John,

Two fiducials are required for correcting both the X-Y position and the 
Theta position in the auto-placement machine. However, most theta error can 
be corrected by the  global fiducials. Thus, you only need single fiducial 
to correct the X-Y position for your fine pitch devices.

Hope This Helps
Michael Yuen

 ----------
From: TechNet-request
To: technet
Subject: ASSY:  Fiducials
Date: Monday, October 14, 1996 9:11AM

     Address,

     From past design reviews we have always used 2 fiducials per 15mil and
     20mil SMT devices (my opinion, standard). Recently our designers are
     placing 1 fiducial in the center of the device location.  I'm not an
     agreement with this change due to possible lead skew on pads and
     similar problems.  Has visual P&P equipment changed such, that 2
     fiducials are no longer required or none at all.  Please advise.

     John Gulley

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************