On Sun, Dec 17, 2017 at 10:28 PM, Luke Kenneth Casson Leighton lkcl@lkcl.net wrote:
aw poop! i went to all the trouble of writing a parser for PADS :)
That is pretty cool. Now you have a way to algorithmically generate traces. I'm sorry we didn't need it, yet.
Are there signals beneath the ESD components on layer 3 or 4?
it seems i am sensible enough not to have done that :)
If not, we could put our ground reference planes on those layers under the ESD components which would move them both one layer deeper. (We already have several conveniently placed ground vias.)
So it might be easier to just put a ground keepout on layer 2 under the ESD component on layer 1 and a corresponding ground fill on layer 3. Likewise a ground keepout on layer 5 under the ESD component(s) on layer 6 and a corresponding ground fill on layer 4.
(The "otherwise" case below is given in case you feel more comfortable putting keepouts on layers 2 and 5 than changing layers 3 and 4.)
Otherwise, I would just copy the lands for the ESD pads connected to the high-speed signals and put them as ground keepouts on the normal ground reference planes.
makes sense to me
(In other words, only keep out the copper on the reference plane just under the signal path where it goes through a wide pad for the ESD component.)
including the 5 mil track *between* the ESD pads, or excluding that? so literally just the ESD pads, yeah?
I was recommending just under the ESD pads specifically for the high-frequency differential signals.
Likewise with the connector, I would put a ground keep out under the lands on layer 2 (probably best to just draw a keepout under the whole connector on layer 2)
including for the HSCL, HHPD and even the GND pads? of course there's VIAs connecting the tracks in between the diff-pairs
Wouldn't have to I suppose but the idea is to move the ground further away from the high-frequency pads to reduce the capacitive coupling thus increasing the impedance. Thus I think it's probably best to extend the layer 2 keepout under the whole connector.
but allow layer 5 to provide a full ground shield. (Provided my assumption is correct that the connector is soldered on layer 1.)
it is.
Yay!