[Arm-netbook] EOMA68-A20 2.7.4 pre-production prototypes received and working
Luke Kenneth Casson Leighton
lkcl at lkcl.net
Fri Jun 16 07:54:28 BST 2017
On Fri, Jun 16, 2017 at 7:51 AM, mike.valk at gmail.com
<mike.valk at gmail.com> wrote:
> 2017-06-16 8:19 GMT+02:00 Luke Kenneth Casson Leighton <lkcl at lkcl.net>:
>> there's not really any other options: you can see how little
>> clearance there is to the edge of the board: it's flat-out impossible
>> to bring tracks in either in between those two sets, or round the
>> back... and you don't want to anyway: they're differential pairs (up
>> to 1ghz clock rate) because this is HDMI.
> Hmm. Then how are other users of this connector doing it? This seems like a
> generic problem. The solder technique is generic afaikt.
> 1. Either they are using smaller width tracks and are passing between the
> left hand pads.
like i said: there's not enough room to get that many tracks between
the pads, and it would violate differential-pair rules to do so.
> 2. They have via's right to the pads. But that's very close to the edge.
> The options I see...
> . find other schematics using this connector.
> . Use smaller width tracks.
> . Cut the pads tight a little shorter and place the via's to the right
> creating a bottleneck but stil far enough from the edge
> . The above but to the left, via's in the middle.
possible but risky.
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