every installation of Eagle (I love Eagle. I really do. I just hate this one footprint). So, if you have 0402 components in your design, please, for the love of all that is honest and good in this world, change that 0402 footprint to the one we recommend.
Here's a video showing me editing this footprint in Eagle.
This video was made using the Eagle EDA tool. But here are the dimensions you'd want to use if you designed this in any other EDA tool.
We have populated hundreds of thousands (probably millions) of 0402's with this footprint. We've had such success with this footprint that I had to reach out to the engineer who designed this footprint originally and thank him for his design. He thought I was ridiculous because it was just the standard dimensions that he found on a datasheet many years ago. But the difference is he actually created his from scratch, rather than relying on the default footprint in his EDA tool's library. And this is the key. Whenever you start using a new footprint, please check it against a datasheet and make sure it matches. Your manufacturer will thank you.
If you ever have any questions, please feel free to reach out to us. We'd love to hear from you. My email is address is firstname.lastname@example.org and our phone number is (413) 624-6879.