Tom Kavendek writes:
> 
> On Board Fiducials:
> 
> Quick guidelines we use -
> 	1. Place them in all four corners of board. At least 2 diagonally.
> 	2. There are light fiducials or dark fiducials -
> 		Light fiducial is 50 mil pad (typically used) with a 20 mil min.
> 			non-interference area (via and etch keepout)
> 		Dark fiducial is a "donut shape" where the "hole" of the donut
> 			is 50 mils and the "donut" is 20 mils.
> 	3. Brd Fiducials should be placed on both top and bottom of the board.
> 	4. Fiducials should not be covered with soldermask. ( 100 mil opening min.)

Tom,

My feeling is whatever works for you is right, but there is a "Fiducial Mark
Standard" available from SMEMA (Surface Mount Equip Manufacturers Assn.)
Their address is:
	SMEMA
	4113 Barberry Drive
	Lafayette Hill, PA 19444
	Ph.(215)825-1008    Fax: (215)941-6773

I've got the standard from 1991. I'd be happy to fax a copy to anyone (up to
a reasonable amount) who needs one and can't wait for SMEMA to send one. It's
always worked for me and I have, on occassion, talked the board house into using
this as the fiducial requirement.

Good Luck,

Mitch Morey
Sr. PCB Designer
TRW, Inc.
Redondo Beach, CA 90278
Phone: (310)814-5765
Fax:   (310)812-4949
EMAIL: [log in to unmask]

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