Thanks Phil (in Melbourne).
The prices look good!
I'm not confident enough with Eagle layout yet and think any file I
send may be totally wrong. I'm guessing some things will be lost in
translation, although I may just try it anyway.
Also, I'm still deliberating over decoupling and EMI protection, so
that's gonna take some time sorting out.
Sorry about dredging-up such an old thread (I saw my name mentioned,
while doing a search). But this might be useful:
To see whether or not your PCB's Gerber files and layout, etc, are
acceptable to a PCB manufacturer, I highly-recommend trying
http://www.freedfm.com
, which is also available via the "FreeDFM" link at
http://www.4pcb.com
, on Advanced Circuits' website. (In this case, DFM stands for Design
For Manufacturability, IIRC.)
The freeDFM facility takes your uploaded ZIPped Gerber file set (which
might need to be in "Extended" Gerber 274-X format, IIRC) and does a
number of automatic tests to try to determine if the board will be
manufacturable, or if there are any other problems. It then
automatically emails you a report that includes lists of "possible
show stoppers", and other errors, with five samples of each type of
error.
For each error sample, it gives the coordinates, the error's
measurement/margin, and drawings with three different zoom-views of
the error's location. ALSO included in the resulting email are PDF
files with high-resolution drawings of your Gerber files' layouts
(essentially an on-line free Gerber file viewer). They also include
their price quotes, etc, of course.
You don't need to worry, much, in advance, about the Gerber filenames
and what they correspond to (although I think that they do require DOS-
style naming, i.e. 8 characters max, and then a 3-char extension),
because their software will immediately list all of your uploaded
files and let you pick from a drop-down list, for each one, to tell it
which PCB layer or other file-type each one is. (But they do also
have a list, there, somewhere, of the standard Gerber file naming
conventions, for several popular PCB layout software packages.)
The FreeDFM utility seems to be quite good, and very useful, and
probably saves their customers and their CAM engineers a ton of time!
I've also used Advanced Circuits to have PCBs made, and have been
extremely satisfied with their work and service, but especially liked
the almost-painless aspect that their freeDFM and automated ordering
system enabled me to experience as a first-timer. Since you're in
Australia, you'll almost-no-doubt be better-off finding a more-local
manufacturer. But at least you can still use the freeDFM service,
first, and be able to be more-confident when initiating contact with a
PCB manufacturer, especially for the first time.
One detail: If you can set your Gerber "device setup" options to
include "Hardware Fill", it might help to avoid "nuisance" errors
related to tracks being too narrow, since, otherwise, poured copper
areas might be filled with lines, instead of being "solid", and the
lines might be mis-interpreted as tracks. I did have that happen,
once, when I first tried freeDFM, but, weirdly, only for a small
portion of my poured copper areas, and never could figure out exactly
why it happened for some poured areas but not for most of them. Oddly-
spaced lines could actually be seen in the "problem areas", in the
PDFs of the Gerbers that they sent back, if they were magnified above
something like 1200x. But, it's better to use "Hardware Fill", anyway
(and "Hardware Arcs"), since the results will be more-accurately
rendered, and the Gerber files will be smaller (assuming you have used
any copper pours, or arcs).
Regarding your deliberations over decoupling and EMI protection, etc:
Those are huge subjects (and are usually well-worth deliberating
over). And I'm no expert. For PCB layout design, apparently a lot
depends on the edge-times of the signals involved (i.e. not
necessarily their frequency, per se). There are some truly-great
appnotes (Application Notes) covering those types of considerations,
at places like Analog Devices' website,
http://www.analog.com , as
well as at other IC manufacturers' sites (e.g. national.com,
linear.com, et al). I can come up with some specific ones that I
think are very good, if you think you don't already have enough of
them. The entire Walt Jung book, "Op Amp Applications Handbook", is
on line, at analog.com, too. That book, also, has a pretty good
section that deals with those topics. For what it's worth, I usually
try to include RF filtering on almost all system inputs, outputs, and
power rails, and on most opamp inputs, and on all opamp power pins
(and wherever else it seems like it might be necessary).
Spice programs (e.g. LT-Spice, the _excellent_ free one from
linear.com) can actually be very useful (and enlightening), for
modeling and simulating a lot of the problems that can occur with
improper grounding schemes, and EMI/RF stuff. But you have to insert
the proper impedances into the models, e.g. PCB traces' and wires'
impedances. At the very least, if you model the inductance and
resistance of your power, ground, and signal traces (and capacitance,
if using a ground plane), it's pretty easy to see what happens when a
ground trace (for example) is shared, that shouldn't be shared. It
can also sometimes be quite eye-opening to add parasitics to the
component models, i.e. parallel capacitance across resistors and
series inductance for capacitors.
Sorry to have blathered-on, for so long, about all of that.
Good luck!
- Tom Gootee
http://www.fullnet.com/~tomg/index.html
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