Matched length routing

[GreggD]

Well I was looking at DDR routes and layers used for the Beaglebone Black.
I translated the layout from Allegro to Pads Standard.
Then did a spreadsheet of the route lengths. Groups of routes matched well.

I then said does Pads or Allegro include route lengths through vias.
Answer no. That was unexpected.

Then I came back to something I have not seen for a long time and could find nothing on the net.
Inner package skew listings. When bonding out a ic there used to be skew, inner BGA rows vs outer rows.
The BB Black had no adjustment for this. Then I looked at a DDR ic under a microscope.

Like most accelerometer and gyro ics, it was not a ic but a circuit board with a ic in it.
There were squiggles in the routes to the solder balls that zeroed out the skew.

Always learning.