[Milkymist-devel] PCB layout instructions

[Adam Wang]

Hi,

>> * Footprint review
>> The PCB footprints need to be reviewed. Compare all data (pin numbers,
>> geometries, plated/non-plated holes, ...) in the footprint libraries with the
>> drawings in the datasheets.
>
> I'm checking them. Will tell you soon.

All went through done and records [1] on Footprint reviews. Some of
them are not big things just for records like 0805POL, etc. According
to your bom, pls also see here[2] for quickly & easily review. For
obvious items in [1] I'll directly change/rebuild footprints for them
during routing. Meanwhile the parts survey & order are moving on, so a
Note column listed in [1] to show the compatible parts.

>> There should be only one discrepancy: I have numbered the pins of the DIN
>> connectors according to the way they are numbered in MIDI rather than the way
>> they are numbered in the datasheet. I have double-checked the current pinout
>> and I strongly believe it to be correct.
>> In case there is anything which is not 100% clear in the datasheet, I have
>> samples of all the components in the BoM and I can make checks using them.

Yeah, the DIN(5 ways 45 degrees) datasheet is not 100% clear, so far I
haven't got those parts. Hope you are right.

>> * Global component/connector placement and board dimensions
>> You are free to do whatever seems good. The current placement and dimensions
>> are only indicative.

Now the placement is moving, I'll provide two versions in 2~3 days
then we discuss. Board size I keep the long side 150mm. The width will
be changed a little bit.

>> * PCB constraints
>> I'm thinking of 6 layers with 4 mil resolution (track width and clearance), 4
>> mil annular rings, and 8 mil holes (yields a via outer diameter of 16 mil).
>> You can of course discuss/improve this, but keep in mind that, for starters, a
>> board with e.g. too many layers is better than no board at all because the
>> project took too long to complete.

Because the FPGA the ball pitch is 1mm & ball diameter is max. 0.6mm,
so it's meant only ONE trace can go through balls. Also includes
etching effect, means only 0.4mm safe between balls. So a 4/4/4
mil(0.3048 mm) resolution for trace & clearance is reasonable and
reachable. All agreed on your suggestions of resolution, what I
concerns that just confirm pcb maker first. So here[3] for list up
first.

[1] http://en.qi-hardware.com/wiki/Milkymist_One_RC1_Footprint_Reviews
[2] http://en.qi-hardware.com/wiki/Milkymist_One_RC1_BOM
[3] http://en.qi-hardware.com/wiki/Milkymist_One_RC1_PCB_Specification