FreeLists / si-list / [SI-LIST] Re: Off Topic Question

["Juergen Flamm" <jflamm@xxxxxxxxxxx>]

From my past experience of working many years in design engineering, I =
recall about 3 to 5 revisions as typical before production release. This =
is an average based on technologies like power supplies, precision =
analog interfaces, digital interfaces, processor modules, memory =
modules, video and graphics modules, RF modules, mixed signal modules =
and cards, etc. =20

Just to a few reasons for revision I recall:

1. Revisions caused by design and/or net list errors (design flaws, =
oversights by the design engineer).

2. Revisions caused by nebulous or changing functional requirements at =
the beginning and during the design process (caused or driven by =
internal and/or external customers).

3. Revisions caused by poor thermal characteristics detected during =
temperature testing (overheated parts).

4. Revisions caused by failing EMI/C requirements detected during =
testing (e.g. conducted and/or radiated emissions).

5. Revisions caused by failing mechanical durability tests (parts flying =
around during vibration or shock tests).

6. Revisions caused by poor parts selection (part was obsolete before =
production release could happen).=20

6. I have also seen many revisions caused by poor project definition and =
coordination, understaffing, staff assigned with wrong skill sets, =
unbearable schedule pressure, .....

Now I am sure you can think of a flexible design process that could be =
implemented to avoid at least some of these revisions.

I decided to change jobs. Now I have the chance to globally influence =
design process flows and tool improvements, which will help users to be =
more productive.=20

 Juergen Flamm
Senior Technical Leader                 Office Phone: 1-818-881-9965 =20
PCB Systems Division            Cell Phone:     1-818-642-2633
Cadence Design Systems, Inc.    Help Desk:      1-877-237-4911
1960 East Grand Ave., Suite 1070        E-Mail:   jflamm@xxxxxxxxxxx
El Segundo, CA 90245    Web Site: http://www.cadencepcb.com

=09
Register for one of our FREE upcoming seminars,=20
visit  http://www.cadencepcb.com/aboutus/events.asp


-----Original Message-----
From: Bill Reams [mailto:breams@xxxxxxxxxxxxxx]
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 =
=3D
work at companies ranging from medium tech to very high tech, this =3D
seemed a good source for a non-scientific poll.

For your "typical" projects, how many circuit board revisions does it =
=3D
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 =
=3D
first prototype is always perfect." But we've probably all seen the =3D
project where we're sent off to design a left-handed widget and =3D
eventually deliver the flux capacitor that they really wanted - but only =
=3D
after a large number of revisions and redesigns because they couldn't =
=3D
figure out how to ask for what they wanted. What I'm interested in is =
=3D
not the extreme revision numbers, but the typical number of revisions =
=3D
for typical projects. And please do include all revisions for DFM, DFT, =
=3D
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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