Hi Li,

I guess it depends on the application, as lines get finer
some backplanes have an issue with series resistance.

Also if circuitry is impedance controlled you should
graph the impedance variation with your min and max tolerance
and ensure it remains in acceptable limits for your customer.

Kind regards
Martyn Gaudion
www.polarinstruments.com



At 08:25 21/03/2002 +0800, you wrote:
>As the circuitry width become finer (3/3 mil, 2.5/2.5mil), I would like to
>know
>whether the line width tolerance got new specification or not.
>For PCB, the general IPC standard is 20% of circuitry width.  Let's say
>circuitry width 6mil got +30um tolerance.  If circuitry width 3mil, do we
>still
>use 20% of circuitry width as the specification.  Does IPC have the new
>specification for fine lines?  Or from the PCB design point of view, what
>should
>be the general tolerance for 3/3mil and 2.5/2.5mil?
>
>Wish your helpful information!
>
>Best regards!
>Li Juan
>
>---------------------------------------------------------------------------------
>Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
>To unsubscribe, send a message to [log in to unmask] with following text in
>the BODY (NOT the subject field): SIGNOFF Technet
>To temporarily halt delivery of Technet send e-mail to [log in to unmask]:
>SET Technet NOMAIL
>To receive ONE mailing per day of all the posts: send e-mail to
>[log in to unmask]: SET Technet Digest
>Search previous postings at: www.ipc.org > On-Line Resources & Databases >
>E-mail Archives
>Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
>information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
>ext.5315
>---------------------------------------------------------------------------------

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------