[SI-LIST] Re: Off Topic Question
- From: "Peter Arnold" <parnold@xxxxxxxxxxxxxxx>
- To: "'Si-List' (E-mail)" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 7 Nov 2002 13:27:15 -0800
Bill,
At my last job we did moderately complex boards, 10-20 layers, up to 400MHz
signaling. We always aimed to do boards in one hit, but usually needed at
least one feature revision and one tweaking revision. I theorize this
happens to board designs because:
1) The spec of any project >3 months long is a moving target.
2) At some point in the review cycle, once a good level of functionality is
assured, it is more efficient to stop checking, reviewing, simulating, and
just make one. You learn a lot about what you did wrong in a very short
time.
3) Component availability, DFM, EMC, and mechanical issues may take a while
to become apparent. Often a final rev was to address these.
4) Relative to project budget, it did not always add much cost to make the
second "build" of boards using updated gerber.
As Fred Brooks wrote, "Plan to throw one away - you will anyway."
peter arnold,
formerly of a different company.
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Bill Reams
Sent: Thursday, November 07, 2002 1:01 PM
To: 'Si-List' (E-mail)
Subject: [SI-LIST] Off Topic Question
Ladies and Gentlemen,
I have a question that is off topic for this list. However, as we all =
work at companies ranging from medium tech to very high tech, this =
seemed a good source for a non-scientific poll.
For your "typical" projects, how many circuit board revisions does it =
take to go from the block diagram stage to full production release?
I know that in the perfect world, everyone would answer "One board, my =
first prototype is always perfect." But we've probably all seen the =
project where we're sent off to design a left-handed widget and =
eventually deliver the flux capacitor that they really wanted - but only =
after a large number of revisions and redesigns because they couldn't =
figure out how to ask for what they wanted. What I'm interested in is =
not the extreme revision numbers, but the typical number of revisions =
for typical projects. And please do include all revisions for DFM, DFT, =
EMC/EMI related modifications.
Thanks for your responses.
Bill
_______________________________________
| |
| Bill Reams - Sr. Hardware Engineer |
| 512-928-7201 (direct) |
| 512-349-0300 (Main) |
| breams@xxxxxxxxxxxxxx (e-mail) |
|______________________________________|
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