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fiducial on land patterns

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v_kumar

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help

1) what is the size of fiducial mark (specifications)
2) where should it be added on the footprint.

can anyone tell some standard about iducial mark to be followed .

thankX in advance
 

Well it all depends on your PCB manafacture you will be using as they are all different.
I have done this before but 4 fiducials on the PCB close to the 4 corners about 1.5-2.0mm and because it was doubel sided PCB with SMT thay where placed on top layer which was ok but my PCB manacture only need 2 fuduials one in each corner so i say the best thing tha you can do is select the PCB manafacture and see how they need it to be set up but at least you have got a couple of ponters there
 

Its depend up on how the PCB Assembler wants it.
consult ur pcb assembler.
what i use is circle 40 mils smd with 60 mils mask open
 

tux said:
Its depend up on how the PCB Assembler wants it.
consult ur pcb assembler.
what i use is circle 40 mils smd with 60 mils mask open
Click to expand...

I use the same, but a much larger opening for soldermask (at least 80 thousandths- cameras for optical placement don't like to see any reflections close by)

Also on small pitch high count SSOPs,PQFPs,BGAs,etc packages, most assembly houses will want at least 1 fiducial in the center of SSOP, and at least 2 fiducials at opposite corners of PQFPs and BGAsto help place high pin count components.

As stated above, your assembly house will let you know what they require, and most assemblers use different requirements.
 

yes ur right... large soldermask opening is required
 

thanks to all guys

in general the diameter of fiducial is 1mm and the opening ie. solder mask is normally twice the fiducial pad on top.

in the mean while i have found some document on TYPES OF FIDUCIALS used on PCB BOARDS. The copy is attached here with, this will be useful to understand what fiducials are.
 

My fiducials are .040 smt dots inside a .120 dia copper and solder mask free circle. This is so the optic system has a matte background. I put three on the board, near the corners and at least two fiducials for every part whose pin spacing is .025 or less. I believe this is the ipc recommendation. Also remember to exclude these parts from your solder paste gerber file.
 

usual fudicial pad size is 40mil with 80 mil resist clearance. if you add three per board, will act as global fudicials
 

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