IPC-2221 Figure 5-6 shows minimum and preferred fiducial dimensions. The
diameter of the clearance [no mask or conductive pattern] around a
fiducial is expressed as 2X [minimim] or 3X [preferred] the size of the
fiducial target. Simply put, a 1mm fiducial should have a 3mm diameter
clearance. 

-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Heather Gregg
Sent: Friday, October 06, 2006 2:46 AM
To: [log in to unmask]
Subject: [DC] Fiducial Problem

I'm being told that our Fuji CP-7 is having trouble reading the board
fiducials. The cause is said to be a build-up of too much SN100 plating
on the fid. We currently use a simple dot fid. The dot is 1mm in
diameter and it is made so that there is a 0.25mm ring of bare board
around it before you get to the solder mask. Our PCB supplier has
recommended going to a doughnut design, but our SMT department is
skeptical that this will solve the build-up of SN100 issue. Personally,
I'm not convinced that it is not a problem with the machine vision
system.

That being said, I'm wondering what the "best" fid design would be. What
are/ where can I find recommendations for fids? Does anyone else have
experience with this sort of problem? Should the fid be covered with
solder mask? What design is the most robust in regards to minimizing the
effects that processing variables cause (such as plating build-up,
uneven plating, camera lighting bumped out of alignment, etc.)?

Inquiring mind,
Hg

------------------------------------------------------------------------
---------
DesignerCouncil 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
DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET
DesignerCouncil NOMAIL/(MAIL) Search previous postings at: www.ipc.org >
On-Line Resources & Databases > E-mail Archives Please visit IPC web
site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100
ext.2815
------------------------------------------------------------------------
---------

---------------------------------------------------------------------------------
DesignerCouncil 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 DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------