Gary:

If the new version / assembly is getting a new 
P/N, then Rev. 0 is fine for that, however it 
should reference Rev. 5 for the bare board on the 
BOM.  The bare board should be just another line item on the BOM.

This is how I have always controlled it and it 
has proven itself over the years.  The numbers in 
the example below are just examples and have no significant meaning.

The 2512340 number is the blank board and this 
number will appear etched in copper on the back side of the board.

The assembly number will appear in silkscreen on 
the board primary side and will look as follows:
121234__   .  The version number will just be a 
silkscreen white block, and depending on how the 
board is stuffed will determine what number will be written in this block.


All PCB Assemblies have two revision letters, the 
blank board revision and the revision of the 
assembly.  All PCB’s start out at PCB Rev. A, Assembly Rev. A


Each time an ECO is implemented, the assembly revision letter increments.

Rev. AA – Released to production
Rev. AB – Implements ECO #072802.1 for amplifier gain improvement
Rev. AC – Implements ECO #081602.1 for timing correction
Rev. AD – Implements ECO #092202.1 for Power Supply noise reduction
Rev. BA – Implements all previous ECO’s into copper and release to production

If another ECO was required that affected both 
bare board revisions, the they would increment to Rev. AE and BB.

Hope this helps.

David Baldwin



At 07:09 AM 2/13/2008, you wrote:
>Thirty-some odd years ago when I was a novice designer, I was trained that
>the revision level of a PCB assembly (PCBA) must match, or be greater than,
>the revision level of the bare PCB fab.
>
>We have a situation now with usable Rev 5 bare board glass that is being
>populated for a different application, requiring a new part number for the
>PCBA and the BOM.
>
>I'm inclined to do the initial release of the new PCBA and BOM at Rev 5,
>based on experience.  My boss wants a Rev 0 release.
>
>I can't remember what document originally specified the form, fit and
>function rules for PCB and PCBA revision level control.
>
>Can someone provide hard copy evidence for revision level control to
>substantiate, or disprove, what I was taught back in the day?
>
>Thanks and Best Regards,
>
>----------------------------
>Gary M. Koven, C.I.D.
>Dynazign, Inc.
>Charlotte, NC, USA
>704.405.1234
>Veteran of the Marsh School
>
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