Hi Ray, 

Fiducials are highly recommended for surface mount component placement. I
think some assembly machines can deal without them by picking an unused pad
nearby but its much harder and more error prone without them. You should try
to use them.

Also you can add global fiducials on the manufacturing panel to help. Local
fiducials are good when you have a fine pitch part like a QFP package or
BGA. 

They are only 3mm in overall diameter counting the clearance and if you
locate them at diagonal opposing corners they work best.

If you contact Jerry or Jeff Hughes over at Hughes Circuits in San Marcos,
he can give you some of the Pro's and Con's... and workarounds.
760-744-0300.

Also a good reference book on the subject of Design for Manufacturability is
available from Printed Circuit Technology, P.O. Box 334. Burlington, MA.
01803 (617)272-0938 called "Bare Board PWB Design Manual by Norman S.
Einarson " A great book that was distributed by Coretec a number of years
ago.

It sounds like your board will be a candidate for fiducials on the panel.

Bill Brooks 
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510


-----Original Message-----
From: Ray Mitchell [mailto:[EMAIL PROTECTED] 
Sent: Friday, April 09, 2004 12:29 PM
To: [EMAIL PROTECTED]
Subject: [PEDA] Are fiducials necessary?

I was reading about fiducials in J-STD-013.  Are they necessary or just 
something that may come in handy?  Might a board assembler tell you he 
can't pick and place if you don't have them?  My board has 4.9mil traces 
and spaces and many of my components are 10mils apart.

Ray Mitchell
Engineer, Code 2732
SPAWAR Systems Center
San Diego, CA. 92152
(619)553-5344
[EMAIL PROTECTED]  


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