Hi hi, I made my Feather shaped prototype and went to solder the E310 and it was too small for the footprint! I had added a “standard” 7x7mm 0.5mm pitch 48 QFN. However, the actual IC is smaller. Based on a ruler I’d say its 6x6mm 0.4mm pitch 48 QFN. Is that correct? Is there a recommended PCB layout from the company that packages it? Thanks!
Yes - there are two “industry standard” 48 QFN - 6x6 and 7x7, with different pad pitches.
Here are dimensions for the one we are using, from Intersil (not the package mfr, but just as an example application of the standard): http://www.intersil.com/content/dam/Intersil/documents/l48_/l48.6x6.pdf
And just a reminder that our own board design files are available here:
Thank you so much for the fast reply! I followed your schematic closely but don’t have Altium to look at the PCB layout. I’m using Kicad for my board. I’ll post it at some point and it can be a second reference.
Oh boy. I just realized (thanks to this thread) that I made the same mistake.
I based my design on the documentation (SiFive-E310-G000-manual-v1.0.1.pdf) which states:
Search results for QFN-48 generally point to the 7 x 7 mm variant. Not knowing that there were multiple variations of this package, I went with the first accurate-looking info that I found.
Anyway, I’d like to suggest that you at least revise the docs to state that this is the 6 x 6 mm, 0.4 mm pitch version of the package, and even better: include a full package specification including dimensional drawings as well as the recommended land pattern.
I’m frustrated to discover that I’ve wasted a few hundred dollars (and a fair amount of time) because of this mistake, and that I’ll be receiving some very useless PCBs soon. I also don’t have Altium, so I wasn’t able to veryify the footprint that way either.
Oh well. It’s ultimately my mistake for making the assumption, and I can’t blame anyone but myself. Thanks very much for sharing the info here, at least I found out about it sooner than I would have otherwise.
In case it’s helpful, here’s my Eagle footprint for the correct 6 x 6 mm QFN-48 package:
Thank you both for the feedback. In the short term we’ve updated the document to clarify so hopefully others won’t have the same problem, and are working on a more thorough specification.
FE310-G000 is currently offered in a single package option, a convenient, industry standard 6x6mm 48-lead QFN package (0.4mm pad pitch).
Thanks for being early adopters and apologies for the inconvenience!
Thank you again for the quick response before and updating the docs. I’m super excited to get it going!
I often laser print the Gerber layers 1:1 and hold up new parts to the print to make sure there is not some big mistake (we’ve done it too). All you need for this is a Gerber viewer. “Standards are a wonderful thing. Everyone should have their own” is often true.
You could use the altium2kicad converter to look at the PCB layout in KiCad: https://github.com/thesourcerer8/altium2kicad