Rev O ToDos

[ppannuto]

Not done from #58:

• HW: Consider heavier copper pour or slightly larger pads for pogo pins #56, or consider added dedicated connector
  • Maybe: Restore optional USB footprint

DFM notes to revisit:

• Much of the silkscreen is not printable.
  • The recommended line thickness for silkscreen is 6-mil (0.15mm).
  • Also, we recommend you avoid, as much as possible, any silkscreen on top of exposed copper. Highlighted are just a few examples. Any silkscreen left on top of exposed copper will be trimmed by our CAM team before the data is sent to the fab.
• Remove silkscreen from nearby fine pitch components
  • We are finding that as components get smaller, the little bit of silkscreen near those components can actually create a small gap between the stencil and the pads. From our experience, eliminating this silkscreen has had a significant impact on our first pass yield.
  • We have all of the polarity information we need from your EDA upload anyway, so we wouldn't need the polarity indicators either.
  • Interestingly, I recently attended a conference and had lunch with a DFM engineer from a very large CM (top 10 in the world) and he told me that they're eliminating silkscreen entirely from all of their projects, except for part numbers and other aesthetic features.
  • We discussed stencil printing on episode 7 of our podcast
    • Ep.7: Solder paste printing
  • We discussed stencil design in a 2 part episode (ep 74 and ep 75)
    • Ep.74:Stencils: The Unsung Heroes of PCB Perfection Pt.1
    • Ep.75:Stencils: The Unsung Heroes of PCB Perfection Pt. 2
• Trace width and gap and min hole (check for opportunities to improve this)
  • Your trace widths and gaps look good for 1oz copper, but it is on the very lowest end of most PCB fabs capabilities.
  • For higher yields and quicker turns, you may want to get to 5-mil gaps wherever possible.
  • The 4-mil drill is very small, but since your PCB is only 0.6mm thick it should be ok.

Manufacturing Notes:

• Part S4 (MM8030 RF bypass) missing solder paste (cream) cutout
• Apollo4 and 9DOF don't multiplex I2C/SPI wires in the same way:
  • The 9DOF has
    • I2C-SCL and SPI-SCLK shared
    • I2C-SDA and SPI-MISO shared
    • n/a, dedicated SPI-MOSI
    • 
  • But the Apollo4 does
    • I2C-SCL and SPI-SCLK shared [okay]
    • I2C-SDA and SPI-MOSI shared [different!!]
    • n/a, dedicated SPI-MISO
    •