gEDA-user: sdram board update

[DJ Delorie <dj@xxxxxxxxxxx>]

Just re-etched the outer layers.  The last time, the traces ended up
too thin and many of them etched through, yet other parts of the board
had shorts.  Go figure.  After some testing, I got a setup that works
(note that PNG has a "bloat" setting now too ;-).  Results at the
bottom of http://www.delorie.com/electronics/sdram/

So far, I've found only one defect - an easily repaired break in one
of the traces on the MCU side.  Yes, all those 6/6 serpentines etched
correctly :-)

Some close ups here: http://www.delorie.com/pcb/lab/

You can also see the results of a custom HID I wrote that sits between
PCB and the PNG exporter.  It checks connectivity on each of the four
layers and adjusts the via patterns accordingly.  For example, if I'm
connecting layers 1 and 3, layer 2 has no copper and layer 4 has a
target that means "drill out completely".  If I'm connecting 1 and 2,
layer 1 has an oval drill that means "drill bigger", layer 2 has no
drill, and layers 3 and 4 have no copper.  I'll pre-drill the outer
layers, adhere the layers together, then drill all the through holes.


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