Re: PCB Layout Designers

On May 24, 4:26 am, John Larkin
<jjlar...@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
On Wed, 23 May 2007 09:23:55 +0800, budgie <m...@xxxxxxxxxxx> wrote:
On 22 May 2007 15:27:32 -0700, j...@xxxxxxxxxxxxxxxxxxxxx wrote:

I've come across a number of commercial designers that still route
manually. They'll go the circuit diagram route only if the board
complexity demands it (say 20 or more packages). They say the main
reason is time saving from not having to fart about creating unique
library components and the ensuing struggle with third rate diagram
editors.

I'm a one-man band when it comes to circuit and pcb design, and I prefer manual
layout (two layers only) over importing a schematic into the pcb software. I
find that:

. package placement is easier without the ratsnest, but with the ability to
have just a selection of interconnections showing.
. the autorouter is great at achieving 85% faster than me, but often fails to
complete and I have to undo sooo much that I haven't used autorouting in the
last five years.
. I have developed a fairly thorough and successful checking process that
hasn't let a layout/connection error through in those five years.

We recently did a board that has over 1000 parts, including a uP and
two FPGAs, 8 layers, parts on both sides. Hand checking that would
probably take two people a week or so, one calling out connections and
the other tracing them. PADS will do a full connectivity check on this
board in about 2 seconds, and a full design-rule check in under 10.

We do the full schematic thing for even the tiniest boards. One nice
thing is that you can ECO a schematic and export the changes to the
PCB and keep things in sync. You can also resequence the ref
designators on the board and back-annotate the schematic. We formally
release the schematic and the PCB files together, and we have a rule
that they *must* fully cross-check.

We go a few steps better with Altium Designer and make sure every part
in our library has the full data*** attached to every component,
along with a physical 3D model, and all the required manufacturing and
sourcing details. It's a lot of work up front, but it really pays
dividends when you can simply hit a button and generate full
manufacturing and purchasing BOM's and *know* it's all correct.
Data*** linking is like having a scrolly-wheel mouse, once you've
used it you never want to go back.

Dave.

.