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Component location related to Fiducial marks

Joe O.B.

#30396

Component location related to Fiducial marks | 6 September, 2004

Hi,

We're going to migrate our boards from through-hole to SMT, and I'm dealing with the PCB layout. I've found a lot of references for fiducial marks but none of them states if components can be placed beyond the marks limits or only within the area they form. Do you have info about this issue? Thank you so much in advance!

Joe

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RDR

#30409

Component location related to Fiducial marks | 7 September, 2004

Components do not have to be in the framework of the fiducials. It is recommended that the fiducials are at the outer extremeties in at least 3 corners of the assembly however. It is also a good idea to keep a minimum "keepout" area around them of 3mm or so.

Fiducials are used by the placement machines to determine the actual position of the board as it is clamped into the machine. and it will then base all placements off of their coordinates. It makes me feel good to know that someone is actually paying attention and asking up front! I continually get boards that have no fiducials and when I ask for them I get "what are those"

Russ

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Darby

#30438

Component location related to Fiducial marks | 8 September, 2004

Yes I agree with Russ about someone asking up front and everything else. Two tips. 1. Keep the marks at least 5mm in from the conveyor edges of the pcb so that clamping systems do not hide the mark. 2. Make sure the marks are eccentric around the pcb so that they can only be read if the pcb is inserted into the system in the correct orientation and right side up. ie if someone puts the board in the wrong way around, upside down, or both, then fids can't be read. Good on you for asking.

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PM

#30457

Component location related to Fiducial marks | 9 September, 2004

Get a hold of the "SMEMA FIDUCIAL MARK STANDARD" . It should answer all your fiducial questions. Like the other repliers, THANKS for your concerns about fiducials, they are SOOOOOOOOO important !!!!!!!!!!

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RDR

#30458

Component location related to Fiducial marks | 9 September, 2004

Good points Darby!

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Darren

#30469

Component location related to Fiducial marks | 10 September, 2004

Joe If you are building these yourself your engineering group should be able to answer your questions, if you will be using a CM they will usually have a basic DFM report which they will gladly give to you as it will make their job much easier if you design the board with the automated processes in mind. It is great that you are asking these questions in advance but you should bring your SMT people in as early as you can, they may have some insights which will save you a lot of grief and possibly money down the line.

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