I decided to change up bityExpress a bit given what I've learned on the last few board builds. The upgrades include:
- The entire design is now single-sided SMT. This should be much easier to paste and assemble myself. I'll only need to order one stencil, and I won't have to worry reflowing the board twice or deal with back-side components preventing the board from being level while I paste the top-side. There may be a SI (signal integrity) price to be paid for moving the decoupling capacitors a little farther away from the FPGA's power pins, but this layout still exceeds Altera's guidelines. I'd also like to start testing my SI rules-of-thumb.
- I've removed the JTAG programmer and switching power supplies that I've already validated. They really only added cost and assembly time at this point. I'll consider re-adding them if I ever decide to build the board in larger volumes.
- The board is now much more rectangular than it was. This should make it fit better inside OSH Stencil's jigs; Pasting should be easier and faster.
3D model of bityExpress-C |
1 comment:
I forgot to mention that I bumped up all of my vias to 20 mils (5 mil annular rings rather than 4 mils). I also restored my BGA pad size to the (slightly larger) Altium defaults for Altera's F484 package.
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